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  1. Host range expansion is density dependent.

    Science.gov (United States)

    Castagneyrol, Bastien; Jactel, Hervé; Brockerhoff, Eckehard G; Perrette, Nicolas; Larter, Maximilien; Delzon, Sylvain; Piou, Dominique

    2016-11-01

    The realized host range of herbivores is expected to increase with herbivore population density. Theory also predicts that trait similarity and phylogenetic relatedness between native and exotic plants is expected to increase the susceptibility of introduced plants to feeding by native herbivores. Whether the ability of native herbivores to extend their host range to introduced species is density dependent is still unknown. We addressed this question by monitoring pine processionary moth (PPM, Thaumetopoea pityocampa) attacks during nine consecutive years on 41 pine species (8 native and 33 introduced) planted in an arboretum. The survey encompassed latent and outbreak periods. A total of 28 pine species were attacked by PPM. There was no difference in the probability of attack between native and introduced pine species. Host range increased and was more phylogenetically clustered during outbreak than latent periods. When population density increased, PPM expanded its diet breadth by attacking introduced pine species that were closely related to native hosts. This study demonstrates the density dependence of host range expansion in a common pine herbivore. Importantly, it supports the idea that the degree of phylogenetic proximity between host species can be a better predictor of attacks than the introduction status, which may help to predict the outcomes of new plant-herbivore interactions.

  2. Mating and host density affect host feeding and parasitism in two species of whitefly parasitoids

    Institute of Scientific and Technical Information of China (English)

    Lian-Sheng Zang; Tong-Xian Liu; Fan Zhang; Shu-Sen Shi; Fang-Hao Wan

    2011-01-01

    The parasitoids in the genera of Encarsia and Eretmocerus(Hymenoptera:Aphelinidae)are important biological control agents of whiteflies,and some of them not only parasitize hosts but also kill them with strong host-feeding capacity.Two whitefly parasitoid species,Encarsia sophia and Eretmocerus melanoscutus were examined to determine if mating and host density affected their host feeding and parasitism.The whitefly host,Bemisia tabaci,was presented to these two wasp species in densities of 10,20,30,40,50 and 60 third-instar nymphs per clip cage.Mated whitefly parasitoid females fed on more hosts than unmated females under a range of host densities(under all six host densities for En.sophia; under the densities of 40 nymphs or more for Er.melanoscutus).Meanwhile,mated females parasitized more whitefly nymphs than unmated females under all host densities for both species.With increase of host density,mated or unmated Er.melanoscutus females killed more hosts by host feeding and parasitism.Mated En.sophia females killed more hosts by host feeding with increase of host density,whereas unmated females did not parasitze whitefly nymphs at all.Our results suggest that only mated female parasitoids with host-feeding behavior should be released in crop systems to increase their bio-control efficiency.

  3. Shifting preference between oviposition vs. host-feeding under changing host densities in two aphelinid parasitoids

    DEFF Research Database (Denmark)

    Yang, Nian-Wan; Ji, Lu-Lu; Lövei, Gabor L;

    2012-01-01

    Destructive host-feeding is common in hymenopteran parasitoids. Such feeding may be restricted to host stages not preferred for oviposition. However, whether this is a fixed strategy or can vary according to resource levels or parasitoid needs is less clear. We tested the trade-off between host...... feeding and oviposition on two whitefly parasitoids under varying host densities. Females of two aphelinid parasitoids, Eretmocerus hayati and Encarsia sophia were exposed to nine different densities of their whitefly host, Bemisia tabaci, in single-instar tests to identify their functional response....... Mixed-instar host choice tests were also conducted by exposing whiteflies at four densities to the parasitoids. We hypothesized that the parasitoid females can detect different host densities, and decide on oviposition vs. host-feeding accordingly. The results showed that both Er. hayati and En. sophia...

  4. Shifting preference between oviposition vs. host-feeding under changing host densities in two aphelinid parasitoids

    DEFF Research Database (Denmark)

    Yang, Nian-Wan; Ji, Lu-Lu; Lövei, Gabor L

    2012-01-01

    feeding and oviposition on two whitefly parasitoids under varying host densities. Females of two aphelinid parasitoids, Eretmocerus hayati and Encarsia sophia were exposed to nine different densities of their whitefly host, Bemisia tabaci, in single-instar tests to identify their functional response....... Mixed-instar host choice tests were also conducted by exposing whiteflies at four densities to the parasitoids. We hypothesized that the parasitoid females can detect different host densities, and decide on oviposition vs. host-feeding accordingly. The results showed that both Er. hayati and En. sophia...... parasitized most on first and second (the optimal ones), and fed most on third nymphal instars (the suboptimal one) of the whitefly host as theory predicts, while at high densities, both parasitism and host-feeding occurred on first and second instars which are preferred for oviposition. En. sophia...

  5. Host density increases parasite recruitment but decreases host risk in a snail-trematode system.

    Science.gov (United States)

    Buck, J C; Hechinger, R F; Wood, A C; Stewart, T E; Kuris, A M; Lafferty, K D

    2017-08-01

    Most species aggregate in local patches. High host density in patches increases contact rate between hosts and parasites, increasing parasite transmission success. At the same time, for environmentally transmitted parasites, high host density can decrease infection risk to individual hosts, because infective stages are divided among all hosts in a patch, leading to safety in numbers. We tested these predictions using the California horn snail, Cerithideopsis californica (=Cerithidea californica), which is the first intermediate host for at least 19 digenean trematode species in California estuaries. Snails become infected by ingesting trematode eggs or through penetration by free-swimming miracidia that hatch from trematode eggs deposited with final-host (bird or mammal) feces. This complex life cycle decouples infective-stage production from transmission, raising the possibility of an inverse relationship between host density and infection risk at local scales. In a field survey, higher snail density was associated with increased trematode (infected snail) density, but decreased trematode prevalence, consistent with either safety in numbers, parasitic castration, or both. To determine the extent to which safety in numbers drove the negative snail-density-trematode-prevalence association, we manipulated uninfected snail density in 83 cages at eight sites within Carpinteria Salt Marsh (California, USA). At each site, we quantified snail density and used data on final-host (bird and raccoon) distributions to control for between-site variation in infective-stage supply. After three months, overall trematode infections per cage increased with snail biomass density. For egg-transmitted trematodes, per-snail infection risk decreased with snail biomass density in the cage and surrounding area, whereas per-snail infection risk did not decrease for miracidium-transmitted trematodes. Furthermore, both trematode recruitment and infection risk increased with infective

  6. Host density increases parasite recruitment but decreases host risk in a snail-trematode system

    Science.gov (United States)

    Buck, Julia C; Hechinger, R.F.; Wood, A.C.; Stewart, T.E.; Kuris, A.M.; Lafferty, Kevin D.

    2017-01-01

    Most species aggregate in local patches. High host density in patches increases contact rate between hosts and parasites, increasing parasite transmission success. At the same time, for environmentally-transmitted parasites, high host density can decrease infection risk to individual hosts, because infective stages are divided among all hosts in a patch, leading to safety in numbers. We tested these predictions using the California horn snail, Cerithideopsis californica (=Cerithidea californica), which is the first intermediate host for at least 19 digenean trematode species in California estuaries. Snails become infected by ingesting trematode eggs or through penetration by free-swimming miracidia that hatch from trematode eggs deposited with final-host (bird or mammal) feces. This complex life cycle decouples infective-stage production from transmission, raising the possibility of an inverse relationship between host density and infection risk. In a field survey, higher snail density was associated with increased trematode (infected snail) density, but decreased trematode prevalence, consistent with either safety in numbers, parasitic castration, or both. To determine the extent to which safety in numbers drove the negative snail density-trematode prevalence association, we manipulated uninfected snail density in 83 cages at eight sites within Carpinteria Salt Marsh (CA, USA). At each site, we quantified snail density and used data on final-host (bird and raccoon) distributions to control for between-site variation in infective-stage supply. After three months, overall trematode infections per cage increased with snail-biomass density. For egg-transmitted trematodes, per-snail infection risk decreased with snail-biomass density in the cage and surrounding area, whereas per-snail infection risk did not decrease for miracidium-transmitted trematodes. Furthermore, both trematode recruitment and infection risk increased with infective-stage input, but this was

  7. Wolbachia-Host Interactions: Host Mating Patterns Affect Wolbachia Density Dynamics.

    Science.gov (United States)

    Zhao, Dong-Xiao; Zhang, Xiang-Fei; Chen, Da-Song; Zhang, Yan-Kai; Hong, Xiao-Yue

    2013-01-01

    Wolbachia are maternally inherited intracellular bacteria that infect a wide range of arthropods and cause an array of effects on host reproduction, fitness and mating behavior. Although our understanding of the Wolbachia-associated effects on hosts is rapidly expanding, our knowledge of the host factors that mediate Wolbachia dynamics is rudimentary. Here, we explore the interactions between Wolbachia and its host, the two-spotted spider mite Tetranychus urticae Koch. Our results indicate that Wolbachia induces strong cytoplasmic incompatibility (CI), increases host fecundity, but has no effects on the longevity of females and the mating competitiveness of males in T. urticae. Most importantly, host mating pattern was found to affect Wolbachia density dynamics during host aging. Mating of an uninfected mite of either sex with an infected mite attenuates the Wolbachia density in the infected mite. According to the results of Wolbachia localization, this finding may be associated with the tropism of Wolbachia for the reproductive tissue in adult spider mites. Our findings describe a new interaction between Wolbachia and their hosts.

  8. Wolbachia-Host Interactions: Host Mating Patterns Affect Wolbachia Density Dynamics

    OpenAIRE

    Dong-Xiao Zhao; Xiang-Fei Zhang; Da-Song Chen; Yan-Kai Zhang; Xiao-Yue Hong

    2013-01-01

    Wolbachia are maternally inherited intracellular bacteria that infect a wide range of arthropods and cause an array of effects on host reproduction, fitness and mating behavior. Although our understanding of the Wolbachia-associated effects on hosts is rapidly expanding, our knowledge of the host factors that mediate Wolbachia dynamics is rudimentary. Here, we explore the interactions between Wolbachia and its host, the two-spotted spider mite Tetranychus urticae Koch. Our results indicate th...

  9. Mosquito host selection varies seasonally with host availability and mosquito density.

    Directory of Open Access Journals (Sweden)

    Tara C Thiemann

    2011-12-01

    Full Text Available Host selection by vector mosquitoes is a critical component of virus proliferation, particularly for viruses such as West Nile (WNV that are transmitted enzootically to a variety of avian hosts, and tangentially to dead-end hosts such as humans. Culex tarsalis is a principal vector of WNV in rural areas of western North America. Based on previous work, Cx. tarsalis utilizes a variety of avian and mammalian hosts and tends to feed more frequently on mammals in the late summer than during the rest of the year. To further explore this and other temporal changes in host selection, bloodfed females were collected at a rural farmstead and heron nesting site in Northern California from May 2008 through May 2009, and bloodmeal hosts identified using either a microsphere-based array or by sequencing of the mitochondrial cytochrome c oxidase I (COI gene. Host composition during summer was dominated by four species of nesting Ardeidae. In addition, the site was populated with various passerine species as well as domestic farm animals and humans. When present, Cx. tarsalis fed predominantly (>80% upon the ardeids, with Black-crowned Night-Herons, a highly competent WNV host, the most prevalent summer host. As the ardeids fledged and left the area and mosquito abundance increased in late summer, Cx. tarsalis feeding shifted to include more mammals, primarily cattle, and a high diversity of avian species. In the winter, Yellow-billed Magpies and House Sparrows were the predominant hosts, and Yellow-billed Magpies and American Robins were fed upon more frequently than expected given their relative abundance. These data demonstrated that host selection was likely based both on host availability and differences in utilization, that the shift of bloodfeeding to include more mammalian hosts was likely the result of both host availability and increased mosquito abundance, and that WNV-competent hosts were fed upon by Cx. tarsalis throughout the year.

  10. High host density favors greater virulence: a model of parasite-host dynamics based on multi-type branching processes

    CERN Document Server

    Borovkov, Konstantin; Rice, Timothy

    2011-01-01

    We use a multitype continuous time Markov branching process model to describe the dynamics of the spread of parasites of two types that can mutate into each other in a common host population. Instead of using a single virulence characteristic which is typical of most mathematical models for infectious diseases, our model uses a combination of two characteristics: lethality and transmissibility. This makes the model capable of reproducing the empirically observed fact that the increase in the host density can lead to the prevalence of the more virulent pathogen type. We provide some numerical illustrations and discuss the effects of the size of the enclosure containing the host population on the encounter rate in our model that plays the key role in determining what pathogen type will eventually prevail. We also present a multistage extension of the model to situations where there are several populations and parasites can be transmitted from one of them to another.

  11. Interaction between host genotype and environmental conditions affects bacterial density in Wolbachia symbiosis

    OpenAIRE

    Mouton, Laurence; Henri, Hélène; Charif, Delphine; Boulétreau, Michel; Vavre, Fabrice

    2007-01-01

    Regulation of microbial population density is a necessity in stable symbiotic interactions. In Wolbachia symbiosis, both bacterial and host genotypes are involved in density regulation, but environmental factors may also affect bacterial population density. Here, we studied the interaction between three strains of Wolbachia in two divergent homozygous lines of the wasp Leptopilina heterotoma at two different temperatures. Wolbachia density varied between the two host genotypes at only one tem...

  12. Habitat selection of a parasitoid mediated by volatiles informing on host and intraguild predator densities

    DEFF Research Database (Denmark)

    Cotes, Belén; Rännbäck, Linda Marie; Björkman, Maria;

    2015-01-01

    To locate and evaluate host patches before oviposition, parasitoids of herbivorous insects utilize plant volatiles and host-derived cues, but also evaluate predator-derived infochemicals to reduce predation risks. When foraging in host habitats infested with entomopathogenic fungi that can infect...... both a parasitoid and its host, parasitoids may reduce the risk of intraguild predation (IGP) by avoiding such patches. In this study, we examined whether the presence of the entomopathogenic fungi Metarhizium brunneum and Beauveria bassiana in soil habitats of a root herbivore, Delia radicum, affects...... the behavior of Trybliographa rapae, a parasitoid of D. radicum. Olfactometer bioassays revealed that T. rapae avoided fungal infested host habitats and that this was dependent on fungal species and density. In particular, the parasitoid avoided habitats with high densities of the more virulent fungus, M...

  13. High nymphal host density and mortality negatively impact parasitoid complex during an insect herbivore outbreak.

    Science.gov (United States)

    Hall, Aidan A G; Johnson, Scott N; Cook, James M; Riegler, Markus

    2017-08-26

    Insect herbivore outbreaks frequently occur and this may be due to factors that restrict top-down control by parasitoids, for example, host-parasitoid asynchrony, hyperparasitisation, resource limitation and climate. Few studies have examined host-parasitoid density relationships during an insect herbivore outbreak in a natural ecosystem with diverse parasitoids. We studied parasitisation patterns of Cardiaspina psyllids during an outbreak in a Eucalyptus woodland. First, we established the trophic roles of the parasitoids through a species-specific multiplex PCR approach on mummies from which parasitoids emerged. Then, we assessed host-parasitoid density relationships across three spatial scales (leaf, tree and site) over one year. We detected four endoparasitoid species of the family Encyrtidae (Hymenoptera); two primary parasitoid and one heteronomous hyperparasitoid Psyllaephagus species (the latter with female development as a primary parasitoid and male development as a hyperparasitoid), and the hyperparasitoid Coccidoctonus psyllae. Parasitoid development was host-synchronised, although synchrony between sites appeared constrained during winter (due to temperature differences). Parasitisation was predominantly driven by one primary parasitoid species and was mostly inversely host-density dependent across the spatial scales. Hyperparasitisation by C. psyllae was psyllid-density dependent at the site scale, however, this only impacted the rarer primary parasitod. High larval parasitoid mortality due to density dependent nymphal psyllid mortality (a consequence of resource limitation) compounded by a summer heat wave was incorporated in the assessment and resulted in density independence of host-parasitoid relationships. As such, high larval parasitoid mortality during insect herbivore outbreaks may contribute to the absence of host density dependent parasitisation during outbreak events. This article is protected by copyright. All rights reserved. This article

  14. Density threshold for Mopeia virus invasion and persistence in its host Mastomys natalensis

    DEFF Research Database (Denmark)

    Goyens, J.; Reijniers, J.; Borremans, B.;

    2013-01-01

    Well-established theoretical models predict host density thresholds for invasion and persistence of parasites with a density-dependent transmission. Studying such thresholds in reality, however, is not obvious because it requires long-term data for several fluctuating populations of different size...... is closely related to Lassa virus but non-pathogenic to humans so can be studied safely in the field. The simulations show that, while host density clearly is important, sharp thresholds are only to be expected for persistence (and not for invasion), since at short time-spans (as during invasion......-igniting the transmission. The model is most sensitive to the duration of the infectious stage, the size of the home range and the transmission coefficient, so these are important factors to determine experimentally in the future....

  15. Location of Symbionts in the Whitefly Bemisia tabaci Affects Their Densities during Host Development and Environmental Stress

    Science.gov (United States)

    Su, Qi; Xie, Wen; Wang, Shaoli; Wu, Qingjun; Ghanim, Murad; Zhang, Youjun

    2014-01-01

    Bacterial symbionts often enhance the physiological capabilities of their arthropod hosts and enable their hosts to expand into formerly unavailable niches, thus leading to biological diversification. Many arthropods, including the worldwide invasive whitefly Bemisia tabaci, have individuals simultaneously infected with symbionts of multiple genera that occur in different locations in the host. This study examined the population dynamics of symbionts that are located in different areas within B. tabaci. While densities of Portiera and Hamiltonella (which are located in bacteriocytes) appeared to be well-regulated during host development, densities of Rickettsia (which are not located in bacteriocytes) were highly variable among individual hosts during host development. Host mating did not significantly affect symbiont densities. Infection by Tomato yellow leaf curl virus did not affect Portiera and Hamiltonella densities in either sex, but increased Rickettsia densities in females. High and low temperatures did not affect Portiera and Hamiltonella densities, but low temperature (15°C) significantly suppressed Rickettsia densities whereas high temperature (35°C) had little effect on Rickettsia densities. The results are consistent with the view that the population dynamics of bacterial symbionts in B. tabaci are regulated by symbiont location within the host and that the regulation reflects adaptation between the bacteria and insect. PMID:24632746

  16. Habitat selection of a parasitoid mediated by volatiles informing on host and intraguild predator densities

    DEFF Research Database (Denmark)

    Cotes, Belén; Rännbäck, Linda Marie; Björkman, Maria

    2015-01-01

    both a parasitoid and its host, parasitoids may reduce the risk of intraguild predation (IGP) by avoiding such patches. In this study, we examined whether the presence of the entomopathogenic fungi Metarhizium brunneum and Beauveria bassiana in soil habitats of a root herbivore, Delia radicum, affects...... volatile compounds to locate high densities of prey, but also compounds related to fungal presence to reduce the risk of IGP towards themselves and their offspring....

  17. Emergency rabies control in a community of two high-density hosts

    Directory of Open Access Journals (Sweden)

    Singer Alexander

    2012-06-01

    Full Text Available Abstract Background Rabies is a fatal viral disease that potentially can affect all mammals. Terrestrial rabies is not present in the United Kingdom and has been eliminated from Western Europe. Nevertheless the possibility remains that rabies could be introduced to England, where it would find two potentially suitable hosts, red foxes and badgers. With the aim to analyse the spread and emergency control of rabies in this two species host community, a simulation model was constructed. Different control strategies involving anti-rabies vaccination and population culling were developed, considering control application rates, spatial extent and timing. These strategies were evaluated for efficacy and feasibility to control rabies in hypothetical rural areas in the South of England immediately after a disease outbreak. Results The model confirmed that both fox and badger populations, separately, were competent hosts for the spread of rabies. Realistic vaccination levels were not sufficient to control rabies in high-density badger populations. The combined species community was a very strong rabies host. However, disease spread within species appeared to be more important than cross-species infection. Thus, the drivers of epidemiology depend on the potential of separate host species to sustain the disease. To control a rabies outbreak in the two species, both species had to be targeted. Realistic and robust control strategies involved vaccination of foxes and badgers, but also required badger culling. Although fox and badger populations in the UK are exceptionally dense, an outbreak of rabies can be controlled with a higher than 90% chance, if control response is quick and follows a strict regime. This requires surveillance and forceful and repeated control campaigns. In contrast, an uncontrolled rabies outbreak in the South of England would quickly develop into a strong epizootic involving tens of thousands of rabid foxes and badgers. Conclusions If

  18. A study of the early detection of insect infestations and density/distribution of host plants

    Science.gov (United States)

    Hart, W. G.; Ingle, S. J.; Davis, M. R. (Principal Investigator)

    1974-01-01

    The author has identified the following significant results. Significant results have been obtained in the identification of citrus, sugarcane, winter vegetables, irrigated pastures, and unimproved pastures which contain brush. Land without vegetation, lakes, roads, and waterways can also be determined. Different densities of vegetation covering some cultivated areas are apparent. The practical applications of these results are many. The abundance of host plants of pests can be determined. Avenues of entry of pests can be plotted, facilitating control or preventing entry of pest species. The boundaries of areas to be quarantined can be accurately established after viewing the S-190B data. Better cultural methods can be employed such as planning where to plant certain crops that indirectly are detrimental to those already growing. This would relate to such factors as pesticide drift or alternate hosts of major pests.

  19. Wolbachia age-sex-specific density in Aedes albopictus: a host evolutionary response to cytoplasmic incompatibility?

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    Pablo Tortosa

    Full Text Available BACKGROUND: Wolbachia bacteria have invaded many arthropod species by inducing Cytoplasmic Incompatibility (CI. These symbionts represent fascinating objects of study for evolutionary biologists, but also powerful potential biocontrol agents. Here, we assess the density dynamics of Wolbachia infections in males and females of the mosquito Aedes albopitcus, an important vector of human pathogens, and interpret the results within an evolutionary framework. METHODOLOGY/PRINCIPAL FINDINGS: Wolbachia densities were measured in natural populations and in age controlled mosquitoes using quantitative PCR. We show that the density dynamics of the wAlbA Wolbachia strain infecting Aedes albopictus drastically differ between males and females, with a very rapid decay of infection in males only. CONCLUSIONS/SIGNIFICANCE: Theory predicts that Wolbachia and its hosts should cooperate to improve the transmission of infection to offspring, because only infected eggs are protected from the effects of CI. However, incompatible matings effectively lower the fertility of infected males, so that selection acting on the host genome should tend to reduce the expression of CI in males, for example, by reducing infection density in males before sexual maturation. The rapid decay of one Wolbachia infection in Aedes albopictus males, but not in females, is consistent with this prediction. We suggest that the commonly observed reduction in CI intensity with male age reflects a similar evolutionary process. Our results also highlight the importance of monitoring infection density dynamics in both males and females to assess the efficiency of Wolbachia-based control strategies.

  20. Plant Killing by Mutualistic Ants Increases the Density of Host Species Seedlings in the Dry Forest of Costa Rica

    OpenAIRE

    Sabrina Amador-Vargas

    2012-01-01

    Some species of plant-mutualistic ants kill the vegetation growing in the vicinities of their host plant, creating an area of bare ground (clearing). The reduced competition in the clearing may facilitate the establishment of host species sprouts (clones and seedlings), which in turn benefits the ants with additional food and shelter (“sprout-establishment hypothesis”). To test this hypothesis, the density and origin of Acacia collinsii sprouts growing inside clearings and in the vicinities o...

  1. A mutualism-parasitism system modeling host and parasite with mutualism at low density.

    Science.gov (United States)

    Wang, Yuanshi; Deangelis, Donald L

    2012-04-01

    A mutualism-parasitism system of two species is considered, where mutualism is the dominant interaction when the predators (parasites) are at low density while parasitism is dominant when the predators are at high density. Our aim is to show that mutualism at low density promotes coexistence of the species and leads to high production of the prey (host). The mutualism-parasitism system presented here is a combination of the Lotka-Volterra cooperative model and Lotka-Volterra predator-prey model. By comparing dynamics of this system with those of the Lotka-Volterra predator-prey model, we present the mechanisms by which the mutualism improves the coexistence of the species and production of the prey. Then the parameter space is divided into six regions, which correspond to the four outcomes of mutualism, commensalism, predation/parasitism and neutralism, respectively. When the parameters are varied continuously among the six regions, it is shown that the interaction outcomes of the system transition smoothly among the four outcomes. By comparing the dynamics of the specific system with those of the Lotka-Volterra cooperative model, we show that the parasitism at high density promotes stability of the system. A novel aspect of this paper is the simplicity of the model, which allows rigorous and thorough analysis and transparency of the results.

  2. Charge transport in disordered organic host-guest systems: effects of carrier density and electric field

    Energy Technology Data Exchange (ETDEWEB)

    Yimer, Y Y; Bobbert, P A [Group Polymer Physics, Eindhoven Polymer Laboratories and Dutch Polymer Institute, 5600 MB Eindhoven (Netherlands); Coehoorn, R [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands)], E-mail: Y.Y.Yimer@tue.nl

    2008-08-20

    We investigate charge transport in disordered organic host-guest systems with a bimodal Gaussian density of states (DOS). The energy difference between the two Gaussians defines the trap depth. By solving the Pauli master equation for the hopping of charge carriers on a regular lattice with site energies randomly drawn from the DOS, we obtain the dependence of the charge-carrier mobility on the relative guest concentration, the trap depth, the energetic disorder, the charge-carrier density and the electric field. At small and high guest concentrations, our work provides support for recent semi-analytical model results on the dependence of the mobility on the charge-carrier density at zero field. However, at the cross-over between the trap-limited and trap-to-trap hopping regimes, where the mobility attains a minimum, our results can almost be one order of magnitude larger than predicted semi-analytically. Furthermore, it is shown that field-induced detrapping can contribute strongly to the electric-field dependence of the mobility. A simple analytical expression is provided which describes the effect. This result can be used in continuum drift-diffusion models for charge transport in devices such as organic light-emitting diodes.

  3. Charge transport in disordered organic host guest systems: effects of carrier density and electric field

    Science.gov (United States)

    Yimer, Y. Y.; Bobbert, P. A.; Coehoorn, R.

    2008-08-01

    We investigate charge transport in disordered organic host-guest systems with a bimodal Gaussian density of states (DOS). The energy difference between the two Gaussians defines the trap depth. By solving the Pauli master equation for the hopping of charge carriers on a regular lattice with site energies randomly drawn from the DOS, we obtain the dependence of the charge-carrier mobility on the relative guest concentration, the trap depth, the energetic disorder, the charge-carrier density and the electric field. At small and high guest concentrations, our work provides support for recent semi-analytical model results on the dependence of the mobility on the charge-carrier density at zero field. However, at the cross-over between the trap-limited and trap-to-trap hopping regimes, where the mobility attains a minimum, our results can almost be one order of magnitude larger than predicted semi-analytically. Furthermore, it is shown that field-induced detrapping can contribute strongly to the electric-field dependence of the mobility. A simple analytical expression is provided which describes the effect. This result can be used in continuum drift-diffusion models for charge transport in devices such as organic light-emitting diodes.

  4. Effects of juvenile host density and food availability on adult immune response, parasite resistance and virulence in a Daphnia-parasite system.

    Directory of Open Access Journals (Sweden)

    Corine N Schoebel

    Full Text Available Host density can increase infection rates and reduce host fitness as increasing population density enhances the risk of becoming infected either through increased encounter rate or because host condition may decline. Conceivably, potential hosts could take high host density as a cue to up-regulate their defence systems. However, as host density usually covaries with food availability, it is difficult to examine the importance of host density in isolation. Thus, we performed two full-factorial experiments that varied juvenile densities of Daphnia magna (a freshwater crustacean and food availability independently. We also included a simulated high-density treatment, where juvenile experimental animals were kept in filtered media that previously maintained Daphnia at high-density. Upon reaching adulthood, we exposed the Daphnia to their sterilizing bacterial parasite, Pasteuria ramosa, and examined how the juvenile treatments influenced the likelihood and severity of infection (Experiment I and host immune investment (Experiment II. Neither juvenile density nor food treatments affected the likelihood of infection; however, well-fed hosts that were well-fed as juveniles produced more offspring prior to sterilization than their less well-fed counterparts. By contrast, parasite growth was independent of host juvenile resources or host density. Parasite-exposed hosts had a greater number of circulating haemocytes than controls (i.e., there was a cellular immune response, but the magnitude of immune response was not mediated by food availability or host density. These results suggest that density dependent effects on disease arise primarily through correlated changes in food availability: low food could limit parasitism and potentially curtail epidemics by reducing both the host's and parasite's reproduction as both depend on the same food.

  5. Density-dependence and within-host competition in a semelparous parasite of leaf-cutting ants

    Directory of Open Access Journals (Sweden)

    Thomsen Lene

    2004-11-01

    Full Text Available Abstract Background Parasite heterogeneity and within-host competition are thought to be important factors influencing the dynamics of host-parasite relationships. Yet, while there have been many theoretical investigations of how these factors may act, empirical data is more limited. We investigated the effects of parasite density and heterogeneity on parasite virulence and fitness using four strains of the entomopathogenic fungus, Metarhizium anisopliae var. anisopliae, and its leaf-cutting ant host Acromyrmex echinatior as the model system. Results The relationship between parasite density and infection was sigmoidal, with there being an invasion threshold for an infection to occur (an Allee effect. Although spore production was positively density-dependent, parasite fitness decreased with increasing parasite density, indicating within-host scramble competition. The dynamics differed little between the four strains tested. In mixed infections of three strains the infection-growth dynamics were unaffected by parasite heterogeneity. Conclusions The strength of within-host competition makes dispersal the best strategy for the parasite. Parasite heterogeneity may not have effected virulence or the infection dynamics either because the most virulent strain outcompeted the others, or because the interaction involved scramble competition that was impervious to parasite heterogeneity. The dynamics observed may be common for virulent parasites, such as Metarhizium, that produce aggregated transmission stages. Such parasites make useful models for investigating infection dynamics and the impact of parasite competition.

  6. Larval helminths in intermediate hosts

    DEFF Research Database (Denmark)

    Fredensborg, Brian Lund; Poulin, R

    2005-01-01

    a reduction in size, caused by crowding, virtually nothing is known about longer-lasting effects after transmission to the definitive host. This study is the first to use in vitro cultivation with feeding of adult trematodes to investigate how numbers of parasites in the intermediate host affect the size......Density-dependent effects on parasite fitness have been documented from adult helminths in their definitive hosts. There have, however, been no studies on the cost of sharing an intermediate host with other parasites in terms of reduced adult parasite fecundity. Even if larval parasites suffer...... and fecundity of adult parasites. For this purpose, we examined two different infracommunities of parasites in crustacean hosts. Firstly, we used experimental infections of Maritrema novaezealandensis in the amphipod, Paracalliope novizealandiae, to investigate potential density-dependent effects in single...

  7. Plant Killing by Mutualistic Ants Increases the Density of Host Species Seedlings in the Dry Forest of Costa Rica

    Directory of Open Access Journals (Sweden)

    Sabrina Amador-Vargas

    2012-01-01

    Full Text Available Some species of plant-mutualistic ants kill the vegetation growing in the vicinities of their host plant, creating an area of bare ground (clearing. The reduced competition in the clearing may facilitate the establishment of host species sprouts (clones and seedlings, which in turn benefits the ants with additional food and shelter (“sprout-establishment hypothesis”. To test this hypothesis, the density and origin of Acacia collinsii sprouts growing inside clearings and in the vicinities of acacia plants without clearings were compared. Also, to assess the pruning selectivity of acacia ants (Pseudomyrmex spinicola, seedlings were transplanted into clearings. The reaction of ants towards unrewarding acacia seedlings (without food and shelter was also tested. The density of acacia sprouts growing inside clearings was almost twice that in the vicinities of host plants without clearings, and sprouts were inhabited by nestmates of the colony that made the clearing. Clones and seedlings were found in similar proportions in the clearings, and ants did not kill unrewarding acacia seedlings or seedlings unrelated to their host. The benefit reported here for the ants could be in conflict with the host plant, especially when the plant has rhizomal reproduction.

  8. Demographic models reveal the shape of density dependence for a specialist insect herbivore on variable host plants.

    Science.gov (United States)

    Miller, Tom E X

    2007-07-01

    1. It is widely accepted that density-dependent processes play an important role in most natural populations. However, persistent challenges in our understanding of density-dependent population dynamics include evaluating the shape of the relationship between density and demographic rates (linear, concave, convex), and identifying extrinsic factors that can mediate this relationship. 2. I studied the population dynamics of the cactus bug Narnia pallidicornis on host plants (Opuntia imbricata) that varied naturally in relative reproductive effort (RRE, the proportion of meristems allocated to reproduction), an important plant quality trait. I manipulated per-plant cactus bug densities, quantified subsequent dynamics, and fit stage-structured models to the experimental data to ask if and how density influences demographic parameters. 3. In the field experiment, I found that populations with variable starting densities quickly converged upon similar growth trajectories. In the model-fitting analyses, the data strongly supported a model that defined the juvenile cactus bug retention parameter (joint probability of surviving and not dispersing) as a nonlinear decreasing function of density. The estimated shape of this relationship shifted from concave to convex with increasing host-plant RRE. 4. The results demonstrate that host-plant traits are critical sources of variation in the strength and shape of density dependence in insects, and highlight the utility of integrated experimental-theoretical approaches for identifying processes underlying patterns of change in natural populations.

  9. Baculovirus Host-Range

    Institute of Scientific and Technical Information of China (English)

    Suzanne M. Thiem; Xiao-Wen Cheng

    2009-01-01

    Baculoviruses are used as microbial insecticides, protein expression vectors, epitope display platforms, and most recently as vectors for gene therapy. Understanding the mechanisms that control baculovirus host-range and tissue tropisms are important for assessing their safety and for improving their properties for these biotechnology applications. In the past two decades some progress has been made and several baculovirus genes that influence host-range have been identified. Despite this progress, our understanding of the underlying mechanisms that restrict baculovirus host-range is still limited. Here we review what is currently known about baculovirus genes that influence virus host-range.

  10. The dynamics of infection of Tribolium confusum by hymenolepis diminuta: the influence of exposure time and host density.

    Science.gov (United States)

    Keymer, A

    1982-02-01

    Survival of Hymenolepis diminuta eggs (as measured by their infectivity to the intermediate host) was found to be age-dependent with an expected value of 11 days when the eggs were retained within the faecal pellet at 10 degree C. The expected life-span of eggs under experimental conditions (i.e. extracted from faecal material and placed on filter paper at 30 degree C) was estimated as 33 min. The mean parasite burden of populations of Tribolium exposed to known densities of H. diminuta eggs was found to rise to a plateau with increasing exposure time. The experimental results provided a method of estimating the instantaneous rate of parasite transmission: a value of 0.0004/egg/min/host/13 cm2 was obtained. The mean parasite burden of populations of T. confusum exposed to known densities of H. diminuta eggs was found to decrease exponentially with increasing host density. A second estimate of the instantaneous rate of parasite transmission of 0.004/egg/min/host/13 cm2 was obtained from the experimental results. No differences in susceptibility to infection between 2-week-old male and female beetles were found. A marked decrease, however, was apparent with increasing beetle age up to 14 weeks post-eclosion.

  11. Influence of host preference, mating, and release density on the parasitism of Telenomus remus (Nixon (Hymenoptera, Platygastridae

    Directory of Open Access Journals (Sweden)

    Ana Paula de Queiroz

    Full Text Available ABSTRACT We evaluated the influence of host preference, mating, and release density on Telenomus remus (Nixon, 1937 (Hymenoptera: Platygastridae parasitizing eggs of Spodoptera frugiperda (Smith, 1797 (Lepidoptera: Noctuidae. First, we tested host preference of T. remus (free choice test offered a choice between eggs of Corcyra cephalonica (Stainton, 1865 (Lepidoptera: Pyralidae and S. frugiperda. Parasitism capacity and host preference (S. frugiperda of T. remus reared on either of the two hosts did not differ. Secondly, we evaluated the influence of mating behavior of T. remus females on its parasitism. Only the offspring sex ratio differed between treatments, indicating that the species reproduces by parthenogenesis of the arrhenotoky type. Finally, we evaluated the influence of release density on T. remus parasitism. This was tested by releasing different numbers of the parasitoid per S. frugiperda egg using T. remus reared for different numbers of generations on C. cephalonica eggs. The regression analysis between percentage of parasitism and density of released T. remus females showed a quadratic effect for all tested parasitoid generations (F35, F40, and F45 with maximum parasitism from 65.07% to 71.69%. Our results allow the conclusion that (a T. remus prefers S. frugiperda eggs, regardless of the host on which this parasitoid was reared, showing no preimaginal conditioning; (b Mating does not affect the number of eggs parasitized by T. remus or the development of its offspring; and (c The optimal T. remus release density when reared on C. cephalonica is between 0.133 and 0.150 females/S. frugiperda.

  12. Individual host factors associated with Onchocerca volvulus microfilarial densities 15, 80 and 180 days after a first dose of ivermectin.

    Science.gov (United States)

    Pion, Sébastien D S; Grout, Lise; Kamgno, Joseph; Nana-Djeunga, Hugues; Boussinesq, Michel

    2011-09-01

    Reduction in Onchocerca volvulus skin microfilarial densities after treatment with ivermectin shows wide between-host variation. Data from two separate studies conducted in Cameroon on onchocerciasis patients treated for the first time with ivermectin were analyzed to identify host factors associated with microfilarial density at different time-points after treatment. In one site (Nkam valley), the dataset included 103 adult males for whom age, number of palpable onchocercal nodules and microfilarial densities on D0 (pre-treatment), D15, D80 and D180 were available. In the other site (Vina valley), analyses were conducted on 965 individuals of both sexes aged 5 years and over; in this dataset, available information included age, gender, exact dose of ivermectin received, onchocerciasis endemicity level in the village of residence and microfilarial densities on D0 and D180. Negative binomial regression models of microfilarial density at the different intervals post-treatment were fitted, using maximum likelihood, with the available independent variables. Gender and age were found to be associated with microfilarial density on D180. The initial microfilarial density influenced post-treatment densities at all the time-points. All other things being equal, microfilarial densities on D180 were higher in individuals harbouring a higher number of nodules or living in communities with high endemicity levels. This study demonstrates that O. volvulus microfilarial density measured after a first treatment with ivermectin, and thus probably the rate of skin repopulation by microfilariae (mf) varies according to several host factors. Should such factors also influence ivermectin efficacy after repeated treatment, then they should be taken into account to determine whether sub-optimal responses to treatment reported from various areas in Africa are actually due to parasite-related factors, particularly to the emergence of resistant populations.

  13. Association and host selectivity in multi-host pathogens.

    Directory of Open Access Journals (Sweden)

    José M Malpica

    Full Text Available The distribution of multi-host pathogens over their host range conditions their population dynamics and structure. Also, host co-infection by different pathogens may have important consequences for the evolution of hosts and pathogens, and host-pathogen co-evolution. Hence it is of interest to know if the distribution of pathogens over their host range is random, or if there are associations between hosts and pathogens, or between pathogens sharing a host. To analyse these issues we propose indices for the observed patterns of host infection by pathogens, and for the observed patterns of co-infection, and tests to analyse if these patterns conform to randomness or reflect associations. Applying these tests to the prevalence of five plant viruses on 21 wild plant species evidenced host-virus associations: most hosts and viruses were selective for viruses and hosts, respectively. Interestingly, the more host-selective viruses were the more prevalent ones, suggesting that host specialisation is a successful strategy for multi-host pathogens. Analyses also showed that viruses tended to associate positively in co-infected hosts. The developed indices and tests provide the tools to analyse how strong and common are these associations among different groups of pathogens, which will help to understand and model the population biology of multi-host pathogens.

  14. Density-dependence and within-host competition in a semelparous parasite of leaf-cutting ants

    DEFF Research Database (Denmark)

    Hughes, William; Petersen, Klaus; Ugelvig, Line;

    2004-01-01

    the effects of parasite density and heterogeneity on parasite virulence and fitness using four strains of the entomopathogenic fungus, Metarhizium anisopliae var. anisopliae, and its leaf-cutting ant host Acromyrmex echinatior as the model system.RESULTS:The relationship between parasite density and infection...... dynamics either because the most virulent strain outcompeted the others, or because the interaction involved scramble competition that was impervious to parasite heterogeneity. The dynamics observed may be common for virulent parasites, such as Metarhizium, that produce aggregated transmission stages...

  15. Does natural larval parasitism of Lobesia botrana (Lepidoptera: Tortricidae) vary between years, generation, density of the host and vine cultivar?

    Science.gov (United States)

    Xuéreb, A; Thiéry, D

    2006-04-01

    Populations of European grapevine moth Lobesia botrana Denis & Schiffermüller and its larval parasitoids were studied for two consecutive years on an experimental insecticide-free vineyard in France planted with adjacent plots of five grape cultivars (Merlot, Cabernet Franc, Sauvignon, Cabernet Sauvignon and Sémillon) using a natural L. botrana population during the first year, and a natural population supplemented with artificially inoculated individuals during the second year. Levels of natural populations of larval parasitoids were measured by their parasitism rate. The ichneumonid Campoplex capitator Aubert was the most common species collected from L. botrana larvae. Its incidence was higher during the spring compared to summer. The overall parasitism rate found on the experimental vineyard varied from 23% in 2000 to 53% in 2001, and was mainly due to C. capitator. Parasitism was not affected by the grape cultivar on which the host developed but was positively correlated with the host density, per bunch or per stock, suggesting that among the five grape cultivars tested, C. capitator females probably do not discriminate between hosts feeding on different grape cultivars, but rather the densities of L. botrana larvae.

  16. Trypanosoma cruzi Infection and Host Lipid Metabolism

    OpenAIRE

    2014-01-01

    Trypanosoma cruzi is the causative agent of Chagas disease. Approximately 8 million people are thought to be affected worldwide. Several players in host lipid metabolism have been implicated in T. cruzi-host interactions in recent research, including macrophages, adipocytes, low density lipoprotein (LDL), low density lipoprotein receptor (LDLR), and high density lipoprotein (HDL). All of these factors are required to maintain host lipid homeostasis and are intricately connected via several me...

  17. Parasite host range and the evolution of host resistance

    NARCIS (Netherlands)

    Gorter, F.A.; Hall, A.R.; A., Buckling; P.D., Scanlan

    2015-01-01

    Parasite host range plays a pivotal role in the evolution and ecology of hosts
    and the emergence of infectious disease. Although the factors that promote
    host range and the epidemiological consequences of variation in host range
    are relatively well characterized, the effect of parasite

  18. Lensed Quasar Hosts

    CERN Document Server

    Peng, C Y; Rix, H W; Keeton, C R; Falco, E E; Kochanek, C S; Lehár, J; McLeod, B A; Peng, Chien Y.; Impey, Chris D.; Rix, Hans-Walter; Keeton, Charles R.; Falco, Emilio E.; Kochanek, Chris S.; Lehar, Joseph; Leod, Brian A. Mc

    2006-01-01

    Gravitational lensing assists in the detection of quasar hosts by amplifying and distorting the host light away from the unresolved quasar core images. We present the results of HST observations of 30 quasar hosts at redshifts 1 1.7 is a factor of 3--6 higher than the local value. But, depending on the stellar content the ratio may decline at z>4 (if E/S0-like), flatten off to 6--10 times the local value (if Sbc-like), or continue to rise (if Im-like). We infer that galaxy bulge masses must have grown by a factor of 3--6 over the redshift range 3>z>1, and then changed little since z~1. This suggests that the peak epoch of galaxy formation for massive galaxies is above z~1. We also estimate the duty cycle of luminous AGNs at z>1 to be ~1%, or 10^7 yrs, with sizable scatter.

  19. Temporal changes of symbiont density and host fitness after rifampicin treatment in a whitefly of the Bemisia tabaci species complex.

    Science.gov (United States)

    Shan, Hong-Wei; Zhang, Chang-Rong; Yan, Ting-Ting; Tang, Hai-Qin; Wang, Xiao-Wei; Liu, Shu-Sheng; Liu, Yin-Quan

    2016-04-01

    Microbial symbionts are essential or important partners to phloem-feeding insects. Antibiotics have been used to selectively eliminate symbionts from their host insects and establish host lines with or without certain symbionts for investigating functions of the symbionts. In this study, using the antibiotic rifampicin we attempted to selectively eliminate certain symbionts from a population of the Middle East-Asia Minor 1 whitefly of the Bemisia tabaci species complex, which harbors the primary symbiont "Candidatus Portiera aleyrodidarum" and two secondary symbionts "Candidatus Hamiltonella defensa" and Rickettsia. Neither the primary nor the secondary symbionts were completely depleted in the adults (F0) that fed for 48 h on a diet treated with rifampicin at concentrations of 1-100 μg/mL. However, both the primary and secondary symbionts were nearly completely depleted in the offspring (F1) of the rifampicin-treated adults. Although the F1 adults produced some eggs (F2), most of the eggs failed to hatch and none of them reached the second instar, and consequently the rifampicin-treated whitefly colony vanished at the F2 generation. Interestingly, quantitative polymerase chain reaction assays showed that in the rifampicin-treated whiteflies, the density of the primary symbiont was reduced at an obviously slower pace than the secondary symbionts. Mating experiments between rifampicin-treated and untreated adults demonstrated that the negative effects of rifampicin on host fitness were expressed when the females were treated by the antibiotic, and whether males were treated or not by the antibiotic had little contribution to the negative effects. These observations indicate that with this whitefly population it is not feasible to selectively eliminate the secondary symbionts using rifampicin without affecting the primary symbiont and establish host lines for experimental studies. However, the extinction of the whitefly colony at the second generation after

  20. Avian host defense peptides

    NARCIS (Netherlands)

    Cuperus, Tryntsje; Coorens, M.; van Dijk, A.; Haagsman, H.P.

    2013-01-01

    Host defense peptides (HDPs) are important effector molecules of the innate immune system of vertebrates. These antimicrobial peptides are also present in invertebrates, plants and fungi. HDPs display broad-spectrum antimicrobial activities and fulfill an important role in the first line of defense

  1. SARS Pathogenesis: Host Factors

    NARCIS (Netherlands)

    A. de Lang (Anna)

    2012-01-01

    textabstractWhile it is hypothesized that Sever Acute Respiratory Syndrome (SARS) in humans is caused by a disproportional immune response illustrated by inappropriate induction of inflammatory cytokines, the exact nature of the host response to SARS coronavirus (CoV) infection causing severe

  2. Host Phylogeny Determines Viral Persistence and Replication in Novel Hosts

    Science.gov (United States)

    Longdon, Ben; Hadfield, Jarrod D.; Webster, Claire L.

    2011-01-01

    Pathogens switching to new hosts can result in the emergence of new infectious diseases, and determining which species are likely to be sources of such host shifts is essential to understanding disease threats to both humans and wildlife. However, the factors that determine whether a pathogen can infect a novel host are poorly understood. We have examined the ability of three host-specific RNA-viruses (Drosophila sigma viruses from the family Rhabdoviridae) to persist and replicate in 51 different species of Drosophilidae. Using a novel analytical approach we found that the host phylogeny could explain most of the variation in viral replication and persistence between different host species. This effect is partly driven by viruses reaching a higher titre in those novel hosts most closely related to the original host. However, there is also a strong effect of host phylogeny that is independent of the distance from the original host, with viral titres being similar in groups of related hosts. Most of this effect could be explained by variation in general susceptibility to all three sigma viruses, as there is a strong phylogenetic correlation in the titres of the three viruses. These results suggest that the source of new emerging diseases may often be predictable from the host phylogeny, but that the effect may be more complex than simply causing most host shifts to occur between closely related hosts. PMID:21966271

  3. Host density and human activities mediate increased parasite prevalence and richness in primates threatened by habitat loss and fragmentation.

    Science.gov (United States)

    Mbora, David N M; McPeek, Mark A

    2009-01-01

    1. Habitat loss and fragmentation are the principal causes of the loss of biological diversity. In addition, parasitic diseases are an emerging threat to many animals. Nevertheless, relatively few studies have tested how habitat loss and fragmentation influence the prevalence and richness of parasites in animals. 2. Several studies of nonhuman primates have shown that measures of human activity and forest fragmentation correlate with parasitism in primates. However, these studies have not tested for the ecological mechanism(s) by which human activities or forest fragmentation influence the prevalence and richness of parasites. 3. We tested the hypothesis that increased host density due to forest fragmentation and loss mediates increases in the prevalence and richness of gastrointestinal parasites in two forest primates, the Tana River red colobus (Procolobus rufomitratus, Peters 1879) and mangabey (Cercocebus galeritus galeritus, Peters 1879). We focused on population density because epidemiological theory states that host density is a key determinant of the prevalence and richness of directly transmitted parasites in animals. 4. The Tana River red colobus and mangabey are endemic to a highly fragmented forest ecosystem in eastern Kenya where habitat changes are caused by a growing human population increasingly dependent on forest resources and on clearing forest for cultivation. 5. We found that the prevalence of parasites in the two monkeys was very high compared to primates elsewhere. Density of monkeys was positively associated with forest area and disturbance in forests. In turn, the prevalence and richness of parasites was significantly associated with monkey density, and attributes indicative of human disturbance in forests. 6. We also found significant differences in the patterns of parasitism between the colobus and the mangabey possibly attributable to differences in their behavioural ecology. Colobus are arboreal folivores while mangabeys are terrestrial

  4. Hydrology and density feedbacks control the ecology of intermediate hosts of schistosomiasis across habitats in seasonal climates.

    Science.gov (United States)

    Perez-Saez, Javier; Mande, Theophile; Ceperley, Natalie; Bertuzzo, Enrico; Mari, Lorenzo; Gatto, Marino; Rinaldo, Andrea

    2016-06-07

    We report about field and theoretical studies on the ecology of the aquatic snails (Bulinus spp. and Biomphalaria pfeifferi) that serve as obligate intermediate hosts in the complex life cycle of the parasites causing human schistosomiasis. Snail abundance fosters disease transmission, and thus the dynamics of snail populations are critically important for schistosomiasis modeling and control. Here, we single out hydrological drivers and density dependence (or lack of it) of ecological growth rates of local snail populations by contrasting novel ecological and environmental data with various models of host demography. Specifically, we study various natural and man-made habitats across Burkina Faso's highly seasonal climatic zones. Demographic models are ranked through formal model comparison and structural risk minimization. The latter allows us to evaluate the suitability of population models while clarifying the relevant covariates that explain empirical observations of snail abundance under the actual climatic forcings experienced by the various field sites. Our results link quantitatively hydrological drivers to distinct population dynamics through specific density feedbacks, and show that statistical methods based on model averaging provide reliable snail abundance projections. The consistency of our ranking results suggests the use of ad hoc models of snail demography depending on habitat type (e.g., natural vs. man-made) and hydrological characteristics (e.g., ephemeral vs. permanent). Implications for risk mapping and space-time allocation of control measures in schistosomiasis-endemic contexts are discussed.

  5. Characterization of exoplanet hosts

    Directory of Open Access Journals (Sweden)

    Valenti Jeff A.

    2013-04-01

    Full Text Available Spectroscopic analysis of exoplanet hosts and the stellar sample from which they are drawn provides abundances and other properties that quantitively constrain models of planet formation. The program Spectroscopy Made Easy (SME determines stellar parameters by fitting observed spectra, though line lists must be selected wisely. For giant planets, it is now well established that stars with higher metallicity are more likely to have detected companions. Stellar metallicity does not seem to affect the formation and/or migration of detectable planets less massive than Neptune, especially when considering only the most massive planet in the system. In systems with at least one planet less than 10 times the mass of Earth, the mass of the most massive planet increases dramatically with host star metallicity. This may reflect metallicity dependent timescales for core formation, envelope accretion, and/or migration into the detection zone.

  6. HostPhinder: A Phage Host Prediction Tool

    DEFF Research Database (Denmark)

    Villarroel, Julia; Kleinheinz, Kortine Annina; Jurtz, Vanessa Isabell

    2016-01-01

    The current dramatic increase of antibiotic resistant bacteria has revitalised the interest in bacteriophages as alternative antibacterial treatment. Meanwhile, the development of bioinformatics methods for analysing genomic data places high-throughput approaches for phage characterization within...... reach. Here, we present HostPhinder, a tool aimed at predicting the bacterial host of phages by examining the phage genome sequence. Using a reference database of 2196 phages with known hosts, HostPhinder predicts the host species of a query phage as the host of the most genomically similar reference...... phages. As a measure of genomic similarity the number of co-occurring k-mers (DNA sequences of length k) is used. Using an independent evaluation set, HostPhinder was able to correctly predict host genus and species for 81% and 74% of the phages respectively, giving predictions for more phages than BLAST...

  7. Illuminating coronavirus-host interactions

    NARCIS (Netherlands)

    Raaben, M.

    2009-01-01

    Viruses are infectious agents incapable of growing or reproducing outside a host cell. They are completely dependent on the cellular machinery of the host for their multiplication. On the other hand, however, viruses also have to deal with the immune defences of the host. Apparently, viruses are wal

  8. HostPhinder: A Phage Host Prediction Tool

    Directory of Open Access Journals (Sweden)

    Julia Villarroel

    2016-05-01

    Full Text Available The current dramatic increase of antibiotic resistant bacteria has revitalised the interest in bacteriophages as alternative antibacterial treatment. Meanwhile, the development of bioinformatics methods for analysing genomic data places high-throughput approaches for phage characterization within reach. Here, we present HostPhinder, a tool aimed at predicting the bacterial host of phages by examining the phage genome sequence. Using a reference database of 2196 phages with known hosts, HostPhinder predicts the host species of a query phage as the host of the most genomically similar reference phages. As a measure of genomic similarity the number of co-occurring k-mers (DNA sequences of length k is used. Using an independent evaluation set, HostPhinder was able to correctly predict host genus and species for 81% and 74% of the phages respectively, giving predictions for more phages than BLAST and significantly outperforming BLAST on phages for which both had predictions. HostPhinder predictions on phage draft genomes from the INTESTI phage cocktail corresponded well with the advertised targets of the cocktail. Our study indicates that for most phages genomic similarity correlates well with related bacterial hosts. HostPhinder is available as an interactive web service [1] and as a stand alone download from the Docker registry [2].

  9. Effects of host plant and larval density on intraspecific competition in larvae of the emerald ash borer (Coleoptera: Buprestidae).

    Science.gov (United States)

    Duan, Jian J; Larson, Kristi; Watt, Tim; Gould, Juli; Lelito, Jonathan P

    2013-12-01

    Competition for food, mates, and space among different individuals of the same insect species can affect density-dependent regulation of insect abundance or population dynamics. The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a serious invasive pest of North American ash (Fraxinus spp.) trees, with its larvae feeding in serpentine galleries between the interface of sapwood and phloem tissues of ash trees. Using artificial infestation of freshly cut logs of green ash (Fraxinus pennsylvanica Marshall) and tropical ash (Fraxinus uhdei [Wenzig] Lingelsh) with a series of egg densities, we evaluated the mechanism and outcome of intraspecific competition in larvae of A. planipennis in relation to larval density and host plant species. Results from our study showed that as the egg densities on each log (1.5-6.5 cm in diameter and 22-25 cm in length) increased from 200 to 1,600 eggs per square meter of surface area, larval survivorship declined from ≍68 to 10% for the green ash logs, and 86 to 55% for tropical ash logs. Accordingly, larval mortality resulting from cannibalism, starvation, or both, significantly increased as egg density increased, and the biomass of surviving larvae significantly decreased on both ash species. When larval density was adjusted to the same level, however, larval mortality from intraspecific competition was significantly higher and mean biomasses of surviving larvae was significantly lower in green ash than in tropical ash. The role of intraspecific competition of A. planipennis larvae in density-dependent regulation of its natural population dynamics is discussed.

  10. The Drosophila melanogaster host model

    Science.gov (United States)

    Igboin, Christina O.; Griffen, Ann L.; Leys, Eugene J.

    2012-01-01

    The deleterious and sometimes fatal outcomes of bacterial infectious diseases are the net result of the interactions between the pathogen and the host, and the genetically tractable fruit fly, Drosophila melanogaster, has emerged as a valuable tool for modeling the pathogen–host interactions of a wide variety of bacteria. These studies have revealed that there is a remarkable conservation of bacterial pathogenesis and host defence mechanisms between higher host organisms and Drosophila. This review presents an in-depth discussion of the Drosophila immune response, the Drosophila killing model, and the use of the model to examine bacterial–host interactions. The recent introduction of the Drosophila model into the oral microbiology field is discussed, specifically the use of the model to examine Porphyromonas gingivalis–host interactions, and finally the potential uses of this powerful model system to further elucidate oral bacterial-host interactions are addressed. PMID:22368770

  11. The Drosophila melanogaster host model

    Directory of Open Access Journals (Sweden)

    Christina O. Igboin

    2012-02-01

    Full Text Available The deleterious and sometimes fatal outcomes of bacterial infectious diseases are the net result of the interactions between the pathogen and the host, and the genetically tractable fruit fly, Drosophila melanogaster, has emerged as a valuable tool for modeling the pathogen–host interactions of a wide variety of bacteria. These studies have revealed that there is a remarkable conservation of bacterial pathogenesis and host defence mechanisms between higher host organisms and Drosophila. This review presents an in-depth discussion of the Drosophila immune response, the Drosophila killing model, and the use of the model to examine bacterial–host interactions. The recent introduction of the Drosophila model into the oral microbiology field is discussed, specifically the use of the model to examine Porphyromonas gingivalis–host interactions, and finally the potential uses of this powerful model system to further elucidate oral bacterial-host interactions are addressed.

  12. Avian host defense peptides.

    Science.gov (United States)

    Cuperus, Tryntsje; Coorens, Maarten; van Dijk, Albert; Haagsman, Henk P

    2013-11-01

    Host defense peptides (HDPs) are important effector molecules of the innate immune system of vertebrates. These antimicrobial peptides are also present in invertebrates, plants and fungi. HDPs display broad-spectrum antimicrobial activities and fulfill an important role in the first line of defense of many organisms. It is becoming increasingly clear that in the animal kingdom the functions of HDPs are not confined to direct antimicrobial actions. Research in mammals has indicated that HDPs have many immunomodulatory functions and are also involved in other physiological processes ranging from development to wound healing. During the past five years our knowledge about avian HDPs has increased considerably. This review addresses our current knowledge on the evolution, regulation and biological functions of HDPs of birds.

  13. Host Integration Server 2004

    Institute of Scientific and Technical Information of China (English)

    PaulThurrott; 杨岩

    2005-01-01

    微软发布的Host Integration Server(HIS)2004,是IBM大型主机集成服务器的一个重要的更新,添加了一些重要的新特点和改进。与大多数微软公司协同工作的产品不同,HIS 2004的设计目的是为了移植,而不是纯粹的集成,事实上它将会帮助客户从现有的传统平台中得到更多的价值——在这种情况下,所指的产品就是IBM大型主机和iSeries(也就是以前的AS/400)系列机型。

  14. Electron collection in host-guest nanostructured hematite photoanodes for water splitting: the influence of scaffold doping density.

    Science.gov (United States)

    Kondofersky, Ilina; Dunn, Halina K; Müller, Alexander; Mandlmeier, Benjamin; Feckl, Johann M; Fattakhova-Rohlfing, Dina; Scheu, Christina; Peter, Laurence M; Bein, Thomas

    2015-03-04

    Nanostructuring has proven to be a successful strategy in overcoming the trade-off between light absorption and hole transport to the solid/electrolyte interface in hematite photoanodes for water splitting. The suggestion that poor electron (majority carrier) collection hinders the performance of nanostructured hematite electrodes has led to the emergence of host-guest architectures in which the absorber layer is deposited onto a transparent high-surface-area electron collector. To date, however, state of the art nanostructured hematite electrodes still outperform their host-guest counterparts, and a quantitative evaluation of the benefits of the host-guest architecture is still lacking. In this paper, we examine the impact of host-guest architectures by comparing nanostructured tin-doped hematite electrodes with hematite nanoparticle layers coated onto two types of conducting macroporous SnO2 scaffolds. Analysis of the external quantum efficiency spectra for substrate (SI) and electrolyte side (EI) illumination reveals that the electron diffusion length in the host-guest electrodes based on an undoped SnO2 scaffold is increased substantially relative to the nanostructured hematite electrode without a supporting scaffold. Nevertheless, electron collection is still incomplete for EI illumination. By contrast, an electron collection efficiency of 100% is achieved by fabricating the scaffold using antimony-doped SnO2, showing that the scaffold conductivity is crucial for the device performance.

  15. Mesoscale spatiotemporal variability in a complex host-parasite system influenced by intermediate host body size.

    Science.gov (United States)

    Rodríguez, Sara M; Valdivia, Nelson

    2017-01-01

    Parasites are essential components of natural communities, but the factors that generate skewed distributions of parasite occurrences and abundances across host populations are not well understood. Here, we analyse at a seascape scale the spatiotemporal relationships of parasite exposure and host body-size with the proportion of infected hosts (i.e., prevalence) and aggregation of parasite burden across ca. 150 km of the coast and over 22 months. We predicted that the effects of parasite exposure on prevalence and aggregation are dependent on host body-sizes. We used an indirect host-parasite interaction in which migratory seagulls, sandy-shore molecrabs, and an acanthocephalan worm constitute the definitive hosts, intermediate hosts, and endoparasite, respectively. In such complex systems, increments in the abundance of definitive hosts imply increments in intermediate hosts' exposure to the parasite's dispersive stages. Linear mixed-effects models showed a significant, albeit highly variable, positive relationship between seagull density and prevalence. This relationship was stronger for small (cephalothorax length >15 mm) than large molecrabs (<15 mm). Independently of seagull density, large molecrabs carried significantly more parasites than small molecrabs. The analysis of the variance-to-mean ratio of per capita parasite burden showed no relationship between seagull density and mean parasite aggregation across host populations. However, the amount of unexplained variability in aggregation was strikingly higher in larger than smaller intermediate hosts. This unexplained variability was driven by a decrease in the mean-variance scaling in heavily infected large molecrabs. These results show complex interdependencies between extrinsic and intrinsic population attributes on the structure of host-parasite interactions. We suggest that parasite accumulation-a characteristic of indirect host-parasite interactions-and subsequent increasing mortality rates over

  16. Investigating the effects of food available and climatic variables on the animal host density of hemorrhagic Fever with renal syndrome in changsha, china.

    Directory of Open Access Journals (Sweden)

    Hong Xiao

    Full Text Available BACKGROUND: The transmission of hemorrhagic fever with renal syndrome (HFRS is influenced by population dynamics of its main host, rodents. It is therefore important to better understand rodents' characteristic in epidemic areas. METHODOLOGY/PRINCIPAL FINDINGS: We examined the potential impact of food available and climatic variability on HFRS rodent host and developed forecasting models. Monthly rodent density of HFRS host and climate data in Changsha from January 2004 to December 2011 were obtained. Monthly normalized difference vegetation index (NDVI and temperature vegetation dryness index (TVDI for rice paddies were extracted from MODIS data. Cross-correlation analysis were carried out to explore correlation between climatic variables and food available with monthly rodent data. We used auto-regressive integrated moving average model with explanatory variables to examine the independent contribution of climatic variables and food supply to rodent density. The results indicated that relative rodent density of HFRS host was significantly correlated with monthly mean temperatures, monthly accumulative precipitation, TVDI and NDVI with lags of 1-6 months. CONCLUSIONS/SIGNIFICANCE: Food available plays a significant role in population fluctuations of HFRS host in Changsha. The model developed in this study has implications for HFRS control and prevention.

  17. Investigating the effects of food available and climatic variables on the animal host density of hemorrhagic Fever with renal syndrome in changsha, china.

    Science.gov (United States)

    Xiao, Hong; Liu, Hai-Ning; Gao, Li-Dong; Huang, Cun-Rui; Li, Zhou; Lin, Xiao-Ling; Chen, Bi-Yun; Tian, Huai-Yu

    2013-01-01

    The transmission of hemorrhagic fever with renal syndrome (HFRS) is influenced by population dynamics of its main host, rodents. It is therefore important to better understand rodents' characteristic in epidemic areas. We examined the potential impact of food available and climatic variability on HFRS rodent host and developed forecasting models. Monthly rodent density of HFRS host and climate data in Changsha from January 2004 to December 2011 were obtained. Monthly normalized difference vegetation index (NDVI) and temperature vegetation dryness index (TVDI) for rice paddies were extracted from MODIS data. Cross-correlation analysis were carried out to explore correlation between climatic variables and food available with monthly rodent data. We used auto-regressive integrated moving average model with explanatory variables to examine the independent contribution of climatic variables and food supply to rodent density. The results indicated that relative rodent density of HFRS host was significantly correlated with monthly mean temperatures, monthly accumulative precipitation, TVDI and NDVI with lags of 1-6 months. Food available plays a significant role in population fluctuations of HFRS host in Changsha. The model developed in this study has implications for HFRS control and prevention.

  18. Mesoscale spatiotemporal variability in a complex host-parasite system influenced by intermediate host body size

    Directory of Open Access Journals (Sweden)

    Sara M. Rodríguez

    2017-08-01

    Full Text Available Background Parasites are essential components of natural communities, but the factors that generate skewed distributions of parasite occurrences and abundances across host populations are not well understood. Methods Here, we analyse at a seascape scale the spatiotemporal relationships of parasite exposure and host body-size with the proportion of infected hosts (i.e., prevalence and aggregation of parasite burden across ca. 150 km of the coast and over 22 months. We predicted that the effects of parasite exposure on prevalence and aggregation are dependent on host body-sizes. We used an indirect host-parasite interaction in which migratory seagulls, sandy-shore molecrabs, and an acanthocephalan worm constitute the definitive hosts, intermediate hosts, and endoparasite, respectively. In such complex systems, increments in the abundance of definitive hosts imply increments in intermediate hosts’ exposure to the parasite’s dispersive stages. Results Linear mixed-effects models showed a significant, albeit highly variable, positive relationship between seagull density and prevalence. This relationship was stronger for small (cephalothorax length >15 mm than large molecrabs (<15 mm. Independently of seagull density, large molecrabs carried significantly more parasites than small molecrabs. The analysis of the variance-to-mean ratio of per capita parasite burden showed no relationship between seagull density and mean parasite aggregation across host populations. However, the amount of unexplained variability in aggregation was strikingly higher in larger than smaller intermediate hosts. This unexplained variability was driven by a decrease in the mean-variance scaling in heavily infected large molecrabs. Conclusions These results show complex interdependencies between extrinsic and intrinsic population attributes on the structure of host-parasite interactions. We suggest that parasite accumulation—a characteristic of indirect host

  19. Influence of geographical scale on the detection of density dependence in the host-parasite system, Arvicola terrestris and Taenia taeniaeformis.

    Science.gov (United States)

    Deter, J; Berthier, K; Chaval, Y; Cosson, J F; Morand, S; Charbonnel, N

    2006-04-01

    Infection by the cestode Taenia taeniaeformis was investigated within numerous cyclic populations of the fossorial water vole Arvicola terrestris sampled during 4 years in Franche-Comté (France). The relative influence of different rodent demographic parameters on the presence of this cestode was assessed by considering (1) the demographic phase of the cycle; (2) density at the local geographical scale (10 km2). The local scale corresponded to the rodent population (intermediate host), while the large scale corresponded to the definitive host population (wild and feral cats). General linear models based on analyses of 1804 voles revealed the importance of local density but also of year, rodent age, season and interactions between year and season and between age and season. Prevalence was significantly higher in low vole densities than during local outbreaks. By contrast, the large geographical scale density and the demographic phase had less influence on infection by the cestode. The potential impacts of the cestode on the fitness of the host were assessed and infection had no effect on the host body mass, litter size or sexual activity of voles.

  20. Host factors in nidovirus replication

    NARCIS (Netherlands)

    Wilde, Adriaan Hugo de

    2013-01-01

    The interplay between nidoviruses and the infected host cell was investigated. Arterivirus RNA-synthesising activity was shown to depend on intact membranes and on a cytosolic host protein which does not cosediment with the RTC. Furthermore, the immunosuppressant drug cyclosporin A (CsA) blocks repl

  1. Host Adaptation of Staphylococcal Leukocidins

    NARCIS (Netherlands)

    Vrieling, M.

    2016-01-01

    Staphylococcus aureus is a human and animal pathogen of global importance and has the capacity to cause disease in distinct host populations, using a large arsenal of secreted proteins to evade the host immune response. Amongst the immune evasion proteins of S. aureus, secreted cytotoxins play a pre

  2. Stennis hosts 2010 Special Olympics

    Science.gov (United States)

    2010-01-01

    Sarah Johnson, 28, of Gulfport, carries in the Olympic torch to signal the start of the 2010 Area III Special Olympic games at NASA's John C. Stennis Space Center on March 27. Stennis volunteers hosted special needs athletes from across the area for the event. Stennis is an annual host of the games.

  3. Parasite transmission in social interacting hosts: Monogenean epidemics in guppies

    Science.gov (United States)

    Johnson, Mirelle B.; Lafferty, Kevin D.; van Oosterhout, Cock; Cable, Joanne

    2011-01-01

    Background Infection incidence increases with the average number of contacts between susceptible and infected individuals. Contact rates are normally assumed to increase linearly with host density. However, social species seek out each other at low density and saturate their contact rates at high densities. Although predicting epidemic behaviour requires knowing how contact rates scale with host density, few empirical studies have investigated the effect of host density. Also, most theory assumes each host has an equal probability of transmitting parasites, even though individual parasite load and infection duration can vary. To our knowledge, the relative importance of characteristics of the primary infected host vs. the susceptible population has never been tested experimentally. Methodology/Principal Findings Here, we examine epidemics using a common ectoparasite, Gyrodactylus turnbulli infecting its guppy host (Poecilia reticulata). Hosts were maintained at different densities (3, 6, 12 and 24 fish in 40 L aquaria), and we monitored gyrodactylids both at a population and individual host level. Although parasite population size increased with host density, the probability of an epidemic did not. Epidemics were more likely when the primary infected fish had a high mean intensity and duration of infection. Epidemics only occurred if the primary infected host experienced more than 23 worm days. Female guppies contracted infections sooner than males, probably because females have a higher propensity for shoaling. Conclusions/Significance These findings suggest that in social hosts like guppies, the frequency of social contact largely governs disease epidemics independent of host density.

  4. Parasite transmission in social interacting hosts: monogenean epidemics in guppies.

    Directory of Open Access Journals (Sweden)

    Mirelle B Johnson

    Full Text Available BACKGROUND: Infection incidence increases with the average number of contacts between susceptible and infected individuals. Contact rates are normally assumed to increase linearly with host density. However, social species seek out each other at low density and saturate their contact rates at high densities. Although predicting epidemic behaviour requires knowing how contact rates scale with host density, few empirical studies have investigated the effect of host density. Also, most theory assumes each host has an equal probability of transmitting parasites, even though individual parasite load and infection duration can vary. To our knowledge, the relative importance of characteristics of the primary infected host vs. the susceptible population has never been tested experimentally. METHODOLOGY/PRINCIPAL FINDINGS: Here, we examine epidemics using a common ectoparasite, Gyrodactylus turnbulli infecting its guppy host (Poecilia reticulata. Hosts were maintained at different densities (3, 6, 12 and 24 fish in 40 L aquaria, and we monitored gyrodactylids both at a population and individual host level. Although parasite population size increased with host density, the probability of an epidemic did not. Epidemics were more likely when the primary infected fish had a high mean intensity and duration of infection. Epidemics only occurred if the primary infected host experienced more than 23 worm days. Female guppies contracted infections sooner than males, probably because females have a higher propensity for shoaling. CONCLUSIONS/SIGNIFICANCE: These findings suggest that in social hosts like guppies, the frequency of social contact largely governs disease epidemics independent of host density.

  5. Salmonellae interactions with host processes.

    Science.gov (United States)

    LaRock, Doris L; Chaudhary, Anu; Miller, Samuel I

    2015-04-01

    Salmonellae invasion and intracellular replication within host cells result in a range of diseases, including gastroenteritis, bacteraemia, enteric fever and focal infections. In recent years, considerable progress has been made in our understanding of the molecular mechanisms that salmonellae use to alter host cell physiology; through the delivery of effector proteins with specific activities and through the modulation of defence and stress response pathways. In this Review, we summarize our current knowledge of the complex interplay between bacterial and host factors that leads to inflammation, disease and, in most cases, control of the infection by its animal hosts, with a particular focus on Salmonella enterica subsp. enterica serovar Typhimurium. We also highlight gaps in our knowledge of the contributions of salmonellae and the host to disease pathogenesis, and we suggest future avenues for further study.

  6. Growth anomalies on the coral genera Acropora and Porites are strongly associated with host density and human population size across the Indo-Pacific

    Science.gov (United States)

    Aeby, G.S.; Williams, G.J.; Franklin, E.C.; Haapkyla, J.; Harvell, C.D.; Neale, S.; Page, C.A.; Raymundo, L.; Vargas-Angel, B.; Willis, B.L.; Work, T.M.; Davy, S.K.

    2011-01-01

    Growth anomalies (GAs) are common, tumor-like diseases that can cause significant morbidity and decreased fecundity in the major Indo-Pacific reef-building coral genera, Acropora and Porites. GAs are unusually tractable for testing hypotheses about drivers of coral disease because of their pan-Pacific distributions, relatively high occurrence, and unambiguous ease of identification. We modeled multiple disease-environment associations that may underlie the prevalence of Acropora growth anomalies (AGA) (n = 304 surveys) and Porites growth anomalies (PGA) (n = 602 surveys) from across the Indo-Pacific. Nine predictor variables were modeled, including coral host abundance, human population size, and sea surface temperature and ultra-violet radiation anomalies. Prevalence of both AGAs and PGAs were strongly host density-dependent. PGAs additionally showed strong positive associations with human population size. Although this association has been widely posited, this is one of the first broad-scale studies unambiguously linking a coral disease with human population size. These results emphasize that individual coral diseases can show relatively distinct patterns of association with environmental predictors, even in similar diseases (growth anomalies) found on different host genera (Acropora vs. Porites). As human densities and environmental degradation increase globally, the prevalence of coral diseases like PGAs could increase accordingly, halted only perhaps by declines in host density below thresholds required for disease establishment.

  7. Environmentally transmitted parasites: Host-jumping in a heterogeneous environment.

    Science.gov (United States)

    Caraco, Thomas; Cizauskas, Carrie A; Wang, Ing-Nang

    2016-05-21

    Groups of chronically infected reservoir-hosts contaminate resource patches by shedding a parasite׳s free-living stage. Novel-host groups visit the same patches, where they are exposed to infection. We treat arrival at patches, levels of parasite deposition, and infection of the novel host as stochastic processes, and derive the expected time elapsing until a host-jump (initial infection of a novel host) occurs. At stationarity, mean parasite densities are independent of reservoir-host group size. But within-patch parasite-density variances increase with reservoir group size. The probability of infecting a novel host declines with parasite-density variance; consequently larger reservoir groups extend the mean waiting time for host-jumping. Larger novel-host groups increase the probability of a host-jump during any single patch visit, but also reduce the total number of visits per unit time. Interaction of these effects implies that the waiting time for the first infection increases with the novel-host group size. If the reservoir-host uses resource patches in any non-uniform manner, reduced spatial overlap between host species increases the waiting time for host-jumping.

  8. Towards host-to-host meeting scheduling negotiation

    Directory of Open Access Journals (Sweden)

    Rani Megasari

    2015-03-01

    Full Text Available This paper presents a different scheme of meeting scheduling negotiation among a large number of personnel in a heterogeneous community. This scheme, named Host-to-Host Negotiation, attempts to produce a stable schedule under uncertain personnel preferences. By collecting information from hosts’ inter organizational meeting, this study intends to guarantee personnel availability. As a consequence, personnel’s and meeting’s profile in this scheme are stored in a centralized manner. This study considers personnel preferences by adapting the Clarke Tax Mechanism, which is categorized as a non manipulated mechanism design. Finally, this paper introduces negotiation strategies based on the conflict handling mode. A host-to-host scheme can give notification if any conflict exist and lead to negotiation process with acceptable disclosed information. Nevertheless, a complete negotiation process will be more elaborated in the future works.

  9. Host factors influencing viral persistence

    DEFF Research Database (Denmark)

    Thomsen, Allan Randrup; Nansen, A; Ørding Andreasen, Susanne

    2000-01-01

    host were used. Our results reveal that very different outcomes may be observed depending on virus strain and immunocompetence of the host. Thus while CD4+ cells are not critical during the initial phase of virus control, infectious virus reappear in mice lacking CD4+ cells, B cells or CD40 ligand...... that these different outcomes may be explained in relatively simple mathematical terms. This suggests that modelling may be used as a means to predict critical host and virus parameters. Therefore, combining mathematical modelling with precise, quantitative, in vivo analyses looks to be a promising approach...

  10. Mistletoe ecophysiology: Host-parasite interactions

    Science.gov (United States)

    G. Glatzel; B. W. Geils

    2009-01-01

    Mistletoes are highly specialized perennial flowering plants adapted to parasitic life on aerial parts of their hosts. In our discussion on the physiological interactions between parasite and host, we focus on water relations, mineral nutrition, and the effect of host vigour. When host photosynthesis is greatest, the xylem water potential of the host is most negative....

  11. Meningococcal interactions with the host.

    Science.gov (United States)

    Carbonnelle, Etienne; Hill, Darryl J; Morand, Philippe; Griffiths, Natalie J; Bourdoulous, Sandrine; Murillo, Isabel; Nassif, Xavier; Virji, Mumtaz

    2009-06-24

    Neisseria meningitidis interacts with host tissues through hierarchical, concerted and co-ordinated actions of a number of adhesins; many of which undergo antigenic and phase variation, a strategy that helps immune evasion. Three major structures, pili, Opa and Opc predominantly influence bacterial adhesion to host cells. Pili and Opa proteins also determine host and tissue specificity while Opa and Opc facilitate efficient cellular invasion. Recent studies have also implied a role of certain adhesin-receptor pairs in determining increased host susceptibility to infection. This chapter examines our current knowledge of meningococcal adhesion and invasion mechanisms particularly related to human epithelial and endothelial cells which are of primary importance in the disease process.

  12. Host species exploitation and discrimination by animal parasites

    Science.gov (United States)

    Forbes, Mark R.; Morrill, André; Schellinck, Jennifer

    2017-01-01

    Parasite species often show differential fitness on different host species. We developed an equation-based model to explore conditions favouring host species exploitation and discrimination. In our model, diploid infective stages randomly encountered hosts of two species; the parasite's relative fitness in exploiting each host species, and its ability to discriminate between them, was determined by the parasite's genotype at two independent diallelic loci. Relative host species frequency determined allele frequencies at the exploitation locus, whereas differential fitness and combined host density determined frequency of discrimination alleles. The model predicts instances where populations contain mixes of discriminatory and non-discriminatory infective stages. Also, non-discriminatory parasites should evolve when differential fitness is low to moderate and when combined host densities are low, but not so low as to cause parasite extinction. A corollary is that parasite discrimination (and host-specificity) increases with higher combined host densities. Instances in nature where parasites fail to discriminate when differential fitness is extreme could be explained by one host species evolving resistance, following from earlier selection for parasite non-discrimination. Similar results overall were obtained for haploid extensions of the model. Our model emulates multi-host associations and has implications for understanding broadening of host species ranges by parasites. This article is part of the themed issue ‘Opening the black box: re-examining the ecology and evolution of parasite transmission’. PMID:28289258

  13. The host of GRB 030323 at z=3.372: A very high column density DLA system with a low metallicity

    OpenAIRE

    Vreeswijk, P. M.; Ellison, S.L.; Ledoux, C.; Wijers, R. A. M. J.; Fynbo, J. P. U.; Møller, P.; Henden, A.; Hjorth, J.; Masi, G

    2004-01-01

    We present photometry and spectroscopy of the afterglow of GRB 030323. VLT spectra of the afterglow show damped Lyalpha (DLA) absorption and low- and high-ionization lines at a redshift z=3.3718B10.0005. The inferred neutral hydrogen column density, log N(H I)=21.90B10.07, is larger than any (GRB- or QSO-) DLA H I column density inferred directly from Lyalpha in absorption. From the afterglow photometry, we derive a conservative upper limit to the host-galaxy extinction: AV

  14. The Smallest AGN Host Galaxies

    CERN Document Server

    Greene, J E; Ho, L C

    2005-01-01

    We describe our efforts to study dwarf galaxies with active nuclei, whose black holes, with masses < 10^6 M_sun, provide the best current observational constraints on the mass distribution of primordial seed black holes. Although these low-mass galaxies do not necessarily contain classical bulges, Barth, Greene, & Ho (2005) show that their stellar velocity dispersions and black hole masses obey the same relation as more massive systems. In order to characterize the properties of the dwarf hosts without the glare of the active nucleus, we have compiled a complementary sample of narrow-line active galaxies with low-mass hosts. The host galaxy properties, both their structures and stellar populations, are consistent with the general properties of low-mass, blue galaxies from Sloan. The black holes in these galaxies are probably radiating close to their Eddington limits, suggesting we may have found Type 2 analogues of narrow-line Seyfert 1 galaxies.

  15. Asteroseismology of Exoplanet Host Stars

    CERN Document Server

    Huber, Daniel

    2015-01-01

    Asteroseismology is among the most powerful observational tools to determine fundamental properties of stars. Space-based photometry has recently enabled the systematic detection of oscillations in exoplanet host stars, allowing a combination of asteroseismology with transit and radial-velocity measurements to characterize planetary systems. In this contribution I will review the key synergies between asteroseismology and exoplanet science such as the precise determination of radii and ages of exoplanet host stars, as well as applications of asteroseismology to measure spin-orbit inclinations in multiplanet systems and orbital eccentricities of small planets. Finally I will give a brief outlook on asteroseismic studies of exoplanet hosts with current and future space-based missions such as K2 and TESS.

  16. The Inflammasome in Host Defense

    Directory of Open Access Journals (Sweden)

    Gang Chen

    2009-12-01

    Full Text Available Nod-like receptors have emerged as an important family of sensors in host defense. These receptors are expressed in macrophages, dendritic cells and monocytes and play an important role in microbial immunity. Some Nod-like receptors form the inflammasome, a protein complex that activates caspase-1 in response to several stimuli. Caspase-1 activation leads to processing and secretion of pro-inflammatory cytokines such as interleukin (IL-1β and IL-18. Here, we discuss recent advances in the inflammasome field with an emphasis on host defense. We also compare differential requirements for inflammasome activation in dendritic cells, macrophages and monocytes.

  17. Noncentrosymmetric Magnets Hosting Magnetic Skyrmions.

    Science.gov (United States)

    Kanazawa, Naoya; Seki, Shinichiro; Tokura, Yoshinori

    2017-03-17

    The concept of a skyrmion, which was first introduced by Tony Skyrme in the field of particle physics, has become widespread in condensed matter physics to describe various topological orders. Skyrmions in magnetic materials have recently received particular attention; they represent vortex-like spin structures with the character of nanometric particles and produce fascinating physical properties rooted in their topological nature. Here, a series of noncentrosymmetric ferromagnets hosting skyrmions is reviewed: B20 metals, Cu2 OSeO3 , Co-Zn-Mn alloys, and GaV4 S8 , where Dzyaloshinskii-Moriya interaction plays a key role in the stabilization of skyrmion spin texture. Their topological spin arrangements and consequent emergent electromagnetic fields give rise to striking features in transport and magnetoelectric properties in metals and insulators, such as the topological Hall effect, efficient electric-drive of skyrmions, and multiferroic behavior. Such electric controllability and nanometric particle natures highlight magnetic skyrmions as a potential information carrier for high-density magnetic storage devices with excellent energy efficiency.

  18. Visual mimicry of host nestlings by cuckoos

    Science.gov (United States)

    Langmore, Naomi E.; Stevens, Martin; Maurer, Golo; Heinsohn, Robert; Hall, Michelle L.; Peters, Anne; Kilner, Rebecca M.

    2011-01-01

    Coevolution between antagonistic species has produced instances of exquisite mimicry. Among brood-parasitic cuckoos, host defences have driven the evolution of mimetic eggs, but the evolutionary arms race was believed to be constrained from progressing to the chick stage, with cuckoo nestlings generally looking unlike host young. However, recent studies on bronze-cuckoos have confounded theoretical expectations by demonstrating cuckoo nestling rejection by hosts. Coevolutionary theory predicts reciprocal selection for visual mimicry of host young by cuckoos, although this has not been demonstrated previously. Here we show that, in the eyes of hosts, nestlings of three bronze-cuckoo species are striking visual mimics of the young of their morphologically diverse hosts, providing the first evidence that coevolution can select for visual mimicry of hosts in cuckoo chicks. Bronze-cuckoos resemble their own hosts more closely than other host species, but the accuracy of mimicry varies according to the diversity of hosts they exploit. PMID:21227972

  19. Influence of host gender on infection rate, density and distribution of the parasitic fungus, Hesperomyces virescens, on the multicolored Asian lady beetle, Harmonia axyridis.

    Science.gov (United States)

    Riddick, E W

    2006-01-01

    Hesperomyces virescens Thaxter (Laboulbeniales: Laboulbeniaceae) is a parasitic fungus that infects lady beetles (Coleoptera: Coccinellidae) via horizontal transmission between adults at overwintering and feeding sites. The differential behavior of male and female hosts could have profound effects on intensity of infection and positioning of fungus on the host's integument. The influence of host gender on infection rate, density and distribution of this parasite on the multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), was determined at a feeding site. Adult H. axyridis were sampled from pecan, Carya illinoinensis (Wangenh.) K. Koch, trees in northern Mississippi, USA, during summer and early fall 2003-2004. Results indicated that the behavior of male or female beetles on pecan trees had only a limited effect on the intensity of infection. When averaged over the entire season, the percentage of H. axyridis infected with H. virescens was not influenced by host gender. In 2003, a seasonal average of 54 and 39% of males and females, respectively, were infected; whereas in 2004, 36 and 41% of male and female beetles, respectively, were infected. The percentage of males infected with H. virescens was correlated with the number of males captured at the site in 2003; infection rate decreased as male abundance increased. Infection rate did not correlate with female abundance in 2003 or male or female abundance in 2004. Host gender had a considerable effect on the density and distribution of the fungus. Hesperomyces virescens mature thalli were denser on male rather than female beetles. Also, thallus density was often greatest on the elytra, meso- and metathorax, and abdomen of males and elytra of females, than on other body parts, in 2003. In 2003 and 2004, approximately 59 and 97% and 67 and 96% of males and females, respectively, had mature thalli distributed on the elytra. Prevalence of H. virescens thalli on the dorsum of H

  20. Biosignatures of Pathogen and Host

    Energy Technology Data Exchange (ETDEWEB)

    Fitch, J P; Chromy, B A; Forde, C E; Garcia, E; Gardner, S N; Gu, P P; Kuczmarksi, T A; Melius, C F; McCutchen-Maloney, S L; Milanovich, F P; Motin, V L; Ott, L L; Quong, A A; Quong, J N; Rocco, J M; Slezak, T R; Sokhansanj, B A; Vitalis, E A; Zemla, A T; McCready, P M

    2002-08-27

    In information theory, a signature is characterized by the information content as well as noise statistics of the communication channel. Biosignatures have analogous properties. A biosignature can be associated with a particular attribute of a pathogen or a host. However, the signature may be lost in backgrounds of similar or even identical signals from other sources. In this paper, we highlight statistical and signal processing challenges associated with identifying good biosignatures for pathogens in host and other environments. In some cases it may be possible to identify useful signatures of pathogens through indirect but amplified signals from the host. Discovery of these signatures requires new approaches to modeling and data interpretation. For environmental biosignal collections, it is possible to use signal processing techniques from other applications (e.g., synthetic aperture radar) to track the natural progression of microbes over large areas. We also present a computer-assisted approach to identify unique nucleic-acid based microbial signatures. Finally, an understanding of host-pathogen interactions will result in better detectors as well as opportunities in vaccines and therapeutics.

  1. Gastrointestinal mucormycosis in immunocompromised hosts.

    Science.gov (United States)

    Dioverti, M Veronica; Cawcutt, Kelly A; Abidi, Maheen; Sohail, M Rizwan; Walker, Randall C; Osmon, Douglas R

    2015-12-01

    Invasive mucormycosis is a rare fungal infection in immunocompromised hosts, but it carries a high mortality rate. Primary gastrointestinal disease is the least frequent form of presentation. Early diagnosis and treatment are critical in the management; however, symptoms are typically non-specific in gastrointestinal disease, leading to delayed therapy. To describe the clinical presentation, diagnosis, treatment and outcomes of gastrointestinal mucormycosis in immunocompromised hosts, we reviewed all cases of primary gastrointestinal mucormycosis in immunocompromised hosts reported in English literature as well as in our Institution from January 1st 1991 to December 31st 2013 for a total of 31 patients. About 52% of patients underwent solid organ transplant (SOT), while the rest had an underlying haematologic malignancy. Abdominal pain was the most common presenting symptom, followed by gastrointestinal bleeding and fever. Gastric disease was more common in SOT, whereas those with haematologic malignancy presented with intestinal disease (P = 0.002). Although gastrointestinal mucormycosis remains an uncommon condition in immunocompromised hosts, it carries significant morbidity and mortality, particularly in cases with intestinal involvement. A high index of suspicion is of utmost importance to institute early and appropriate therapy and improve outcomes.

  2. Host Defence to Pulmonary Mycosis

    Directory of Open Access Journals (Sweden)

    Christopher H Mody

    1999-01-01

    Full Text Available OBJECTIVE: To provide a basic understanding of the mechanisms of host defense to pathogenic fungi. This will help physicians understand why some patients are predisposed to fungal infections and update basic scientists on how microbial immunology applies to fungal disease.

  3. Host Event Based Network Monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Jonathan Chugg

    2013-01-01

    The purpose of INL’s research on this project is to demonstrate the feasibility of a host event based network monitoring tool and the effects on host performance. Current host based network monitoring tools work on polling which can miss activity if it occurs between polls. Instead of polling, a tool could be developed that makes use of event APIs in the operating system to receive asynchronous notifications of network activity. Analysis and logging of these events will allow the tool to construct the complete real-time and historical network configuration of the host while the tool is running. This research focused on three major operating systems commonly used by SCADA systems: Linux, WindowsXP, and Windows7. Windows 7 offers two paths that have minimal impact on the system and should be seriously considered. First is the new Windows Event Logging API, and, second, Windows 7 offers the ALE API within WFP. Any future work should focus on these methods.

  4. Location of Host and Host Habitat by Fruit Fly Parasitoids

    Directory of Open Access Journals (Sweden)

    Pascal Rousse

    2012-11-01

    Full Text Available Augmentative releases of parasitoids may be a useful tool for the area-wide management of tephritid pests. The latter are parasitized by many wasp species, though only a few of them are relevant for augmentative biocontrol purposes. To date, nearly all the actual or potential biocontrol agents for such programs are egg or larval Opiinae parasitoids (Hymenoptera: Braconidae. Here, we review the literature published on their habitat and host location behavior, as well as the factors that modulate this behavior, which is assumed to be sequential; parasitoids forage first for the host habitat and then for the host itself. Parasitoids rely on chemical, visual, and mechanical stimuli, often strongly related to their ecology. Behavioral modulation factors include biotic and abiotic factors including learning, climatic conditions and physiological state of the insect. Finally, conclusions and perspectives for future research are briefly highlighted. A detailed knowledge of this behavior may be very useful for selecting the release sites for both inundative/augmentative releases of mass-reared parasitoids and inoculative releases for classical biocontrol.

  5. Host modulation by therapeutic agents

    Directory of Open Access Journals (Sweden)

    Sugumari Elavarasu

    2012-01-01

    Full Text Available Periodontal disease susceptible group present advanced periodontal breakdown even though they achieve a high standard of oral hygiene. Various destructive enzymes and inflammatory mediators are involved in destruction. These are elevated in case of periodontal destruction. Host modulation aims at bringing these enzymes and mediators to normal level. Doxycycline, nonsteroidal anti-inflammatory drugs (NSAIDs, bisphosphonates, nitrous oxide (NO synthase inhibitors, recombinant human interleukin-11 (rhIL-11, omega-3 fatty acid, mouse anti-human interleukin-6 receptor antibody (MRA, mitogen-activated protein kinase (MAPK inhibitors, nuclear factor-kappa B (NF-kb inhibitors, osteoprotegerin, and tumor necrosis factor antagonist (TNF-α are some of the therapeutic agents that have host modulation properties.

  6. Host thin films incorporating nanoparticles

    Science.gov (United States)

    Qureshi, Uzma

    The focus of this research project was the investigation of the functional properties of thin films that incorporate a secondary nanoparticulate phase. In particular to assess if the secondary nanoparticulate material enhanced a functional property of the coating on glass. In order to achieve this, new thin film deposition methods were developed, namely use of nanopowder precursors, an aerosol assisted transport technique and an aerosol into atmospheric pressure chemical vapour deposition system. Aerosol assisted chemical vapour deposition (AACVD) was used to deposit 8 series of thin films on glass. Five different nanoparticles silver, gold, ceria, tungsten oxide and zinc oxide were tested and shown to successfully deposit thin films incorporating nanoparticles within a host matrix. Silver nanoparticles were synthesised and doped within a titania film by AACVD. This improved solar control properties. A unique aerosol assisted chemical vapour deposition (AACVD) into atmospheric pressure chemical vapour deposition (APCVD) system was used to deposit films of Au nanoparticles and thin films of gold nanoparticles incorporated within a host titania matrix. Incorporation of high refractive index contrast metal oxide particles within a host film altered the film colour. The key goal was to test the potential of nanopowder forms and transfer the suspended nanopowder via an aerosol to a substrate in order to deposit a thin film. Discrete tungsten oxide nanoparticles or ceria nanoparticles within a titanium dioxide thin film enhanced the self-cleaning and photo-induced super-hydrophilicity. The nanopowder precursor study was extended by deposition of zinc oxide thin films incorporating Au nanoparticles and also ZnO films deposited from a ZnO nanopowder precursor. Incorporation of Au nanoparticles within a VO: host matrix improved the thermochromic response, optical and colour properties. Composite VC/TiC and Au nanoparticle/V02/Ti02 thin films displayed three useful

  7. Do symbiotic bacteria subvert host immunity?

    Science.gov (United States)

    Hooper, Lora V

    2009-05-01

    The mammalian intestine is home to dense and complex indigenous bacterial communities. Most of these bacteria establish beneficial symbiotic relationships with their hosts, making important contributions to host metabolism and digestive efficiency. The vast numbers of intestinal bacteria and their proximity to host tissues raise the question of how symbiotic host-bacterial relationships are established without eliciting potentially harmful immune responses. In light of the varied ways in which pathogenic bacteria manipulate host immunity, this Opinion article explores the role of immune suppression, subversion and evasion in the establishment of symbiotic host-bacterial associations.

  8. Hosting anions. The energetic perspective.

    Science.gov (United States)

    Schmidtchen, Franz P

    2010-10-01

    Hosting anions addresses the widely spread molecular recognition event of negatively charged species by dedicated organic compounds in condensed phases at equilibrium. The experimentally accessible energetic features comprise the entire system including the solvent, any buffers, background electrolytes or other components introduced for e.g. analysis. The deconvolution of all these interaction types and their dependence on subtle structural variation is required to arrive at a structure-energy correlation that may serve as a guide in receptor construction. The focus on direct host-guest interactions (lock-and-key complementarity) that have dominated the binding concepts of artificial receptors in the past must be widened in order to account for entropic contributions which constitute very significant fractions of the total free energy of interaction. Including entropy necessarily addresses the ambiguity and fuzziness of the host-guest structural ensemble and requires the appreciation of the fact that most liquid phases possess distinct structures of their own. Apparently, it is the perturbation of the intrinsic solvent structure occurring upon association that rules ion binding in polar media where ions are soluble and abundant. Rather than specifying peculiar structural elements useful in anion binding this critical review attempts an illumination of the concepts and individual energetic contributions resulting in the final observation of specific anion recognition (95 references).

  9. Host compatibility rather than vector-host-encounter rate determines the host range of avian Plasmodium parasites.

    Science.gov (United States)

    Medeiros, Matthew C I; Hamer, Gabriel L; Ricklefs, Robert E

    2013-06-07

    Blood-feeding arthropod vectors are responsible for transmitting many parasites between vertebrate hosts. While arthropod vectors often feed on limited subsets of potential host species, little is known about the extent to which this influences the distribution of vector-borne parasites in some systems. Here, we test the hypothesis that different vector species structure parasite-host relationships by restricting access of certain parasites to a subset of available hosts. Specifically, we investigate how the feeding patterns of Culex mosquito vectors relate to distributions of avian malaria parasites among hosts in suburban Chicago, IL, USA. We show that Plasmodium lineages, defined by cytochrome b haplotypes, are heterogeneously distributed across avian hosts. However, the feeding patterns of the dominant vectors (Culex restuans and Culex pipiens) are similar across these hosts, and do not explain the distributions of Plasmodium parasites. Phylogenetic similarity of avian hosts predicts similarity in their Plasmodium parasites. This effect was driven primarily by the general association of Plasmodium parasites with particular host superfamilies. Our results suggest that a mosquito-imposed encounter rate does not limit the distribution of avian Plasmodium parasites across hosts. This implies that compatibility between parasites and their avian hosts structure Plasmodium host range.

  10. Spatial and host-associated variation in prevalence and population density of wheat curl mite (Aceria tosichella) cryptic genotypes in agricultural landscapes.

    Science.gov (United States)

    The wheat curl mite (WCM), Aceria tosichella Keifer, is a major pest of cereals worldwide that also comprises a complex of at least 16 genetic lineages with divergent physiological traits, including host preference and specificity. The goal of this study was to test the extent to which host-plant sp...

  11. Patterns of gregarine parasitism in dragonflies: host, habitat, and seasonality.

    Science.gov (United States)

    Locklin, Jason L; Vodopich, Darrell S

    2010-06-01

    Gregarines are ubiquitous protozoan parasites that infect arthropods worldwide. More than 1,600 gregarine species have been described, but only a small percentage of invertebrates have been surveyed for these apicomplexan parasites. Adult dragonfly populations were surveyed for gregarines at two reservoirs in Texas, USA for 2 years. Gregarine prevalence and intensity were compared intraspecifically between host genders and reservoirs, among wing loads, and through time. Of the 29 dragonfly species collected, 41% hosted gregarines. Nine of these dragonfly species were previously undocumented as hosts. Among the commonly collected hosts, prevalence ranged from 18 to 52%. Parasites were aggregated among hosts and had a median intensity of five parasites per host. Gregarines were found only in hosts exceeding a minimum wing load, indicating that gregarines are likely not transferred from the naiad to adult during emergence. Prevalence and intensity increased during both years, suggesting that gregarine oocyst viability parallels increasing host population densities and may be short-lived. Prevalence and intensity also differed between dragonfly populations at two reservoirs. Regression analyses revealed that host species, host gender, month, and year were significant explanatory variables related to gregarine prevalence and intensity. Abundant information on odonate distributions, diversity, and mating activities makes dragonfly-gregarine systems excellent avenues for ecological, evolutionary, and parasitological research. Our results emphasize the importance of considering season, hosts, and habitat when studying gregarine-dragonfly ecology.

  12. The tritrophic system hyptis suaveolens (Lamiaceae - agromyzid leafminers (Diptera: Agromyzidae - parasitoids (Hymenoptera: effects of herbivore density, host plant patch size, and habitat complexity on parasitism rate

    Directory of Open Access Journals (Sweden)

    Jarbas Marcal de Queiroz

    2009-06-01

    Full Text Available In this study a tritrophic system was evaluated to measure the contributions of the insect host density and its host plant concentration in simple and diversified habitat on the rate of parasitism. The system was composed of the plant Hyptis suaveolens, two species of agromyzid leafminers, and three morphospecies of parasitoids. The parasitism rate, patch size, and habitat complexity were found to be interdependent. If only the habitat complexity or patch size was take into account the differences in parasitism rate are not significant, although habitat diversity seemed to contribute more than the host plant concentration to increase the parasitism rate. The leaves or plants with different number of mines were equally attacked by the parasitoids. The results were representative of what happened to the leafminers at different host plant densities under the homogeneous and heterogeneous habitat condition. This work could help to reinforce the idea of the importance of the plant diversity for enhancing the biological control of the pests by the parasitoids in the managed ecosystems.Foi avaliado um sistema tritrófico para medir os efeitos da densidade de insetos minadores e a concentração da planta hospedeira em habitats simples e diversificados sobre a taxa de parasitismo. O sistema era composto pela planta Hyptis suaveolens, duas espécies de agromizídeos minadores de folhas e três morfoespécies de parasitóides. A taxa de parasitismo, tamanho da mancha e a complexidade do habitat foram interdependentes. Se levarmos em consideração apenas a complexidade ou tamanho de mancha, as diferenças na taxa de parasitismo não foram significativas, embora a diversidade de habitat pareça ter contribuido mais do que a concentração da planta hospedeira para aumentar a taxa de parasitismo. Folhas ou plantas com diferentes números de minas foram igualmente parasitadas. Nossos resultados são representativos do que acontece com insetos minadores em

  13. Carp erythrodermatitis: host defense-pathogen interaction.

    OpenAIRE

    Pourreau, C.N.

    1990-01-01

    The outcome of a bacterial infection depends on the interaction between pathogen and host. The ability of the microbe to survive in the host depends on its invasive potential (i.e. spreading and multiplication), and its ability to obtain essential nutrients and to resist the host's defense system. On the other hand, the host's resistance to a bacterial attack depends on its physiological state, the intensity of the bacterial attack and the efficacy of the defense system to neutralize toxins a...

  14. Modified host cells with efflux pumps

    Science.gov (United States)

    Dunlop, Mary J.; Keasling, Jay D.; Mukhopadhyay, Aindrila

    2016-08-30

    The present invention provides for a modified host cell comprising a heterologous expression of an efflux pump capable of transporting an organic molecule out of the host cell wherein the organic molecule at a sufficiently high concentration reduces the growth rate of or is lethal to the host cell.

  15. Carp erythrodermatitis: host defense-pathogen interaction.

    NARCIS (Netherlands)

    Pourreau, C.N.

    1990-01-01

    The outcome of a bacterial infection depends on the interaction between pathogen and host. The ability of the microbe to survive in the host depends on its invasive potential (i.e. spreading and multiplication), and its ability to obtain essential nutrients and to resist the host's defense syste

  16. Carp erythrodermatitis : host defense-pathogen interaction

    NARCIS (Netherlands)

    Pourreau, C.N.

    1990-01-01

    The outcome of a bacterial infection depends on the interaction between pathogen and host. The ability of the microbe to survive in the host depends on its invasive potential (i.e. spreading and multiplication), and its ability to obtain essential nutrients and to resist the host'

  17. Acute graft versus host disease

    Directory of Open Access Journals (Sweden)

    Vogelsang Georgia B

    2007-09-01

    Full Text Available Abstract Acute graft-versus-host disease (GVHD occurs after allogeneic hematopoietic stem cell transplant and is a reaction of donor immune cells against host tissues. Activated donor T cells damage host epithelial cells after an inflammatory cascade that begins with the preparative regimen. About 35%–50% of hematopoietic stem cell transplant (HSCT recipients will develop acute GVHD. The exact risk is dependent on the stem cell source, age of the patient, conditioning, and GVHD prophylaxis used. Given the number of transplants performed, we can expect about 5500 patients/year to develop acute GVHD. Patients can have involvement of three organs: skin (rash/dermatitis, liver (hepatitis/jaundice, and gastrointestinal tract (abdominal pain/diarrhea. One or more organs may be involved. GVHD is a clinical diagnosis that may be supported with appropriate biopsies. The reason to pursue a tissue biopsy is to help differentiate from other diagnoses which may mimic GVHD, such as viral infection (hepatitis, colitis or drug reaction (causing skin rash. Acute GVHD is staged and graded (grade 0-IV by the number and extent of organ involvement. Patients with grade III/IV acute GVHD tend to have a poor outcome. Generally the patient is treated by optimizing their immunosuppression and adding methylprednisolone. About 50% of patients will have a solid response to methylprednisolone. If patients progress after 3 days or are not improved after 7 days, they will get salvage (second-line immunosuppressive therapy for which there is currently no standard-of-care. Well-organized clinical trials are imperative to better define second-line therapies for this disease. Additional management issues are attention to wound infections in skin GVHD and fluid/nutrition management in gastrointestinal GVHD. About 50% of patients with acute GVHD will eventually have manifestations of chronic GVHD.

  18. Intercultural Competence in Host Students?

    DEFF Research Database (Denmark)

    Egekvist, Ulla Egidiussen; Lyngdorf, Niels Erik; Du, Xiangyun

    2016-01-01

    Although substantial work in intercultural education has been done on the intercultural competences of mobile students engaging in international study visits, there is a need to explore intercultural competences in host students. This chapter seeks to answer questions about the challenges...... and possibilities of using short-term study visits to develop these competences. Theoretically, this chapter finds inspiration in social constructivist understandings of culture and Byram’s research on intercultural competence. Empirically, the data used in this paper were derived from a study of 22 Danish lower...

  19. Generic Model Host System Design

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Chungming; /SLAC; Wu, Juhao; /SLAC; Qiang, Ji; /LBL, Berkeley; Shen, Guobao; /Brookhaven

    2012-06-22

    There are many simulation codes for accelerator modelling; each one has some strength but not all. A platform which can host multiple modelling tools would be ideal for various purposes. The model platform along with infrastructure support can be used not only for online applications but also for offline purposes. Collaboration is formed for the effort of providing such a platform. In order to achieve such a platform, a set of common physics data structure has to be set. Application Programming Interface (API) for physics applications should also be defined within a model data provider. A preliminary platform design and prototype is discussed.

  20. A spatial model of mosquito host-seeking behavior.

    Science.gov (United States)

    Cummins, Bree; Cortez, Ricardo; Foppa, Ivo M; Walbeck, Justin; Hyman, James M

    2012-01-01

    Mosquito host-seeking behavior and heterogeneity in host distribution are important factors in predicting the transmission dynamics of mosquito-borne infections such as dengue fever, malaria, chikungunya, and West Nile virus. We develop and analyze a new mathematical model to describe the effect of spatial heterogeneity on the contact rate between mosquito vectors and hosts. The model includes odor plumes generated by spatially distributed hosts, wind velocity, and mosquito behavior based on both the prevailing wind and the odor plume. On a spatial scale of meters and a time scale of minutes, we compare the effectiveness of different plume-finding and plume-tracking strategies that mosquitoes could use to locate a host. The results show that two different models of chemotaxis are capable of producing comparable results given appropriate parameter choices and that host finding is optimized by a strategy of flying across the wind until the odor plume is intercepted. We also assess the impact of changing the level of host aggregation on mosquito host-finding success near the end of the host-seeking flight. When clusters of hosts are more tightly associated on smaller patches, the odor plume is narrower and the biting rate per host is decreased. For two host groups of unequal number but equal spatial density, the biting rate per host is lower in the group with more individuals, indicative of an attack abatement effect of host aggregation. We discuss how this approach could assist parameter choices in compartmental models that do not explicitly model the spatial arrangement of individuals and how the model could address larger spatial scales and other probability models for mosquito behavior, such as Lévy distributions.

  1. A spatial model of mosquito host-seeking behavior.

    Directory of Open Access Journals (Sweden)

    Bree Cummins

    Full Text Available Mosquito host-seeking behavior and heterogeneity in host distribution are important factors in predicting the transmission dynamics of mosquito-borne infections such as dengue fever, malaria, chikungunya, and West Nile virus. We develop and analyze a new mathematical model to describe the effect of spatial heterogeneity on the contact rate between mosquito vectors and hosts. The model includes odor plumes generated by spatially distributed hosts, wind velocity, and mosquito behavior based on both the prevailing wind and the odor plume. On a spatial scale of meters and a time scale of minutes, we compare the effectiveness of different plume-finding and plume-tracking strategies that mosquitoes could use to locate a host. The results show that two different models of chemotaxis are capable of producing comparable results given appropriate parameter choices and that host finding is optimized by a strategy of flying across the wind until the odor plume is intercepted. We also assess the impact of changing the level of host aggregation on mosquito host-finding success near the end of the host-seeking flight. When clusters of hosts are more tightly associated on smaller patches, the odor plume is narrower and the biting rate per host is decreased. For two host groups of unequal number but equal spatial density, the biting rate per host is lower in the group with more individuals, indicative of an attack abatement effect of host aggregation. We discuss how this approach could assist parameter choices in compartmental models that do not explicitly model the spatial arrangement of individuals and how the model could address larger spatial scales and other probability models for mosquito behavior, such as Lévy distributions.

  2. Winds of Planet Hosting Stars

    CERN Document Server

    Nicholson, B A; Brookshaw, L; Vidotto, A A; Carter, B D; Marsden, S C; Soutter, J; Waite, I A; Horner, J

    2015-01-01

    The field of exoplanetary science is one of the most rapidly growing areas of astrophysical research. As more planets are discovered around other stars, new techniques have been developed that have allowed astronomers to begin to characterise them. Two of the most important factors in understanding the evolution of these planets, and potentially determining whether they are habitable, are the behaviour of the winds of the host star and the way in which they interact with the planet. The purpose of this project is to reconstruct the magnetic fields of planet hosting stars from spectropolarimetric observations, and to use these magnetic field maps to inform simulations of the stellar winds in those systems using the Block Adaptive Tree Solar-wind Roe Upwind Scheme (BATS-R-US) code. The BATS-R-US code was originally written to investigate the behaviour of the Solar wind, and so has been altered to be used in the context of other stellar systems. These simulations will give information about the velocity, pressur...

  3. Host evasion by Burkholderia cenocepacia

    Directory of Open Access Journals (Sweden)

    Shyamala eGanesan

    2012-01-01

    Full Text Available Burkholderia cenocepacia is an opportunistic respiratory pathogen of individuals with cystic fibrosis (CF. It is one of the highly transmissible species of Burkholderia cepacia complex and very resistant to almost all the antibiotics. Approximately 1/3rd of B. cenocepacia infected CF patients go on to develop fatal ‘cepacia syndrome’. During the last two decades, substantial progress has been made with regards to evasion of host innate defense mechanisms by B. cenocepacia. Almost all strains of B. cenocepacia has capacity to survive and replicate intracellularly in both airway epithelial cells and macrophages, which are primary centennials of the lung and play a pivotal role in clearance of infecting bacteria. Some strains of B. cenocepaica, which express cable pili and the associated 22kDa adhesin are also capable of transmigrating across airway epithelium and persist in mouse models of infection. In this review, we will discuss how this type of interaction between B. cenocepacia and host may lead to persistence of bacteria and contribute to lung inflammation in CF patients.

  4. Host defences against Giardia lamblia.

    Science.gov (United States)

    Lopez-Romero, G; Quintero, J; Astiazarán-García, H; Velazquez, C

    2015-08-01

    Giardia spp. is a protozoan parasite that inhabits the upper small intestine of mammals and other species and is the aetiological agent of giardiasis. It has been demonstrated that nitric oxide, mast cells and dendritic cells are the first line of defence against Giardia. IL-6 and IL-17 play an important role during infection. Several cytokines possess overlapping functions in regulating innate and adaptive immune responses. IgA and CD4(+) T cells are fundamental to the process of Giardia clearance. It has been suggested that CD4(+) T cells play a double role during the anti-Giardia immune response. First, they activate and stimulate the differentiation of B cells to generate Giardia-specific antibodies. Second, they act through a B-cell-independent mechanism that is probably mediated by Th17 cells. Several Giardia proteins that stimulate humoral and cellular immune responses have been described. Variant surface proteins, α-1 giardin, and cyst wall protein 2 can induce host protective responses to future Giardia challenges. The characterization and evaluation of the protective potential of the immunogenic proteins that are associated with Giardia will offer new insights into host-parasite interactions and may aid in the development of an effective vaccine against the parasite. © 2015 John Wiley & Sons Ltd.

  5. Ability of a Generalist Seed Beetle to Colonize an Exotic Host: Effects of Host Plant Origin and Oviposition Host.

    Science.gov (United States)

    Amarillo-Suárez, A; Repizo, A; Robles, J; Diaz, J; Bustamante, S

    2017-02-02

    The colonization of an exotic species by native herbivores is more likely to occur if that herbivore is a generalist. There is little information on the life-history mechanisms used by native generalist insects to colonize exotic hosts and how these mechanisms are affected by host properties. We examined the ability of the generalist seed beetle Stator limbatus Horn to colonize an exotic species. We compared its host preference, acceptability, performance, and egg size when ovipositing and developing on two native (Pithecellobium dulce (Roxb.) Benth and Senegalia riparia (Kunth)) and one exotic legume species (Leucaena leucocephala (Lam.)). We also analyzed the seed chemistry. We found that females recognize the exotic species as an unfavorable host for larval development and that they delayed oviposition and laid fewer and larger eggs on the exotic species than on the native species. Survivorship on the exotic host was 0%. Additionally, seeds of the native species contain five chemical compounds that are absent in the exotic species, and the exotic species contains three sterols, which are absent in the native legumes. Genetically based differences between beetles adapted to different hosts, plastic responses toward new hosts, and chemical differences among seeds are important in host colonization and recognition of the exotic host. In conclusion, the generalist nature of S. limbatus does not influence its ability to colonize L. leucocephala. Explanations for the colonization of exotic hosts by generalist native species and for the success of invasive species must be complemented with studies measuring local adaptation and plasticity.

  6. Genetic architecture underlying host choice differentiation in the sympatric host races of Lochmaea capreae leaf beetles.

    Science.gov (United States)

    Soudi, Shaghayegh; Reinhold, Klaus; Engqvist, Leif

    2016-04-01

    Speciation in herbivorous insects has received considerable attention during the last few decades. Much of this group's diversity originates from adaptive population divergence onto different host plants, which often involves the evolution of specialized patterns of host choice behaviour. Differences in host choice often translates directly into divergence in mating sites, and therefore positive assortative mating will be created which will act as a strong barrier to gene flow. In this study, we first explored whether host choice is a genetically determined trait in the sympatric willow and birch host races of the leaf feeding beetle Lochmaea capreae, or whether larval experience influences adult host choice. Once we had established that host choice is a genetically based trait we determined its genetic architecture. To achieve this, we employed a reciprocal transplant design in which offspring from pure willow and birch cross-types, F1, F2 and backcrosses were raised on each host plant and their preference was determined upon reaching adulthood. We then applied joint-scaling analysis to uncover the genetic architecture of host preference. Our results suggest that rearing host does not have a pronounced effect on adult's host choice; rather the segregation pattern implies the existence of genetic loci affecting host choice in these host races. The joint-scaling analysis revealed that population differences in host choice are mainly influenced by the contribution of additive genetic effects and also maternally inherited cytoplasmic effects. We explore the implications of our findings for evolutionary dynamics of sympatric host race formation and speciation.

  7. Anonymous Web Browsing and Hosting

    Directory of Open Access Journals (Sweden)

    MANOJ KUMAR

    2013-02-01

    Full Text Available In today’s high tech environment every organization, individual computer users use internet for accessing web data. To maintain high confidentiality and security of the data secure web solutions are required. In this paper we described dedicated anonymous web browsing solutions which makes our browsing faster and secure. Web application which play important role for transferring our secret information including like email need more and more security concerns. This paper also describes that how we can choose safe web hosting solutions and what the main functions are which provides more security over server data. With the browser security network security is also important which can be implemented using cryptography solutions, VPN and by implementing firewalls on the network. Hackers always try to steal our identity and data, they track our activities using the network application software’s and do harmful activities. So in this paper we described that how we can monitor them from security purposes.

  8. Penetration of Bdellovibrio bacteriovorus into host cells.

    Science.gov (United States)

    Abram, D; Castro e Melo, J; Chou, D

    1974-05-01

    Electron microscopy reveals that, in Bdellovibrio infection, after the formation of a passage pore in the host cell wall, the differentiated parasite penetration pole is associated with the host protoplast. This firm contact persists throughout the parasite penetration and after this process is completed. In penetrated hosts this contact is also apparent by phase microscopy. The association between the walls of the parasite and the host at the passage pore, on the other hand, is transient. Bdellovibrio do not penetrate hosts whose protoplast and cell walls are separated by plasmolysis, or in which the membrane-wall relationship is affected by low turgor pressure. It is concluded, therefore, that for penetration to occur it is essential that the host protoplast be within reach of the parasite, so that a firm contact can be established between them. A penetration mechanism is proposed that is effected by forces generated by fluxes of water and solutes due to structural changes in the infected host envelope. These forces cause a differential expansion of the host protoplast and cell wall and their separation from each other around the entry site, while the parasite remains firmly anchored to the host protoplast. Consequently, the parasite ends up enclosed in the expanded host periplasm. The actual entry, therefore, is a passive act of the parasite.

  9. MHC polymorphism under host-pathogen coevolution.

    Science.gov (United States)

    Borghans, José A M; Beltman, Joost B; De Boer, Rob J

    2004-02-01

    The genes encoding major histocompatibility (MHC) molecules are among the most polymorphic genes known for vertebrates. Since MHC molecules play an important role in the induction of immune responses, the evolution of MHC polymorphism is often explained in terms of increased protection of hosts against pathogens. Two selective pressures that are thought to be involved are (1) selection favoring MHC heterozygous hosts, and (2) selection for rare MHC alleles by host-pathogen coevolution. We have developed a computer simulation of coevolving hosts and pathogens to study the relative impact of these two mechanisms on the evolution of MHC polymorphism. We found that heterozygote advantage per se is insufficient to explain the high degree of polymorphism at the MHC, even in very large host populations. Host-pathogen coevolution, on the other hand, can easily account for realistic polymorphisms of more than 50 alleles per MHC locus. Since evolving pathogens mainly evade presentation by the most common MHC alleles in the host population, they provide a selective pressure for a large variety of rare MHC alleles. Provided that the host population is sufficiently large, a large set of MHC alleles can persist over many host generations under host-pathogen coevolution, despite the fact that allele frequencies continuously change.

  10. Tree spatial structure, host composition and resource availability influence mirid density or black pod prevalence in cacao agroforests in Cameroon.

    Science.gov (United States)

    Gidoin, Cynthia; Babin, Régis; Bagny Beilhe, Leïla; Cilas, Christian; ten Hoopen, Gerben Martijn; Bieng, Marie Ange Ngo

    2014-01-01

    Combining crop plants with other plant species in agro-ecosystems is one way to enhance ecological pest and disease regulation mechanisms. Resource availability and microclimatic variation mechanisms affect processes related to pest and pathogen life cycles. These mechanisms are supported both by empirical research and by epidemiological models, yet their relative importance in a real complex agro-ecosystem is still not known. Our aim was thus to assess the independent effects and the relative importance of different variables related to resource availability and microclimatic variation that explain pest and disease occurrence at the plot scale in real complex agro-ecosystems. The study was conducted in cacao (Theobroma cacao) agroforests in Cameroon, where cocoa production is mainly impacted by the mirid bug, Sahlbergella singularis, and black pod disease, caused by Phytophthora megakarya. Vegetation composition and spatial structure, resource availability and pest and disease occurrence were characterized in 20 real agroforest plots. Hierarchical partitioning was used to identify the causal variables that explain mirid density and black pod prevalence. The results of this study show that cacao agroforests can be differentiated on the basis of vegetation composition and spatial structure. This original approach revealed that mirid density decreased when a minimum number of randomly distributed forest trees were present compared with the aggregated distribution of forest trees, or when forest tree density was low. Moreover, a decrease in mirid density was also related to decreased availability of sensitive tissue, independently of the effect of forest tree structure. Contrary to expectations, black pod prevalence decreased with increasing cacao tree abundance. By revealing the effects of vegetation composition and spatial structure on mirids and black pod, this study opens new perspectives for the joint agro-ecological management of cacao pests and diseases at the

  11. Local host specialization, host-switching, and dispersal shape the regional distributions of avian haemosporidian parasites.

    Science.gov (United States)

    Ellis, Vincenzo A; Collins, Michael D; Medeiros, Matthew C I; Sari, Eloisa H R; Coffey, Elyse D; Dickerson, Rebecca C; Lugarini, Camile; Stratford, Jeffrey A; Henry, Donata R; Merrill, Loren; Matthews, Alix E; Hanson, Alison A; Roberts, Jackson R; Joyce, Michael; Kunkel, Melanie R; Ricklefs, Robert E

    2015-09-08

    The drivers of regional parasite distributions are poorly understood, especially in comparison with those of free-living species. For vector-transmitted parasites, in particular, distributions might be influenced by host-switching and by parasite dispersal with primary hosts and vectors. We surveyed haemosporidian blood parasites (Plasmodium and Haemoproteus) of small land birds in eastern North America to characterize a regional parasite community. Distributions of parasite populations generally reflected distributions of their hosts across the region. However, when the interdependence between hosts and parasites was controlled statistically, local host assemblages were related to regional climatic gradients, but parasite assemblages were not. Moreover, because parasite assemblage similarity does not decrease with distance when controlling for host assemblages and climate, parasites evidently disperse readily within the distributions of their hosts. The degree of specialization on hosts varied in some parasite lineages over short periods and small geographic distances independently of the diversity of available hosts and potentially competing parasite lineages. Nonrandom spatial turnover was apparent in parasite lineages infecting one host species that was well-sampled within a single year across its range, plausibly reflecting localized adaptations of hosts and parasites. Overall, populations of avian hosts generally determine the geographic distributions of haemosporidian parasites. However, parasites are not dispersal-limited within their host distributions, and they may switch hosts readily.

  12. Salmonella - at home in the host cell.

    Directory of Open Access Journals (Sweden)

    Preeti eMalik Kale

    2011-06-01

    Full Text Available The Gram-negative bacterium Salmonella enterica has developed an array of sophisticated tools to manipulate the host cell and establish an intracellular niche, for successful propagation as a facultative intracellular pathogen. While Salmonella exerts diverse effects on its host cell, only the cell biology of the classic trigger-mediated invasion process and the subsequent development of the Salmonella-containing vacuole have been investigated extensively. These processes are dependent on cohorts of effector proteins translocated into host cells by two type III secretion systems (T3SS, although T3SS-independent mechanisms of entry may be important for invasion of certain host cell-types. Recent studies into the intracellular lifestyle of Salmonella have provided new insights into the mechanisms used by this pathogen to modulate its intracellular environment. Here we discuss current knowledge of Salmonella-host interactions including invasion and establishment of an intracellular niche within the host.

  13. Host country language ability and expatriate adjustment

    DEFF Research Database (Denmark)

    Selmer, Jan; Lauring, Jakob

    2015-01-01

    Research has shown that expatriates’ host country language ability is positively associated with their adjustment. But does the advantage of expatriates’ language ability depend on the difficulty of the host language? To examine this issue, data were collected from expatriates in two European...... countries, one with an easy, relatively simple language and the other with a difficult, highly complex language. Consistent with Goal-Setting Theory, results indicated a relative advantage of expatriates’ language ability in terms of their adjustment in the host country with the difficult language...... as opposed to the host country with an easy language....

  14. Expatriate contact with a local host

    DEFF Research Database (Denmark)

    van Bakel, Marian; van Oudenhoven, Jan Pieter; Gerritsen, Marinel

    2017-01-01

    Social capital is a crucial factor for expatriates to employ as they cope with the demands of an international assignment. This longitudinal study used a mixed method approach to examine the social support benefits of expatriate contact with a local host. Western expatriates in the Netherlands were...... a host. This study shows that HRD professionals may develop the social capital of expatriates by bringing them into contact with a local host, which can produce more social support from host nationals. Increased social capital may lead to a higher performance at both the individual and organisational...

  15. Expatriate contact with a local host

    DEFF Research Database (Denmark)

    van Bakel, Marian; van Oudenhoven, Jan Pieter; Gerritsen, Marinel

    2016-01-01

    Social capital is a crucial factor for expatriates to employ as they cope with the demands of an international assignment. This longitudinal study used a mixed method approach to examine the social support benefits of expatriate contact with a local host. Western expatriates in the Netherlands were...... a host. This study shows that HRD professionals may develop the social capital of expatriates by bringing them into contact with a local host, which can produce more social support from host nationals. Increased social capital may lead to a higher performance at both the individual and organisational...

  16. Host Galaxy Identification for Supernova Surveys

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Ravi R.; Kuhlmann, Steve; Kovacs, Eve; Spinka, Harold; Kessler, Richard; Goldstein, Daniel A.; Liotine, Camille; Pomian, Katarzyna; D’Andrea, Chris B.; Sullivan, Mark; Carretero, Jorge; Castander, Francisco J.; Nichol, Robert C.; Finley, David A.; Fischer, John A.; Foley, Ryan J.; Kim, Alex G.; Papadopoulos, Andreas; Sako, Masao; Scolnic, Daniel M.; Smith, Mathew; Tucker, Brad E.; Uddin, Syed; Wolf, Rachel C.; Yuan, Fang; Abbott, Tim M. C.; Abdalla, Filipe B.; Benoit-Lévy, Aurélien; Bertin, Emmanuel; Brooks, David; Rosell, Aurelio Carnero; Kind, Matias Carrasco; Cunha, Carlos E.; Costa, Luiz N. da; Desai, Shantanu; Doel, Peter; Eifler, Tim F.; Evrard, August E.; Flaugher, Brenna; Fosalba, Pablo; Gaztañaga, Enrique; Gruen, Daniel; Gruendl, Robert; James, David J.; Kuehn, Kyler; Kuropatkin, Nikolay; Maia, Marcio A. G.; Marshall, Jennifer L.; Miquel, Ramon; Plazas, Andrés A.; Romer, A. Kathy; Sánchez, Eusebio; Schubnell, Michael; Sevilla-Noarbe, Ignacio; Sobreira, Flávia; Suchyta, Eric; Swanson, Molly E. C.; Tarle, Gregory; Walker, Alistair R.; Wester, William

    2016-11-08

    Host galaxy identification is a crucial step for modern supernova (SN) surveys such as the Dark Energy Survey (DES) and the Large Synoptic Survey Telescope (LSST), which will discover SNe by the thousands. Spectroscopic resources are limited, so in the absence of real-time SN spectra these surveys must rely on host galaxy spectra to obtain accurate redshifts for the Hubble diagram and to improve photometric classification of SNe. In addition, SN luminosities are known to correlate with host-galaxy properties. Therefore, reliable identification of host galaxies is essential for cosmology and SN science. We simulate SN events and their locations within their host galaxies to develop and test methods for matching SNe to their hosts. We use both real and simulated galaxy catalog data from the Advanced Camera for Surveys General Catalog and MICECATv2.0, respectively. We also incorporate "hostless" SNe residing in undetected faint hosts into our analysis, with an assumed hostless rate of 5%. Our fully automated algorithm is run on catalog data and matches SNe to their hosts with 91% accuracy. We find that including a machine learning component, run after the initial matching algorithm, improves the accuracy (purity) of the matching to 97% with a 2% cost in efficiency (true positive rate). Although the exact results are dependent on the details of the survey and the galaxy catalogs used, the method of identifying host galaxies we outline here can be applied to any transient survey.

  17. Host Galaxy Identification for Supernova Surveys

    Science.gov (United States)

    Gupta, Ravi R.; Kuhlmann, Steve; Kovacs, Eve; Spinka, Harold; Kessler, Richard; Goldstein, Daniel A.; Liotine, Camille; Pomian, Katarzyna; D'Andrea, Chris B.; Sullivan, Mark; Carretero, Jorge; Castander, Francisco J.; Nichol, Robert C.; Finley, David A.; Fischer, John A.; Foley, Ryan J.; Kim, Alex G.; Papadopoulos, Andreas; Sako, Masao; Scolnic, Daniel M.; Smith, Mathew; Tucker, Brad E.; Uddin, Syed; Wolf, Rachel C.; Yuan, Fang; Abbott, Tim M. C.; Abdalla, Filipe B.; Benoit-Lévy, Aurélien; Bertin, Emmanuel; Brooks, David; Carnero Rosell, Aurelio; Carrasco Kind, Matias; Cunha, Carlos E.; da Costa, Luiz N.; Desai, Shantanu; Doel, Peter; Eifler, Tim F.; Evrard, August E.; Flaugher, Brenna; Fosalba, Pablo; Gaztañaga, Enrique; Gruen, Daniel; Gruendl, Robert; James, David J.; Kuehn, Kyler; Kuropatkin, Nikolay; Maia, Marcio A. G.; Marshall, Jennifer L.; Miquel, Ramon; Plazas, Andrés A.; Romer, A. Kathy; Sánchez, Eusebio; Schubnell, Michael; Sevilla-Noarbe, Ignacio; Sobreira, Flávia; Suchyta, Eric; Swanson, Molly E. C.; Tarle, Gregory; Walker, Alistair R.; Wester, William

    2016-12-01

    Host galaxy identification is a crucial step for modern supernova (SN) surveys such as the Dark Energy Survey and the Large Synoptic Survey Telescope, which will discover SNe by the thousands. Spectroscopic resources are limited, and so in the absence of real-time SN spectra these surveys must rely on host galaxy spectra to obtain accurate redshifts for the Hubble diagram and to improve photometric classification of SNe. In addition, SN luminosities are known to correlate with host-galaxy properties. Therefore, reliable identification of host galaxies is essential for cosmology and SN science. We simulate SN events and their locations within their host galaxies to develop and test methods for matching SNe to their hosts. We use both real and simulated galaxy catalog data from the Advanced Camera for Surveys General Catalog and MICECATv2.0, respectively. We also incorporate “hostless” SNe residing in undetected faint hosts into our analysis, with an assumed hostless rate of 5%. Our fully automated algorithm is run on catalog data and matches SNe to their hosts with 91% accuracy. We find that including a machine learning component, run after the initial matching algorithm, improves the accuracy (purity) of the matching to 97% with a 2% cost in efficiency (true positive rate). Although the exact results are dependent on the details of the survey and the galaxy catalogs used, the method of identifying host galaxies we outline here can be applied to any transient survey.

  18. Host Galaxy Identification for Supernova Surveys

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Ravi R.; et al.

    2016-04-20

    Host galaxy identification is a crucial step for modern supernova (SN) surveys such as the Dark Energy Survey (DES) and the Large Synoptic Survey Telescope (LSST), which will discover SNe by the thousands. Spectroscopic resources are limited, so in the absence of real-time SN spectra these surveys must rely on host galaxy spectra to obtain accurate redshifts for the Hubble diagram and to improve photometric classification of SNe. In addition, SN luminosities are known to correlate with host-galaxy properties. Therefore, reliable identification of host galaxies is essential for cosmology and SN science. We simulate SN events and their locations within their host galaxies to develop and test methods for matching SNe to their hosts. We use both real and simulated galaxy catalog data from the Advanced Camera for Surveys General Catalog and MICECATv2.0, respectively. We also incorporate "hostless" SNe residing in undetected faint hosts into our analysis, with an assumed hostless rate of 5%. Our fully automated algorithm is run on catalog data and matches SNe to their hosts with 91% accuracy. We find that including a machine learning component, run after the initial matching algorithm, improves the accuracy (purity) of the matching to 97% with a 2% cost in efficiency (true positive rate). Although the exact results are dependent on the details of the survey and the galaxy catalogs used, the method of identifying host galaxies we outline here can be applied to any transient survey.

  19. Host plant adaptation in Drosophila mettleri populations.

    Directory of Open Access Journals (Sweden)

    Sergio Castrezana

    Full Text Available The process of local adaptation creates diversity among allopatric populations, and may eventually lead to speciation. Plant-feeding insect populations that specialize on different host species provide an excellent opportunity to evaluate the causes of ecological specialization and the subsequent consequences for diversity. In this study, we used geographically separated Drosophila mettleri populations that specialize on different host cacti to examine oviposition preference for and larval performance on an array of natural and non-natural hosts (eight total. We found evidence of local adaptation in performance on saguaro cactus (Carnegiea gigantea for populations that are typically associated with this host, and to chemically divergent prickly pear species (Opuntia spp. in a genetically isolated population on Santa Catalina Island. Moreover, each population exhibited reduced performance on the alternative host. This finding is consistent with trade-offs associated with adaptation to these chemically divergent hosts, although we also discuss alternative explanations for this pattern. For oviposition preference, Santa Catalina Island flies were more likely to oviposit on some prickly pear species, but all populations readily laid eggs on saguaro. Experiments with non-natural hosts suggest that factors such as ecological opportunity may play a more important role than host plant chemistry in explaining the lack of natural associations with some hosts.

  20. Critical rearing parameters of Tetrastichus planipennisi (Hymenoptera: Eulophidae) as affected by host plant substrate and host-parasitoid group structure.

    Science.gov (United States)

    Duan, Jian J; Oppel, Craig

    2012-06-01

    In laboratory assays, we evaluated the potential impact of host plant substrate types, host-parasitoid group sizes (densities), and parasitoid-to-host ratios on select fitness parameters of the larval endoparasitoid Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae), newly introduced for biological control of emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), in the United States. Results from our study showed that offspring production and critical fitness parameters (body size and sex ratio) of T. planipennisi from parasitized emerald ash borer larvae are significantly influenced by host plant substrate type, host-parasitoid group size, parasitoid-to-host ratio, or a combination in the primary exposure assay. The number of both female and male T. planipennisi progeny was significantly greater when emerald ash borer larvae were inserted into tropical ash [Fraxinus uhdei (Wenz.) Lingelsh.] logs rather than green ash (Fraxinus pensylvanica Marshall). When maintained at a constant 1:1 parasitoid-to-host ratio, assays with larger host-parasitoid group sizes (3:3-12:12) produced significantly greater numbers of both male and female offspring per parental wasp compared with those with the single host-parasitoid (1:1) group treatment. As the parasitoid-to-host ratio increased from 1:1 to 8:1 in the assay, the average brood size (number of offspring per parasitized emerald ash borer larva) increased significantly, whereas the average brood sex ratio (female to male) changed from being female-biased (6:1) to male-biased (1:2); body size of female offspring as measured by the length of ovipositor and left hind tibia also was reduced significantly. Based on these findings, we suggest that the current method of rearing T. planipennisi with artificially infested-emerald ash borer larvae use the tropical ash logs for emerald ash borer insertion, a larger (> or = 3:3) host-parasitoid group size and 1:1 parasitoid-to-host ratio in the primary

  1. Unexpected hosts: imaging parasitic diseases.

    Science.gov (United States)

    Rodríguez Carnero, Pablo; Hernández Mateo, Paula; Martín-Garre, Susana; García Pérez, Ángela; Del Campo, Lourdes

    2017-02-01

    Radiologists seldom encounter parasitic diseases in their daily practice in most of Europe, although the incidence of these diseases is increasing due to migration and tourism from/to endemic areas. Moreover, some parasitic diseases are still endemic in certain European regions, and immunocompromised individuals also pose a higher risk of developing these conditions. This article reviews and summarises the imaging findings of some of the most important and frequent human parasitic diseases, including information about the parasite's life cycle, pathophysiology, clinical findings, diagnosis, and treatment. We include malaria, amoebiasis, toxoplasmosis, trypanosomiasis, leishmaniasis, echinococcosis, cysticercosis, clonorchiasis, schistosomiasis, fascioliasis, ascariasis, anisakiasis, dracunculiasis, and strongyloidiasis. The aim of this review is to help radiologists when dealing with these diseases or in cases where they are suspected. Teaching Points • Incidence of parasitic diseases is increasing due to migratory movements and travelling. • Some parasitic diseases are still endemic in certain regions in Europe. • Parasitic diseases can have complex life cycles often involving different hosts. • Prompt diagnosis and treatment is essential for patient management in parasitic diseases. • Radiologists should be able to recognise and suspect the most relevant parasitic diseases.

  2. The path to host extinction can lead to loss of generalist parasites.

    Science.gov (United States)

    Farrell, Maxwell J; Stephens, Patrick R; Berrang-Ford, Lea; Gittleman, John L; Davies, T Jonathan

    2015-07-01

    Host extinction can alter disease transmission dynamics, influence parasite extinction and ultimately change the nature of host-parasite systems. While theory predicts that single-host parasites are among the parasite species most susceptible to extinction following declines in their hosts, documented parasite extinctions are rare. Using a comparative approach, we investigate how the richness of single-host and multi-host parasites is influenced by extinction risk among ungulate and carnivore hosts. Host-parasite associations for free-living carnivores (order Carnivora) and terrestrial ungulates (orders Perissodactyla + Cetartiodactyla minus cetaceans) were merged with host trait data and IUCN Red List status to explore the distribution of single-host and multi-host parasites among threatened and non-threatened hosts. We find that threatened ungulates harbour a higher proportion of single-host parasites compared to non-threatened ungulates, which is explained by decreases in the richness of multi-host parasites. However, among carnivores threat status is not a significant predictor of the proportion of single-host parasites, or the richness of single-host or multi-host parasites. The loss of multi-host parasites from threatened ungulates may be explained by decreased cross-species contact as hosts decline and habitats become fragmented. Among carnivores, threat status may not be important in predicting patterns of parasite specificity because host decline results in equal losses of both single-host parasites and multi-host parasites through reduction in average population density and frequency of cross-species contact. Our results contrast with current models of parasite coextinction and highlight the need for updated theories that are applicable across host groups and account for both inter- and intraspecific contact.

  3. Cosmological Inference from Host-Selected Type Ia Supernova Samples

    Science.gov (United States)

    Uddin, Syed A.; Mould, Jeremy; Lidman, Chris; Ruhlmann-Kleider, Vanina; Hardin, Delphine

    2017-01-01

    We compare two Type Ia supernova samples that are drawn from a spectroscopically confirmed Type Ia supernova sample: a host-selected sample in which SNe Ia are restricted to those that have a spectroscopic redshift from the host; and a broader, more traditional sample in which the redshift could come from either the SN or the host. The host-selected sample is representative of SN samples that will use the redshift of the host to infer the SN redshift, long after the SN has faded from view. We find that SNe Ia that are selected on the availability of a redshift from the host differ from SNe Ia that are from the broader sample. The former tend to be redder, have narrower light curves, live in more massive hosts, and tend to be at lower redshifts. We find that constraints on the equation of state of dark energy, w, and the matter density, ΩM, remain consistent between these two types of samples. Our results are important for ongoing and future supernova surveys, which unlike previous supernova surveys, will have limited real-time follow-up to spectroscopically classify the SNe they discover. Most of the redshifts in these surveys will come from the hosts.

  4. Nestedness of ectoparasite-vertebrate host networks.

    Directory of Open Access Journals (Sweden)

    Sean P Graham

    Full Text Available Determining the structure of ectoparasite-host networks will enable disease ecologists to better understand and predict the spread of vector-borne diseases. If these networks have consistent properties, then studying the structure of well-understood networks could lead to extrapolation of these properties to others, including those that support emerging pathogens. Borrowing a quantitative measure of network structure from studies of mutualistic relationships between plants and their pollinators, we analyzed 29 ectoparasite-vertebrate host networks--including three derived from molecular bloodmeal analysis of mosquito feeding patterns--using measures of nestedness to identify non-random interactions among species. We found significant nestedness in ectoparasite-vertebrate host lists for habitats ranging from tropical rainforests to polar environments. These networks showed non-random patterns of nesting, and did not differ significantly from published estimates of nestedness from mutualistic networks. Mutualistic and antagonistic networks appear to be organized similarly, with generalized ectoparasites interacting with hosts that attract many ectoparasites and more specialized ectoparasites usually interacting with these same "generalized" hosts. This finding has implications for understanding the network dynamics of vector-born pathogens. We suggest that nestedness (rather than random ectoparasite-host associations can allow rapid transfer of pathogens throughout a network, and expand upon such concepts as the dilution effect, bridge vectors, and host switching in the context of nested ectoparasite-vertebrate host networks.

  5. Host-pathogen interactions during apoptosis

    Indian Academy of Sciences (India)

    Seyed E Hasnain; Rasheeda Begum; K V A Ramaiah; Sudhir Sahdev; E M Shajil; Tarvinder K Taneja; Manjari Mohan; M Athar; Nand K Sah; M Krishnaveni

    2003-04-01

    Host pathogen interaction results in a variety of responses, which include phagocytosis of the pathogen, release of cytokines, secretion of toxins, as well as production of reactive oxygen species (ROS). Recent studies have shown that many pathogens exert control on the processes that regulate apoptosis in the host. The induction of apoptosis upon infection results from a complex interaction of parasite proteins with cellular host proteins. Abrogation of host cell apoptosis is often beneficial for the pathogen and results in a successful host invasion. However, in some cases, it has been shown that induction of apoptosis in the infected cells significantly imparts protection to the host from the pathogen. There is a strong correlation between apoptosis and the host protein translation machinery: the pathogen makes all possible efforts to modify this process so as to inhibit cell suicide and ensure that it can survive and, in some cases, establish latent infection. This review discusses the significance of various pathways/steps during virus-mediated modulation of host cell apoptosis.

  6. Warfare between Host Immunity and Bacterial Weapons.

    Science.gov (United States)

    Yu, Manda; Lai, Erh-Min

    2017-01-11

    Bacterial pathogens deploy protein secretion systems to facilitate infection and colonization of their hosts. In this issue of Cell Host & Microbe, Chen et al. (2017) report a new role for a type VI secretion effector in promoting bacterial colonization by preventing inflammasome activation induced by a type III secretion system. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Host preferences of blood-feeding mosquitoes

    NARCIS (Netherlands)

    Takken, W.; Verhulst, N.O.

    2013-01-01

    Mosquitoes use plant sugars and vertebrate blood as nutritional resources. When searching for blood hosts, some mosquitoes express preferential behavior for selected species. Here, we review the available knowledge on host preference, as this is expected to affect the life history and transmission

  8. From Dietary Fiber to Host Physiology

    DEFF Research Database (Denmark)

    Koh, Ara; De Vadder, Filipe; Kovatcheva-Datchary, Petia

    2016-01-01

    A compelling set of links between the composition of the gut microbiota, the host diet, and host physiology has emerged. Do these links reflect cause-and-effect relationships, and what might be their mechanistic basis? A growing body of work implicates microbially produced metabolites as crucial...

  9. The Extreme Hosts of Extreme Supernovae

    CERN Document Server

    Neill, James D; Gal-Yam, Avishay; Quimby, Robert; Ofek, Eran; Wyder, Ted K; Howell, D Andrew; Nugent, Peter; Seibert, Mark; Martin, D Christopher; Overzier, Roderik; Barlow, Tom A; Foster, Karl; Friedman, Peter G; Morrissey, Patrick; Neff, Susan G; Schiminovich, David; Bianchi, Luciana; Donas, José; Heckman, Timothy M; Lee, Young-Wook; Madore, Barry F; Milliard, Bruno; Rich, R Michael; Szalay, Alex S

    2010-01-01

    We use GALEX ultraviolet (UV) and optical integrated photometry of the hosts of seventeen luminous supernovae (LSNe, having peak M_V 100 M_sun), by appearing in low-SFR hosts, are potential tests for theories of the initial mass function that limit the maximum mass of a star based on the S FR.

  10. Quantifying Heterogeneity in Host-Vector Contact: Tsetse (Glossina swynnertoni and G. pallidipes) Host Choice in Serengeti National Park, Tanzania

    Science.gov (United States)

    Auty, Harriet; Cleaveland, Sarah; Malele, Imna; Masoy, Joseph; Lembo, Tiziana; Bessell, Paul; Torr, Stephen; Picozzi, Kim; Welburn, Susan C.

    2016-01-01

    Background Identifying hosts of blood-feeding insect vectors is crucial in understanding their role in disease transmission. Rhodesian human African trypanosomiasis (rHAT), also known as acute sleeping sickness is caused by Trypanosoma brucei rhodesiense and transmitted by tsetse flies. The disease is commonly associated with wilderness areas of east and southern Africa. Such areas hold a diverse range of species which form communities of hosts for disease maintenance. The relative importance of different wildlife hosts remains unclear. This study quantified tsetse feeding preferences in a wilderness area of great host species richness, Serengeti National Park, Tanzania, assessing tsetse feeding and host density contemporaneously. Methods Glossina swynnertoni and G. pallidipes were collected from six study sites. Bloodmeal sources were identified through matching Cytochrome B sequences amplified from bloodmeals from recently fed flies to published sequences. Densities of large mammal species in each site were quantified, and feeding indices calculated to assess the relative selection or avoidance of each host species by tsetse. Results The host species most commonly identified in G. swynnertoni bloodmeals, warthog (94/220), buffalo (48/220) and giraffe (46/220), were found at relatively low densities (3-11/km2) and fed on up to 15 times more frequently than expected by their relative density. Wildebeest, zebra, impala and Thomson’s gazelle, found at the highest densities, were never identified in bloodmeals. Commonly identified hosts for G. pallidipes were buffalo (26/46), giraffe (9/46) and elephant (5/46). Conclusions This study is the first to quantify tsetse host range by molecular analysis of tsetse diet with simultaneous assessment of host density in a wilderness area. Although G. swynnertoni and G. pallidipes can feed on a range of species, they are highly selective. Many host species are rarely fed on, despite being present in areas where tsetse are

  11. The Role of Within-Host Competition for Coexistence in Multiparasitoid-Host Systems.

    Science.gov (United States)

    van Velzen, Ellen; Pérez-Vila, Saleta; Etienne, Rampal S

    2016-01-01

    Multiparasitism (females of multiple species parasitizing the same host) is a ubiquitous phenomenon in parasitoids, yet the role of within-host competition has been mostly ignored in multiparasitoid-host models. Here we study the effect of varying the degree of competition at different life stages: competition over oviposition sites (between-adult competition) and larval competition over resources within the host (within-host competition). We adapt a Nicholson-Bailey model to allow for varying levels of between-adult competition (varying the overlap in species distributions) and within-host competition (varying the number of offspring that can successfully emerge from a host). Surprisingly, while stronger between-adult competition reduces coexistence, stronger within-host competition promotes it. Asymmetric between-adult competition (a fecundity difference between the two species) reduces coexistence when compared to symmetric competition; this can be counteracted by asymmetric within-host competition (within-host competitive advantage of the lower-fecundity species), but only when within-host competition is strong and the correlation between the parasitoids' distributions is intermediate. We discuss our results in the context of the interaction between two parasitoid species, Nasonia vitripennis and Nasonia giraulti, which have strongly correlated distributions and high levels of multiparasitism in the field. We conclude that either low or asymmetric within-host competition is unlikely to explain their coexistence.

  12. Magnetism and activity of planet hosting stars

    Science.gov (United States)

    Wright, Jason T.; Miller, Brendan P.

    The magnetic activity levels of planet host stars may differ from that of stars not known to host planets in several ways. Hot Jupiters may induce activity in their hosts through magnetic interactions, or through tidal interactions by affecting their host's rotation or convection. Measurements of photospheric, chromospheric, or coronal activity might then be abnormally high or low compared to control stars that do not host hot Jupiters, or might be modulated at the planet's orbital period. Such detections are complicated by the small amplitude of the expected signal, by the fact that the signals may be transient, and by the difficulty of constructing control samples due to exoplanet detection biases and the uncertainty of field star ages. We review these issues, and discuss avenues for future progress in the field.

  13. Host range of meliolaceous fungi in India

    Directory of Open Access Journals (Sweden)

    V.B. Hosagoudar

    2009-05-01

    Full Text Available The order Meliolales comprises two families, namely, Armatellaceae and Meliolaceae. Except the genera Endomeliola and Pauhia, India represents rest of the nine genera of this group. The family Armatellaceae includes two genera, namely, Armatella and Basavamyces. The family Meliolaceae includes seven genera: Amazonia, Appendiculella, Asteridiella, Ectendomeliola, Irenopsis, Meliola and Prataprajella. All these nine genera represent 613 species and infra-specific taxa known till the year 2006, infected 766 host plants belonging to 349 host genera distributed among 104 families. All the host families and the fungal genera are arranged alphabetically with their corresponding parasite and the host plant. The corresponding number after the host family represents the number of meliolaceous taxa known on the members of that family.

  14. The population density of Lymnaea columella (Say, 1817) (Mollusca, Lymnaeidae) an intermediate host of Fasciola hepatica (Linnaeus, 1758), in the Caparaó microregion, ES, Brazil.

    Science.gov (United States)

    D'Almeida, S C G; Freitas, D F; Carneiro, M B; Camargo, P F; Azevedo, J C; Martins, I V F

    2016-06-01

    The aim of this study was to monitor the population density of Lymnaea columella, an intermediate host of Fasciola hepatica, in various aquatic habitats and in drinking water in the area of the Instituto Federal de Educação, Ciência e Tecnologia do Espírito Santo, on Caparaó Microregion, municipality of Alegre, state of Espírito Santo, Brazil. Monthly samplings were performed at certain points between drainage areas and drinking water in cattle and goat production systems during the years 2010 to 2013. The mean temperature, precipitation and the frequency of samples of L. columella were analysed graphically according the monthly average during the study period. A total of 2,038 molluscs were collected, 1558 of which were L. columella, that predominated in all sampled points. The highest average of specimens observed for L. columella was in the years 2010 and 2013 (51.0), and occurred decreased in 2011 (19.8). The temperature and precipitation averaged is 23.7 °C and 141 mm/year, respectively. Rainfall peak occurred in March (2011, 2013) and November (2012), during these periods the population of L. columella growth. There was no significant difference in the relationship between the specimens observed with seasons (dry-wet), thus the population of L. columella remained stable and can be found throughout the year.

  15. The population density of Lymnaea columella (Say, 1817 (Mollusca, Lymnaeidae an intermediate host of Fasciola hepatica (Linnaeus, 1758, in the Caparaó microregion, ES, Brazil

    Directory of Open Access Journals (Sweden)

    S. C. G. D’Almeida

    Full Text Available Abstract The aim of this study was to monitor the population density of Lymnaea columella, an intermediate host of Fasciola hepatica, in various aquatic habitats and in drinking water in the area of the Instituto Federal de Educação, Ciência e Tecnologia do Espírito Santo, on Caparaó Microregion, municipality of Alegre, state of Espírito Santo, Brazil. Monthly samplings were performed at certain points between drainage areas and drinking water in cattle and goat production systems during the years 2010 to 2013. The mean temperature, precipitation and the frequency of samples of L. columella were analysed graphically according the monthly average during the study period. A total of 2,038 molluscs were collected, 1558 of which were L. columella, that predominated in all sampled points. The highest average of specimens observed for L. columella was in the years 2010 and 2013 (51.0, and occurred decreased in 2011 (19.8. The temperature and precipitation averaged is 23.7 °C and 141 mm/year, respectively. Rainfall peak occurred in March (2011, 2013 and November (2012, during these periods the population of L. columella growth. There was no significant difference in the relationship between the specimens observed with seasons (dry-wet, thus the population of L. columella remained stable and can be found throughout the year.

  16. Codivergence of mycoviruses with their hosts.

    Directory of Open Access Journals (Sweden)

    Markus Göker

    Full Text Available BACKGROUND: The associations between pathogens and their hosts are complex and can result from any combination of evolutionary events such as codivergence, switching, and duplication of the pathogen. Mycoviruses are RNA viruses which infect fungi and for which natural vectors are so far unknown. Thus, lateral transfer might be improbable and codivergence their dominant mode of evolution. Accordingly, mycoviruses are a suitable target for statistical tests of virus-host codivergence, but inference of mycovirus phylogenies might be difficult because of low sequence similarity even within families. METHODOLOGY: We analyzed here the evolutionary dynamics of all mycovirus families by comparing virus and host phylogenies. Additionally, we assessed the sensitivity of the co-phylogenetic tests to the settings for inferring virus trees from their genome sequences and approximate, taxonomy-based host trees. CONCLUSIONS: While sequence alignment filtering modes affected branch support, the overall results of the co-phylogenetic tests were significantly influenced only by the number of viruses sampled per family. The trees of the two largest families, Partitiviridae and Totiviridae, were significantly more similar to those of their hosts than expected by chance, and most individual host-virus links had a significant positive impact on the global fit, indicating that codivergence is the dominant mode of virus diversification. However, in this regard mycoviruses did not differ from closely related viruses sampled from non-fungus hosts. The remaining virus families were either dominated by other evolutionary modes or lacked an apparent overall pattern. As this negative result might be caused by insufficient taxon sampling, the most parsimonious hypothesis still is that host-parasite evolution is basically the same in all mycovirus families. This is the first study of mycovirus-host codivergence, and the results shed light not only on how mycovirus biology

  17. Effect of Intermediate Hosts on Emerging Zoonoses.

    Science.gov (United States)

    Cui, Jing-An; Chen, Fangyuan; Fan, Shengjie

    2017-08-01

    Most emerging zoonotic pathogens originate from animals. They can directly infect humans through natural reservoirs or indirectly through intermediate hosts. As a bridge, an intermediate host plays different roles in the transmission of zoonotic pathogens. In this study, we present three types of pathogen transmission to evaluate the effect of intermediate hosts on emerging zoonotic diseases in human epidemics. These types are identified as follows: TYPE 1, pathogen transmission without an intermediate host for comparison; TYPE 2, pathogen transmission with an intermediate host as an amplifier; and TYPE 3, pathogen transmission with an intermediate host as a vessel for genetic variation. In addition, we established three mathematical models to elucidate the mechanisms underlying zoonotic disease transmission according to these three types. Stability analysis indicated that the existence of intermediate hosts increased the difficulty of controlling zoonotic diseases because of more difficult conditions to satisfy for the disease to die out. The human epidemic would die out under the following conditions: TYPE 1: [Formula: see text] and [Formula: see text]; TYPE 2: [Formula: see text], [Formula: see text], and [Formula: see text]; and TYPE 3: [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] Simulation with similar parameters demonstrated that intermediate hosts could change the peak time and number of infected humans during a human epidemic; intermediate hosts also exerted different effects on controlling the prevalence of a human epidemic with natural reservoirs in different periods, which is important in addressing problems in public health. Monitoring and controlling the number of natural reservoirs and intermediate hosts at the right time would successfully manage and prevent the prevalence of emerging zoonoses in humans.

  18. Uncovering Wolbachia diversity upon artificial host transfer.

    Directory of Open Access Journals (Sweden)

    Daniela I Schneider

    Full Text Available The common endosymbiotic Wolbachia bacteria influence arthropod hosts in multiple ways. They are mostly recognized for their manipulations of host reproduction, yet, more recent studies demonstrate that Wolbachia also impact host behavior, metabolic pathways and immunity. Besides their biological and evolutionary roles, Wolbachia are new potential biological control agents for pest and vector management. Importantly, Wolbachia-based control strategies require controlled symbiont transfer between host species and predictable outcomes of novel Wolbachia-host associations. Theoretically, this artificial horizontal transfer could inflict genetic changes within transferred Wolbachia populations. This could be facilitated through de novo mutations in the novel recipient host or changes of haplotype frequencies of polymorphic Wolbachia populations when transferred from donor to recipient hosts. Here we show that Wolbachia resident in the European cherry fruit fly, Rhagoletis cerasi, exhibit ancestral and cryptic sequence polymorphism in three symbiont genes, which are exposed upon microinjection into the new hosts Drosophila simulans and Ceratitis capitata. Our analyses of Wolbachia in microinjected D. simulans over 150 generations after microinjection uncovered infections with multiple Wolbachia strains in trans-infected lines that had previously been typed as single infections. This confirms the persistence of low-titer Wolbachia strains in microinjection experiments that had previously escaped standard detection techniques. Our study demonstrates that infections by multiple Wolbachia strains can shift in prevalence after artificial host transfer driven by either stochastic or selective processes. Trans-infection of Wolbachia can claim fitness costs in new hosts and we speculate that these costs may have driven the shifts of Wolbachia strains that we saw in our model system.

  19. Host response to biomaterials the impact of host response on biomaterial selection

    CERN Document Server

    Badylak, Stephen F

    2015-01-01

    Host Response to Biomaterials: The Impact of Host Response on Biomaterial Selection explains the various categories of biomaterials and their significance for clinical applications, focusing on the host response to each biomaterial. It is one of the first books to connect immunology and biomaterials with regard to host response. The text also explores the role of the immune system in host response, and covers the regulatory environment for biomaterials, along with the benefits of synthetic versus natural biomaterials, and the transition from simple to complex biomaterial solutions. Fiel

  20. Prediction of HIV-1 virus-host protein interactions using virus and host sequence motifs

    Directory of Open Access Journals (Sweden)

    Tozeren Aydin

    2009-05-01

    Full Text Available Abstract Background Host protein-protein interaction networks are altered by invading virus proteins, which create new interactions, and modify or destroy others. The resulting network topology favors excessive amounts of virus production in a stressed host cell network. Short linear peptide motifs common to both virus and host provide the basis for host network modification. Methods We focused our host-pathogen study on the binding and competing interactions of HIV-1 and human proteins. We showed that peptide motifs conserved across 70% of HIV-1 subtype B and C samples occurred in similar positions on HIV-1 proteins, and we documented protein domains that interact with these conserved motifs. We predicted which human proteins may be targeted by HIV-1 by taking pairs of human proteins that may interact via a motif conserved in HIV-1 and the corresponding interacting protein domain. Results Our predictions were enriched with host proteins known to interact with HIV-1 proteins ENV, NEF, and TAT (p-value Conclusion A list of host proteins highly enriched with those targeted by HIV-1 proteins can be obtained by searching for host protein motifs along virus protein sequences. The resulting set of host proteins predicted to be targeted by virus proteins will become more accurate with better annotations of motifs and domains. Nevertheless, our study validates the role of linear binding motifs shared by virus and host proteins as an important part of the crosstalk between virus and host.

  1. Host Genotype and Coinfection Modify the Relationship of within and between Host Transmission.

    Science.gov (United States)

    Susi, Hanna; Vale, Pedro F; Laine, Anna-Liisa

    2015-08-01

    Variation in individual-level disease transmission is well documented, but the underlying causes of this variation are challenging to disentangle in natural epidemics. In general, within-host replication is critical in determining the extent to which infected hosts shed transmission propagules, but which factors cause variation in this relationship are poorly understood. Here, using a plant host, Plantago lanceolata, and the powdery mildew fungus Podosphaera plantaginis, we quantify how the distinct stages of within-host spread (autoinfection), spore release, and successful transmission to new hosts (alloinfection) are influenced by host genotype, pathogen genotype, and the coinfection status of the host. We find that within-host spread alone fails to predict transmission rates, as this relationship is modified by genetic variation in hosts and pathogens. Their contributions change throughout the course of the epidemic. Host genotype and coinfection had particularly pronounced effects on the dynamics of spore release from infected hosts. Confidently predicting disease spread from local levels of individual transmission, therefore, requires a more nuanced understanding of genotype-specific infection outcomes. This knowledge is key to better understanding the drivers of epidemiological dynamics and the resulting evolutionary trajectories of infectious disease.

  2. Host allometry influences the evolution of parasite host-generalism: theory and meta-analysis

    Science.gov (United States)

    Hurford, Amy; Ellison, Amy R.

    2017-01-01

    Parasites vary widely in the diversity of hosts they infect: some parasite species are specialists—infecting just a single host species, while others are generalists, capable of infecting many. Understanding the factors that drive parasite host-generalism is of basic biological interest, but also directly relevant to predicting disease emergence in new host species, identifying parasites that are likely to have unidentified additional hosts, and assessing transmission risk. Here, we use mathematical models to investigate how variation in host body size and environmental temperature affect the evolution of parasite host-generalism. We predict that parasites are more likely to evolve a generalist strategy when hosts are large-bodied, when variation in host body size is large, and in cooler environments. We then explore these predictions using a newly updated database of over 20 000 fish–macroparasite associations. Within the database we see some evidence supporting these predictions, but also highlight mismatches between theory and data. By combining these two approaches, we establish a theoretical basis for interpreting empirical data on parasites' host specificity and identify key areas for future work that will help untangle the drivers of parasite host-generalism. This article is part of the themed issue ‘Opening the black box: re-examining the ecology and evolution of parasite transmission’. PMID:28289257

  3. Bartonella entry mechanisms into mammalian host cells.

    Science.gov (United States)

    Eicher, Simone C; Dehio, Christoph

    2012-08-01

    The Gram-negative genus Bartonella comprises arthropod-borne pathogens that typically infect mammals in a host-specific manner. Bartonella bacilliformis and Bartonella quintana are human-specific pathogens, while several zoonotic bartonellae specific for diverse animal hosts infect humans as an incidental host. Clinical manifestations of Bartonella infections range from mild symptoms to life-threatening disease. Following transmission by blood-sucking arthropods or traumatic contact with infected animals, bartonellae display sequential tropisms towards endothelial and possibly other nucleated cells and erythrocytes, the latter in a host-specific manner. Attachment to the extracellular matrix (ECM) and to nucleated cells is mediated by surface-exposed bacterial adhesins, in particular trimeric autotransporter adhesins (TAAs). The subsequent engulfment of the pathogen into a vacuolar structure follows a unique series of events whereby the pathogen avoids the endolysosomal compartments. For Bartonella henselae and assumingly most other species, the infection process is aided at different steps by Bartonella effector proteins (Beps). They are injected into host cells through the type IV secretion system (T4SS) VirB/D4 and subvert host cellular functions to favour pathogen uptake. Bacterial binding to erythrocytes is mediated by Trw, another T4SS, in a strictly host-specific manner, followed by pathogen-forced uptake involving the IalB invasin and subsequent replication and persistence within a membrane-bound intra-erythrocytic compartment.

  4. Mechanisms of host seeking by parasitic nematodes.

    Science.gov (United States)

    Gang, Spencer S; Hallem, Elissa A

    2016-07-01

    The phylum Nematoda comprises a diverse group of roundworms that includes parasites of vertebrates, invertebrates, and plants. Human-parasitic nematodes infect more than one billion people worldwide and cause some of the most common neglected tropical diseases, particularly in low-resource countries [1]. Parasitic nematodes of livestock and crops result in billions of dollars in losses each year [1]. Many nematode infections are treatable with low-cost anthelmintic drugs, but repeated infections are common in endemic areas and drug resistance is a growing concern with increasing therapeutic and agricultural administration [1]. Many parasitic nematodes have an environmental infective larval stage that engages in host seeking, a process whereby the infective larvae use sensory cues to search for hosts. Host seeking is a complex behavior that involves multiple sensory modalities, including olfaction, gustation, thermosensation, and humidity sensation. As the initial step of the parasite-host interaction, host seeking could be a powerful target for preventative intervention. However, host-seeking behavior remains poorly understood. Here we review what is currently known about the host-seeking behaviors of different parasitic nematodes, including insect-parasitic nematodes, mammalian-parasitic nematodes, and plant-parasitic nematodes. We also discuss the neural bases of these behaviors.

  5. The coevolutionary implications of host tolerance.

    Science.gov (United States)

    Best, Alex; White, Andy; Boots, Mike

    2014-05-01

    Host tolerance to infectious disease, whereby hosts do not directly "fight" parasites but instead ameliorate the damage caused, is an important defense mechanism in both plants and animals. Because tolerance to parasite virulence may lead to higher prevalence of disease in a population, evolutionary theory tells us that while the spread of resistance genes will result in negative frequency dependence and the potential for diversification, the evolution of tolerance is instead likely to result in fixation. However, our understanding of the broader implications of tolerance is limited by a lack of fully coevolutionary theory. Here we examine the coevolution of tolerance across a comprehensive range of classic coevolutionary host-parasite frameworks, including equivalents of gene-for-gene and matching allele and evolutionary invasion models. Our models show that the coevolution of host tolerance and parasite virulence does not lead to the generation and maintenance of diversity through either static polymorphisms or through "Red-queen" cycles. Coevolution of tolerance may however lead to multiple stable states leading to sudden shifts in parasite impacts on host health. More broadly, we emphasize that tolerance may change host-parasite interactions from antagonistic to a form of "apparent commensalism," but may also lead to the evolution of parasites that are highly virulent in nontolerant hosts.

  6. Host Galaxy Identification for Supernova Surveys

    CERN Document Server

    Gupta, Ravi R; Kovacs, Eve; Spinka, Harold; Kessler, Richard; Goldstein, Daniel A; Liotine, Camille; Pomian, Katarzyna; D'Andrea, Chris B; Sullivan, Mark; Carretero, Jorge; Castander, Francisco J; Nichol, Robert C; Finley, David A; Fischer, John A; Foley, Ryan J; Kim, Alex G; Papadopoulos, Andreas; Sako, Masao; Scolnic, Daniel M; Smith, Mathew; Tucker, Brad E; Uddin, Syed; Wolf, Rachel C; Yuan, Fang; Abbott, Tim M C; Abdalla, Filipe B; Benoit-Levy, Aurelien; Bertin, Emmanuel; Brooks, David; Rosell, Aurelio Carnero; Kind, Matias Carrasco; Cunha, Carlos E; da Costa, Luiz N; Desai, Shantanu; Doel, Peter; Eifler, Tim F; Evrard, August E; Flaugher, Brenna; Fosalba, Pablo; Gaztanaga, Enrique; Gruen, Daniel; Gruendl, Robert; James, David J; Kuehn, Kyler; Kuropatkin, Nikolay; Maia, Marcio A G; Marshall, Jennifer L; Miquel, Ramon; Plazas, Andres A; Romer, A Kathy; Sanchez, Eusebio; Schubnell, Michael; Sevilla-Noarbe, Ignacio; Sobreira, Flavia; Suchyta, Eric; Swanson, Molly E C; Tarle, Gregory; Walker, Alistair R; Wester, William

    2016-01-01

    Host galaxy identification is a crucial step for modern supernova (SN) surveys such as the Dark Energy Survey (DES) and the Large Synoptic Survey Telescope (LSST), which will discover SNe by the thousands. Spectroscopic resources are limited, so in the absence of real-time SN spectra these surveys must rely on host galaxy spectra to obtain accurate redshifts for the Hubble diagram and to improve photometric classification of SNe. In addition, SN luminosities are known to correlate with host-galaxy properties. Therefore, reliable identification of host galaxies is essential for cosmology and SN science. We simulate SN events and their locations within their host galaxies to develop and test methods for matching SNe to their hosts. We use both real and simulated galaxy catalog data from the Advanced Camera for Surveys General Catalog and MICECATv2.0, respectively. We also incorporate "hostless" SNe residing in undetected faint hosts into our analysis, with an assumed hostless rate of 5%. Our fully automated alg...

  7. The Local Hosts of Type Ia Supernovae

    CERN Document Server

    Neill, James D; Howell, D Andy; Conley, Alex; Seibert, Mark; Martin, D Christopher; Barlow, Tom A; Foster, Karl; Friedman, Peter G; Morrissey, Patrick; Neff, Susan G; Schiminovich, David; Wyder, Ted K; Bianchi, Luciana; Donas, José; Heckman, Timothy M; Lee, Young-Wook; Madore, Barry F; Milliard, Bruno; Rich, R Michael; Szalay, A S

    2009-01-01

    We use multi-wavelength, matched aperture, integrated photometry from GALEX, SDSS and the RC3 to estimate the physical properties of 166 nearby galaxies hosting 168 well-observed Type Ia supernovae (SNe Ia). Our data corroborate well-known features that have been seen in other SN Ia samples. Specifically, hosts with active star formation produce brighter and slower SNe Ia on average, and hosts with luminosity-weighted ages older than 1 Gyr produce on average more faint, fast and fewer bright, slow SNe Ia than younger hosts. New results include that in our sample, the faintest and fastest SNe Ia occur only in galaxies exceeding a stellar mass threshhold of ~10^10 M_sun, indicating that their progenitors must arise in populations that are older and/or more metal rich than the general SN Ia population. A low host extinction sub-sample hints at a residual trend in peak luminosity with host age, after correcting for light-curve shape, giving the appearance that older hosts produce less-extincted SNe Ia on average....

  8. Host conservatism or host specialization? Patterns of fungal diversification are influenced by host specificity in Ophiognomonia (Gnomoniaceae, Diaporthales)

    Science.gov (United States)

    Species of Ophiognomonia (Gnomoniaceae) are perithecial fungi that occur as endophytes, pathogens, and latent saprobes on leaf and stem tissue of plants in the Betulaceae, Fagaceae, Juglandaceae, Lauraceae, Malvaceae, Platanaceae, Rosaceae, Salicaceae, and Sapindaceae. In this study host plant patte...

  9. Multiplicity-Study of Exoplanet Host Stars

    OpenAIRE

    Mugrauer, M.; Neuhäuser, R.; Ginski, C.; Eisenbeiss, T.

    2005-01-01

    We carry out a systematic search campaign for wide companions of exoplanet host stars to study their multiplicity and its influence on the long-term stability and the orbital parameters of the exoplanets. We have already found 6 wide companions, raising the number of confirmed binaries among the exoplanet host stars to 20 systems. We have also searched for wide companions of Gl86, the first known exoplanet host star with a white dwarf companion. Our Sofi/NTT observations are sensitive to subs...

  10. Treatment of candidiasis: insights from host genetics.

    Science.gov (United States)

    Delsing, Corine E; Bleeker-Rovers, Chantal P; Kullberg, Bart-Jan; Netea, Mihai G

    2012-08-01

    Candida species are major causes of mucosal and invasive infections, leading to substantial morbidity and mortality. Despite the development of new classes of antifungal drugs, mortality in patients with systemic candidiasis remains high. Host-Candida interaction plays an important role in effective elimination of the pathogen. Genetic studies have rendered important insights into antifungal host defense and have identified potential targets for adjunctive therapy. In this article, the authors review the genetic variations in the host defense to Candida and their implications for the treatment of mucosal and systemic candidiasis.

  11. Protective host immune responses to Salmonella infection.

    Science.gov (United States)

    Pham, Oanh H; McSorley, Stephen J

    2015-01-01

    Salmonella enterica serovars Typhi and Paratyphi are the causative agents of human typhoid fever. Current typhoid vaccines are ineffective and are not widely used in endemic areas. Greater understanding of host-pathogen interactions during Salmonella infection should facilitate the development of improved vaccines to combat typhoid and nontyphoidal Salmonellosis. This review will focus on our current understanding of Salmonella pathogenesis and the major host immune components that participate in immunity to Salmonella infection. In addition, recent findings regarding host immune mechanisms in response to Salmonella infection will be also discussed, providing a new perspective on the utility of improved tools to study the immune response to Salmonella infections.

  12. Chemical similarity between historical and novel host plants promotes range and host expansion of the mountain pine beetle in a naïve host ecosystem.

    Science.gov (United States)

    Erbilgin, Nadir; Ma, Cary; Whitehouse, Caroline; Shan, Bin; Najar, Ahmed; Evenden, Maya

    2014-02-01

    Host plant secondary chemistry can have cascading impacts on host and range expansion of herbivorous insect populations. We investigated the role of host secondary compounds on pheromone production by the mountain pine beetle (Dendroctonus ponderosae) (MPB) and beetle attraction in response to a historical (lodgepole pine, Pinus contorta var. latifolia) and a novel (jack pine, Pinus banksiana) hosts, as pheromones regulate the host colonization process. Beetles emit the same pheromones from both hosts, but more trans-verbenol, the primary aggregation pheromone, was emitted by female beetles on the novel host. The phloem of the novel host contains more α-pinene, a secondary compound that is the precursor for trans-verbenol production in beetle, than the historical host. Beetle-induced emission of 3-carene, another secondary compound found in both hosts, was also higher from the novel host. Field tests showed that the addition of 3-carene to the pheromone mixture mimicking the aggregation pheromones produced from the two host species increased beetle capture. We conclude that chemical similarity between historical and novel hosts has facilitated host expansion of MPB in jack pine forests through the exploitation of common host secondary compounds for pheromone production and aggregation on the hosts. Furthermore, broods emerging from the novel host were larger in terms of body size.

  13. Improved spectroscopic parameters for transiting planet hosts

    CERN Document Server

    Torres, Guillermo; Sozzetti, Alessandro; Buchhave, Lars A; Winn, Joshua N; Holman, Matthew J; Carter, Joshua A

    2012-01-01

    We report homogeneous spectroscopic determinations of the effective temperature, metallicity, and projected rotational velocity for the host stars of 56 transiting planets. Our analysis is based primarily on the Stellar Parameter Classification (SPC) technique. We investigate systematic errors by examining subsets of the data with two other methods that have often been used in previous studies (SME and MOOG). The SPC and SME results, both based on comparisons between synthetic spectra and actual spectra, show strong correlations between temperature, [Fe/H], and log g when solving for all three quantities simultaneously. In contrast the MOOG results, based on a more traditional curve-of-growth approach, show no such correlations. To combat the correlations and improve the accuracy of the temperatures and metallicities, we repeat the SPC analysis with a constraint on log g based on the mean stellar density that can be derived from the analysis of the transit light curves. Previous studies that have not taken ad...

  14. PERCEPTION OF HOST COMMUNITIES TOWARD THE ...

    African Journals Online (AJOL)

    DORCAS

    ABSTRACT. This research examined the reactions of the host communities towards the implementation of ... sharing of certain benefits accruing from tourism to the people would promote a better .... information during the period under review.

  15. CERN to host conference on information society

    CERN Multimedia

    CERN will host a conference on the Role of Science in the Information Society (RSIS) in December. This conference will focus on ensuring that the information society benefits people to the greatest extent possible, especially in developing regions.

  16. Host-bacterial interplay in periodontal disease

    Directory of Open Access Journals (Sweden)

    Rudrakshi Chickanna

    2015-01-01

    Full Text Available A literature search was performed using MEDLINE (PubMed and other electronic basis from 1991 to 2014. Search included books and journals based on the systematic and critical reviews, in vitro and in vivo clinical studies on molecular basis of host microbial interactions. Clearly, an understanding of the host susceptibility factor in addition to microbial factors by elucidating the molecular basis offers opportunity for therapeutic manipulation of advancing periodontal destruction. One of the hallmarks of pathogenesis is the ability of pathogenic organisms to invade surrounding tissues and to evade the host defence. This paper focuses the general overview of molecular mechanisms involved in the microbiota and host response to bacterial inimical behavior in periodontics.

  17. Host reproductive phenology drives seasonal patterns of host use in mosquitoes.

    Directory of Open Access Journals (Sweden)

    Nathan D Burkett-Cadena

    Full Text Available Seasonal shifts in host use by mosquitoes from birds to mammals drive the timing and intensity of annual epidemics of mosquito-borne viruses, such as West Nile virus, in North America. The biological mechanism underlying these shifts has been a matter of debate, with hypotheses falling into two camps: (1 the shift is driven by changes in host abundance, or (2 the shift is driven by seasonal changes in the foraging behavior of mosquitoes. Here we explored the idea that seasonal changes in host use by mosquitoes are driven by temporal patterns of host reproduction. We investigated the relationship between seasonal patterns of host use by mosquitoes and host reproductive phenology by examining a seven-year dataset of blood meal identifications from a site in Tuskegee National Forest, Alabama USA and data on reproduction from the most commonly utilized endothermic (white-tailed deer, great blue heron, yellow-crowned night heron and ectothermic (frogs hosts. Our analysis revealed that feeding on each host peaked during periods of reproductive activity. Specifically, mosquitoes utilized herons in the spring and early summer, during periods of peak nest occupancy, whereas deer were fed upon most during the late summer and fall, the period corresponding to the peak in births for deer. For frogs, however, feeding on early- and late-season breeders paralleled peaks in male vocalization. We demonstrate for the first time that seasonal patterns of host use by mosquitoes track the reproductive phenology of the hosts. Peaks in relative mosquito feeding on each host during reproductive phases are likely the result of increased tolerance and decreased vigilance to attacking mosquitoes by nestlings and brooding adults (avian hosts, quiescent young (avian and mammalian hosts, and mate-seeking males (frogs.

  18. Ultramafic-Hosted Talc-Magnesite Deposits

    Science.gov (United States)

    Robinson,, Gilpin R.; Van Gosen, Bradley S.; Foley, Nora K.

    2006-01-01

    This presentation on the geology of ultramafic-hosted talc-magnesite deposits was given at the 42nd Forum on the Geology of Industrial Minerals, May 7-13, 2006, in Asheville, North Carolina (USA). Talc is a soft inert industrial mineral commodity commonly used as a component or filler in ceramic, paint, paper, plastic, roofing, and electrical applications. Ultramafic-hosted talc-magnesite deposits are important sources of talc.

  19. Data hosting infrastructure for primary biodiversity data

    Science.gov (United States)

    2011-01-01

    Background Today, an unprecedented volume of primary biodiversity data are being generated worldwide, yet significant amounts of these data have been and will continue to be lost after the conclusion of the projects tasked with collecting them. To get the most value out of these data it is imperative to seek a solution whereby these data are rescued, archived and made available to the biodiversity community. To this end, the biodiversity informatics community requires investment in processes and infrastructure to mitigate data loss and provide solutions for long-term hosting and sharing of biodiversity data. Discussion We review the current state of biodiversity data hosting and investigate the technological and sociological barriers to proper data management. We further explore the rescuing and re-hosting of legacy data, the state of existing toolsets and propose a future direction for the development of new discovery tools. We also explore the role of data standards and licensing in the context of data hosting and preservation. We provide five recommendations for the biodiversity community that will foster better data preservation and access: (1) encourage the community's use of data standards, (2) promote the public domain licensing of data, (3) establish a community of those involved in data hosting and archival, (4) establish hosting centers for biodiversity data, and (5) develop tools for data discovery. Conclusion The community's adoption of standards and development of tools to enable data discovery is essential to sustainable data preservation. Furthermore, the increased adoption of open content licensing, the establishment of data hosting infrastructure and the creation of a data hosting and archiving community are all necessary steps towards the community ensuring that data archival policies become standardized. PMID:22373257

  20. Herpes simplex virus virion host shutoff function.

    Science.gov (United States)

    Kwong, A D; Kruper, J A; Frenkel, N

    1988-03-01

    Herpes simplex virus (HSV) virions contain one or more functions which mediate the shutoff of host protein synthesis and the degradation of host mRNA. HSV type 1 (HSV-1) mutants deficient in the virion shutoff of host protein synthesis (vhs mutants) were isolated and were found to be defective in their ability to degrade host mRNA. Furthermore, it was found that viral mRNAs in cells infected with the vhs 1 mutant have a significantly longer functional half-life than viral mRNAs in wild-type virus-infected cells. In the present study we have mapped the vhs1 mutation affecting the virion shutoff of host protein synthesis to a 265-base-pair NruI-XmaIII fragment spanning map coordinates 0.604 to 0.606 of the HSV-1 genome. The mutation(s) affecting the functional half-lives of host mRNA as well as the alpha (immediate-early), beta (early), and gamma (late) viral mRNAs were also mapped within this 265-base-pair fragment. Thus, the shutoff of host protein synthesis is most likely mediated by the same function which decreases the half-life of viral mRNA. The shorter half-life of infected-cell mRNAs may allow a more rapid modulation of viral gene expression in response to changes in the transcription of viral genes. Interestingly, the vhs1 mutation of HSV-1 maps within a region which overlaps the Bg/II-N sequences of HSV-2 DNA shown previously to transform cells in culture. The possible relationship between the transformation and host shutoff functions are discussed.

  1. A remote host facility for Intel hypercubes

    Energy Technology Data Exchange (ETDEWEB)

    Dunigan, T.H.

    1989-04-01

    The structure and use of a remote host facility for controlling application programs on an Intel hypercube are described. The facility permits an alternate UNIX host, such as a graphics workstation or supercomputer, connected by a TCP/IP network to the Intel cube manager processor to communicate with application programs running on the hypercube nodes. The facility supports both C and FORTRAN applications. 5 refs., 1 fig., 2 tabs.

  2. Treponema denticola interactions with host proteins

    Directory of Open Access Journals (Sweden)

    J. Christopher Fenno

    2012-02-01

    Full Text Available Oral Treponema species, most notably T. denticola, are implicated in the destructive effects of human periodontal disease. Progress in the molecular analysis of interactions between T. denticola and host proteins is reviewed here, with particular emphasis on the characterization of surface-expressed and secreted proteins of T. denticola involved in interactions with host cells, extracellular matrix components, and components of the innate immune system.

  3. Natal Host Plants Can Alter Herbivore Competition

    OpenAIRE

    Pan, Huipeng; Evan L. Preisser; Su, Qi; Jiao, Xiaoguo; Xie, Wen; Wang, Shaoli; Wu, Qingjun; Zhang, Youjun

    2016-01-01

    Interspecific competition between herbivores is widely recognized as an important determinant of community structure. Although researchers have identified a number of factors capable of altering competitive interactions, few studies have addressed the influence of neighboring plant species. If adaptation to/ epigenetic effects of an herbivore’s natal host plant alter its performance on other host plants, then interspecific herbivore interactions may play out differently in heterogeneous and h...

  4. Biodiversity decreases disease through predictable changes in host community competence.

    Science.gov (United States)

    Johnson, Pieter T J; Preston, Daniel L; Hoverman, Jason T; Richgels, Katherine L D

    2013-02-14

    Accelerating rates of species extinctions and disease emergence underscore the importance of understanding how changes in biodiversity affect disease outcomes. Over the past decade, a growing number of studies have reported negative correlations between host biodiversity and disease risk, prompting suggestions that biodiversity conservation could promote human and wildlife health. Yet the generality of the diversity-disease linkage remains conjectural, in part because empirical evidence of a relationship between host competence (the ability to maintain and transmit infections) and the order in which communities assemble has proven elusive. Here we integrate high-resolution field data with multi-scale experiments to show that host diversity inhibits transmission of the virulent pathogen Ribeiroia ondatrae and reduces amphibian disease as a result of consistent linkages among species richness, host composition and community competence. Surveys of 345 wetlands indicated that community composition changed nonrandomly with species richness, such that highly competent hosts dominated in species-poor assemblages whereas more resistant species became progressively more common in diverse assemblages. As a result, amphibian species richness strongly moderated pathogen transmission and disease pathology among 24,215 examined hosts, with a 78.4% decline in realized transmission in richer assemblages. Laboratory and mesocosm manipulations revealed an approximately 50% decrease in pathogen transmission and host pathology across a realistic diversity gradient while controlling for host density, helping to establish mechanisms underlying the diversity-disease relationship and their consequences for host fitness. By revealing a consistent link between species richness and community competence, these findings highlight the influence of biodiversity on infection risk and emphasize the benefit of a community-based approach to understanding infectious diseases.

  5. Protein Complex Production in Alternative Prokaryotic Hosts.

    Science.gov (United States)

    Gómez, Sara; López-Estepa, Miguel; Fernández, Francisco J; Vega, M Cristina

    2016-01-01

    Research for multiprotein expression in nonconventional bacterial and archaeal expression systems aims to exploit particular properties of "alternative" prokaryotic hosts that might make them more efficient than E. coli for particular applications, especially in those areas where more conventional bacterial hosts traditionally do not perform well. Currently, a wide range of products with clinical or industrial application have to be isolated from their native source, often microorganisms whose growth present numerous problems owing to very slow growth phenotypes or because they are unculturable under laboratory conditions. In those cases, transfer of the gene pathway responsible for synthesizing the product of interest into a suitable recombinant host becomes an attractive alternative solution. Despite many efforts dedicated to improving E. coli systems due to low cost, ease of use, and its dominant position as a ubiquitous expression host model, many alternative prokaryotic systems have been developed for heterologous protein expression mostly for biotechnological applications. Continuous research has led to improvements in expression yield through these non-conventional models, including Pseudomonas, Streptomyces and Mycobacterium as alternative bacterial expression hosts. Advantageous properties shared by these systems include low costs, high levels of secreted protein products and their safety of use, with non-pathogenic strains been commercialized. In addition, the use of extremophilic and halotolerant archaea as expression hosts has to be considered as a potential tool for the production of mammalian membrane proteins such as GPCRs.

  6. Sumoylation at the Host-Pathogen Interface

    Directory of Open Access Journals (Sweden)

    Van G. Wilson

    2012-04-01

    Full Text Available Many viral proteins have been shown to be sumoylated with corresponding regulatory effects on their protein function, indicating that this host cell modification process is widely exploited by viral pathogens to control viral activity. In addition to using sumoylation to regulate their own proteins, several viral pathogens have been shown to modulate overall host sumoylation levels. Given the large number of cellular targets for SUMO addition and the breadth of critical cellular processes that are regulated via sumoylation, viral modulation of overall sumoylation presumably alters the cellular environment to ensure that it is favorable for viral reproduction and/or persistence. Like some viruses, certain bacterial plant pathogens also target the sumoylation system, usually decreasing sumoylation to disrupt host anti-pathogen responses. The recent demonstration that Listeria monocytogenes also disrupts host sumoylation, and that this is required for efficient infection, extends the plant pathogen observations to a human pathogen and suggests that pathogen modulation of host sumoylation may be more widespread than previously appreciated. This review will focus on recent aspects of how pathogens modulate the host sumoylation system and how this benefits the pathogen.

  7. A short, high-temperature treatment of host larvae to analyze Wolbachia-host interactions in the moth Ostrinia scapulalis.

    Science.gov (United States)

    Sugimoto, Takafumi N; Kayukawa, Takumi; Matsuo, Takashi; Tsuchida, Tsutomu; Ishikawa, Yukio

    2015-10-01

    Maternally inherited endosymbiotic bacteria of the genus Wolbachia cause various reproductive alterations in their hosts. Wolbachia induces male-specific death during embryonic and larval stages in the moth Ostrinia scapulalis. To investigate how the density of Wolbachia affects their performance in the host, we attempted to reduce its density using a short, high-temperature treatment of the host at the larval stage. Individuals cured of infection as well as sexual mosaics, which harbor Wolbachia, were obtained by this method in the next generation. The sex of uninfected offspring was exclusively male, similar to that of the offspring of larvae treated with antibiotics. A strong correlation was found between Wolbachia density in female moths and the sex ratio of their progeny. These results suggest that a short, high-temperature treatment at the larval stage reduced the density of Wolbachia in the adult stage, and, hence, inhibited interference with the host's development in the next generation. Since the direct effects of the heat treatment on Wolbachia were transient, this method may be useful for specifying the critical time for interference by Wolbachia in host development.

  8. Local host adaptation and use of a novel host in the seed beetle Megacerus eulophus.

    Directory of Open Access Journals (Sweden)

    Gisela C Stotz

    Full Text Available Spatial variation in host plant availability may lead to specialization in host use and local host adaptation in herbivorous insects, which may involve a cost in performance on other hosts. We studied two geographically separated populations of the seed beetle Megacerus eulophus (Coleoptera: Bruchidae in central Chile: a population from the host Convolvulus chilensis (in Aucó and a population from C. bonariensis (in Algarrobo. In Aucó C. chilensis is the only host plant, while in Algarrobo both C. bonariensis and C. chilensis are available. We tested local adaptation to these native host plants and its influence on the use of another, exotic host plant. We hypothesized that local adaptation would be verified, particularly for the one-host population (Aucó, and that the Aucó population would be less able to use an alternative, high-quality host. We found evidence of local adaptation in the population from C. chilensis. Thus, when reared on C. chilensis, adults from the C. chilensis population were larger and lived longer than individuals from the C. bonariensis population, while bruchids from the two populations had the same body size and longevity when reared on C. bonariensis. Overall, bruchids from the C. chilensis population showed greater performance traits than those from the C. bonariensis population. There were no differences between the bruchid populations in their ability to use the alternative, exotic host Calystegia sepium, as shown by body size and longevity patterns. Results suggest that differences in local adaptation might be explained by differential host availability in the study populations.

  9. Local host adaptation and use of a novel host in the seed beetle Megacerus eulophus.

    Science.gov (United States)

    Stotz, Gisela C; Suárez, Lorena H; Gonzáles, Wilfredo L; Gianoli, Ernesto

    2013-01-01

    Spatial variation in host plant availability may lead to specialization in host use and local host adaptation in herbivorous insects, which may involve a cost in performance on other hosts. We studied two geographically separated populations of the seed beetle Megacerus eulophus (Coleoptera: Bruchidae) in central Chile: a population from the host Convolvulus chilensis (in Aucó) and a population from C. bonariensis (in Algarrobo). In Aucó C. chilensis is the only host plant, while in Algarrobo both C. bonariensis and C. chilensis are available. We tested local adaptation to these native host plants and its influence on the use of another, exotic host plant. We hypothesized that local adaptation would be verified, particularly for the one-host population (Aucó), and that the Aucó population would be less able to use an alternative, high-quality host. We found evidence of local adaptation in the population from C. chilensis. Thus, when reared on C. chilensis, adults from the C. chilensis population were larger and lived longer than individuals from the C. bonariensis population, while bruchids from the two populations had the same body size and longevity when reared on C. bonariensis. Overall, bruchids from the C. chilensis population showed greater performance traits than those from the C. bonariensis population. There were no differences between the bruchid populations in their ability to use the alternative, exotic host Calystegia sepium, as shown by body size and longevity patterns. Results suggest that differences in local adaptation might be explained by differential host availability in the study populations.

  10. Transcriptome dynamics of a broad host-range cyanophage and its hosts.

    Science.gov (United States)

    Doron, Shany; Fedida, Ayalla; Hernández-Prieto, Miguel A; Sabehi, Gazalah; Karunker, Iris; Stazic, Damir; Feingersch, Roi; Steglich, Claudia; Futschik, Matthias; Lindell, Debbie; Sorek, Rotem

    2016-06-01

    Cyanobacteria are highly abundant in the oceans and are constantly exposed to lytic viruses. The T4-like cyanomyoviruses are abundant in the marine environment and have broad host-ranges relative to other cyanophages. It is currently unknown whether broad host-range phages specifically tailor their infection program for each host, or employ the same program irrespective of the host infected. Also unknown is how different hosts respond to infection by the same phage. Here we used microarray and RNA-seq analyses to investigate the interaction between the Syn9 T4-like cyanophage and three phylogenetically, ecologically and genomically distinct marine Synechococcus strains: WH7803, WH8102 and WH8109. Strikingly, Syn9 led a nearly identical infection and transcriptional program in all three hosts. Different to previous assumptions for T4-like cyanophages, three temporally regulated gene expression classes were observed. Furthermore, a novel regulatory element controlled early-gene transcription, and host-like promoters drove middle gene transcription, different to the regulatory paradigm for T4. Similar results were found for the P-TIM40 phage during infection of Prochlorococcus NATL2A. Moreover, genomic and metagenomic analyses indicate that these regulatory elements are abundant and conserved among T4-like cyanophages. In contrast to the near-identical transcriptional program employed by Syn9, host responses to infection involved host-specific genes primarily located in hypervariable genomic islands, substantiating islands as a major axis of phage-cyanobacteria interactions. Our findings suggest that the ability of broad host-range phages to infect multiple hosts is more likely dependent on the effectiveness of host defense strategies than on differential tailoring of the infection process by the phage.

  11. Animal salmonelloses: a brief review of “host adaptation and host specificity” of Salmonella spp.

    Directory of Open Access Journals (Sweden)

    Grammato Evangelopoulou

    2013-07-01

    Full Text Available Salmonella enterica, the most pathogenic species of the genusSalmonella, includes more than 2,500 serovars, many of which are of great veterinary and medical significance. The emergence of food-borne pathogens, such as Salmonella spp., has increased knowledge about the mechanisms helping microorganisms to persist and spread within new host populations. It has also increased information about the properties they acquire for adapting in the biological environment of a new host. Thedifferences observed between serovars in their host preference and clinical manifestations are referred to as “serovar-host specificity” or “serovar-host adaptation”. The genus Salmonella, highly adaptive to vertebrate hosts, has many pathogenic serovars showing host specificity. Serovar Salmonella Typhi, causing disease to man and higher primates, is a good example of host specificity. Thus, understanding the mechanisms that Salmonella serovars use to overcome animal species' barriers or adapt to new hosts is also important for understanding the origins of any other infectious diseases or the emergence of new pathogens. In addition, molecular methods used to study the virulence determinants of Salmonella serovars, could also be used to model ways of studying the virulence determinants used by bacteria in general, when causing disease to a specific animal species

  12. Host Chemical Footprints Induce Host Sex Discrimination Ability in Egg Parasitoids: e79054

    National Research Council Canada - National Science Library

    Peri, Ezio; Frati, Francesca; Salerno, Gianandrea; Conti, Eric; Colazza, Stefano

    2013-01-01

    Trissolcus egg parasitoids, when perceiving the chemical footprints left on a substrate by pentatomid host bugs, adopt a motivated searching behaviour characterized by longer searching time on patches...

  13. A parasite's modification of host behavior reduces predation on its host.

    Science.gov (United States)

    Soghigian, John; Valsdottir, Linda R; Livdahl, Todd P

    2017-03-01

    Parasite modification of host behavior is common, and the literature is dominated by demonstrations of enhanced predation on parasitized prey resulting in transmission of parasites to their next host. We present a case in which predation on parasitized prey is reduced. Despite theoretical modeling suggesting that this phenomenon should be common, it has been reported in only a few host-parasite-predator systems. Using a system of gregarine endosymbionts in host mosquitoes, we designed experiments to compare the vulnerability of parasitized and unparasitized mosquito larvae to predation by obligate predatory mosquito larvae and then compared behavioral features known to change in the presence of predatory cues. We exposed Aedes triseriatus larvae to the parasite Ascogregarina barretti and the predator Toxohrynchites rutilus and assessed larval mortality rate under each treatment condition. Further, we assessed behavioral differences in larvae due to infection and predation stimuli by recording larvae and scoring behaviors and positions within microcosms. Infection with gregarines reduced cohort mortality in the presence of the predator, but the parasite did not affect mortality alone. Further, infection by parasites altered behavior such that infected hosts thrashed less frequently than uninfected hosts and were found more frequently on or in a refuge within the microcosm. By reducing predation on their host, gregarines may be acting as mutualists in the presence of predation on their hosts. These results illustrate a higher-order interaction, in which a relationship between a species pair (host-endosymbiont or predator-prey) is altered by the presence of a third species.

  14. Host plant utilization, host range oscillations and diversification in nymphalid butterflies: a phylogenetic investigation.

    Science.gov (United States)

    Nylin, Sören; Slove, Jessica; Janz, Niklas

    2014-01-01

    It has been suggested that phenotypic plasticity is a major factor in the diversification of life, and that variation in host range in phytophagous insects is a good model for investigating this claim. We explore the use of angiosperm plants as hosts for nymphalid butterflies, and in particular the evidence for past oscillations in host range and how they are linked to host shifts and to diversification. At the level of orders of plants, a relatively simple pattern of host use and host shifts emerges, despite the 100 million years of history of the family Nymphalidae. We review the evidence that these host shifts and the accompanying diversifications were associated with transient polyphagous stages, as suggested by the "oscillation hypothesis." In addition, we investigate all currently polyphagous nymphalid species and demonstrate that the state of polyphagy is rare, has a weak phylogenetic signal, and a very apical distribution in the phylogeny; we argue that these are signs of its transient nature. We contrast our results with data from the bark beetles Dendroctonus, in which a more specialized host use is instead the apical state. We conclude that plasticity in host use is likely to have contributed to diversification in nymphalid butterflies. © 2013 The Authors. Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

  15. The Host RNAs in Retroviral Particles

    Directory of Open Access Journals (Sweden)

    Alice Telesnitsky

    2016-08-01

    Full Text Available As they assemble, retroviruses encapsidate both their genomic RNAs and several types of host RNA. Whereas limited amounts of messenger RNA (mRNA are detectable within virion populations, the predominant classes of encapsidated host RNAs do not encode proteins, but instead include endogenous retroelements and several classes of non-coding RNA (ncRNA, some of which are packaged in significant molar excess to the viral genome. Surprisingly, although the most abundant host RNAs in retroviruses are also abundant in cells, unusual forms of these RNAs are packaged preferentially, suggesting that these RNAs are recruited early in their biogenesis: before associating with their cognate protein partners, and/or from transient or rare RNA populations. These RNAs’ packaging determinants differ from the viral genome’s, and several of the abundantly packaged host ncRNAs serve cells as the scaffolds of ribonucleoprotein particles. Because virion assembly is equally efficient whether or not genomic RNA is available, yet RNA appears critical to the structural integrity of retroviral particles, it seems possible that the selectively encapsidated host ncRNAs might play roles in assembly. Indeed, some host ncRNAs appear to act during replication, as some transfer RNA (tRNA species may contribute to nuclear import of human immunodeficiency virus 1 (HIV-1 reverse transcription complexes, and other tRNA interactions with the viral Gag protein aid correct trafficking to plasma membrane assembly sites. However, despite high conservation of packaging for certain host RNAs, replication roles for most of these selectively encapsidated RNAs—if any—have remained elusive.

  16. Virus-host coevolution: common patterns of nucleotide motif usage in Flaviviridae and their hosts.

    Directory of Open Access Journals (Sweden)

    Francisco P Lobo

    Full Text Available Virus-host biological interaction is a continuous coevolutionary process involving both host immune system and viral escape mechanisms. Flaviviridae family is composed of fast evolving RNA viruses that infects vertebrate (mammals and birds and/or invertebrate (ticks and mosquitoes organisms. These host groups are very distinct life forms separated by a long evolutionary time, so lineage-specific anti-viral mechanisms are likely to have evolved. Flaviviridae viruses which infect a single host lineage would be subjected to specific host-induced pressures and, therefore, selected by them. In this work we compare the genomic evolutionary patterns of Flaviviridae viruses and their hosts in an attempt to uncover coevolutionary processes inducing common features in such disparate groups. Especially, we have analyzed dinucleotide and codon usage patterns in the coding regions of vertebrate and invertebrate organisms as well as in Flaviviridae viruses which specifically infect one or both host types. The two host groups posses very distinctive dinucleotide and codon usage patterns. A pronounced CpG under-representation was found in the vertebrate group, possibly induced by the methylation-deamination process, as well as a prominent TpA decrease. The invertebrate group displayed only a TpA frequency reduction bias. Flaviviridae viruses mimicked host nucleotide motif usage in a host-specific manner. Vertebrate-infecting viruses possessed under-representation of CpG and TpA, and insect-only viruses displayed only a TpA under-representation bias. Single-host Flaviviridae members which persistently infect mammals or insect hosts (Hepacivirus and insect-only Flavivirus, respectively were found to posses a codon usage profile more similar to that of their hosts than to related Flaviviridae. We demonstrated that vertebrates and mosquitoes genomes are under very distinct lineage-specific constraints, and Flaviviridae viruses which specifically infect these

  17. Early-season host switching in Adelphocoris spp. (Hemiptera: Miridae of differing host breadth.

    Directory of Open Access Journals (Sweden)

    Hongsheng Pan

    Full Text Available The mirid bugs Adelphocoris suturalis (Jakovlev, Adelphocoris lineolatus (Goeze and Adelphocoris fasciaticollis (Reuter (Hemiptera: Miridae are common pests of several agricultural crops. These three species have vastly different geographical distributions, phenologies and abundances, all of which are linked to their reliance on local plants. Previous work has shown notable differences in Adelphocoris spp. host use for overwintering. In this study, we assessed the extent to which each of the Adelphocoris spp. relies on some of its major overwinter hosts for spring development. Over the course of four consecutive years (2009-2012, we conducted population surveys on 77 different plant species from 39 families. During the spring, A. fasciaticollis used the broadest range of hosts, as it was found on 35 plant species, followed by A. suturalis (15 species and A. lineolatus (7 species. Abundances of the species greatly differed between host plants, with A. fasciaticollis reaching the highest abundance on Chinese date (Ziziphus jujuba Mill., whereas both A. suturalis and A. lineolatus preferred alfalfa (Medicago sativa L.. The host breadths of the three Adelphocoris spp. differed greatly between subsequent spring and winter seasons. The generalist species exhibited the least host fidelity, with A. suturalis and A. lineolatus using 8 of 22 and 4 of 12 overwinter host species for spring development, respectively. By contrast, the comparative specialist A. fasciaticollis relied on 9 of its 11 overwinter plants as early-season hosts. We highlight important seasonal changes in host breadth and interspecific differences in the extent of host switching behavior between the winter and spring seasons. These findings benefit our understanding of the evolutionary interactions between mirid bugs and their host plants and can be used to guide early-season population management.

  18. The host galaxy of GRB 990712

    DEFF Research Database (Denmark)

    Christensen, L.; Hjorth, J.; Gorosabel, J.

    2004-01-01

    We present a comprehensive study of the z = 0.43 host galaxy of GRB 990712, involving ground-based photometry, spectroscopy, and HST imaging. The broad-band UBVRIJHKs photometry is used to determine the global spectral energy distribution (SED) of the host galaxy. Comparison with that of known...... galaxy types shows that the host is similar to a moderately kreddened starburst galaxy with a young stellar population. The estimated internal extinction in the host is A(V) = 0.15 +/- 0.1 and the star-formation rate (SFR) from the UV continuum is 1.3 +/- 0.3 M-circle dot yr(-1) (not corrected...... for the effects of extinction). Other galaxy template spectra than starbursts failed to reproduce the observed SED. We also present VLT spectra leading to the detection of Halpha from the GRB host galaxy. A SFR of 2.8 +/- 0.7 M-circle dot yr(-1) is inferred from the Halpha line flux, and the presence of a young...

  19. Deconstructing host-pathogen interactions in Drosophila

    Directory of Open Access Journals (Sweden)

    Ethan Bier

    2012-01-01

    Full Text Available Many of the cellular mechanisms underlying host responses to pathogens have been well conserved during evolution. As a result, Drosophila can be used to deconstruct many of the key events in host-pathogen interactions by using a wealth of well-developed molecular and genetic tools. In this review, we aim to emphasize the great leverage provided by the suite of genomic and classical genetic approaches available in flies for decoding details of host-pathogen interactions; these findings can then be applied to studies in higher organisms. We first briefly summarize the general strategies by which Drosophila resists and responds to pathogens. We then focus on how recently developed genome-wide RNA interference (RNAi screens conducted in cells and flies, combined with classical genetic methods, have provided molecular insight into host-pathogen interactions, covering examples of bacteria, fungi and viruses. Finally, we discuss novel strategies for how flies can be used as a tool to examine how specific isolated virulence factors act on an intact host.

  20. Proteinaceous molecules mediating Bifidobacterium-host interactions

    Directory of Open Access Journals (Sweden)

    Lorena Ruiz

    2016-08-01

    Full Text Available Bifidobacteria are commensal microoganisms found in the gastrointestinal tract.Several strains have been attributed beneficial traits at local and systemic levels, through pathogen exclusion or immune modulation, among other benefits. This has promoted a growing industrial and scientific interest in bifidobacteria as probiotic supplements. However, the molecular mechanisms mediating this cross-talk with the human host remain unknown. High-throughput technologies, from functional genomics to transcriptomics, proteomics and interactomics coupled to the development of both in vitro and in vivo models to study the dynamics of the intestinal microbiota and their effects on host cells, have eased the identification of key molecules in these interactions. Numerous secreted or surface-associated proteins or peptides have been identified as potential mediators of bifidobacteria-host interactions and molecular cross-talk, directly participating in sensing environmental factors, promoting intestinal colonization or mediating a dialogue with mucosa-associated immune cells. On the other hand, bifidobacteria induce the production of proteins in the intestine, by epithelial or immune cells, and other gut bacteria, which are key elements in orchestrating interactions among bifidobacteria, gut microbiota and host cells. This review aims to give a comprehensive overview on proteinaceous molecules described and characterized to date, as mediators of the dynamic interplay between bifidobacteria and the human host, providing a framework to identify knowledge gaps and future research needs.

  1. Study of GRBs Hosts Galaxies Vicinity Properties

    Science.gov (United States)

    Bernal, S.; Vasquez, N.; Hoyle, F.

    2017-07-01

    The study of GRBs host galaxies and its vicinity could provide constrains on the progenitor and an opportunity to use these violent explosions to characterize the nature of the highredshift universe. Studies of GRB host galaxies reveal a population of starforming galaxies with great diversity, spanning a wide range of masses, star formation rate, and redshifts. In order to study the galactic ambient of GRBs we used the S. Savaglio catalog from 2015 where 245 GRBs are listed with RA-Dec position and z. We choose 22 GRBs Hosts galaxies from Savaglio catalog and SDSS DR12, with z range 0work we provide characteristics on the regions for future works related with highredsift universe that using the GRBs.

  2. Resolved Host Studies of Stellar Explosions

    CERN Document Server

    Levesque, Emily M

    2016-01-01

    The host galaxies of nearby (z<0.3) core-collapse supernovae and long-duration gamma-ray bursts offer an excellent means of probing the environments and populations that produce these events' varied massive progenitors. These same young stellar progenitors make LGRBs and SNe valuable and potentially powerful tracers of star formation, metallicity, the IMF, and the end phases of stellar evolution. However, properly utilizing these progenitors as tools requires a thorough understanding of their formation and, consequently, the physical properties of their parent host environments. This review looks at some of the recent work on LGRB and SN hosts with resolved environments that allows us to probe the precise explosion sites and surrounding environments of these events in incredible detail.

  3. New Hosts of The Lassa Virus.

    Science.gov (United States)

    Olayemi, Ayodeji; Cadar, Daniel; Magassouba, N'Faly; Obadare, Adeoba; Kourouma, Fode; Oyeyiola, Akinlabi; Fasogbon, Samuel; Igbokwe, Joseph; Rieger, Toni; Bockholt, Sabrina; Jérôme, Hanna; Schmidt-Chanasit, Jonas; Garigliany, Mutien; Lorenzen, Stephan; Igbahenah, Felix; Fichet, Jean-Nicolas; Ortsega, Daniel; Omilabu, Sunday; Günther, Stephan; Fichet-Calvet, Elisabeth

    2016-05-03

    Lassa virus (LASV) causes a deadly haemorrhagic fever in humans, killing several thousand people in West Africa annually. For 40 years, the Natal multimammate rat, Mastomys natalensis, has been assumed to be the sole host of LASV. We found evidence that LASV is also hosted by other rodent species: the African wood mouse Hylomyscus pamfi in Nigeria, and the Guinea multimammate mouse Mastomys erythroleucus in both Nigeria and Guinea. Virus strains from these animals were isolated in the BSL-4 laboratory and fully sequenced. Phylogenetic analyses of viral genes coding for glycoprotein, nucleoprotein, polymerase and matrix protein show that Lassa strains detected in M. erythroleucus belong to lineages III and IV. The strain from H. pamfi clusters close to lineage I (for S gene) and between II &III (for L gene). Discovery of new rodent hosts has implications for LASV evolution and its spread into new areas within West Africa.

  4. Salt, chloride, bleach, and innate host defense.

    Science.gov (United States)

    Wang, Guoshun; Nauseef, William M

    2015-08-01

    Salt provides 2 life-essential elements: sodium and chlorine. Chloride, the ionic form of chlorine, derived exclusively from dietary absorption and constituting the most abundant anion in the human body, plays critical roles in many vital physiologic functions, from fluid retention and secretion to osmotic maintenance and pH balance. However, an often overlooked role of chloride is its function in innate host defense against infection. Chloride serves as a substrate for the generation of the potent microbicide chlorine bleach by stimulated neutrophils and also contributes to regulation of ionic homeostasis for optimal antimicrobial activity within phagosomes. An inadequate supply of chloride to phagocytes and their phagosomes, such as in CF disease and other chloride channel disorders, severely compromises host defense against infection. We provide an overview of the roles that chloride plays in normal innate immunity, highlighting specific links between defective chloride channel function and failures in host defense.

  5. Disproportionate mosquito feeding on aggregated hosts.

    Science.gov (United States)

    Foppa, Ivo M; Moore, Jerrilynn; Caillouët, Kevin A; Wesson, Dawn M

    2011-11-01

    Despite the importance of per-capita feeding rates for mosquito-borne transmission dynamics, the relationship between host aggregation and per-capita feeding rates remains poorly characterized. We conducted indoor experiments to investigate how Culex quinquefasciatus (Say) mosquitoes distribute their blood feeding on variably aggregated domestic chickens (Callus gallus domesticus L.) (one chicken vs. a flock of seven to nine birds). Mosquitoes were always more likely to feed on the larger chicken group; yet, the single chicken tended to be fed on at a higher per-capita rate. When 10 chickens were available the feeding intensity was 4.5 times higher for the single chicken compared with the flock. We conclude that more highly aggregated hosts may experience lower exposure to mosquito bites than less aggregated hosts.

  6. Salt, chloride, bleach, and innate host defense

    Science.gov (United States)

    Wang, Guoshun; Nauseef, William M.

    2015-01-01

    Salt provides 2 life-essential elements: sodium and chlorine. Chloride, the ionic form of chlorine, derived exclusively from dietary absorption and constituting the most abundant anion in the human body, plays critical roles in many vital physiologic functions, from fluid retention and secretion to osmotic maintenance and pH balance. However, an often overlooked role of chloride is its function in innate host defense against infection. Chloride serves as a substrate for the generation of the potent microbicide chlorine bleach by stimulated neutrophils and also contributes to regulation of ionic homeostasis for optimal antimicrobial activity within phagosomes. An inadequate supply of chloride to phagocytes and their phagosomes, such as in CF disease and other chloride channel disorders, severely compromises host defense against infection. We provide an overview of the roles that chloride plays in normal innate immunity, highlighting specific links between defective chloride channel function and failures in host defense. PMID:26048979

  7. Lymphadenectomy prior to rat hind limb allotransplantation prevents graft-versus-host disease in chimeric hosts

    NARCIS (Netherlands)

    Brouha, PCR; Perez-Abadia, G; Francois, CG; Laurentin-Perez, LA; Gorantla, [No Value; Vossen, M; Tai, C; Pidwell, D; Anderson, GL; Stadelmann, WK; Hewitt, CW; Kon, M; Barker, JH; Maldonado, C

    2004-01-01

    In previous rat studies, the use of mixed allogeneic chimerism (MAC) to induce host tolerance to hind limb allografts has resulted in severe graft-versus-host disease (GVHD). The purpose of this study was to determine if immunocompetent cells in bone marrow (BM) and/or lymph nodes (LNs) of transplan

  8. Host preference of an introduced 'generalist' parasite for a non-native host.

    Science.gov (United States)

    Frankel, Victor M; Hendry, Andrew P; Rolshausen, Gregor; Torchin, Mark E

    2015-09-01

    Parasites can invade new ecosystems if they are introduced with their native hosts or if they successfully infect and colonise new hosts upon arrival. Here, we ask to what extent an introduced parasite demonstrates specialisation among novel host species. Infection surveys across three field sites in Gatun Lake, Panama, revealed that the invasive peacock bass, Cichla monoculus, was more commonly infected by the introduced trematode parasite Centrocestus formosanus than were three other common cichlid fishes. Laboratory infection experiments were conducted to determine whether parasitism might be driven by differential encounter/exposure to parasites or by differential infection susceptibility/preference across different host species. These experiments were performed by controlling for parasite exposure in single host (compatibility) experiments and in mixed host (preference) experiments. In all cases, the peacock bass exhibited higher infection rates with viable metacercariae relative to the other potential fish hosts. Our experiments thus support that an introduced generalist parasite shows apparent specialisation on a specific novel host. Further studies are needed to determine whether these patterns of specialisation are the result of local adaptation following invasion by the parasite.

  9. Host-parasite interactions under extreme climatic conditions

    Institute of Scientific and Technical Information of China (English)

    J. MARTINEZ; S. MERINO

    2011-01-01

    The effect that climatic changes can exert on parasitic interactions represents a multifactor problem whose results are difficult to predict. The actual impact of changes will depend on their magnitude and the physiological tolerance of affected organisms. When the change is considered extreme (I.e. Unusual weather events that are at the extremes of the historical distribution for a given area), the probability of an alteration in an organisms' homeostasis increases dramatically. However, factors determining the altered dynamics of host-parasite interactions due to an extreme change are the same as those acting in response to changes of lower magnitude. Only a deep knowledge of these factors will help to produce more accurate predictive models for the effects of extreme changes on parasitic interactions. Extreme environmental conditions may affect pathogens directly when they include free-living stages in their life-cycles and indirectly through reduced resource availability for hosts and thus reduced ability to produce efficient anti-parasite defenses, or by effects on host density affecting transmission dynamics of diseases or the frequency of intraspecific contact. What are the consequences for host-parasite interactions? Here we summarize the present knowledge on three principal factors in determining host-parasite associations; biodiversity, population density and immunocompetence. In addition, we analyzed examples of the effects of environmental alteration of anthropogenic origin on parasitic systems because the effects are analogous to that exerted by an extreme climatic change.

  10. Charting the host adaptation of influenza viruses.

    Science.gov (United States)

    dos Reis, Mario; Tamuri, Asif U; Hay, Alan J; Goldstein, Richard A

    2011-06-01

    Four influenza pandemics have struck the human population during the last 100 years causing substantial morbidity and mortality. The pandemics were caused by the introduction of a new virus into the human population from an avian or swine host or through the mixing of virus segments from an animal host with a human virus to create a new reassortant subtype virus. Understanding which changes have contributed to the adaptation of the virus to the human host is essential in assessing the pandemic potential of current and future animal viruses. Here, we develop a measure of the level of adaptation of a given virus strain to a particular host. We show that adaptation to the human host has been gradual with a timescale of decades and that none of the virus proteins have yet achieved full adaptation to the selective constraints. When the measure is applied to historical data, our results indicate that the 1918 influenza virus had undergone a period of preadaptation prior to the 1918 pandemic. Yet, ancestral reconstruction of the avian virus that founded the classical swine and 1918 human influenza lineages shows no evidence that this virus was exceptionally preadapted to humans. These results indicate that adaptation to humans occurred following the initial host shift from birds to mammals, including a significant amount prior to 1918. The 2009 pandemic virus seems to have undergone preadaptation to human-like selective constraints during its period of circulation in swine. Ancestral reconstruction along the human virus tree indicates that mutations that have increased the adaptation of the virus have occurred preferentially along the trunk of the tree. The method should be helpful in assessing the potential of current viruses to found future epidemics or pandemics.

  11. Monitoring host responses to the gut microbiota.

    Science.gov (United States)

    Lichtman, Joshua S; Sonnenburg, Justin L; Elias, Joshua E

    2015-09-01

    The gastrointestinal (GI) ecosystem is increasingly understood to be a fundamental component of health, and has been identified as a new focal point for diagnosing, correcting and preventing countless disorders. Shotgun DNA sequencing has emerged as the dominant technology for determining the genetic and microbial composition of the gut microbiota. This technology has linked microbiota dysbioses to numerous GI diseases including inflammatory bowel disease, obesity and allergy, and to non-GI diseases like autism and depression. The importance of establishing causality in the deterioration of the host-microbiota relationship is well appreciated; however, discovery of candidate molecules and pathways that underlie mechanisms remains a major challenge. Targeted approaches, transcriptional assays, cytokine panels and imaging analyses, applied to animals, have yielded important insight into host responses to the microbiota. However, non-invasive, hypothesis-independent means of measuring host responses in humans are necessary to keep pace with similarly unbiased sequencing efforts that monitor microbes. Mass spectrometry-based proteomics has served this purpose in many other fields, but stool proteins exist in such diversity and dynamic range as to overwhelm conventional proteomics technologies. Focused analysis of host protein secretion into the gut lumen and monitoring proteome-level dynamics in stool provides a tractable route toward non-invasively evaluating dietary, microbial, surgical or pharmacological intervention efficacies. This review is intended to guide GI biologists and clinicians through the methods currently used to elucidate host responses in the gut, with a specific focus on mass spectrometry-based shotgun proteomics applied to the study of host protein dynamics within the GI ecosystem.

  12. Does multiple hosts mean multiple parasites? Population genetic structure of Schistosoma japonicum between definitive host species.

    Science.gov (United States)

    Wang, T P; Shrivastava, J; Johansen, M V; Zhang, S Q; Wang, F F; Webster, J P

    2006-10-01

    Multi-host parasites, those capable of infecting more than one species of host, are responsible for the majority of all zoonotic, emerging or persistent human and animal diseases and are considered one of the major challenges for the biomedical sciences in the 21st century. We characterized the population structure of the multi-host parasite Schistosoma japonicum in relation to its definitive host species by genotyping miracidia collected from humans and domestic animals across five villages around the Yangtze River in Anhui Province, mainland China, using microsatellite markers. High levels of polymorphisms were observed and two main genetic clusters were identified which separated water buffalo, cattle and humans from goats, pigs, dogs and cats. We thereby believe that we present the first evidence of definitive host-based genetic variation in Schistosoma japonicum which has important epidemiological, evolutionary, medical and veterinary implications.

  13. Disease dynamics in a coupled cholera model linking within-host and between-host interactions.

    Science.gov (United States)

    Wang, Xueying; Wang, Jin

    2016-09-19

    A new modelling framework is proposed to study the within-host and between-host dynamics of cholera, a severe intestinal infection caused by the bacterium Vibrio cholerae. The within-host dynamics are characterized by the growth of highly infectious vibrios inside the human body. These vibrios shed from humans contribute to the environmental bacterial growth and the transmission of the disease among humans, providing a link from the within-host dynamics at the individual level to the between-host dynamics at the population and environmental level. A fast-slow analysis is conducted based on the two different time scales in our model. In particular, a bifurcation study is performed, and sufficient and necessary conditions are derived that lead to a backward bifurcation in cholera epidemics. Our result regarding the backward bifurcation highlights the challenges in the prevention and control of cholera.

  14. AGN Host Galaxy Properties and Mass Function

    OpenAIRE

    Bongiorno, Angela

    2016-01-01

    Supermassive black hole growth, nuclear activity, and galaxy evolution have been found to be closely related. In the context of AGN-galaxy coevolution, I will discuss about the relation found between the host galaxy properties and the central BH and I will present the latest determination of the host galaxy stellar mass function (HGMF), and the specific accretion rate distribution function (SARDF), derived from the XMM-COSMOS sample up to z∼2.5, with particular focus on AGN feedback as possib...

  15. AGN Host Galaxy Properties And Mass Function

    Science.gov (United States)

    Bongiorno, Angela

    2016-10-01

    Supermassive black hole growth, nuclear activity, and galaxy evolution have been found to be closely related. In the context of AGN-galaxy coevolution, I will discuss about the relation found between the host galaxy properties and the central BH and I will present the latest determination of the host galaxy stellar mass function (HGMF), and the specific accretion rate distribution function (SARDF), derived from the XMM-COSMOS sample up to z˜2.5, with particular focus on AGN feedback as possible responsible mechanism for galaxy quenching.

  16. Glycoconjugates in host-helminth interactions

    Directory of Open Access Journals (Sweden)

    Nina Salinger Prasanphanich

    2013-08-01

    Full Text Available Helminths are multicellular parasitic worms that comprise a major class of human pathogens and cause an immense amount of suffering worldwide. Helminths possess an abundance of complex and unique glycoconjugates that interact with both the innate and adaptive arms of immunity in definitive and intermediate hosts. These glycoconjugates represent a major untapped reservoir of immunomodulatory compounds, which have the potential to treat autoimmune and inflammatory disorders, and antigenic glycans, which could be exploited as vaccines and diagnostics. This review will survey current knowledge of the interactions between helminth glycans and host immunity and highlight the gaps in our understanding which are relevant to advancing therapeutics, vaccine development and diagnostics.

  17. Glycoconjugates in Host-Helminth Interactions

    Science.gov (United States)

    Prasanphanich, Nina Salinger; Mickum, Megan L.; Heimburg-Molinaro, Jamie; Cummings, Richard D.

    2013-01-01

    Helminths are multicellular parasitic worms that comprise a major class of human pathogens and cause an immense amount of suffering worldwide. Helminths possess an abundance of complex and unique glycoconjugates that interact with both the innate and adaptive arms of immunity in definitive and intermediate hosts. These glycoconjugates represent a major untapped reservoir of immunomodulatory compounds, which have the potential to treat autoimmune and inflammatory disorders, and antigenic glycans, which could be exploited as vaccines and diagnostics. This review will survey current knowledge of the interactions between helminth glycans and host immunity and highlight the gaps in our understanding which are relevant to advancing therapeutics, vaccine development, and diagnostics. PMID:24009607

  18. The influence of Hymenolepis diminuta on the survival and fecundity of the intermediate host, Tribolium confusum.

    Science.gov (United States)

    Keymer, A E

    1980-10-01

    An experimental study of the effects of parasitism by H. diminuta on the intermediate host, Tribolium confusum, is described. No density-dependent constraints on parasite establishment within individual hosts are evident, although a reduction in cysticercoid size at high parasite burdens is demonstrated. The relationship between parasite burden, host mortality and host fecundity is investigated. Host mortality is linearly related to parasite burden, whereas the relationship between parasite burden and host fecundity is non-linear. There is no difference in viability between eggs from infected and uninfected females. The generative causes of these effects are not investigated experimentally, although it is postulated that survival is related to the degree of damage to the midgut wall caused by parasite penetration, and fecundity to the biomass of parasites harboured by the host. The significance of these effects is discussed in relation to the overall dynamics of the host-parasite association.

  19. Ceramic Hosts for Fission Products Immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Peter C Kong

    2010-07-01

    Natural spinel, perovskite and zirconolite rank among the most leach resistant of mineral forms. They also have a strong affinity for a large number of other elements and including actinides. Specimens of natural perovskite and zirconolite were radioisotope dated and found to have survived at least 2 billion years of natural process while still remain their loading of uranium and thorium . Developers of the Synroc waste form recognized and exploited the capability of these minerals to securely immobilize TRU elements in high-level waste . However, the Synroc process requires a relatively uniform input and hot pressing equipment to produce the waste form. It is desirable to develop alternative approaches to fabricate these durable waste forms to immobilize the radioactive elements. One approach is using a high temperature process to synthesize these mineral host phases to incorporate the fission products in their crystalline structures. These mineral assemblages with immobilized fission products are then isolated in a durable high temperature glass for periods measured on a geologic time scale. This is a long term research concept and will begin with the laboratory synthesis of the pure spinel (MgAl2O4), perovskite (CaTiO3) and zirconolite (CaZrTi2O7) from their constituent oxides. High temperature furnace and/or thermal plasma will be used for the synthesis of these ceramic host phases. Nonradioactive strontium oxide will be doped into these ceramic phases to investigate the development of substitutional phases such as Mg1-xSrxAl2O4, Ca1-xSrxTiO3 and Ca1-xSrxZrTi2O7. X-ray diffraction will be used to establish the crystalline structures of the pure ceramic hosts and the substitution phases. Scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX) will be performed for product morphology and fission product surrogates distribution in the crystalline hosts. The range of strontium doping is planned to reach the full substitution of the divalent

  20. Host-lipidome as a potential target of protozoan parasites.

    Science.gov (United States)

    Rub, Abdur; Arish, Mohd; Husain, Syed Akhtar; Ahmed, Niyaz; Akhter, Yusuf

    2013-01-01

    Host-lipidome caters parasite interaction by acting as first line of recognition, attachment on the cell surface, intracellular trafficking, and survival of the parasite inside the host cell. Here, we summarize how protozoan parasites exploit host-lipidome by suppressing, augmenting, engulfing, remodeling and metabolizing lipids to achieve successful parasitism inside the host.

  1. Accurate Stellar Parameters for Exoplanet Host Stars

    Science.gov (United States)

    Brewer, John Michael; Fischer, Debra; Basu, Sarbani; Valenti, Jeff A.

    2015-01-01

    A large impedement to our understanding of planet formation is obtaining a clear picture of planet radii and densities. Although determining precise ratios between planet and stellar host are relatively easy, determining accurate stellar parameters is still a difficult and costly undertaking. High resolution spectral analysis has traditionally yielded precise values for some stellar parameters but stars in common between catalogs from different authors or analyzed using different techniques often show offsets far in excess of their uncertainties. Most analyses now use some external constraint, when available, to break observed degeneracies between surface gravity, effective temperature, and metallicity which can otherwise lead to correlated errors in results. However, these external constraints are impossible to obtain for all stars and can require more costly observations than the initial high resolution spectra. We demonstrate that these discrepencies can be mitigated by use of a larger line list that has carefully tuned atomic line data. We use an iterative modeling technique that does not require external constraints. We compare the surface gravity obtained with our spectral synthesis modeling to asteroseismically determined values for 42 Kepler stars. Our analysis agrees well with only a 0.048 dex offset and an rms scatter of 0.05 dex. Such accurate stellar gravities can reduce the primary source of uncertainty in radii by almost an order of magnitude over unconstrained spectral analysis.

  2. A Fast Radio Burst Host Galaxy

    CERN Document Server

    Keane, E F; Bhandari, S; Barr, E; Bhat, N D R; Burgay, M; Caleb, M; Flynn, C; Jameson, A; Kramer, M; Petroff, E; Possenti, A; van Straten, W; Bailes, M; Burke-Spolaor, S; Eatough, R P; Stappers, B W; Totani, T; Honma, M; Furusawa, H; Hattori, T; Morokuma, T; Niino, Y; Sugai, H; Terai, T; Tominaga, N; Yamasaki, S; Yasuda, N; Allen, R; Cooke, J; Jencson, J; Kasliwal, M M; Kaplan, D L; Tingay, S J; Williams, A; Wayth, R; Chandra, P; Perrodin, D; Berezina, M; Mickaliger, M; Bassa, C

    2016-01-01

    In recent years, millisecond duration radio signals originating from distant galaxies appear to have been discovered in the so-called Fast Radio Bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity which, in tandem with a redshift measurement, can be used for fundamental physical investigations. While every fast radio burst has a dispersion measurement, none before now have had a redshift measurement, due to the difficulty in pinpointing their celestial coordinates. Here we present the discovery of a fast radio burst and the identification of a fading radio transient lasting $\\sim 6$ days after the event, which we use to identify the host galaxy; we measure the galaxy's redshift to be $z=0.492\\pm0.008$. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionised baryons in the intergalactic medium of $\\Omega_{\\mathrm{IGM}}=4.9 \\pm 1.3\\%$, in agreement with the expectation from WMAP, and i...

  3. Beryllium abundances in stars hosting giant planets

    CERN Document Server

    Santos, N C; Israelian, G; Mayor, M; Rebolo, R; García-Gíl, A; Pérez de Taoro, M R; Randich, S

    2002-01-01

    We have derived beryllium abundances in a wide sample of stars hosting planets, with spectral types in the range F7V-K0V, aimed at studying in detail the effects of the presence of planets on the structure and evolution of the associated stars. Predictions from current models are compared with the derived abundances and suggestions are provided to explain the observed inconsistencies. We show that while still not clear, the results suggest that theoretical models may have to be revised for stars with Teff<5500K. On the other hand, a comparison between planet host and non-planet host stars shows no clear difference between both populations. Although preliminary, this result favors a ``primordial'' origin for the metallicity ``excess'' observed for the planetary host stars. Under this assumption, i.e. that there would be no differences between stars with and without giant planets, the light element depletion pattern of our sample of stars may also be used to further investigate and constraint Li and Be deple...

  4. Studies of Reservoir Hosts for Marburg virus

    DEFF Research Database (Denmark)

    Swanepoel, Robert; Smit, Sheilagh B; Rollin, Pierre E

    2007-01-01

    To determine reservoir hosts for Marburg virus (MARV), we examined the fauna of a mine in northeastern Democratic Republic of the Congo. The mine was associated with a protracted outbreak of Marburg hemorrhagic fever during 1998-2000. We found MARV nucleic acid in 12 bats, comprising 3.0%-3.6% of 2...

  5. Microbial manipulation of host sex determination

    NARCIS (Netherlands)

    Beukeboom, Leo W.

    A recent study in the lepidopteran Ostrinia scapulalis shows that endosymbionts can actively manipulate the sex determination mechanism of their host. Wolbachia bacteria alter the sex-specific splicing of the doublesex master switch gene. In ZZ males of this female heterogametic system, the female

  6. Host-pathogen interactions in typhoid fever

    NARCIS (Netherlands)

    de Jong, H.K.

    2015-01-01

    This thesis focuses on host-pathogen interactions in Salmonella Typhi and Burkholderia pseudomallei infections and explores the interplay between these bacteria and the innate immune system. Typhoid fever is one of the most common causes of bacterial infection in low-income countries. With adequate

  7. Tidal Disruption Events Prefer Unusual Host Galaxies

    CERN Document Server

    French, K Decker; Zabludoff, Ann

    2016-01-01

    Tidal Disruption Events (TDEs) are transient events observed when a star passes close enough to a supermassive black hole to be tidally destroyed. Many TDE candidates have been discovered in host galaxies whose spectra have weak or no line emission yet strong Balmer line absorption, indicating a period of intense star formation that has recently ended. As such, TDE host galaxies fall into the rare class of quiescent Balmer-strong galaxies. Here, we quantify the fraction of galaxies in the Sloan Digital Sky Survey (SDSS) with spectral properties like those of TDE hosts, determining the extent to which TDEs are over-represented in such galaxies. Galaxies whose spectra have Balmer absorption H$\\delta_{\\rm A}$ $-$ $\\sigma$(H$\\delta_{\\rm A}$) $>$ 4 \\AA\\ (where $\\sigma$(H$\\delta_{\\rm A}$) is the error in the Lick H$\\delta_{\\rm A}$ index) and H$\\alpha$ emission EW $$ 1.31 \\AA\\ and H$\\alpha$ EW $80\\times$ enhancement in such hosts and providing an observational link between the $\\gamma$/X-ray-bright and optical/UV-br...

  8. Host-pathogen interactions in typhoid fever

    NARCIS (Netherlands)

    de Jong, H.K.

    2015-01-01

    This thesis focuses on host-pathogen interactions in Salmonella Typhi and Burkholderia pseudomallei infections and explores the interplay between these bacteria and the innate immune system. Typhoid fever is one of the most common causes of bacterial infection in low-income countries. With adequate

  9. [Selective pressure in host-parasite systems].

    Science.gov (United States)

    Combes, C

    2000-01-01

    Selective pressures in host-parasite systems are the result of a continuous conflict between the divergent interests of each partner, on the long run. Whereas the fitness (lifetime reproductive success) of parasites is usually increased by a higher frequency of encounters with susceptible hosts and a better survival rate after infection, the fitness of hosts is increased by opposite processes, avoidance of encounters with infective stages and destruction of the parasites. These selective processes, often referred to as coevolution or arms races are in agreement with the Red Queen hypothesis of Van Valen, which assumes indefinite adaptive changes in both partners, in order to set up counter-measures against the weapons of "the other". Arms races in host-parasite systems thus suggest a gradualistic evolution, but this does not contradict the present day ideas on the tempo changes in the course of evolution (punctuated equilibria). Numerous factors, either genetic (evolutionary lag...), environmental (nutritional status...) or cultural (prevention, vaccination, therapy...) influence the severity of infections at an individual scale. The "terrain", which is a component of the individual phenotype, is thus at the cross-roads of genes, environment and culture. Humans must count more on their intelligence than on natural selection to prevent and cure infectious and parasitic diseases.

  10. Detecting Intermediary Hosts by TCP Latency Measurements

    Science.gov (United States)

    Singh, Gurvinder; Eian, Martin; Willassen, Svein Y.; Mjølsnes, Stig Fr.

    Use of intermediary hosts as stepping stones to conceal tracks is common in Internet misuse. It is therefore desirable to find a method to detect whether the originating party is using an intermediary host. Such a detection technique would allow the activation of a number of countermeasures that would neutralize the effects of misuse, and make it easier to trace a perpetrator. This work explores a new approach in determining if a host communicating via TCP is the data originator or if it is acting as a mere TCP proxy. The approach is based on measuring the inter packet arrival time at the receiving end of the connection only, and correlating the observed results with the network latency between the receiver and the proxy. The results presented here indicate that determining the use of a proxy host is possible, if the network latency between the originator and proxy is larger than the network latency between the proxy and the receiver. We show that this technique has potential to be used to detect connections were data is sent through a TCP proxy, such as remote login through TCP proxies, or rejecting spam sent through a bot network.

  11. Symbiosis: Gut Bacteria Manipulate Host Behaviour.

    Science.gov (United States)

    Yuval, Boaz

    2017-08-07

    Bacteria resident in the gut of Drosophila modify the fly's innate chemosensory responses to nutritional stimuli. In effect, the gut microbiome compels the host to forage on food patches that favour particular assemblages of bacteria. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Microbial manipulation of host sex determination

    NARCIS (Netherlands)

    Beukeboom, Leo W.

    2012-01-01

    A recent study in the lepidopteran Ostrinia scapulalis shows that endosymbionts can actively manipulate the sex determination mechanism of their host. Wolbachia bacteria alter the sex-specific splicing of the doublesex master switch gene. In ZZ males of this female heterogametic system, the female i

  13. Host country language ability and expatriate adjustment

    DEFF Research Database (Denmark)

    Selmer, Jan; Lauring, Jakob

    2015-01-01

    countries, one with an easy, relatively simple language and the other with a difficult, highly complex language. Consistent with Goal-Setting Theory, results indicated a relative advantage of expatriates’ language ability in terms of their adjustment in the host country with the difficult language...

  14. In Search of Quasar Host Galaxies

    Science.gov (United States)

    Young, Jason; Eracleous, M.; Gronwall, C.; Shemmer, O.; Netzer, H.; Sturm, E.; Ciardullo, R.

    2011-01-01

    We present a study of the morphology and intensity of star formation in the host galaxies of eight Palomar-Green quasars using observations with the Hubble Space Telescope. Accretion-powered and star formation activity have been shown to coincide, motivating us to search for the star-forming regions in the host galaxies of quasars and to determine the star-formation rates. In this work we use calibrated narrow band emission line (H-beta and Pa-alpha) WFPC2 and NICMOS images as maps for total star formation rate. The main challenge in imaging quasar host galaxies is the separation of the quasar light from the galaxy light, especially in the case of z approximately 0.1 quasars in WFPC2 images where the PSF radius closely matches the expected host scale radius. To this this end we present a novel technique for image decomposition and subtraction of quasar light, which we have validated through extensive simulations using artificial quasar+galaxy images. The other significant challenge in mapping and measuring star forming regions is correcting for extinction, which we address using extinction maps created from the Pa-alpha/H-beta ratio. To determine the source of excitation, we utilize H-beta along with [OIII]5007 and [OII]3727 images in diagnostic line ratio (BPT) diagrams. We detect extended line emission in our targets on scales of order 1-2 kpc. A preliminary analysis suggests star formation rates of order 10 solar masses per year.

  15. Natal Host Plants Can Alter Herbivore Competition

    Science.gov (United States)

    Pan, Huipeng; Preisser, Evan L.; Su, Qi; Jiao, Xiaoguo; Xie, Wen; Wang, Shaoli; Wu, Qingjun

    2016-01-01

    Interspecific competition between herbivores is widely recognized as an important determinant of community structure. Although researchers have identified a number of factors capable of altering competitive interactions, few studies have addressed the influence of neighboring plant species. If adaptation to/ epigenetic effects of an herbivore’s natal host plant alter its performance on other host plants, then interspecific herbivore interactions may play out differently in heterogeneous and homogenous plant communities. We tested wether the natal host plant of a whitefly population affected interactions between the Middle-east Asia Minor 1 (MEAM1) and Mediterranean (MED) cryptic species of the whitefly Bemisia tabaci by rearing the offspring of a cabbage-derived MEAM1 population and a poinsettia-derived MED population together on three different host plants: cotton, poinsettia, and cabbage. We found that MED dominated on poinsettia and that MEAM1 dominated on cabbage, results consistent with previous research. MED also dominated when reared with MEAM1 on cotton, however, a result at odds with multiple otherwise-similar studies that reared both species on the same natal plant. Our work provides evidence that natal plants affect competitive interactions on another plant species, and highlights the potential importance of neighboring plant species on herbivore community composition in agricultral systems. PMID:28030636

  16. Host Defense against Opportunist Microorganisms Following Trauma.

    Science.gov (United States)

    1988-06-30

    02ELEMENT NO. NO.3S162 jNO. ACESSION NO. Frdeic, arlnd210150262772A 772A874 AA280 11. TITLF (Include Securrty Classification) (U) Host Defense Against...copy Dean School of Medicine Uniformed Services University of the Hlealth Sciences 4301 Jones Bridge Road’ Bethesda, MD 20814-4799 1 copy Commandant

  17. Host selection by a kleptobiotic spider

    Science.gov (United States)

    Hénaut, Yann; Delme, Juliette; Legal, Luc; Williams, Trevor

    2005-02-01

    Why do kleptobiotic spiders of the genus Argyrodes seem to be associated with spiders of the genus Nephila worldwide? Observations following introduction of experimental insect prey of different sizes and weights on to host webs revealed that: (1) small prey are more effectively retained on the web of Nephila clavipes than on the web of another common host, Leucauge venusta. (2) N. clavipes did not consume small prey that accumulated on the web whereas larger, heavier prey were enveloped and stored. (3) We observed clear partitioning of prey items between N. clavipes and Argyrodes spp.; diet selection by Argyrodes did not overlap with that of N. clavipes but closely overlapped with that of L. venusta. (4) L. venusta responds very quickly to prey impact whereas N. clavipes is slower, offering a temporal window of opportunity for Argyrodes foraging. (5) The ability of L. venusta to detect and respond to small items also means that it acts aggressively to Argyrodes spp., whereas N. clavipes does not. Consequently, food-acquisition behaviours of Argyrodes were clearly less risky with N. clavipes compared with L. venusta. We conclude that when a kleptobiotic organism has a choice of various host species, it will opt for the least risky host that presents the highest rate of availability of food items. The fact that Nephila species present such characteristics explains the worldwide association with Argyrodes kleptobiotic spiders.

  18. Correlated Resource Models of Internet End Hosts

    CERN Document Server

    Heien, Eric M; David, Anderson

    2010-01-01

    Understanding and modelling resources of Internet end hosts is essential for the design of desktop software and Internet-distributed applications. In this paper we develop a correlated resource model of Internet end hosts based on real trace data taken from the SETI@home project. This data covers a 5-year period with statistics for 2.7 million hosts. The resource model is based on statistical analysis of host computational power, memory, and storage as well as how these resources change over time and the correlations between them. We find that resources with few discrete values (core count, memory) are well modeled by exponential laws governing the change of relative resource quantities over time. Resources with a continuous range of values are well modeled with either correlated normal distributions (processor speed for integer operations and floating point operations) or log-normal distributions (available disk space). We validate and show the utility of the models by applying them to a resource allocation ...

  19. Five bid to host Middle East synchroton

    CERN Multimedia

    McCabe, H

    1999-01-01

    Germany is willing to donate a synchrotron to a research centre to be built somewhere in the Middle East. Bids to host the centre were submitted by Turkey, Cyprus, Iran, the Palestinian Authority and Egypt. Funding of at least 30 million US dollars still needs to be found (1 page).

  20. Probing Pseudomonas syringae host interactions using metatranscriptomics

    Science.gov (United States)

    Transcriptome analyses during the interaction of plants and pathogens can be used to provide insights into molecular mechanisms of plant resistance as well as the mechanisms used by bacteria to adapt to hosts and cause disease. We performed a dual in planta RNA-Seq experiment to profile RNA expressi...

  1. Natal Host Plants Can Alter Herbivore Competition.

    Science.gov (United States)

    Pan, Huipeng; Preisser, Evan L; Su, Qi; Jiao, Xiaoguo; Xie, Wen; Wang, Shaoli; Wu, Qingjun; Zhang, Youjun

    2016-01-01

    Interspecific competition between herbivores is widely recognized as an important determinant of community structure. Although researchers have identified a number of factors capable of altering competitive interactions, few studies have addressed the influence of neighboring plant species. If adaptation to/ epigenetic effects of an herbivore's natal host plant alter its performance on other host plants, then interspecific herbivore interactions may play out differently in heterogeneous and homogenous plant communities. We tested wether the natal host plant of a whitefly population affected interactions between the Middle-east Asia Minor 1 (MEAM1) and Mediterranean (MED) cryptic species of the whitefly Bemisia tabaci by rearing the offspring of a cabbage-derived MEAM1 population and a poinsettia-derived MED population together on three different host plants: cotton, poinsettia, and cabbage. We found that MED dominated on poinsettia and that MEAM1 dominated on cabbage, results consistent with previous research. MED also dominated when reared with MEAM1 on cotton, however, a result at odds with multiple otherwise-similar studies that reared both species on the same natal plant. Our work provides evidence that natal plants affect competitive interactions on another plant species, and highlights the potential importance of neighboring plant species on herbivore community composition in agricultral systems.

  2. Pollination niche overlap between a parasitic plant and its host.

    Science.gov (United States)

    Ollerton, Jeff; Stott, Adrian; Allnutt, Emma; Shove, Sam; Taylor, Chloe; Lamborn, Ellen

    2007-03-01

    Niche theory predicts that species which share resources should evolve strategies to minimise competition for those resources, or the less competitive species would be extirpated. Some plant species are constrained to co-occur, for example parasitic plants and their hosts, and may overlap in their pollination niche if they flower at the same time and attract the same pollinators. Using field observations and experiments between 1996 and 2006, we tested a series of hypotheses regarding pollination niche overlap between a specialist parasitic plant Orobanche elatior (Orobanchaceae) and its host Centaurea scabiosa (Asteraceae). These species flower more or less at the same time, with some year-to-year variation. The host is pollinated by a diverse range of insects, which vary in their effectiveness, whilst the parasite is pollinated by a single species of bumblebee, Bombus pascuorum, which is also an effective pollinator of the host plant. The two species therefore have partially overlapping pollination niches. These niches are not finely subdivided by differential pollen placement, or by diurnal segregation of the niches. We therefore found no evidence of character displacement within the pollination niches of these species, possibly because pollinators are not a limiting resource for these plants. Direct observation of pollinator movements, coupled with experimental manipulations of host plant inflorescence density, showed that Bombus pascuorum only rarely moves between inflorescences of the host and the parasite and therefore the presence of one plant is unlikely to be facilitating pollination in the other. This is the first detailed examination of pollination niche overlap in a plant parasite system and we suggest avenues for future research in relation to pollination and other shared interactions between parasitic plants and their hosts.

  3. Genome characteristics of facultatively symbiotic Frankia sp. strains reflect host range and host plant biogeography

    Science.gov (United States)

    Normand, Philippe; Lapierre, Pascal; Tisa, Louis S.; Gogarten, Johann Peter; Alloisio, Nicole; Bagnarol, Emilie; Bassi, Carla A.; Berry, Alison M.; Bickhart, Derek M.; Choisne, Nathalie; Couloux, Arnaud; Cournoyer, Benoit; Cruveiller, Stephane; Daubin, Vincent; Demange, Nadia; Francino, Maria Pilar; Goltsman, Eugene; Huang, Ying; Kopp, Olga R.; Labarre, Laurent; Lapidus, Alla; Lavire, Celine; Marechal, Joelle; Martinez, Michele; Mastronunzio, Juliana E.; Mullin, Beth C.; Niemann, James; Pujic, Pierre; Rawnsley, Tania; Rouy, Zoe; Schenowitz, Chantal; Sellstedt, Anita; Tavares, Fernando; Tomkins, Jeffrey P.; Vallenet, David; Valverde, Claudio; Wall, Luis G.; Wang, Ying; Medigue, Claudine; Benson, David R.

    2007-01-01

    Soil bacteria that also form mutualistic symbioses in plants encounter two major levels of selection. One occurs during adaptation to and survival in soil, and the other occurs in concert with host plant speciation and adaptation. Actinobacteria from the genus Frankia are facultative symbionts that form N2-fixing root nodules on diverse and globally distributed angiosperms in the “actinorhizal” symbioses. Three closely related clades of Frankia sp. strains are recognized; members of each clade infect a subset of plants from among eight angiosperm families. We sequenced the genomes from three strains; their sizes varied from 5.43 Mbp for a narrow host range strain (Frankia sp. strain HFPCcI3) to 7.50 Mbp for a medium host range strain (Frankia alni strain ACN14a) to 9.04 Mbp for a broad host range strain (Frankia sp. strain EAN1pec.) This size divergence is the largest yet reported for such closely related soil bacteria (97.8%–98.9% identity of 16S rRNA genes). The extent of gene deletion, duplication, and acquisition is in concert with the biogeographic history of the symbioses and host plant speciation. Host plant isolation favored genome contraction, whereas host plant diversification favored genome expansion. The results support the idea that major genome expansions as well as reductions can occur in facultative symbiotic soil bacteria as they respond to new environments in the context of their symbioses. PMID:17151343

  4. Host-released dimethylsulphide activates the dinoflagellate parasitoid Parvilucifera sinerae.

    Science.gov (United States)

    Garcés, Esther; Alacid, Elisabet; Reñé, Albert; Petrou, Katherina; Simó, Rafel

    2013-05-01

    Parasitoids are a major top-down cause of mortality of coastal harmful algae, but the mechanisms and strategies they have evolved to efficiently infect ephemeral blooms are largely unknown. Here, we show that the generalist dinoflagellate parasitoid Parvilucifera sinerae (Perkinsozoa, Alveolata) is activated from dormancy, not only by Alexandrium minutum cells but also by culture filtrates. We unequivocally identified the algal metabolite dimethylsulphide (DMS) as the density-dependent cue of the presence of potential host. This allows the parasitoid to alternate between a sporangium-hosted dormant stage and a chemically-activated, free-living virulent stage. DMS-rich exudates of resistant dinoflagellates also induced parasitoid activation, which we interpret as an example of coevolutionary arms race between parasitoid and host. These results further expand the involvement of dimethylated sulphur compounds in marine chemical ecology, where they have been described as foraging cues and chemoattractants for mammals, turtles, birds, fish, invertebrates and plankton microbes.

  5. Trophic relationships between the parasitic plant species Phelipanche ramosa (L. and different hosts depending on host phenological stage and host growth rate

    Directory of Open Access Journals (Sweden)

    Delphine Moreau

    2016-07-01

    Full Text Available Phelipanche ramosa (L. Pomel (branched broomrape is a holoparasitic plant that reproduces on crops and also on weeds, which contributes to increase the parasite seed bank in fields. This parasite extracts all its nutrients at the host's expense so that host-parasite trophic relationships are crucial to determine host and parasite growth. This study quantified the intensity with which P. ramosa draws assimilates from its host and analyzed whether it varied with host species, host phenological stage and host growth rate. A greenhouse experiment was conducted on three host species: the crop species Brassica napus (L. (oilseed rape and two weed species, Capsella bursa-pastoris (L. Medik. and Geranium dissectum (L.. Plants were grown with or without P. ramosa and under three light levels to modulate host growth rate. The proportion of host biomass loss due to parasitism by P. ramosa differed between host species (at host fructification, biomass loss ranged from 34% to 84%. Brassica napus and C. bursa-pastoris displayed a similar response to P. ramosa, probably because they belong to the same botanical family. The sensitivity to P. ramosa in each host species could be related to the precocity of P. ramosa development on them. Host compartments could be ranked as a function of their sensitivity to parasitism, with the reproductive compartment being the most severely affected, followed by stems and roots. The proportion of biomass allocated to leaves was not reduced by parasitism. The proportion of pathosystem biomass allocated to the parasite depended on host species. It generally increased with host stage progression but was constant across light induced-host growth rate, showing that P. ramosa adapts its growth to host biomass production. The rank order of host species in terms of sink strength differed from that in terms of host sensitivity. Finally, for B. napus, the biomass of individual parasite shoots decreased with increasing their number per

  6. Citrus tristeza virus-host interactions

    Directory of Open Access Journals (Sweden)

    William O. Dawson

    2013-05-01

    Full Text Available Citrus tristeza virus (CTV is a phloem-limited virus whose natural host range is restricted to citrus and related species. Although the virus has killed millions of trees, almost destroying whole industries, and continually limits production in many citrus growing areas, most isolates are mild or symptomless in most of their host range. There is little understanding of how the virus causes severe disease in some citrus and none in others. Movement and distribution of CTV differs considerably from that of well-studied viruses of herbaceous plants where movement occurs largely through adjacent cells. In contrast, CTV systemically infects plants mainly by long-distance movement with only limited cell-to-cell movement. The virus is transported through sieve elements and occasionally enters an adjacent companion or phloem parenchyma cell where virus replication occurs. In some plants this is followed by cell-to-cell movement into only a small cluster of adjacent cells, while in others there is no cell-to-cell movement. Different proportions of cells adjacent to sieve elements become infected in different plant species. This appears to be related to how well viral gene products interact with specific hosts. CTV has three genes that are not necessary for infection of most of its hosts, but are needed in different combinations for infection of certain citrus species. These genes apparently were acquired by the virus to extend its host range. Some specific viral gene products have been implicated in symptom induction. Remarkably, the deletion of these genes from the virus genome can induce large increases in stem pitting symptoms. The p23 gene, which is a suppressor of RNA silencing and a regulator of viral RNA synthesis, has been shown to be the cause of seedling yellows symptoms in sour orange. Most isolates of CTV in nature are populations of different strains of CTV. The next frontier of CTV biology is the understanding how the virus variants in

  7. Different Host Exploitation Strategies in Two Zebra Mussel-Trematode Systems: Adjustments of Host Life History Traits

    OpenAIRE

    Laëtitia Minguez; Thierry Buronfosse; Laure Giambérini

    2012-01-01

    The zebra mussel is the intermediate host for two digenean trematodes, Phyllodistomum folium and Bucephalus polymorphus, infecting gills and the gonad respectively. Many gray areas exist relating to the host physiological disturbances associated with these infections, and the strategies used by these parasites to exploit their host without killing it. The aim of this study was to examine the host exploitation strategies of these trematodes and the associated host physiological disturbances. W...

  8. Host preference of the bean weevil Zabrotes subfasciatus

    Institute of Scientific and Technical Information of China (English)

    Isabel Ribeiro do Valle Teixeira; Angel Roberto Barchuk; Fernando Sérgio Zucoloto

    2008-01-01

    It is largely known that the range of an insect diet is mostly determined by oviposition behavior, mainly in species with endophytic larvae such as Zabrotes subfasciatus.However, the proximate factors determining host choice and the subsequent steps leading to the expansion or reduction of the host number and occasional host shifts are largelyun known. We analyzed various factors determining host preference of Z. subfasciatus through the evaluation of: (i) oviposition preference of a wild population of Z. subfasciatus on the usual host (bean) and unusual hosts (lentil, chickpea and soy), and the performance of the offspring; (ii) artificial selection for increasing preference for hosts initially less frequently chosen; (iii) comparison of oviposition behavior between two different popula-tions (reared for~30 generations in beans or chickpeas, respectively); (iv) oviposition timing on usual and unusual hosts; and (v) identification of preference hierarchies. We found that when using unusual hosts, there is no correlation between performance and preference and that the preference hierarchy changes only slightly when the population passes through several generations on the less frequently accepted host. We also found a positive response to artificial selection for increasing oviposition on the less preferred host; however, when the host-choice experiment involved two varieties of the usual host, the response was faster than when the choice involved usual and unusual hosts. Finally, beetles reared on an unusual host (chickpea) for 26 generations showed similar good fitness on both usual and unusual hosts,indicating that the use of a new host does not necessarily result in the loss of performance on the original host. Nevertheless, this population showed lower fitness on the usual host than that of the original population, suggesting an underlying partial trade-off phenomenon which may contribute to a broadening of diet of this insect species.

  9. Susceptibility to Phytophthora ramorum in a key infectious host: landscape variation in host genotype, host phenotype, and environmental factors.

    Science.gov (United States)

    Anacker, Brian L; Rank, Nathan E; Hüberli, Daniel; Garbelotto, Matteo; Gordon, Sarah; Harnik, Tami; Whitkus, Richard; Meentemeyer, Ross

    2008-01-01

    Sudden oak death is an emerging forest disease caused by the invasive pathogen Phytophthora ramorum. Genetic and environmental factors affecting susceptibility to P. ramorum in the key inoculum-producing host tree Umbellularia californica (bay laurel) were examined across a heterogeneous landscape in California, USA. Laboratory susceptibility trials were conducted on detached leaves and assessed field disease levels for 97 host trees from 12 225-m(2) plots. Genotype and phenotype characteristics were assessed for each tree. Effects of plot-level environmental conditions (understory microclimate, amount of solar radiation and topographic moisture potential) on disease expression were also evaluated. Susceptibility varied significantly among U. californica trees, with a fivefold difference in leaf lesion size. Lesion size was positively related to leaf area, but not to other phenotypic traits or to field disease level. Genetic diversity was structured at three spatial scales, but primarily among individuals within plots. Lesion size was significantly related to amplified fragment length polymorphism (AFLP) markers, but local environment explained most variation in field disease level. Thus, substantial genetic variation in susceptibility to P. ramorum occurs in its principal foliar host U. californica, but local environment mediates expression of susceptibility in nature.

  10. The baculovirus uses a captured host phosphatase to induce enhanced locomotory activity in host caterpillars.

    Directory of Open Access Journals (Sweden)

    Susumu Katsuma

    Full Text Available The baculovirus is a classic example of a parasite that alters the behavior or physiology of its host so that progeny transmission is maximized. Baculoviruses do this by inducing enhanced locomotory activity (ELA that causes the host caterpillars to climb to the upper foliage of plants. We previously reported that this behavior is not induced in silkworms that are infected with a mutant baculovirus lacking its protein tyrosine phosphatase (ptp gene, a gene likely captured from an ancestral host. Here we show that the product of the ptp gene, PTP, associates with baculovirus ORF1629 as a virion structural protein, but surprisingly phosphatase activity associated with PTP was not required for the induction of ELA. Interestingly, the ptp knockout baculovirus showed significantly reduced infectivity of larval brain tissues. Collectively, we show that the modern baculovirus uses the host-derived phosphatase to establish adequate infection for ELA as a virion-associated structural protein rather than as an enzyme.

  11. Divergence in olfactory host plant preference in D. mojavensis in response to cactus host use.

    Science.gov (United States)

    Date, Priya; Dweck, Hany K M; Stensmyr, Marcus C; Shann, Jodi; Hansson, Bill S; Rollmann, Stephanie M

    2013-01-01

    Divergence in host adaptive traits has been well studied from an ecological and evolutionary perspective, but identification of the proximate mechanisms underlying such divergence is less well understood. Behavioral preferences for host plants are often mediated by olfaction and shifts in preference may be accompanied by changes in the olfactory system. In this study, we examine the evolution of host plant preferences in cactophilic Drosophila mojavensis that feeds and breeds on different cacti throughout its range. We show divergence in electrophysiological responses and olfactory behavior among populations with host plant shifts. Specifically, significant divergence was observed in the Mojave Desert population that specializes on barrel cactus. Differences were observed in electrophysiological responses of the olfactory organs and in behavioral responses to barrel cactus volatiles. Together our results suggest that the peripheral nervous system has changed in response to different ecological environments and that these changes likely contribute to divergence among D. mojavensis populations.

  12. Host Specificity in the Parasitic Plant Cytinus hypocistis

    Directory of Open Access Journals (Sweden)

    C. J. Thorogood

    2007-01-01

    Full Text Available Host specificity in the parasitic plant Cytinus hypocistis was quantified at four sites in the Algarve region of Portugal from 2002 to 2007. The parasite was found to be locally host specific, and only two hosts were consistently infected: Halimium halimifolium and Cistus monspeliensis. C. hypocistis did not infect hosts in proportion to their abundance; at three sites, 100% of parasites occurred on H. halimifolium which represented just 42.4%, 3% and 19.7% of potential hosts available, respectively. At the remaining site, where H. halimifolium was absent, 100% of parasites occurred on C. monspeliensis which represented 81.1% of potential hosts available. Other species of potential host were consistently uninfected irrespective of their abundance. Ecological niche divergence of host plants H. halimifolium and C. monspeliensis may isolate host-specific races of C. hypocistis, thereby potentially driving allopatric divergence in this parasitic plant.

  13. Host-Associated Differentiation: The Gape-and-Pinch Model

    Directory of Open Access Journals (Sweden)

    Stephen B. Heard

    2012-01-01

    Full Text Available Ecological speciation via host shifting has contributed to the astonishing diversity of phytophagous insects. The importance for host shifting of trait differences between alternative host plants is well established, but much less is known about trait variation within hosts. I outline a conceptual model, the “gape-and-pinch” (GAP model, of insect response to host-plant trait variation during host shifting and host-associated differentiation. I offer four hypotheses about insect use of plant trait variation on two alternative hosts, for insects at different stages of host-associated differentiation. Collectively, these hypotheses suggest that insect responses to plant trait variation can favour or oppose critical steps in herbivore diversification. I provide statistical tools for analysing herbivore trait-space use, demonstrate their application for four herbivores of the goldenrods Solidago altissima and S. gigantea, and discuss their broader potential to advance our understanding of diet breadth and ecological speciation in phytophagous insects.

  14. Constraints on host choice: why do parasitic birds rarely exploit some common potential hosts?

    Science.gov (United States)

    Grim, Tomáš; Samaš, Peter; Moskát, Csaba; Kleven, Oddmund; Honza, Marcel; Moksnes, Arne; Røskaft, Eivin; Stokke, Bård G

    2011-05-01

    1. Why are some common and apparently suitable resources avoided by potential users? This interesting ecological and evolutionary conundrum is vividly illustrated by obligate brood parasites. Parasitic birds lay their eggs into nests of a wide range of host species, including many rare ones, but do not parasitize some commonly co-occurring potential hosts. 2. Attempts to explain the absence of parasitism in common potential hosts are limited and typically focused on single-factor explanations while ignoring other potential factors. We tested why thrushes Turdus spp. are extremely rarely parasitized by common cuckoos Cuculus canorus despite breeding commonly in sympatry and building the most conspicuous nests among forest-breeding passerines. 3. No single examined factor explained cuckoo avoidance of thrushes. Life-history traits of all six European thrush species and the 10 most frequently used cuckoo hosts in Europe were similar except body/egg size, nest design and nestling diet. 4. Experiments (n = 1211) in several populations across Europe showed that host defences at egg-laying and incubation stages did not account for the lack of cuckoo parasitism in thrushes. However, cross-fostering experiments disclosed that various factors during the nestling period prevent cuckoos from successfully parasitizing thrushes. Specifically, in some thrush species, the nest cup design forced cuckoo chicks to compete with host chicks with fatal consequences for the parasite. Other species were reluctant to care even for lone cuckoo chicks. 5. Importantly, in an apparently phylogenetically homogenous group of hosts, there were interspecific differences in factors responsible for the absence of cuckoo parasitism. 6. This study highlights the importance of considering multiple potential factors and their interactions for understanding absence of parasitism in potential hosts of parasitic birds. In the present study, comparative and experimental procedures are integrated, which

  15. Species formation by host shifting in avian malaria parasites.

    Science.gov (United States)

    Ricklefs, Robert E; Outlaw, Diana C; Svensson-Coelho, Maria; Medeiros, Matthew C I; Ellis, Vincenzo A; Latta, Steven

    2014-10-14

    The malaria parasites (Apicomplexa: Haemosporida) of birds are believed to have diversified across the avian host phylogeny well after the origin of most major host lineages. Although many symbionts with direct transmission codiversify with their hosts, mechanisms of species formation in vector-borne parasites, including the role of host shifting, are poorly understood. Here, we examine the hosts of sister lineages in a phylogeny of 181 putative species of malaria parasites of New World terrestrial birds to determine the role of shifts between host taxa in the formation of new parasite species. We find that host shifting, often across host genera and families, is the rule. Sympatric speciation by host shifting would require local reproductive isolation as a prerequisite to divergent selection, but this mechanism is not supported by the generalized host-biting behavior of most vectors of avian malaria parasites. Instead, the geographic distribution of individual parasite lineages in diverse hosts suggests that species formation is predominantly allopatric and involves host expansion followed by local host-pathogen coevolution and secondary sympatry, resulting in local shifting of parasite lineages across hosts.

  16. CERN hosts Physics and Society Forum

    CERN Multimedia

    Katarina Anthony

    2012-01-01

    On 28-29 March, CERN hosted the fifth edition of the European Physical Society's “Physics and Society” forum. The forum addresses the role of physicists in general society – be they in education, politics, industry or communication. This year, attendees looked at how physicists have adapted - and can continue to adapt - to work in the economic marketplace.   “The forums began back in 2006, as a special closing event for the 2005 World Year of Physics,” explains Martial Ducloy, former President of the French Physical Society and Chair of the EPS Forum Physics and Society. “We decided to keep the sessions going, as they gave physicists a venue to discuss the non-scientific issues that influence their daily work. As the world's largest international physics laboratory – and the venue for this year's EPS Council – CERN seemed the ideal place to host this year's forum.” The forum ...

  17. Planets, debris and their host metallicity correlations

    CERN Document Server

    Fletcher, Mark

    2016-01-01

    Recent observations of debris discs, believed to be made up of remnant planetesimals, brought a number of surprises. Debris disc presence does not correlate with the host star's metallicity, and may anti-correlate with the presence of gas giant planets. These observations contradict both assumptions and predictions of the highly successful Core Accretion model of planet formation. Here we explore predictions of the alternative Tidal Downsizing (TD) scenario of planet formation. In TD, small planets and planetesimal debris is made only when gas fragments, predecessors of giant planets, are tidally disrupted. We show that these disruptions are rare in discs around high metallicity stars but release more debris per disruption than their low [M/H] analogs. This predicts no simple relation between debris disc presence and host star's [M/H], as observed. A detected gas giant planet implies in TD that its predecessor fragment was not disputed, potentially explaining why DDs are less likely to be found around stars w...

  18. Exploitation of host cells by Burkholderia pseudomallei.

    Science.gov (United States)

    Stevens, Mark P; Galyov, Edouard E

    2004-04-01

    Intracellular bacterial pathogens have evolved mechanisms to enter and exit eukaryotic cells using the power of actin polymerisation and to subvert the activity of cellular enzymes and signal transduction pathways. The proteins deployed by bacteria to subvert cellular processes often mimic eukaryotic proteins in their structure or function. Studies on the exploitation of host cells by the facultative intracellular pathogen Burkholderia pseudomallei are providing novel insights into the pathogenesis of melioidosis, a serious invasive disease of animals and humans that is endemic in tropical and subtropical areas. B. pseudomallei can invade epithelial cells, survive and proliferate inside phagocytes, escape from endocytic vesicles, form actin-based membrane protrusions and induce host cell fusion. Here we review current understanding of the molecular mechanisms underlying these processes.

  19. Giardia duodenalis genetic assemblages and hosts

    Directory of Open Access Journals (Sweden)

    Heyworth Martin F.

    2016-01-01

    Full Text Available Techniques for sub-classifying morphologically identical Giardia duodenalis trophozoites have included comparisons of the electrophoretic mobility of enzymes and of chromosomes, and sequencing of genes encoding β-giardin, triose phosphate isomerase, the small subunit of ribosomal RNA and glutamate dehydrogenase. To date, G. duodenalis organisms have been sub-classified into eight genetic assemblages (designated A–H. Genotyping of G. duodenalis organisms isolated from various hosts has shown that assemblages A and B infect the largest range of host species, and appear to be the main (or possibly only G. duodenalis assemblages that undeniably infect human subjects. In at least some cases of assemblage A or B infection in wild mammals, there is suggestive evidence that the infection had resulted from environmental contamination by G. duodenalis cysts of human origin.

  20. Prokaryotes Versus Eukaryotes: Who is Hosting Whom?

    Science.gov (United States)

    Tellez, Guillermo

    2014-01-01

    Microorganisms represent the largest component of biodiversity in our world. For millions of years, prokaryotic microorganisms have functioned as a major selective force shaping eukaryotic evolution. Microbes that live inside and on animals outnumber the animals' actual somatic and germ cells by an estimated 10-fold. Collectively, the intestinal microbiome represents a "forgotten organ," functioning as an organ inside another that can execute many physiological responsibilities. The nature of primitive eukaryotes was drastically changed due to the association with symbiotic prokaryotes facilitating mutual coevolution of host and microbe. Phytophagous insects have long been used to test theories of evolutionary diversification; moreover, the diversification of a number of phytophagous insect lineages has been linked to mutualisms with microbes. From termites and honey bees to ruminants and mammals, depending on novel biochemistries provided by the prokaryotic microbiome, the association helps to metabolize several nutrients that the host cannot digest and converting these into useful end products (such as short-chain fatty acids), a process, which has huge impact on the biology and homeostasis of metazoans. More importantly, in a direct and/or indirect way, the intestinal microbiota influences the assembly of gut-associated lymphoid tissue, helps to educate immune system, affects the integrity of the intestinal mucosal barrier, modulates proliferation and differentiation of its epithelial lineages, regulates angiogenesis, and modifies the activity of enteric as well as the central nervous system. Despite these important effects, the mechanisms by which the gut microbial community influences the host's biology remain almost entirely unknown. Our aim here is to encourage empirical inquiry into the relationship between mutualism and evolutionary diversification between prokaryotes and eukaryotes, which encourage us to postulate: who is hosting whom?

  1. Host-pathogen interactions in typhoid fever

    OpenAIRE

    de Jong, H.K.

    2015-01-01

    This thesis focuses on host-pathogen interactions in Salmonella Typhi and Burkholderia pseudomallei infections and explores the interplay between these bacteria and the innate immune system. Typhoid fever is one of the most common causes of bacterial infection in low-income countries. With adequate antibiotic treatment it has a low mortality rate. Melioidosis also commonly causes community-acquired sepsis in Southeast Asia and northern Australia but even with appropriate antibiotic treatment ...

  2. Linking Virus Genomes with Host Taxonomy.

    Science.gov (United States)

    Mihara, Tomoko; Nishimura, Yosuke; Shimizu, Yugo; Nishiyama, Hiroki; Yoshikawa, Genki; Uehara, Hideya; Hingamp, Pascal; Goto, Susumu; Ogata, Hiroyuki

    2016-03-01

    Environmental genomics can describe all forms of organisms--cellular and viral--present in a community. The analysis of such eco-systems biology data relies heavily on reference databases, e.g., taxonomy or gene function databases. Reference databases of symbiosis sensu lato, although essential for the analysis of organism interaction networks, are lacking. By mining existing databases and literature, we here provide a comprehensive and manually curated database of taxonomic links between viruses and their cellular hosts.

  3. Protective host immune responses to Salmonella infection

    OpenAIRE

    Pham, Oanh H.; McSorley, Stephen J.

    2015-01-01

    Salmonella enterica serovars Typhi and Paratyphi are the causative agents of human typhoid fever. Current typhoid vaccines are ineffective and are not widely used in endemic areas. Greater understanding of host–pathogen interactions during Salmonella infection should facilitate the development of improved vaccines to combat typhoid and nontyphoidal Salmonellosis. This review will focus on our current understanding of Salmonella pathogenesis and the major host immune components that participat...

  4. Identification of host response signatures of infection.

    Energy Technology Data Exchange (ETDEWEB)

    Branda, Steven S.; Sinha, Anupama; Bent, Zachary

    2013-02-01

    Biological weapons of mass destruction and emerging infectious diseases represent a serious and growing threat to our national security. Effective response to a bioattack or disease outbreak critically depends upon efficient and reliable distinguishing between infected vs healthy individuals, to enable rational use of scarce, invasive, and/or costly countermeasures (diagnostics, therapies, quarantine). Screening based on direct detection of the causative pathogen can be problematic, because culture- and probe-based assays are confounded by unanticipated pathogens (e.g., deeply diverged, engineered), and readily-accessible specimens (e.g., blood) often contain little or no pathogen, particularly at pre-symptomatic stages of disease. Thus, in addition to the pathogen itself, one would like to detect infection-specific host response signatures in the specimen, preferably ones comprised of nucleic acids (NA), which can be recovered and amplified from tiny specimens (e.g., fingerstick draws). Proof-of-concept studies have not been definitive, however, largely due to use of sub-optimal sample preparation and detection technologies. For purposes of pathogen detection, Sandia has developed novel molecular biology methods that enable selective isolation of NA unique to, or shared between, complex samples, followed by identification and quantitation via Second Generation Sequencing (SGS). The central hypothesis of the current study is that variations on this approach will support efficient identification and verification of NA-based host response signatures of infectious disease. To test this hypothesis, we re-engineered Sandia's sophisticated sample preparation pipelines, and developed new SGS data analysis tools and strategies, in order to pioneer use of SGS for identification of host NA correlating with infection. Proof-of-concept studies were carried out using specimens drawn from pathogen-infected non-human primates (NHP). This work provides a strong foundation for

  5. Probability of Transmission of Malaria from Mosquito to Human Is Regulated by Mosquito Parasite Density in Naïve and Vaccinated Hosts.

    Directory of Open Access Journals (Sweden)

    Thomas S Churcher

    2017-01-01

    Full Text Available Over a century since Ronald Ross discovered that malaria is caused by the bite of an infectious mosquito it is still unclear how the number of parasites injected influences disease transmission. Currently it is assumed that all mosquitoes with salivary gland sporozoites are equally infectious irrespective of the number of parasites they harbour, though this has never been rigorously tested. Here we analyse >1000 experimental infections of humans and mice and demonstrate a dose-dependency for probability of infection and the length of the host pre-patent period. Mosquitoes with a higher numbers of sporozoites in their salivary glands following blood-feeding are more likely to have caused infection (and have done so quicker than mosquitoes with fewer parasites. A similar dose response for the probability of infection was seen for humans given a pre-erythrocytic vaccine candidate targeting circumsporozoite protein (CSP, and in mice with and without transfusion of anti-CSP antibodies. These interventions prevented infection more efficiently from bites made by mosquitoes with fewer parasites. The importance of parasite number has widespread implications across malariology, ranging from our basic understanding of the parasite, how vaccines are evaluated and the way in which transmission should be measured in the field. It also provides direct evidence for why the only registered malaria vaccine RTS,S was partially effective in recent clinical trials.

  6. Probability of Transmission of Malaria from Mosquito to Human Is Regulated by Mosquito Parasite Density in Naïve and Vaccinated Hosts

    Science.gov (United States)

    Sinden, Robert E.; Poulton, Ian D.; Griffin, Jamie T.; Upton, Leanna M.; Sala, Katarzyna A.; Angrisano, Fiona; Hill, Adrian V. S.; Blagborough, Andrew M.

    2017-01-01

    Over a century since Ronald Ross discovered that malaria is caused by the bite of an infectious mosquito it is still unclear how the number of parasites injected influences disease transmission. Currently it is assumed that all mosquitoes with salivary gland sporozoites are equally infectious irrespective of the number of parasites they harbour, though this has never been rigorously tested. Here we analyse >1000 experimental infections of humans and mice and demonstrate a dose-dependency for probability of infection and the length of the host pre-patent period. Mosquitoes with a higher numbers of sporozoites in their salivary glands following blood-feeding are more likely to have caused infection (and have done so quicker) than mosquitoes with fewer parasites. A similar dose response for the probability of infection was seen for humans given a pre-erythrocytic vaccine candidate targeting circumsporozoite protein (CSP), and in mice with and without transfusion of anti-CSP antibodies. These interventions prevented infection more efficiently from bites made by mosquitoes with fewer parasites. The importance of parasite number has widespread implications across malariology, ranging from our basic understanding of the parasite, how vaccines are evaluated and the way in which transmission should be measured in the field. It also provides direct evidence for why the only registered malaria vaccine RTS,S was partially effective in recent clinical trials. PMID:28081253

  7. Deforestation homogenizes tropical parasitoid-host networks.

    Science.gov (United States)

    Laliberté, Etienne; Tylianakis, Jason M

    2010-06-01

    Human activities drive biotic homogenization (loss of regional diversity) of many taxa. However, whether species interaction networks (e.g., food webs) can also become homogenized remains largely unexplored. Using 48 quantitative parasitoid-host networks replicated through space and time across five tropical habitats, we show that deforestation greatly homogenized network structure at a regional level, such that interaction composition became more similar across rice and pasture sites compared with forested habitats. This was not simply caused by altered consumer and resource community composition, but was associated with altered consumer foraging success, such that parasitoids were more likely to locate their hosts in deforested habitats. Furthermore, deforestation indirectly homogenized networks in time through altered mean consumer and prey body size, which decreased in deforested habitats. Similar patterns were obtained with binary networks, suggesting that interaction (link) presence-absence data may be sufficient to detect network homogenization effects. Our results show that tropical agroforestry systems can support regionally diverse parasitoid-host networks, but that removal of canopy cover greatly homogenizes the structure of these networks in space, and to a lesser degree in time. Spatiotemporal homogenization of interaction networks may alter coevolutionary outcomes and reduce ecological resilience at regional scales, but may not necessarily be predictable from community changes observed within individual trophic levels.

  8. Planet Host Stars: Mass, Age and Kinematics

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    We determine the mass, age and kinematics of 51 extra-solar planet host stars. The results are then used to search for signs of connection of the data with metallicity and to investigate the population nature. We find that the increase in mean metallicity with stellar mass is similar to that in normal field stars, so it seems unsuitable to use this relation as a constraint on the theory of planet formation. The age and kinematic distributions seem to favour the metallicity of extra-solar planet host stars being initial. Although the kinematic data of these stars indicate their origin from two populations - the thin and the thick disks, kinematics may not help in the maintenance of the planet around the host. Stars with planets, brown dwarfs or stellar companions are sorted into three groups and re-investigated separately for their formation mechanism. The main results indicate that stars with M2 < 25MJ have [Fe/H] > -0.1 and a wide period range, but there are no other differences.Thus, there does not seem to be any physically distinguishable characteristics among the three star groups.

  9. Characterization of Kepler Exoplanet Host Stars

    Science.gov (United States)

    Howell, Steve B.; Everett, M.; Ciardi, D. R.; Silva, D.; Szkody, P.

    2014-01-01

    Using a sample of 220 Exoplanet host stars in the Kepler field for which spectroscopic properties have been determined, we examine their spatial, physical, and time variable properties. Covering effective temperatures from 4670K to 6400K (K4 to F4) and masses from 0.7 to 1.4 M-sun, this sample represents host stars covering the entire Kepler field of view. The majority of the host stars contain one or more Earth-sized exoplanet and range in log g from 4.0 to 4.7 and [Fe/H] from -02.4 to +0.3. Using Yale-Yonsei isochrone fits and photometric information form the Howell-Everett UBV survey of the Kepler field, we examine a complete set of parameters for these stars including their likely residence in the thin or thick disk of the Galaxy. the variability of this sample, in terms of time sale and amplitude, is examined as well.

  10. Inflammasomes in host response to protozoan parasites.

    Science.gov (United States)

    Zamboni, Dario S; Lima-Junior, Djalma S

    2015-05-01

    Inflammasomes are multimeric complexes of proteins that are assembled in the host cell cytoplasm in response to specific stress signals or contamination of the cytoplasm by microbial molecules. The canonical inflammasomes are composed of at least three main components: an inflammatory caspase (caspase-1, caspase-11), an adapter molecule (such as ASC), and a sensor protein (such as NLRP1, NLRP3, NLRP12, NAIP1, NAIP2, NAIP5, or AIM2). The sensor molecule determines the inflammasome specificity by detecting specific microbial products or cell stress signals. Upon activation, these molecular platforms facilitate restriction of microbial replication and trigger an inflammatory form of cell death called pyroptosis, thus accounting for the genesis of inflammatory processes. Inflammasome activation has been widely reported in response to pathogenic bacteria. However, recent reports have highlighted the important role of the inflammasomes in the host response to the pathogenesis of infections caused by intracellular protozoan parasites. Herein, we review the activation and specific roles of inflammasomes in recognition and host responses to intracellular protozoan parasites such as Trypanosoma cruzi, Toxoplasma gondii, Plasmodium spp., and Leishmania spp.

  11. AGN Absorption Linked to Host Galaxies

    CERN Document Server

    Juneau, Stéphanie

    2013-01-01

    Multiwavelength identification of AGN is crucial not only to obtain a more complete census, but also to learn about the physical state of the nuclear activity (obscuration, efficiency, etc.). A panchromatic strategy plays an especially important role when the host galaxies are star-forming. Selecting far-Infrared galaxies at 0.3host galaxies, indicating a physical link between X-ray absorption and either the gas fraction or the gas geometry in the hosts. These findings have implications for our current understanding of both the AGN unification model and the nature of the black hole-galaxy connection. These proceedi...

  12. Clustering of supernova Ia host galaxies

    CERN Document Server

    Carlberg, R G; Le Borgne, D; Conley, A; Howell, D A; Perrett, K; Astier, Pierre; Balam, D; Balland, C; Basa, S; Hardin, D; Fouchez, D; Guy, J; Hook, I; Pain, R; Pritchet, C J; Regnault, N; Rich, J; Perlmutter, S

    2008-01-01

    For the first time the cross-correlation between type Ia supernova host galaxies and surrounding field galaxies is measured using the Supernova Legacy Survey sample. Over the z=0.2 to 0.9 redshift range we find that supernova hosts are correlated an average of 60% more strongly than similarly selected field galaxies over the 3-100 arcsec range and about a factor of 3 more strongly below 10 arcsec. The correlation errors are empirically established with a jackknife analysis of the four SNLS fields. The hosts are more correlated than the field at a significance of 99% in the fitted amplitude and slope, with the point-by-point difference of the two correlation functions having a reduced $\\chi^2$ for 8 degrees of freedom of 4.3, which has a probability of random occurrence of less than 3x10^{-5}. The correlation angle is 1.5+/-0.5 arcsec, which deprojects to a fixed co-moving correlation length of approximately 6.5+/- 2/h mpc. Weighting the field galaxies with the mass and star formation rate supernova frequencie...

  13. Citrus tristeza virus-host interactions

    Science.gov (United States)

    Dawson, W. O.; Garnsey, S. M.; Tatineni, S.; Folimonova, S. Y.; Harper, S. J.; Gowda, S.

    2013-01-01

    Citrus tristeza virus (CTV) is a phloem-limited virus whose natural host range is restricted to citrus and related species. Although the virus has killed millions of trees, almost destroying whole industries, and continually limits production in many citrus growing areas, most isolates are mild or symptomless in most of their host range. There is little understanding of how the virus causes severe disease in some citrus and none in others. Movement and distribution of CTV differs considerably from that of well-studied viruses of herbaceous plants where movement occurs largely through adjacent cells. In contrast, CTV systemically infects plants mainly by long-distance movement with only limited cell-to-cell movement. The virus is transported through sieve elements and occasionally enters an adjacent companion or phloem parenchyma cell where virus replication occurs. In some plants this is followed by cell-to-cell movement into only a small cluster of adjacent cells, while in others there is no cell-to-cell movement. Different proportions of cells adjacent to sieve elements become infected in different plant species. This appears to be related to how well viral gene products interact with specific hosts. CTV has three genes (p33, p18, and p13) that are not necessary for infection of most of its hosts, but are needed in different combinations for infection of certain citrus species. These genes apparently were acquired by the virus to extend its host range. Some specific viral gene products have been implicated in symptom induction. Remarkably, the deletion of these genes from the virus genome can induce large increases in stem pitting (SP) symptoms. The p23 gene, which is a suppressor of RNA silencing and a regulator of viral RNA synthesis, has been shown to be the cause of seedling yellows (SY) symptoms in sour orange. Most isolates of CTV in nature are populations of different strains of CTV. The next frontier of CTV biology is the understanding how the virus

  14. Host range, host ecology, and distribution of more than 11800 fish parasite species

    Science.gov (United States)

    Strona, Giovanni; Palomares, Maria Lourdes D.; Bailly, Nicholas; Galli, Paolo; Lafferty, Kevin D.

    2013-01-01

    Our data set includes 38 008 fish parasite records (for Acanthocephala, Cestoda, Monogenea, Nematoda, Trematoda) compiled from the scientific literature, Internet databases, and museum collections paired to the corresponding host ecological, biogeographical, and phylogenetic traits (maximum length, growth rate, life span, age at maturity, trophic level, habitat preference, geographical range size, taxonomy). The data focus on host features, because specific parasite traits are not consistently available across records. For this reason, the data set is intended as a flexible resource able to extend the principles of ecological niche modeling to the host–parasite system, providing researchers with the data to model parasite niches based on their distribution in host species and the associated host features. In this sense, the database offers a framework for testing general ecological, biogeographical, and phylogenetic hypotheses based on the identification of hosts as parasite habitat. Potential applications of the data set are, for example, the investigation of species–area relationships or the taxonomic distribution of host-specificity. The provided host–parasite list is that currently used by Fish Parasite Ecology Software Tool (FishPEST, http://purl.oclc.org/fishpest), which is a website that allows researchers to model several aspects of the relationships between fish parasites and their hosts. The database is intended for researchers who wish to have more freedom to analyze the database than currently possible with FishPEST. However, for readers who have not seen FishPEST, we recommend using this as a starting point for interacting with the database.

  15. Tuberculosis epidemiology in islands: insularity, hosts and trade.

    Science.gov (United States)

    Acevedo, Pelayo; Romero, Beatriz; Vicente, Joaquin; Caracappa, Santo; Galluzzo, Paola; Marineo, Sandra; Vicari, Domenico; Torina, Alessandra; Casal, Carmen; de la Fuente, Jose; Gortazar, Christian

    2013-01-01

    Because of their relative simplicity and the barriers to gene flow, islands are ideal systems to study the distribution of biodiversity. However, the knowledge that can be extracted from this peculiar ecosystem regarding epidemiology of economically relevant diseases has not been widely addressed. We used information available in the scientific literature for 10 old world islands or archipelagos and original data on Sicily to gain new insights into the epidemiology of the Mycobacterium tuberculosis complex (MTC). We explored three nonexclusive working hypotheses on the processes modulating bovine tuberculosis (bTB) herd prevalence in cattle and MTC strain diversity: insularity, hosts and trade. Results suggest that bTB herd prevalence was positively correlated with island size, the presence of wild hosts, and the number of imported cattle, but neither with isolation nor with cattle density. MTC strain diversity was positively related with cattle bTB prevalence, presence of wild hosts and the number of imported cattle, but not with island size, isolation, and cattle density. The three most common spoligotype patterns coincided between Sicily and mainland Italy. However in Sicily, these common patterns showed a clearer dominance than on the Italian mainland, and seven of 19 patterns (37%) found in Sicily had not been reported from continental Italy. Strain patterns were not spatially clustered in Sicily. We were able to infer several aspects of MTC epidemiology and control in islands and thus in fragmented host and pathogen populations. Our results point out the relevance of the intensity of the cattle commercial networks in the epidemiology of MTC, and suggest that eradication will prove more difficult with increasing size of the island and its environmental complexity, mainly in terms of the diversity of suitable domestic and wild MTC hosts.

  16. Infrared Characters of Host Galaxies with H2O Megamaser

    Institute of Scientific and Technical Information of China (English)

    俞志尧

    2001-01-01

    Infrared characters of all the host galaxies with the H2O megamaser have been studied. The most striking featureis the anticorrelation of S(60)/S(100) versus S(12)/S(25), and S(25)/S(60) versus S(12)/S(25). The anticorrelationin the tlux density ratio can been explained by coexistence of large and very small dust particles. The latter, whichare heated by absorption of single photon, are believed to be responsible for the bulk of 12μm radiation. If thephoton energy of the host galaxy is small, this implies large S(12)/S(25) and small S(60)/S(100). However, whenphoton energy density becomes larger, the infrared spectrum will peak at wavelengths ≤ 100 μm and enhanceemission at 25 μm. As a consequence small S(12)/S(25) and large S(60)/S(100) are observed.

  17. Host plant quality mediates competition between arbuscular mycorrhizal fungi

    NARCIS (Netherlands)

    B. Knegt; J. Jansa; O. Franken; D.J.P. Engelmoer; G.D.A. Werner; H. Bücking; E.T. Kiers

    2014-01-01

    Arbuscular mycorrhizal fungi exchange soil nutrients for carbon from plant hosts. Empirical works suggests that hosts may selectively provide resources to different fungal species, ultimately affecting fungal competition. However, fungal competition may also be mediated by colonization strategies of

  18. Host plant quality mediates competition between arbuscular mycorrhizal fungi

    NARCIS (Netherlands)

    Knegt, B.; Jansa, J.; Franken, O.; Engelmoer, D.J.P.; Werner, G.D.A.; Bücking, H.; Kiers, E.T.

    2016-01-01

    Arbuscular mycorrhizal fungi exchange soil nutrients for carbon from plant hosts. Empirical works suggests that hosts may selectively provide resources to different fungal species, ultimately affecting fungal competition. However, fungal competition may also be mediated by colonization strategies of

  19. Host plant quality mediates competition between arbuscular mycorrhizal fungi

    NARCIS (Netherlands)

    Knegt, B.; Jansa, J.; Franken, O.; Engelmoer, D.J.P.; Werner, G.D.A.; Bücking, H.; Kiers, E.T.

    2016-01-01

    Arbuscular mycorrhizal fungi exchange soil nutrients for carbon from plant hosts. Empirical works suggests that hosts may selectively provide resources to different fungal species, ultimately affecting fungal competition. However, fungal competition may also be mediated by colonization strategies of

  20. The host of GRB 060206: kinematics of a distant galaxy

    CERN Document Server

    Thoene, Christina C; Ledoux, Cedric; Starling, Rhaana L C; Fynbo, Johan P U; Curran, Peter A; Gorosabel, Javier; van der Horst, Alexander J; Kewley, Lisa J; Levan, Andrew J; LLorente, Alvaro; Rol, Evert; Tanvir, Nial R; Postigo, Antonio de Ugarte; Vreeswijk, Paul M; Wijers, Ralph A M J

    2007-01-01

    Context. The spectra of afterglows can provide us with detailed information on the line-of-sight towards high redshift gamma-ray bursts (GRBs). This allows us to use GRB afterglows as sensitive probes of interstellar matter in their host galaxies, and the circumstellar material around the progenitor star. Aims. In this paper we present early WHT/ISIS optical spectroscopy of the afterglow of the gamma-ray burst GRB 060206 at z = 4.048, detecting a range of metal absorption lines and their fine-structure transitions. Additional information is provided by properties derived from the afterglow lightcurve and from deep imaging of the host galaxy. Methods. The resolution and wavelength range of the spectra and the bright afterglow facilitate a detailed study of the circumburst and host galaxy environment through fitting of the absorption line systems. Their column densities allow us to derive properties for the different detected velocity components. We also use the deep imaging to detect the host galaxy and probe ...

  1. Role of host GTPases in infection by Listeria monocytogenes.

    Science.gov (United States)

    Ireton, Keith; Rigano, Luciano A; Dowd, Georgina C

    2014-09-01

    The bacterial pathogen Listeria monocytogenes induces internalization into mammalian cells and uses actin-based motility to spread within tissues. Listeria accomplishes this intracellular life cycle by exploiting or antagonizing several host GTPases. Internalization into human cells is mediated by the bacterial surface proteins InlA or InlB. These two modes of uptake each require a host actin polymerization pathway comprised of the GTPase Rac1, nucleation promotion factors, and the Arp2/3 complex. In addition to Rac1, InlB-mediated internalization involves inhibition of the GTPase Arf6 and participation of Dynamin and septin family GTPases. After uptake, Listeria is encased in host phagosomes. The bacterial protein GAPDH inactivates the human GTPase Rab5, thereby delaying phagosomal acquisition of antimicrobial properties. After bacterial-induced destruction of the phagosome, cytosolic Listeria uses the surface protein ActA to stimulate actin-based motility. The GTPase Dynamin 2 reduces the density of microtubules that would otherwise limit bacterial movement. Cell-to-cell spread results when motile Listeria remodel the host plasma membrane into protrusions that are engulfed by neighbouring cells. The human GTPase Cdc42, its activator Tuba, and its effector N-WASP form a complex with the potential to restrict Listeria protrusions. Bacteria overcome this restriction through two microbial factors that inhibit Cdc42-GTP or Tuba/N-WASP interaction.

  2. Hijacking host cell highways: manipulation of the host actin cytoskeleton by obligate intracellular bacterial pathogens

    Directory of Open Access Journals (Sweden)

    Punsiri M Colonne

    2016-09-01

    Full Text Available Intracellular bacterial pathogens replicate within eukaryotic cells and display unique adaptations that support key infection events including invasion, replication, immune evasion, and dissemination. From invasion to dissemination, all stages of the intracellular bacterial life cycle share the same three-dimensional cytosolic space containing the host cytoskeleton. For successful infection and replication, many pathogens hijack the cytoskeleton using effector proteins introduced into the host cytosol by specialized secretion systems. A subset of effectors contains eukaryotic-like motifs that mimic host proteins to exploit signaling and modify specific cytoskeletal components such as actin and microtubules. Cytoskeletal rearrangement promotes numerous events that are beneficial to the pathogen, including internalization of bacteria, subversion of cell intrinsic immunity, structural support for bacteria-containing vacuoles, altered vesicular trafficking, actin-dependent bacterial movement, and pathogen dissemination. This review highlights a diverse group of obligate intracellular bacterial pathogens that manipulate the host cytoskeleton to thrive within eukaryotic cells and discusses underlying molecular mechanisms that promote these dynamic host-pathogen interactions.

  3. Host preferences in host-seeking and blood-fed mosquitoes in Switzerland.

    Science.gov (United States)

    Schönenberger, A C; Wagner, S; Tuten, H C; Schaffner, F; Torgerson, P; Furrer, S; Mathis, A; Silaghi, C

    2016-03-01

    The avian zoonotic agent for West Nile virus (WNV) can cause neuroinvasive disease in horses and humans and is expanding its range in Europe. Analyses of the risk for transmission to these hosts in non-endemic areas are necessary. Host preferences of mosquitoes (Diptera: Culicidae), the main vectors of WNV, were determined in Switzerland using animal-baited trap (horse, chickens) experiments at a natural and a periurban site. This was undertaken on four occasions during May-September 2014. In addition, the hosts of 505 blood-fed mosquitoes collected in a zoo and in the field were determined. Mosquito data obtained in the animal bait experiments were corrected for host weight and body surface area and by Kleiber's scaling factor. Collections of 11-14 different mosquito species were achieved with these approaches. Statistically significant host preferences were identified in three species in both approaches. The other species showed opportunistic feeding behaviours to varying extents. Specifically, the invasive species Hulecoeteomyia japonica (= Aedes japonicus) was identified for the first time as feeding on avians in nature. Abundance data, spatiotemporal activity and laboratory vector competence for WNV suggested that, in addition to the main WNV vector Culex pipiens, H. japonica and Aedimorphus vexans (= Aedes vexans) are the most likely candidate bridge vectors for WNV transmission in Switzerland.

  4. Microsporidia infection impacts the host cell's cycle and reduces host cell apoptosis

    Science.gov (United States)

    Higes, Mariano; Sagastume, Soledad; Juarranz, Ángeles; Dias-Almeida, Joyce; Budge, Giles E.; Meana, Aránzazu; Boonham, Neil

    2017-01-01

    Intracellular parasites can alter the cellular machinery of host cells to create a safe haven for their survival. In this regard, microsporidia are obligate intracellular fungal parasites with extremely reduced genomes and hence, they are strongly dependent on their host for energy and resources. To date, there are few studies into host cell manipulation by microsporidia, most of which have focused on morphological aspects. The microsporidia Nosema apis and Nosema ceranae are worldwide parasites of honey bees, infecting their ventricular epithelial cells. In this work, quantitative gene expression and histology were studied to investigate how these two parasites manipulate their host’s cells at the molecular level. Both these microsporidia provoke infection-induced regulation of genes involved in apoptosis and the cell cycle. The up-regulation of buffy (which encodes a pro-survival protein) and BIRC5 (belonging to the Inhibitor Apoptosis protein family) was observed after infection, shedding light on the pathways that these pathogens use to inhibit host cell apoptosis. Curiously, different routes related to cell cycle were modified after infection by each microsporidia. In the case of N. apis, cyclin B1, dacapo and E2F2 were up-regulated, whereas only cyclin E was up-regulated by N. ceranae, in both cases promoting the G1/S phase transition. This is the first report describing molecular pathways related to parasite-host interactions that are probably intended to ensure the parasite’s survival within the cell. PMID:28152065

  5. Optimal foraging predicts the ecology but not the evolution of host specialization in bacteriophages.

    Directory of Open Access Journals (Sweden)

    Sébastien Guyader

    Full Text Available We explore the ability of optimal foraging theory to explain the observation among marine bacteriophages that host range appears to be negatively correlated with host abundance in the local marine environment. We modified Charnov's classic diet composition model to describe the ecological dynamics of the related generalist and specialist bacteriophages phiX174 and G4, and confirmed that specialist phages are ecologically favored only at high host densities. Our modified model accurately predicted the ecological dynamics of phage populations in laboratory microcosms, but had only limited success predicting evolutionary dynamics. We monitored evolution of attachment rate, the phenotype that governs diet breadth, in phage populations adapting to both low and high host density microcosms. Although generalist phiX174 populations evolved even broader diets at low host density, they did not show a tendency to evolve the predicted specialist foraging strategy at high host density. Similarly, specialist G4 populations were unable to evolve the predicted generalist foraging strategy at low host density. These results demonstrate that optimal foraging models developed to explain the behaviorally determined diets of predators may have only limited success predicting the genetically determined diets of bacteriophage, and that optimal foraging probably plays a smaller role than genetic constraints in the evolution of host specialization in bacteriophages.

  6. Functional response, host stage preference and interference of two whitefly parasitoids.

    Science.gov (United States)

    Xu, Hai-Yun; Yang, Nian-Wan; Duan, Min; Wan, Fang-Hao

    2016-02-01

    The functional responses of two parasitoids, Eretmocerus hayati Zolnerowich & Rose and Encarsia sophia Girault & Dodd, of whitefly Bemisia tabaci Gennadius Middle East-Asia Minor 1 were studied under laboratory conditions. In addition, the influence of host density and host stage on the competitive interactions between the two parasitoids, and biological control effect on whitefly were evaluated. In the functional response study, adult parasitoids were tested individually, with a conspecific or heterospecific competitor. Both Er. hayati and En. sophia exhibited a type II response to increasing host density, whether a conspecific or heterospecific competitor was present or not. Difference of searching rates and handling times between treatments suggested interference interactions existed between two parasitoid species. In the host stage preference study, two parasitoid species were jointly tested. Er. hayati had a competitive advantage over En. sophia when provided young host instars (first and second instar), whereas no advantage was found on old host instars (third and fourth instar). The biological control effect of Er. hayati and En. sophia in different introductions varied with host density. However, the effect of host instar on host mortality was not significant. These findings provide information for the practice of biological control and give better insight into how parasitoid species may coexist in diverse environments.

  7. ALMA Examines a Distant Quasar Host

    Science.gov (United States)

    Kohler, Susanna

    2017-04-01

    The dust continuum (top) and the [CII] emission (bottom) maps for the region around J1120+0641. [Adapted from Venemans et al. 2017]A team of scientists has used the Atacama Large Millimeter/submillimeter Array (ALMA) to explore the host galaxy of the most distant quasar known. Their observations may help us to build a picture of how the first supermassive black holes in the universe formed and evolved.Faraway Monsters and Their GalaxiesWe know that quasars the incredibly luminous and active centers of some distant galaxies are powered by accreting, supermassive black holes. These monstrous powerhouses have been detected out to redshifts of z 7, when the universe was younger than a billion years old.Though weve observed over a hundred quasars at high redshift, we still dont understand how these early supermassive black holes formed, or whether the black holes and the galaxies that host them co-evolved. In order to answer questions like these, however, we first need to gather information about the properties and behavior of various supermassive black holes and their host galaxies.A team of scientists led by Bram Venemans (Max-Planck Institute for Astronomy, Germany) recently used the unprecedented sensitivity and angular resolution of ALMA as well as the Very Large Array and the IRAM Plateau de Bure Interferometer to examine the most distant quasar currently known, J1120+0641, located at a redshift of z = 7.1.A High-Resolution LookThe teams observations of the dust and gas emission from the quasars host galaxy revealed a number of intriguing things:The red and blue sides of the [CII] emission line are shown here as contours, demonstrating that theres no ordered rotational motion of the gas on kpc scales. [Adapted from Venemans et al. 2017]The majority of the galaxys emission is very compact. Around 80% of the observed flux came from a region of only 11.5 kpc in diameter.Despite the fact that the 2.4-billion-solar-mass black hole at the galaxys center is accreting at

  8. How the Host Nation's Boundary Drawing Affects Immigrants' Belonging

    DEFF Research Database (Denmark)

    Simonsen, Kristina Bakkær

    2016-01-01

    Across Western democracies, the place for newcomers in the host society is debated, involving often a questioning of immigrants’ belonging to their new nation. This article argues that immigrants’ feeling of host national belonging depends on how the host nation imagines its community and its...

  9. 42 CFR 71.54 - Etiological agents, hosts, and vectors.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Etiological agents, hosts, and vectors. 71.54..., INSPECTION, LICENSING FOREIGN QUARANTINE Importations § 71.54 Etiological agents, hosts, and vectors. (a) A... any arthropod or other animal host or vector of human disease, or any exotic living arthropod or...

  10. More Is Better: Selecting for Broad Host Range Bacteriophages

    Science.gov (United States)

    Ross, Alexa; Ward, Samantha; Hyman, Paul

    2016-01-01

    Bacteriophages are viruses that infect bacteria. In this perspective, we discuss several aspects of a characteristic feature of bacteriophages, their host range. Each phage has its own particular host range, the range of bacteria that it can infect. While some phages can only infect one or a few bacterial strains, other phages can infect many species or even bacteria from different genera. Different methods for determining host range may give different results, reflecting the multiple mechanisms bacteria have to resist phage infection and reflecting the different steps of infection each method depends on. This makes defining host range difficult. Another difficulty in describing host range arises from the inconsistent use of the words “narrow” and especially “broad” when describing the breadth of the host range. Nearly all bacteriophages have been isolated using a single host strain of bacteria. While this procedure is fairly standard, it may more likely produce narrow rather than broad host range phage. Our results and those of others suggest that using multiple host strains during isolation can more reliably produce broader host range phages. This challenges the common belief that most bacteriophages have a narrow host range. We highlight the implications of this for several areas that are affected by host range including horizontal gene transfer and phage therapy. PMID:27660623

  11. More Is Better: Selecting for Broad Host Range Bacteriophages.

    Science.gov (United States)

    Ross, Alexa; Ward, Samantha; Hyman, Paul

    2016-01-01

    Bacteriophages are viruses that infect bacteria. In this perspective, we discuss several aspects of a characteristic feature of bacteriophages, their host range. Each phage has its own particular host range, the range of bacteria that it can infect. While some phages can only infect one or a few bacterial strains, other phages can infect many species or even bacteria from different genera. Different methods for determining host range may give different results, reflecting the multiple mechanisms bacteria have to resist phage infection and reflecting the different steps of infection each method depends on. This makes defining host range difficult. Another difficulty in describing host range arises from the inconsistent use of the words "narrow" and especially "broad" when describing the breadth of the host range. Nearly all bacteriophages have been isolated using a single host strain of bacteria. While this procedure is fairly standard, it may more likely produce narrow rather than broad host range phage. Our results and those of others suggest that using multiple host strains during isolation can more reliably produce broader host range phages. This challenges the common belief that most bacteriophages have a narrow host range. We highlight the implications of this for several areas that are affected by host range including horizontal gene transfer and phage therapy.

  12. Immunoregulation by Trichinella spiralis: Benefits for parasite and host

    NARCIS (Netherlands)

    Aranzamendi Esteban, C.R.

    2013-01-01

    Several studies indicate that certain helminths suppress the host immune responses. This suppression may benefit the parasite since it increases the chances of survival in their host. By doing so, the hosts may also benefit due to concomitant reduction of immune pathology associated with allergies a

  13. Oviposition choice of two fall armyworm (Lepidoptera: Noctuidae) host strains

    Science.gov (United States)

    Fall armyworm, Spodoptera frugiperda (J. E. Smith), is a noctuid species that is composed of two morphologically identical sympatric host strains (corn and rice) that differ in their distribution among plant hosts. In an effort to explain observations of host fidelity in the field, ovipositional pre...

  14. Host exopolysaccharide quantity and composition impact Erwinia amylovora bacteriophage pathogenesis.

    Science.gov (United States)

    Roach, Dwayne R; Sjaarda, David R; Castle, Alan J; Svircev, Antonet M

    2013-05-01

    Erwinia amylovora bacteriophages (phages) belonging to the Myoviridae and Podoviridae families demonstrated a preference for either high-exopolysaccharide-producing (HEP) or low-exopolysaccharide-producing (LEP) bacterial hosts when grown on artificial medium without or with sugar supplementation. Myoviridae phages produced clear plaques on LEP hosts and turbid plaques on HEP hosts. The reverse preference was demonstrated by most Podoviridae phages, where clear plaques were seen on HEP hosts. Efficiency of plating (EOP) was determined by comparing phage growth on the original isolation host to the that on the LEP or HEP host. Nine of 10 Myoviridae phages showed highest EOPs on LEP hosts, and 8 of 11 Podoviridae phages had highest EOPs on HEP hosts. Increasing the production of EPS on sugar-supplemented medium or decreasing production by knocking out the synthesis of amylovoran or levan, the two EPSs produced by E. amylovora, indicated that these components play crucial roles in phage infection. Amylovoran was virtually essential for proliferation of most Podoviridae phages when phage population growth was compared to the wild type. Decreased levan production resulted in a significant reduction of progeny from phages in the Myoviridae family. Thus, Podoviridae phages are adapted to hosts that produce high levels of exopolysaccharides and are dependent on host-produced amylovoran for pathogenesis. Myoviridae phages are adapted to hosts that produce lower levels of exopolysaccharides and host-produced levan.

  15. Evolution in action : host race formation in Galerucella nymphaeae

    NARCIS (Netherlands)

    Pappers, Stephanie Maria

    2001-01-01

    A host race is a population which is partially reproductively isolated as a direct consequence of adaptation to a certain host. For host race formation to occur five conditions should be met. First of all, the populations should occur in sympatry, which means that they co-occur within the normal cru

  16. Nestling polymorphism in a cuckoo-host system.

    Science.gov (United States)

    Sato, Nozomu J; Tanaka, Keita D; Okahisa, Yuji; Yamamichi, Masato; Kuehn, Ralph; Gula, Roman; Ueda, Keisuke; Theuerkauf, Jörn

    2015-12-21

    Virulence of avian brood parasites can trigger a coevolutionary arms race, which favours rejection of parasitic eggs or chicks by host parents, and in turn leads to mimicry in parasite eggs or chicks [1-7]. The appearance of host offspring is critical to enable host parents to detect parasites. Thus, increasing accuracy of parasites' mimicry can favour a newly emerged host morph to escape parasites' mimicry. If parasites catch up with the hosts with a newly acquired mimetic morph, host polymorphism should be maintained through apostatic (negative frequency-dependent) selection, which favours hosts rarer morphs [1-3,7]. Among population-wide polymorphism, uniformity of respective host morphs in single host nests stochastically prevents parasites from targeting any specific morph of hosts and thus helps parents detect parasitism. Polymorphism in such a state is well-known in egg appearances of hosts of brood parasitic birds [2,3,7], which might also occur in chick appearances when arms races escalate. Here, we present evidence of polymorphism in chick skin coloration in a cuckoo-host system: the fan-tailed gerygone Gerygone flavolateralis and its specialist brood parasite, the shining bronze-cuckoo Chalcites lucidus in New Caledonia (Figure 1A-C). Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Temperature alters host genotype-specific susceptibility to chytrid infection

    NARCIS (Netherlands)

    Gsell, A.S.; De Senerpont Domis, L.N.; Van Donk, E.; Ibelings, B.W.

    2013-01-01

    The cost of parasitism often depends on environmental conditions and host identity. Therefore, variation in the biotic and abiotic environment can have repercussions on both, species-level host-parasite interaction patterns but also on host genotype-specific susceptibility to disease. We exposed sev

  18. Prokaryotes versus Eukaryotes: Who is hosting whom?

    Directory of Open Access Journals (Sweden)

    Guillermo eTellez

    2014-10-01

    Full Text Available Microorganisms represent the largest component of biodiversity in our world. For millions of years, prokaryotic microorganisms have functioned as a major selective force shaping eukaryotic evolution. Microbes that live inside and on animals outnumber the animals’ actual somatic and germ cells by an estimated 10-fold. Collectively, the intestinal microbiome represents a ‘forgotten organ’, functioning as an organ inside another that can execute many physiological responsibilities. The nature of primitive eukaryotes was drastically changed due to the association with symbiotic prokaryotes facilitating mutual coevolution of host and microbe. Phytophagous insects have long been used to test theories of evolutionary diversification; moreover, the diversification of a number of phytophagous insect lineages has been linked to mutualisms with microbes. From termites and honey bees to ruminants and mammals, depending on novel biochemistries provided by the prokaryotic microbiome, the association helps to metabolize several nutrients that the host cannot digest and converting these into useful end products (such as short chain fatty acids, a process which has huge impact on the biology and homeostasis of metazoans. More importantly, in a direct and/or indirect way, the intestinal microbiota influences the assembly of gut-associated lymphoid tissue, helps to educate immune system, affects the integrity of the intestinal mucosal barrier, modulates proliferation and differentiation of its epithelial lineages, regulates angiogenesis, and modifies the activity of enteric as well as the central nervous system,. Despite these important effects, the mechanisms by which the gut microbial community influences the host’s biology remains almost entirely unknown. Our aim here is to encourage empirical inquiry into the relationship between mutualism and evolutionary diversification between prokaryotes and eukaryotes which encourage us to postulate: Who is

  19. Natural invertebrate hosts of iridoviruses (Iridoviridae)

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Trevor [Instituto de Ecologia A.C., Veracruz (Mexico)]. E-mail: trevor.williams@inecol.edu.mx

    2008-11-15

    Invertebrate iridescent viruses (IIVs) are icosahedral DNA viruses that infect invertebrates, mainly insects and terrestrial isopods, in damp and aquatic habitats. Exhaustive searches of databases resulted in the identification of 79 articles reporting 108 invertebrate species naturally infected by confirmed or putative iridoviruses. Of these, 103 (95%) were arthropods and the remainder were molluscs, an annelid worm and a nematode. Nine species were from marine habitats. Of the 99 non-marine species, 49 were from terrestrial habitats and 50 were aquatic, especially the aquatic stages of Diptera (44 species). The abundance of records from species of Aedes, Ochlerotatus and Psorophora contrasts markedly with a paucity of records from species of Anopheles, Culex and Culiseta. Records from terrestrial isopods are numerous (19 species), although the diversity of IIVs that infect them is mostly unstudied. IIV infections have been reported from every continent, except Antarctica, but there are few records from Africa, southern Asia and Latin America. Most reports describe patent IIV infections as rare whereas inapparent (covert) infection may be common in certain species. The relationship between particle size and iridescent colour of the host is found to be consistent with optical theory in the great majority of cases. Only 24 reported IIVs from insect hosts have partial characterization data and only two have been subjected to complete genome sequencing. I show that the rate of publication on IIVs has slowed from 1990 to the present, and I draw a number of conclusions and suggestions from the host list and make recommendations for future research efforts. (author)

  20. MORPHOLOGY OF METHANE HYDRATE HOST SEDIMENTS.

    Energy Technology Data Exchange (ETDEWEB)

    JONES,K.W.; FENG,H.; TOMOV,S.; WINTER,W.J.; EATON,M.; MAHAJAN,D.

    2004-12-01

    Results from simulated experiments in several laboratories show that host sediments influence hydrate formation in accord with known heterogeneity of host sediments at sites of gas hydrate occurrence (1). For example, in Mackenzie Delta, NWT Canada (Mallik 2L-38 well), coarser-grained units (pore-filling model) are found whereas in the Gulf of Mexico, the found hydrate samples do not appear to be lithologically controlled. We have initiated a systematic study of sediments, initially focusing on samples from various depths at a specific site, to establish a correlation with hydrate occurrence (or variations thereof) to establish differences in their microstructure, porosity, and other associated properties. The synchrotron computed microtomography (CMT) set-up at the X-27A tomography beam line at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory was used as a tool to study sediments from Blake Ridge at three sub bottom depths of 0.2, 50, and 667 meters. Results from the tomographic analysis of the deepest sample (667 m) are presented here to illustrate how tomography can be used to obtain new insights into the structures of methane hydrate host sediments. The investigation shows the internal grain/pore space resolution in the microstructure and a 3-D visualization of the connecting pathways obtained following data segmentation into pore space and grains within the sediment sample. The analysis gives the sample porosity, specific surface area, mean particle size, and tortuosity, as well. An earlier report on the experimental program has been given by Mahajan et al. (2).

  1. Host-pathogen interaction in invasive Salmonellosis.

    Directory of Open Access Journals (Sweden)

    Hanna K de Jong

    Full Text Available Salmonella enterica infections result in diverse clinical manifestations. Typhoid fever, caused by S. enterica serovar Typhi (S. Typhi and S. Paratyphi A, is a bacteremic illness but whose clinical features differ from other Gram-negative bacteremias. Non-typhoidal Salmonella (NTS serovars cause self-limiting diarrhea with occasional secondary bacteremia. Primary NTS bacteremia can occur in the immunocompromised host and infants in sub-Saharan Africa. Recent studies on host-pathogen interactions in Salmonellosis using genome sequencing, murine models, and patient studies have provided new insights. The full genome sequences of numerous S. enterica serovars have been determined. The S. Typhi genome, compared to that of S. Typhimurium, harbors many inactivated or disrupted genes. This can partly explain the different immune responses both serovars induce upon entering their host. Similar genome degradation is also observed in the ST313 S. Typhimurium strain implicated in invasive infection in sub-Saharan Africa. Virulence factors, most notably, type III secretion systems, Vi antigen, lipopolysaccharide and other surface polysaccharides, flagella, and various factors essential for the intracellular life cycle of S. enterica have been characterized. Genes for these factors are commonly carried on Salmonella Pathogenicity Islands (SPIs. Plasmids also carry putative virulence-associated genes as well as those responsible for antimicrobial resistance. The interaction of Salmonella pathogen-associated molecular patterns (PAMPs with Toll-like receptors (TLRs and NOD-like receptors (NLRs leads to inflammasome formation, activation, and recruitment of neutrophils and macrophages and the production of pro-inflammatory cytokines, most notably interleukin (IL-6, IL-1β, tumor necrosis factor (TNF-α, and interferon-gamma (IFN-γ. The gut microbiome may be an important modulator of this immune response. S. Typhimurium usually causes a local intestinal immune

  2. Effect of modifying host oil on coprocessing

    Energy Technology Data Exchange (ETDEWEB)

    Hajdu, P.E.; Tierney, J.W.; Wender, I.

    1995-05-01

    The world`s supply of petroleum crudes is becoming heavier in nature so that the amount of vacuum bottoms has been steadily increasing. Coprocessing of coal with these resids (1,000 F+) is an attractive way of obtaining useful distillates from these readily available cheap materials. The objective of this work is to pretreat the host oil in ways that would improve its performance in coprocessing with coal. The following are examples of some ways in which heavy oil could be made into a better host oil: converting aromatic structures to hydroaromatics capable of donating hydrogen to coal, cracking the heavy oil to lower molecular weight material that would be a better solvent, and removing metals, sulfur, and nitrogen. The work reported here used a Venezuelan oil obtained from the Corpus Christi refinery of Citgo. Two coals, Illinois No. 6 and Wyodak subbituminous, were coprocessed with host oils. The authors have found that mild pretreatment of a Citgo resid (1,000 F) using either Mo naphthenate or Mo/Fe{sub 2}O{sub 3}/SO{sub 4}, as well as a pretreatment using the homogeneous catalyst Co{sub 2}(CO){sub 8} under synthesis gas can increase the available (donatable) hydrogen content of the resid. When these pretreated oils were thermally (no added catalyst) coprocessed with an Illinois No. 6 coal, about 90 wt% of the coal (maf) was converted to soluble products. This high coal conversion was realized even at a high coal loading of 50 wt%. The products from coprocessing coal and oil were equally split between high boiling material, mostly asphaltenes, and distillate. Distillate yields appeared to be affected by the concentration of coal in the feed, with maximum yields at coal loadings below 50 wt%.

  3. Bacterial receptors for host transferrin and lactoferrin: molecular mechanisms and role in host-microbe interactions.

    Science.gov (United States)

    Morgenthau, Ari; Pogoutse, Anastassia; Adamiak, Paul; Moraes, Trevor F; Schryvers, Anthony B

    2013-12-01

    Iron homeostasis in the mammalian host limits the availability of iron to invading pathogens and is thought to restrict iron availability for microbes inhabiting mucosal surfaces. The presence of surface receptors for the host iron-binding glycoproteins transferrin (Tf) and lactoferrin (Lf) in globally important Gram-negative bacterial pathogens of humans and food production animals suggests that Tf and Lf are important sources of iron in the upper respiratory or genitourinary tracts, where they exclusively reside. Lf receptors have the additional function of protecting against host cationic antimicrobial peptides, suggesting that the bacteria expressing these receptors reside in a niche where exposure is likely. In this review we compare Tf and Lf receptors with respect to their structural and functional features, their role in colonization and infection, and their distribution among pathogenic and commensal bacteria.

  4. Overseas Military Bases: Understanding Host Nation Support

    Science.gov (United States)

    2012-02-15

    complex nature of host nation interests. Camp Lemonier , a combined joint base leased by the US from the Government of Djibouti, encompasses the primary...Joseph. “U.S. military plans to expand Camp Lemonier in Djibouti.” Stars and Stripes, 9 July 2006. http://www.stripes.com/. Gordon, Michael R...Concept, 11-12. 9. CRS, U.S. Military Overseas Basing, 2-3. 10. Giordono, “U.S. Military Plans to expand Camp Lemonier in Djibouti.” 11. US

  5. Spectroscopy of superluminous supernova host galaxies

    DEFF Research Database (Denmark)

    Leloudas, G.; Kruehler, T.; Schulze, S

    2015-01-01

    Superluminous supernovae (SLSNe) are very bright explosions that were only discovered recently and that show a preference for occurring in faint dwarf galaxies. Understanding why stellar evolution yields different types of stellar explosions in these environments is fundamental in order to both...... uncover the elusive progenitors of SLSNe and to study star formation in dwarf galaxies. In this paper, we present the first results of our project to study SUperluminous Supernova Host galaxIES, focusing on the sample for which we have obtained spectroscopy. We show that SLSNe-I and SLSNe-R (hydrogen...

  6. Recombinant protein production in bacterial hosts.

    Science.gov (United States)

    Overton, Tim W

    2014-05-01

    The production of recombinant proteins is crucial for both the development of new protein drugs and the structural determination of drug targets. As such, recombinant protein production has a major role in drug development. Bacterial hosts are commonly used for the production of recombinant proteins, accounting for approximately 30% of current biopharmaceuticals on the market. In this review, I introduce fundamental concepts in recombinant protein production in bacteria, from drug development to production scales. Recombinant protein production processes can often fail, but how can this failure be minimised to rapidly deliver maximum yields of high-quality protein and so accelerate drug discovery?

  7. Studies of reservoir hosts for Marburg virus.

    Science.gov (United States)

    Swanepoel, Robert; Smit, Sheilagh B; Rollin, Pierre E; Formenty, Pierre; Leman, Patricia A; Kemp, Alan; Burt, Felicity J; Grobbelaar, Antoinette A; Croft, Janice; Bausch, Daniel G; Zeller, Hervé; Leirs, Herwig; Braack, L E O; Libande, Modeste L; Zaki, Sherif; Nichol, Stuart T; Ksiazek, Thomas G; Paweska, Janusz T

    2007-12-01

    To determine reservoir hosts for Marburg virus (MARV), we examined the fauna of a mine in northeastern Democratic Republic of the Congo. The mine was associated with a protracted outbreak of Marburg hemorrhagic fever during 1998-2000. We found MARV nucleic acid in 12 bats, comprising 3.0%-3.6% of 2 species of insectivorous bat and 1 species of fruit bat. We found antibody to the virus in the serum of 9.7% of 1 of the insectivorous species and in 20.5% of the fruit bat species, but attempts to isolate virus were unsuccessful.

  8. Collaborative web hosting challenges and research directions

    CERN Document Server

    Ahmed, Reaz

    2014-01-01

    This brief presents a peer-to-peer (P2P) web-hosting infrastructure (named pWeb) that can transform networked, home-entertainment devices into lightweight collaborating Web servers for persistently storing and serving multimedia and web content. The issues addressed include ensuring content availability, Plexus routing and indexing, naming schemes, web ID, collaborative web search, network architecture and content indexing. In pWeb, user-generated voluminous multimedia content is proactively uploaded to a nearby network location (preferably within the same LAN or at least, within the same ISP)

  9. Coral bleaching: the role of the host.

    Science.gov (United States)

    Baird, Andrew H; Bhagooli, Ranjeet; Ralph, Peter J; Takahashi, Shunichi

    2009-01-01

    Coral bleaching caused by global warming is one of the major threats to coral reefs. Very recently, research has focused on the possibility of corals switching symbionts as a means of adjusting to accelerating increases in sea surface temperature. Although symbionts are clearly of fundamental importance, many aspects of coral bleaching cannot be readily explained by differences in symbionts among coral species. Here we outline several potential mechanisms by which the host might influence the bleaching response, and conclude that predicting the fate of corals in response to climate change requires both members of the symbiosis to be considered equally.

  10. Studies of Reservoir Hosts for Marburg virus

    DEFF Research Database (Denmark)

    Swanepoel, Robert; Smit, Sheilagh B; Rollin, Pierre E

    2007-01-01

    To determine reservoir hosts for Marburg virus (MARV), we examined the fauna of a mine in northeastern Democratic Republic of the Congo. The mine was associated with a protracted outbreak of Marburg hemorrhagic fever during 1998-2000. We found MARV nucleic acid in 12 bats, comprising 3.0%-3.6% of 2...... species of insectivorous bat and 1 species of fruit bat. We found antibody to the virus in the serum of 9.7% of 1 of the insectivorous species and in 20.5% of the fruit bat species, but attempts to isolate virus were unsuccessful. ...

  11. Mycobacterium tuberculosis effectors interfering host apoptosis signaling.

    Science.gov (United States)

    Liu, Minqiang; Li, Wu; Xiang, Xiaohong; Xie, Jianping

    2015-07-01

    Tuberculosis remains a serious human public health concern. The coevolution between its pathogen Mycobacterium tuberculosis and human host complicated the way to prevent and cure TB. Apoptosis plays subtle role in this interaction. The pathogen endeavors to manipulate the apoptosis via diverse effectors targeting key signaling nodes. In this paper, we summarized the effectors pathogen used to subvert the apoptosis, such as LpqH, ESAT-6/CFP-10, LAMs. The interplay between different forms of cell deaths, such as apoptosis, autophagy, necrosis, is also discussed with a focus on the modes of action of effectors, and implications for better TB control.

  12. Salmonella-host interactions - modulation of the host innate immune system

    Directory of Open Access Journals (Sweden)

    Daniel eHurley

    2014-10-01

    Full Text Available Salmonella enterica (S. enterica are Gram-negative bacteria that can invade a broad range of hosts causing both acute and chronic infections. This phenotype is related to its ability to replicate and persist within non-phagocytic host epithelial cells as well as phagocytic dendritic cells and macrophages of the innate immune system.Infection with S. enterica manifests itself through a broad range of clinical symptoms and can result in asymptomatic carriage, gastroenteritis, systemic disease such as typhoid fever and in severe cases, death (Gunn et al. 2014. Exposure to S. enterica serovars Typhi and Paratyphi exhibits clinical symptoms including diarrhoea, fatigue, fever and temperature fluctuations. Other serovars such as the non-typhoidal Salmonella (NTS, of which there are over 2,500, are commonly contracted as, but not limited to, food-borne sources causing gastrointestinal symptoms, which include diarrhoea and vomiting.The availability of complete genome sequences for many S. enterica serovars has facilitated research into the genetic determinants of virulence for this pathogen. This work has led to the identification of important bacterial components, including flagella, type III secretion systems, lipopolysaccharides and Salmonella pathogenicity islands, all of which support the intracellular life cycle of S. enterica. Studies focusing on the host-pathogen interaction have provided insights into receptor activation of the innate immune system. Therefore, characterising the host-S. enterica interaction is critical to understand the pathogenicity of the bacteria in a clinically relevant context. This review outlines salmonellosis and the clinical manifestations between typhoidal and NTS infections as well as discussing the host immune response to infection and the models that are being used to elucidate the mechanisms involved on Salmonella pathogenicity.

  13. Salmonella-host interactions - modulation of the host innate immune system.

    Science.gov (United States)

    Hurley, Daniel; McCusker, Matthew P; Fanning, Séamus; Martins, Marta

    2014-01-01

    Salmonella enterica (S. enterica) are Gram-negative bacteria that can invade a broad range of hosts causing both acute and chronic infections. This phenotype is related to its ability to replicate and persist within non-phagocytic host epithelial cells as well as phagocytic dendritic cells and macrophages of the innate immune system. Infection with S. enterica manifests itself through a broad range of clinical symptoms and can result in asymptomatic carriage, gastroenteritis, systemic disease such as typhoid fever and in severe cases, death (1). Exposure to S. enterica serovars Typhi and Paratyphi exhibits clinical symptoms including diarrhea, fatigue, fever, and temperature fluctuations. Other serovars such as the non-typhoidal Salmonella (NTS), of which there are over 2,500, are commonly contracted as, but not limited to, food-borne sources causing gastrointestinal symptoms, which include diarrhea and vomiting. The availability of complete genome sequences for many S. enterica serovars has facilitated research into the genetic determinants of virulence for this pathogen. This work has led to the identification of important bacterial components, including flagella, type III secretion systems, lipopolysaccharides, and Salmonella pathogenicity islands, all of which support the intracellular life cycle of S. enterica. Studies focusing on the host-pathogen interaction have provided insights into receptor activation of the innate immune system. Therefore, characterizing the host-S. enterica interaction is critical to understand the pathogenicity of the bacteria in a clinically relevant context. This review outlines salmonellosis and the clinical manifestations between typhoidal and NTS infections as well as discussing the host immune response to infection and the models that are being used to elucidate the mechanisms involved in Salmonella pathogenicity.

  14. The distribution of weaver ant pheromones on host trees

    DEFF Research Database (Denmark)

    Offenberg, Joachim

    2007-01-01

    The visible anal spots deposited by Oecophylla smaragdina ants have been suggested to deter ant prey, affect interspecific competition and facilitate mutualists and parasites in tracking down Oecophylla ants. I measured the density of anal spots on host trees with and without ants and tested for ...... to leaves. Also there was a positive correlation between spot density and the likelihood of being detected by ants. Anal spots may thus function as reliable cues to interacting species and be an important factor in shaping the community around Oecophylla colonies.......The visible anal spots deposited by Oecophylla smaragdina ants have been suggested to deter ant prey, affect interspecific competition and facilitate mutualists and parasites in tracking down Oecophylla ants. I measured the density of anal spots on host trees with and without ants and tested...... for correlations between spot density, ant activity and the likelihood of being detected by an ant. Spots were only found on trees with ants. On ant-trees, spots were distributed throughout the trees but with higher densities in areas with high ant activity and pheromone densities were higher on twigs compared...

  15. Optimum and maximum host size at parasitism for the endoparasitoid Hyposoter didymator (Hymenoptera: Ichneumonidae) differ greatly between two host species

    NARCIS (Netherlands)

    Reudler Talsma, J.H.; Elzinga, J.A.; Harvey, J.A.; Biere, A.

    2007-01-01

    Host size is considered a reliable indicator of host quality and an important determinant of parasitoid fitness. Koinobiont parasitoids attack hosts that continue feeding and growing during parasitism. In contrast with hemolymph-feeding koinobionts, tissue-feeding koinobionts face not only a minimum

  16. HOW STRONG IS POLISH FOOTBALL? "HOST PARADOX" IN FIFA'S RANKING

    Directory of Open Access Journals (Sweden)

    Marek M. Kamiński

    2012-06-01

    Full Text Available The paper analyzes unintiutive properties (paradoxes of the FIFA's ranking of national football teams. The most surprising phenomenon is underrating the teams of the main championship tournament hosts. This "host effect" follows the absence of hosts in preliminaries and the resulting restriction of hosts' pre-tournament matches to friendlies that enter the FIFA system with low weights. Various models built with the FIFA data allow to estimate that the place of the Polish team as a host of Euro 2012 was lowered from 16 to 35 positions.

  17. Pathogenetic Consequences of Cytomegalovirus-Host Co-evolution

    Institute of Scientific and Technical Information of China (English)

    Gerardo Abenes; Fenyong Liu

    2008-01-01

    Co-evolution has been shown to result in an adaptive reciprocal modification in the respective behaviors of interacting populations over time.In the case of host-parasite co-evolution,the adaptive behavior is most evident from the reciprocal change in fitness of host and parasite-manifested in terms of pathogen survival versus host resistance.Cytomegaloviruses and their hosts represent a pairing of populations that has co-evolved over hundreds of years.This review explores the pathogenetic consequences emerging from the behavioral changes caused by co-evolutionary forces on the virus and its host.

  18. Bipolar Host Materials for Organic Light-Emitting Diodes.

    Science.gov (United States)

    Yook, Kyoung Soo; Lee, Jun Yeob

    2016-02-01

    It is important to balance holes and electrons in the emitting layer of organic light-emitting diodes to maximize recombination efficiency and the accompanying external quantum efficiency. Therefore, the host materials of the emitting layer should transport both holes and electrons for the charge balance. From this perspective, bipolar hosts have been popular as the host materials of thermally activated delayed fluorescent devices and phosphorescent organic light-emitting diodes. In this review, we have summarized recent developments of bipolar hosts and suggested perspectives of host materials for organic light-emitting diodes.

  19. Unusually High Metallicity Host Of The Dark LGRB 051022

    CERN Document Server

    Graham, J F; Kewley, L J; Levesque, E M; Levan, A J; Tanvir, N R; Reichart, D E; Nysewander, M

    2009-01-01

    We present spectroscopy of the host of GRB 051022 with GMOS nod and shuffle on Gemini South and NIRSPEC on Keck II. We determine a metallicity for the host of log(O/H)+12 = 8.77 using the R23 method (Kobulnicky & Kewley 2004 scale) making this the highest metallicity long burst host yet observed. The galaxy itself is unusually luminous for a LGRB host with a rest frame B band absolute magnitude -21.5 and has the spectrum of a rapidly star-forming galaxy. Our work raises the question of whether other dark burst hosts will show high metallicities.

  20. Planet host stars in open clusters

    Science.gov (United States)

    Yang, XiaoLing; Chen, YuQin; Zhao, Gang

    2015-03-01

    We have compiled a list of all planet host star candidates reported in the literature, which are likely to be cluster members, and we checked their memberships by the spatial location, radial velocity, proper motion and photometric criteria. We found that only six stars, BD-13 2130, HD 28305, Kepler-66, Kepler-67, Pr0201 and Pr0211, are planet orbiting stars in open clusters to date. Two stars, HD 70573 and HD 89744, belong to moving groups and one star, TYC 8975-2606-1, may not be a planet host star, while three stars, HD 16175, HD 46375 and HD 108874 are not members of open clusters. We note that all these six planetary systems in the stellar cluster environment are younger than ˜1 Gyr, which might indicate that the planetary system in open cluster can not survive for a long time, and we speculate that close stellar encounters between member stars in open cluster can potentially destroy, or at least strongly affect, the presence of planetary systems.

  1. Tumour-host dynamics under radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Placeres Jimenez, Rolando, E-mail: rpjcu@yahoo.com [Departamento de Fi' sica, Universidade Federal de Sao Carlos, Sao Carlos - SP (Brazil); Ortiz Hernandez, Eloy [Centre of Medicine and Complexity, Medical University Carlos J. Finlay, Carretera Central s/n, Camagueey (Cuba)

    2011-09-15

    Highlight: > Tumour-host interaction is modelled by Lotka-Volterra equations. > A brief review of the motion integral and analysis of linear stability is presented. > Radiotherapy is introduced into the model, using a periodic Dirac delta function. > A two-dimensional logistic map is derived from the modified Lotka-Volterra model. > It is shown that tumour can be controlled by a correct selection of therapy strategy. - Abstract: Tumour-host interaction is modelled by the Lotka-Volterra equations. Qualitative analysis and simulations show that this model reproduces all known states of development for tumours. Radiotherapy effect is introduced into the model by means of the linear-quadratic model and the periodic Dirac delta function. The evolution of the system under the action of radiotherapy is simulated and parameter space is obtained, from which certain threshold of effectiveness values for the frequency and applied doses are derived. A two-dimensional logistic map is derived from the modified Lotka-Volterra model and used to simulate the effectiveness of radiotherapy in different regimens of tumour development. The results show the possibility of achieving a successful treatment in each individual case by employing the correct therapeutic strategy.

  2. Host social behavior and parasitic infection: A multifactorial approach

    Science.gov (United States)

    Ezenwa, V.O.

    2004-01-01

    I examined associations between several components of host social organization, including group size and gregariousness, group stability, territoriality and social class, and gastrointestinal parasite load in African bovids. At an intraspecific level, group size was positively correlated with parasite prevalence, but only when the parasite was relatively host specific and only among host species living in stable groups. Social class was also an important predictor of infection rates. Among gazelles, territorial males had higher parasite intensities than did either bachelor males or females and juveniles, suggesting that highly territorial individuals may be either more exposed or more susceptible to parasites. Associations among territoriality, grouping, and parasitism were also found across taxa. Territorial host genera were more likely to be infected with strongyle nematodes than were nonterritorial hosts, and gregarious hosts were more infected than were solitary hosts. Analyses also revealed that gregariousness and territoriality had an interactive effect on individual parasite richness, whereby hosts with both traits harbored significantly more parasite groups than did hosts with only one or neither trait. Overall, study results indicate that multiple features of host social behavior influence infection risk and suggest that synergism between traits also has important effects on host parasite load.

  3. Raiders from the sky: slavemaker founding queens select for aggressive host colonies

    Science.gov (United States)

    Pamminger, Tobias; Modlmeier, Andreas P.; Suette, Stefan; Pennings, Pleuni S.; Foitzik, Susanne

    2012-01-01

    Reciprocal selection pressures in host–parasite systems drive coevolutionary arms races that lead to advanced adaptations in both opponents. In the interactions between social parasites and their hosts, aggression is one of the major behavioural traits under selection. In a field manipulation, we aimed to disentangle the impact of slavemaking ants and nest density on aggression of Temnothorax longispinosus ants. An early slavemaker mating flight provided us with the unique opportunity to study the influence of host aggression and demography on founding decisions and success. We discovered that parasite queens avoided colony foundation in parasitized areas and were able to capture more brood from less aggressive host colonies. Host colony aggression remained consistent over the two-month experiment, but did not respond to our manipulation. However, as one-fifth of all host colonies were successfully invaded by parasite queens, slavemaker nest foundation acts as a strong selection event selecting for high aggression in host colonies. PMID:22809720

  4. Gamma-ray Bursts: Radio Afterglow and Host Galaxy Study with The FAST Telescope

    Science.gov (United States)

    Li, L. B.; Huang, Y. F.; Kong, S. W.; Zhang, Z. B.; Li, D.; Luo, J. J.

    2016-02-01

    For four types of GRBs, namely high-luminosity, low-luminosity, standard and failed GRBs, we calculated their radio afterglow light curves. Meanwhile, considering contributions from host galaxies in radio bands, we statistically investigated the effect of hosts on radio afterglows. It is found that a tight anti-correlation exists between the ratio of radio flux (RRF) of host galaxy to the total radio afterglow peak flux and the observed frequency. Using this method, the host flux densities of those bursts without host measurements can be estimated at low or medium frequencies. We predicted that almost all types of radio afterglows, except that of low-luminosity GRBs, can be observed by FAST up to z = 15 or even more. FAST is expected to significantly expand the samples of GRB radio afterglows and host galaxies.

  5. Proteomic Characterization of Host Response to Yersinia pestis

    Energy Technology Data Exchange (ETDEWEB)

    Chromy, B; Perkins, J; Heidbrink, J; Gonzales, A; Murhpy, G; Fitch, J P; McCutchen-Maloney, S

    2004-05-11

    Host-pathogen interactions result in protein expression changes within both the host and the pathogen. Here, results from proteomic characterization of host response following exposure to Yersinia pestis, the causative agent of plague, and to two near neighbors, Y. pseudotuberculosis and Y. enterocolitica, are reported. Human monocyte-like cells were chosen as a model for macrophage immune response to pathogen exposure. Two-dimensional electrophoresis followed by mass spectrometry was used to identify host proteins with differential expression following exposure to these three closely related Yersinia species. This comparative proteomic characterization of host response clearly shows that host protein expression patterns are distinct for the different pathogen exposures, and contributes to further understanding of Y. pestis virulence and host defense mechanisms. This work also lays the foundation for future studies aimed at defining biomarkers for presymptomatic detection of plague.

  6. Host-microbe interactions in the developing zebrafish

    Science.gov (United States)

    Kanther, Michelle; Rawls, John F.

    2010-01-01

    Summary of recent advances The amenability of the zebrafish to in vivo imaging and genetic analysis has fueled expanded use of this vertebrate model to investigate the molecular and cellular foundations of host-microbe relationships. Study of microbial encounters in zebrafish hosts has concentrated on developing embryonic and larval stages, when the advantages of the zebrafish model are maximized. A comprehensive understanding of these host-microbe interactions requires appreciation of the developmental context into which a microbe is introduced, as well as the effects of that microbial challenge on host ontogeny. In this review, we discuss how in vivo imaging and genetic analysis in zebrafish has advanced our knowledge of host-microbe interactions in the context of a developing vertebrate host. We focus on recent insights into immune cell ontogeny and function, commensal microbial relationships in the intestine, and microbial pathogenesis in zebrafish hosts. PMID:20153622

  7. Climate change, phenology, and butterfly host plant utilization.

    Science.gov (United States)

    Navarro-Cano, Jose A; Karlsson, Bengt; Posledovich, Diana; Toftegaard, Tenna; Wiklund, Christer; Ehrlén, Johan; Gotthard, Karl

    2015-01-01

    Knowledge of how species interactions are influenced by climate warming is paramount to understand current biodiversity changes. We review phenological changes of Swedish butterflies during the latest decades and explore potential climate effects on butterfly-host plant interactions using the Orange tip butterfly Anthocharis cardamines and its host plants as a model system. This butterfly has advanced its appearance dates substantially, and its mean flight date shows a positive correlation with latitude. We show that there is a large latitudinal variation in host use and that butterfly populations select plant individuals based on their flowering phenology. We conclude that A. cardamines is a phenological specialist but a host species generalist. This implies that thermal plasticity for spring development influences host utilization of the butterfly through effects on the phenological matching with its host plants. However, the host utilization strategy of A. cardamines appears to render it resilient to relatively large variation in climate.

  8. Metabolic crosstalk between host and pathogen: sensing, adapting and competing.

    Science.gov (United States)

    Olive, Andrew J; Sassetti, Christopher M

    2016-04-01

    Our understanding of bacterial pathogenesis is dominated by the cell biology of the host-pathogen interaction. However, the majority of metabolites that are used in prokaryotic and eukaryotic physiology and signalling are chemically similar or identical. Therefore, the metabolic crosstalk between pathogens and host cells may be as important as the interactions between bacterial effector proteins and their host targets. In this Review we focus on host-pathogen interactions at the metabolic level: chemical signalling events that enable pathogens to sense anatomical location and the local physiology of the host; microbial metabolic pathways that are dedicated to circumvent host immune mechanisms; and a few metabolites as central points of competition between the host and bacterial pathogens.

  9. An HST study of three very faint GRB host galaxies

    DEFF Research Database (Denmark)

    Jaunsen, A.O.; Andersen, M.I.; Hjorth, J.;

    2003-01-01

    . (2002). We obtain a revised and much higher probability that the galaxies identified as hosts indeed are related to the GRBs (P(n(chance))=0.69, following Bloom et al. 2002), thereby strengthening the conclusion that GRBs are preferentially located in star-forming regions in their hosts. Apart from......As part of the HST/STIS GRB host survey program we present the detection of three faint gamma-ray burst (GRB) host galaxies based on an accurate localisation using ground-based data of the optical afterglows (OAs). A common property of these three hosts is their extreme faintness. The location...... at which GRBs occur with respect to their host galaxies and surrounding environments are robust indicators of the nature of GRB progenitors. The bursts studied here are among the four most extreme outliers, in terms of relative distance from the host center, in the recent comprehensive study of Bloom et al...

  10. Viral Evasion and Manipulation of Host RNA Quality Control Pathways.

    Science.gov (United States)

    Hogg, J Robert

    2016-08-15

    Viruses have evolved diverse strategies to maximize the functional and coding capacities of their genetic material. Individual viral RNAs are often used as substrates for both replication and translation and can contain multiple, sometimes overlapping open reading frames. Further, viral RNAs engage in a wide variety of interactions with both host and viral proteins to modify the activities of important cellular factors and direct their own trafficking, packaging, localization, stability, and translation. However, adaptations increasing the information density of small viral genomes can have unintended consequences. In particular, viral RNAs have developed features that mark them as potential targets of host RNA quality control pathways. This minireview focuses on ways in which viral RNAs run afoul of the cellular mRNA quality control and decay machinery, as well as on strategies developed by viruses to circumvent or exploit cellular mRNA surveillance.

  11. The optical afterglow and host galaxy of GRB 000926

    DEFF Research Database (Denmark)

    Fynbo, J.U.; Gorosabel, J.; Dall, T.H.;

    2002-01-01

    In this paper we illustrate with the case of GRB 000926 how Gamma Ray Bursts (GRBs) can be used as cosmological lighthouses to identify and study star forming galaxies at high redshifts. The optical afterglow of the burst was located with optical imaging at the Nordic Optical Telescope 20.7 hours...... after the burst. Rapid follow-up spectroscopy allowed the determination of the redshift of the burst and a measurement of the host galaxy HI-column density in front of the burst. With late-time narrow band Lyalpha as well as broad band imaging, we have studied the emission from the host galaxy and found...... that it is a strong Lyalpha emitter in a state of active star formation....

  12. Mechanistic and genetic overlap of barley host and non-host resistance to Blumeria graminis

    NARCIS (Netherlands)

    Trujillo, M.; Troeger, M.; Niks, R.E.; Kogel, K.H.; Huckelhoven, R.

    2004-01-01

    Non-host resistance of barley to Blumeria graminis f.sp. tritici (Bgt), an inappropriate forma specialis of the grass powdery mildew fungus, is associated with formation of cell wall appositions (papillae) at sites of attempted fungal penetration and a hypersensitive cell death reaction (HR) of sing

  13. Volatile chemical cues guide host location and host selection by parasitic plants

    Science.gov (United States)

    Justin B. Runyon; Mark C. Mescher; Consuelo M. De Moraes

    2006-01-01

    The importance of plant volatiles in mediating interactions between plant species is much debated. Here, we demonstrate that the parasitic plant Cuscuta pentagona (dodder) uses volatile cues for host location. Cuscuta pentagona seedlings exhibit directed growth toward nearby tomato plants (Lycopersicon esculentum...

  14. Molecular phylogenies reveal host-specific divergence of Ophiocordyceps unilateralis sensu lato following its host ants.

    Science.gov (United States)

    Kobmoo, N; Mongkolsamrit, S; Tasanathai, K; Thanakitpipattana, D; Luangsa-Ard, J J

    2012-06-01

    Ophiocordyceps unilateralis (Hypocreales, Ascomycetes) is an entomopathogenic fungus specific to formicine ants (Formicinae, Hymenoptera). Previous works have shown that the carpenter ant Camponotus leonardi acts as the principal host with occasional infections of ants from the genus Polyrhachis (sister genus of Camponotus). Observations were made on the permanent plots of Mo Singto, Khao Yai National Park of Thailand according to which O. unilateralis was found to occur predominantly on three host species: C. leonardi, C. saundersi and P. furcata. Molecular phylogenies of the elongation factor 1-α and β-Tubulin genes indicate a separation of O. unilateralis samples into three clades, reflecting specificity to each of the three different ant species. Samples collected from P. furcata and from C. leonardi were found to form sister groups with samples from C. saundersi forming an outgroup to the latter. Additional samples collected from unidentified ant species of Camponotus and Polyrhachis were positioned as outgroups to those samples on identified species. These results demonstrate that O. unilateralis is clearly not a single phylogenetic species and comprises at least three species that are specific to different host ant species. These cryptic species may arise through recent events of speciation driven by their specificity to host ant species.

  15. Emerging pathogen in immunocompromised hosts: Exophiala dermatitidis mycosis in graft-versus-host disease.

    Science.gov (United States)

    Chalkias, S; Alonso, C D; Levine, J D; Wong, M T

    2014-08-01

    Infection with the dematiaceous environmental fungus Exophiala, an emerging pathogen in immunocompromised individuals, poses a diagnostic and therapeutic challenge. Herein, we report the first Exophiala dermatitidis fungemia case, to our knowledge, in an allogeneic hematopoietic stem cell transplant patient with graft-versus-host disease, expanding the clinical setting where Exophiala species mycosis should be suspected.

  16. Host transcript accumulation during lytic KSHV infection reveals several classes of host responses.

    Directory of Open Access Journals (Sweden)

    Sanjay Chandriani

    Full Text Available Lytic infection by Kaposi's sarcoma-associated herpesvirus (KSHV is associated with an extensive shutoff of host gene expression, mediated chiefly by accelerated mRNA turnover due to expression of the viral SOX protein. We have previously identified a small number of host mRNAs that can escape SOX-mediated degradation. Here we present a detailed, transcriptome-wide analysis of host shutoff, with careful microarray normalization to allow rigorous determination of the magnitude and extent of transcript loss. We find that the extent of transcript reduction represents a continuum of susceptibilities of transcripts to virus-mediated shutoff. Our results affirm that the levels of over 75% of host transcripts are substantially reduced during lytic infection, but also show that another approximately 20% of cellular mRNAs declines only slightly (less than 2-fold during the course of infection. Approximately 2% of examined cellular genes are strongly upregulated during lytic infection, most likely due to transcriptional induction of mRNAs that display intrinsic SOX-resistance.

  17. Host responses to the pathogen Mycobacterium avium subsp. paratuberculosis and beneficial microbes exhibit host sex specificity.

    Science.gov (United States)

    Karunasena, Enusha; McMahon, K Wyatt; Chang, David; Brashears, Mindy M

    2014-08-01

    Differences between microbial pathogenesis in male and female hosts are well characterized in disease conditions connected to sexual transmission. However, limited biological insight is available on variances attributed to sex specificity in host-microbe interactions, and it is most often a minimized variable outside these transmission events. In this work, we studied two gut microbes-a pathogen, Mycobacterium avium subsp. paratuberculosis, and a probiotic, Lactobacillus animalis NP-51-and the interaction between each agent and the male and female gastrointestinal systems. This trial was conducted in BALB/c mice (n=5 per experimental group and per sex at a given time point), with analysis at four time points over 180 days. Host responses to M.avium subsp. paratuberculosis and L. animalis were sensitive to sex. Cytokines that were significantly different (P ≤ 0.05) betweenthe sexes included interleukin-1α/β (IL-1α/β), IL-17, IL-6, IL-10, IL-12, and gamma interferon (IFN-) and were dependent on experimental conditions. However, granulocyte-macrophage colony-stimulating factor (GM-CSF), vascular endothelial growth factor (VEGF), and IL-13/23 showed no sex specificity. A metabolomics study indicated a 0.5- to 2.0-fold (log2 scale) increase in short-chain fatty acids (butyrate and acetate) in males and greater increases in o-phosphocholine or histidine from female colon tissues; variances distinct to each sex were observed with age or long-term probiotic consumption. Two genera, Staphylococcus and Roseburia, were consistently overrepresented in females compared to males; other species were specific to one sex but fluctuated depending on experimental conditions. The differences observed suggest that male and female gut tissues and microbiota respond to newly introduced microorganisms differently and that gut-associated microorganisms with host immune system responses and metabolic activity are supported by biology distinct to the host sex.

  18. Host plant use by competing acacia-ants: mutualists monopolize while parasites share hosts.

    Science.gov (United States)

    Kautz, Stefanie; Ballhorn, Daniel J; Kroiss, Johannes; Pauls, Steffen U; Moreau, Corrie S; Eilmus, Sascha; Strohm, Erhard; Heil, Martin

    2012-01-01

    Protective ant-plant mutualisms that are exploited by non-defending parasitic ants represent prominent model systems for ecology and evolutionary biology. The mutualist Pseudomyrmex ferrugineus is an obligate plant-ant and fully depends on acacias for nesting space and food. The parasite Pseudomyrmex gracilis facultatively nests on acacias and uses host-derived food rewards but also external food sources. Integrative analyses of genetic microsatellite data, cuticular hydrocarbons and behavioral assays showed that an individual acacia might be inhabited by the workers of several P. gracilis queens, whereas one P. ferrugineus colony monopolizes one or more host trees. Despite these differences in social organization, neither of the species exhibited aggressive behavior among conspecific workers sharing a tree regardless of their relatedness. This lack of aggression corresponds to the high similarity of cuticular hydrocarbon profiles among ants living on the same tree. Host sharing by unrelated colonies, or the presence of several queens in a single colony are discussed as strategies by which parasite colonies could achieve the observed social organization. We argue that in ecological terms, the non-aggressive behavior of non-sibling P. gracilis workers--regardless of the route to achieve this social structure--enables this species to efficiently occupy and exploit a host plant. By contrast, single large and long-lived colonies of the mutualist P. ferrugineus monopolize individual host plants and defend them aggressively against invaders from other trees. Our findings highlight the necessity for using several methods in combination to fully understand how differing life history strategies affect social organization in ants.

  19. Host plant use by competing acacia-ants: mutualists monopolize while parasites share hosts.

    Directory of Open Access Journals (Sweden)

    Stefanie Kautz

    Full Text Available Protective ant-plant mutualisms that are exploited by non-defending parasitic ants represent prominent model systems for ecology and evolutionary biology. The mutualist Pseudomyrmex ferrugineus is an obligate plant-ant and fully depends on acacias for nesting space and food. The parasite Pseudomyrmex gracilis facultatively nests on acacias and uses host-derived food rewards but also external food sources. Integrative analyses of genetic microsatellite data, cuticular hydrocarbons and behavioral assays showed that an individual acacia might be inhabited by the workers of several P. gracilis queens, whereas one P. ferrugineus colony monopolizes one or more host trees. Despite these differences in social organization, neither of the species exhibited aggressive behavior among conspecific workers sharing a tree regardless of their relatedness. This lack of aggression corresponds to the high similarity of cuticular hydrocarbon profiles among ants living on the same tree. Host sharing by unrelated colonies, or the presence of several queens in a single colony are discussed as strategies by which parasite colonies could achieve the observed social organization. We argue that in ecological terms, the non-aggressive behavior of non-sibling P. gracilis workers--regardless of the route to achieve this social structure--enables this species to efficiently occupy and exploit a host plant. By contrast, single large and long-lived colonies of the mutualist P. ferrugineus monopolize individual host plants and defend them aggressively against invaders from other trees. Our findings highlight the necessity for using several methods in combination to fully understand how differing life history strategies affect social organization in ants.

  20. Extrasolar planets and their host stars

    CERN Document Server

    von Braun, Kaspar

    2017-01-01

    This book explores the relations between physical parameters of extrasolar planets and their respective parent stars. Planetary parameters are often directly dependent upon their stellar counterparts. In addition, the star is almost always the only visible component of the system and contains most of the system mass. Consequently, the parent star heavily influences every aspect of planetary physics and astrophysics. Drs. Kaspar von Braun and Tabetha Boyajian use direct methods to characterize exoplanet host starts that minimize the number of assumptions needed to be made in the process. The book provides a background on interferometric techniques for stellar diameter measurements, illustrates the authors' approach on using additional data to fully characterize the stars, provides a comprehensive update on the current state of the field, and examines in detail a number of historically significant and well-studied exoplanetary systems.

  1. Apprenticeships at CERN: a host of awards

    CERN Multimedia

    2009-01-01

    This year again, two CERN apprentices have received awards at the end of their training. CERN’s broad range of technical skills means that it can provide training in a wide variety of trades and professions. Denis Fernier receives congratulations from Pierre-François Unger, Counsel state of the canton of Geneva in charge of the department of economics and health. Denis Fernier and Coralie Husi (right) at the prize-giving ceremony of the Union Industrielle de Genève.Every year, CERN hosts six technical apprentices for a four-year period: three electronics technicians and three physics lab technicians. And every year, at the end of their apprenticeships, one or more of them receives an award for being among the best apprentices in Geneva. On 23 September, two young apprentices were honoured by the Union industrielle genevoise (UIG) on passing their exams: Coralie Husi, a physics lab apprentice...

  2. Hepatitis C virus host cell interactions uncovered

    DEFF Research Database (Denmark)

    Gottwein, Judith; Bukh, Jens

    2007-01-01

      Insights into virus-host cell interactions as uncovered by Randall et al. (1) in a recent issue of PNAS further our understanding of the hepatitis C virus (HCV) life cycle, persistence, and pathogenesis and might lead to the identification of new therapeutic targets. HCV persistently infects 180...... million individuals worldwide, causing chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. The only approved treatment, combination therapy with IFN- and ribavirin, targets cellular pathways (2); however, a sustained virologic response is achieved only in approximately half of the patients...... treated. Therefore, there is a pressing need for the identification of novel drugs against hepatitis C. Although most research focuses on the development of HCV-specific antivirals, such as protease and polymerase inhibitors (3), cellular targets could be pursued and might allow the development of broad...

  3. Hepatitis C virus host cell interactions uncovered

    DEFF Research Database (Denmark)

    Gottwein, Judith; Bukh, Jens

    2007-01-01

      Insights into virus-host cell interactions as uncovered by Randall et al. (1) in a recent issue of PNAS further our understanding of the hepatitis C virus (HCV) life cycle, persistence, and pathogenesis and might lead to the identification of new therapeutic targets. HCV persistently infects 180...... million individuals worldwide, causing chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. The only approved treatment, combination therapy with IFN- and ribavirin, targets cellular pathways (2); however, a sustained virologic response is achieved only in approximately half of the patients...... treated. Therefore, there is a pressing need for the identification of novel drugs against hepatitis C. Although most research focuses on the development of HCV-specific antivirals, such as protease and polymerase inhibitors (3), cellular targets could be pursued and might allow the development of broad...

  4. A Taxonomy of Metrics for Hosted Databases

    Directory of Open Access Journals (Sweden)

    Jordan Shropshire

    2006-04-01

    Full Text Available The past three years has seen exponential growth in the number of organizations who have elected to entrust core information technology functions to application service providers. Of particular interest is the outsourcing of critical systems such as corporate databases. Major banks and financial service firms are contracting with third party organizations, sometimes overseas, for their database needs. These sophisticated contracts require careful supervision by both parties. Due to the complexities of web- based applications and the complicated nature of databases, an entire class of software suites has been developed to measure the quality of service the database is providing. This article investigates the performance metrics which have evolved to satisfy this need and describes a taxonomy of performance metrics for hosted databases.

  5. Social host policies and underage drinking parties.

    Science.gov (United States)

    Wagoner, Kimberly G; Sparks, Michael; Francisco, Vincent T; Wyrick, David; Nichols, Tracy; Wolfson, Mark

    2013-01-01

    Social host policies focused on underage drinking parties are implemented to reduce social availability of alcohol and high-risk drinking by adolescents in private locations. We examined the policies' relationship with drinking location, peer-group drinking size, heavy episodic drinking, and nonviolent consequences. Cross-sectional data from 11,205, 14-20-year olds, were analyzed using multilevel modeling. Policies were not associated with drinking location, decreased heavy episodic drinking, or nonviolent consequences. However, adolescents from communities with a preexisting policy had lower odds of drinking in large peer groups compared to those from communities without a policy at baseline. Additional research is needed to examine their effectiveness. The study's limitations are noted.

  6. HOST PLANT PREFERENCES OF BEMISIA TABACI GENNADIUS

    Institute of Scientific and Technical Information of China (English)

    JINGYing; HUANGJian; MARui-yan; HANJu-cai

    2003-01-01

    The preferences of Bemisia tabaci Gennadius for five host plants:poinsettia, tomato, cabbage,sweet potato and flowering Chinese cabbage, was tested using a Y-tube olfactometer and a desiccator in the labo-ratory. The results show that B. tabaci adults were attracted by the odors of the five plants. The order of prefer-ence was poinsettia > flowering Chinese cabbage > sweet potato > cabbage > tomato. Preference was extremely sig-nificant between poinsettia and the other four plants, and between flowering Chinese cabbage, cabbage and toma-to. There was no significant difference in preference for flowering Chinese cabbage and sweet potato, sweet pota-to, cabbage and tomato or between cabbage and tomato.

  7. Habitat selection for parasite-free space by hosts of parasitic cowbirds

    Science.gov (United States)

    Forsman, J.T.; Martin, T.E.

    2009-01-01

    Choice of breeding habitat can have a major impact on fitness. Sensitivity of habitat choice to environmental cues predicting reproductive success, such as density of harmful enemy species, should be favored by natural selection. Yet, experimental tests of this idea are in short supply. Brown-headed cowbirds Molothrus ater commonly reduce reproductive success of a wide diversity of birds by parasitizing their nests. We used song playbacks to simulate high cowbird density and tested whether cowbird hosts avoid such areas in habitat selection. Host species that made settlement decisions during manipulations were significantly less abundant in the cowbird treatment as a group. In contrast, hosts that settled before manipulations started and non-host species did not respond to treatments. These results suggest that hosts of cowbirds can use vocal cues to assess parasitism risk among potential habitat patches and avoid high risk habitats. This can affect community structure by affecting habitat choices of species with differential vulnerability.

  8. Models of microbiome evolution incorporating host and microbial selection.

    Science.gov (United States)

    Zeng, Qinglong; Wu, Steven; Sukumaran, Jeet; Rodrigo, Allen

    2017-09-25

    Numerous empirical studies suggest that hosts and microbes exert reciprocal selective effects on their ecological partners. Nonetheless, we still lack an explicit framework to model the dynamics of both hosts and microbes under selection. In a previous study, we developed an agent-based forward-time computational framework to simulate the neutral evolution of host-associated microbial communities in a constant-sized, unstructured population of hosts. These neutral models allowed offspring to sample microbes randomly from parents and/or from the environment. Additionally, the environmental pool of available microbes was constituted by fixed and persistent microbial OTUs and by contributions from host individuals in the preceding generation. In this paper, we extend our neutral models to allow selection to operate on both hosts and microbes. We do this by constructing a phenome for each microbial OTU consisting of a sample of traits that influence host and microbial fitnesses independently. Microbial traits can influence the fitness of hosts ("host selection") and the fitness of microbes ("trait-mediated microbial selection"). Additionally, the fitness effects of traits on microbes can be modified by their hosts ("host-mediated microbial selection"). We simulate the effects of these three types of selection, individually or in combination, on microbiome diversities and the fitnesses of hosts and microbes over several thousand generations of hosts. We show that microbiome diversity is strongly influenced by selection acting on microbes. Selection acting on hosts only influences microbiome diversity when there is near-complete direct or indirect parental contribution to the microbiomes of offspring. Unsurprisingly, microbial fitness increases under microbial selection. Interestingly, when host selection operates, host fitness only increases under two conditions: (1) when there is a strong parental contribution to microbial communities or (2) in the absence of a strong

  9. The evolution of host associations in the parasitic wasp genus Ichneumon (Hymenoptera: Ichneumonidae): convergent adaptations to host pupation sites.

    Science.gov (United States)

    Tschopp, Andreas; Riedel, Matthias; Kropf, Christian; Nentwig, Wolfgang; Klopfstein, Seraina

    2013-03-27

    The diversification of organisms with a parasitic lifestyle is often tightly linked to the evolution of their host associations. If a tight host association exists, closely related species tend to attack closely related hosts; host associations are less stable if associations are determined by more plastic traits like parasitoid searching and oviposition behaviour. The pupal-parasitoids of the genus Ichneumon attack a variety of macrolepidopteran hosts. They are either monophagous or polyphagous, and therefore offer a promissing system to investigate the evolution of host associations. Ichneumon was previously divided into two groups based on general body shape; however, a stout shape has been suggested as an adaptation to buried host pupation sites, and might thus not represent a reliable phylogenetic character. We here reconstruct the first molecular phylogeny of the genus Ichneumon using two mitochondrial (CO1 and NADH1) and one nuclear marker (28S). The resulting phylogeny only supports monophyly of Ichneumon when Ichneumon lugens Gravenhorst, 1829 (formerly in Chasmias, stat. rev.) and Ichneumon deliratorius Linnaeus, 1758 (formerly Coelichneumon) are included. Neither parasitoid species that attack hosts belonging to one family nor those attacking butterflies (Rhopalocera) form monophyletic clades. Ancestral state reconstructions suggest multiple transitions between searching for hosts above versus below ground and between a stout versus elongated body shape. A model assuming correlated evolution between the two characters was preferred over independent evolution of host-searching niche and body shape. Host relations, both in terms of phylogeny and ecology, evolved at a high pace in the genus Ichneumon. Numerous switches between hosts of different lepidopteran families have occurred, a pattern that seems to be the rule among idiobiont parasitoids. A stout body and antennal shape in the parasitoid female is confirmed as an ecological adaptation to host

  10. Type I Interferons Direct Gammaherpesvirus Host Colonization.

    Directory of Open Access Journals (Sweden)

    Cindy S E Tan

    2016-05-01

    Full Text Available Gamma-herpesviruses colonise lymphocytes. Murid Herpesvirus-4 (MuHV-4 infects B cells via epithelial to myeloid to lymphoid transfer. This indirect route entails exposure to host defences, and type I interferons (IFN-I limit infection while viral evasion promotes it. To understand how IFN-I and its evasion both control infection outcomes, we used Mx1-cre mice to tag floxed viral genomes in IFN-I responding cells. Epithelial-derived MuHV-4 showed low IFN-I exposure, and neither disrupting viral evasion nor blocking IFN-I signalling markedly affected acute viral replication in the lungs. Maximising IFN-I induction with poly(I:C increased virus tagging in lung macrophages, but the tagged virus spread poorly. Lymphoid-derived MuHV-4 showed contrastingly high IFN-I exposure. This occurred mainly in B cells. IFN-I induction increased tagging without reducing viral loads; disrupting viral evasion caused marked attenuation; and blocking IFN-I signalling opened up new lytic spread between macrophages. Thus, the impact of IFN-I on viral replication was strongly cell type-dependent: epithelial infection induced little response; IFN-I largely suppressed macrophage infection; and viral evasion allowed passage through B cells despite IFN-I responses. As a result, IFN-I and its evasion promoted a switch in infection from acutely lytic in myeloid cells to chronically latent in B cells. Murine cytomegalovirus also showed a capacity to pass through IFN-I-responding cells, arguing that this is a core feature of herpesvirus host colonization.

  11. Transmission of ranavirus between ectothermic vertebrate hosts.

    Directory of Open Access Journals (Sweden)

    Roberto Brenes

    Full Text Available Transmission is an essential process that contributes to the survival of pathogens. Ranaviruses are known to infect different classes of lower vertebrates including amphibians, fishes and reptiles. Differences in the likelihood of infection among ectothermic vertebrate hosts could explain the successful yearlong persistence of ranaviruses in aquatic environments. The goal of this study was to determine if transmission of a Frog Virus 3 (FV3-like ranavirus was possible among three species from different ectothermic vertebrate classes: Cope's gray treefrog (Hyla chrysoscelis larvae, mosquito fish (Gambusia affinis, and red-eared slider (Trachemys scripta elegans. We housed individuals previously exposed to the FV3-like ranavirus with naïve (unexposed individuals in containers divided by plastic mesh screen to permit water flow between subjects. Our results showed that infected gray treefrog larvae were capable of transmitting ranavirus to naïve larval conspecifics and turtles (60% and 30% infection, respectively, but not to fish. Also, infected turtles and fish transmitted ranavirus to 50% and 10% of the naïve gray treefrog larvae, respectively. Nearly all infected amphibians experienced mortality, whereas infected turtles and fish did not die. Our results demonstrate that ranavirus can be transmitted through water among ectothermic vertebrate classes, which has not been reported previously. Moreover, fish and reptiles might serve as reservoirs for ranavirus given their ability to live with subclinical infections. Subclinical infections of ranavirus in fish and aquatic turtles could contribute to the pathogen's persistence, especially when highly susceptible hosts like amphibians are absent as a result of seasonal fluctuations in relative abundance.

  12. Can hemozoin alone cause host anaemia?

    Science.gov (United States)

    Sun, Jun; Wang, Su-Wen; Jin, Chang-Long; Zeng, Xiao-Li; Piao, Xing-Yu; Bai, Ling; Tang, Dan-Li; Ji, Chang-Le

    2016-12-01

    Both schistosomes and malaria parasites produce hemozoin and cause host anaemia. However, the relationship between anaemia and hemozoin is unclear. Although some studies have proposed that hemozoin is related to anaemia in malaria patients, whether hemozoin alone can cause anaemia in patients infected by malaria parasites or schistosomes is uncertain. To investigate the effect of hemozoin on hosts, β-haematin was injected intravenously to normal mice. Then, liver and spleen tissues were observed. Mouse blood was examined. Red blood cells (RBCs), white blood cells (WBCs) and haemoglobin were analysed. Macrophage changes in the spleens and marrow cells were compared using immunofluorescence and H&E or Giemsa stain, respectively. We found that after 15 injections of β-haematin, a large amount of β-haematin was observed to deposit in the livers and spleens. Splenomegaly and bone marrow mild hyperplasia were detected. The average number of RBCs, average number of WBCs and average concentration of haemoglobin decreased significantly from 9.36 × 10(12) cells/L to 8.7 × 10(12) cells/L, 3.8 × 10(9) cells/L to 1.7 × 10(9) cells/L and 142.8 g/L to 131.8 g/L, respectively. In specific, the number of macrophages in the spleens greatly increased after β-haematin infection. The results showed that injections of β-haematin alone can cause anaemia possibly through hypersplenism.

  13. Weed hosts of cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae).

    Science.gov (United States)

    Vennila, S; Prasad, Y G; Prabhakar, M; Agarwal, Meenu; Sreedevi, G; Bambawale, O M

    2013-03-01

    The exotic cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) invaded India during 2006, and caused widespread infestation across all nine cotton growing states. P. solenopsis also infested weeds that aided its faster spread and increased severity across cotton fields. Two year survey carried out to document host plants of P. solenopsis between 2008 and 2010 revealed 27, 83, 59 and 108 weeds belonging to 8, 18, 10 and 32 families serving as alternate hosts at North, Central, South and All India cotton growing zones, respectively. Plant species of four families viz., Asteraceae, Amaranthaceae, Malvaceae and Lamiaceae constituted almost 50% of the weed hosts. While 39 weed species supported P. solenopsis multiplication during the cotton season, 37 were hosts during off season. Higher number of weeds as off season hosts (17) outnumbering cotton season (13) at Central over other zones indicated the strong carryover of the pest aided by weeds between two cotton seasons. Six, two and seven weed hosts had the extreme severity of Grade 4 during cotton, off and cotton + off seasons, respectively. Higher number of weed hosts of P. solenopsis were located at roadside: South (12) > Central (8) > North (3) zones. Commonality of weed hosts was higher between C+S zones, while no weed host was common between N+S zones. Paper furnishes the wide range of weed hosts of P. solenopsis, discusses their significance, and formulated general and specific cultural management strategies for nationwide implementation to prevent its outbreaks.

  14. Pathogen mimicry of host protein-protein interfaces modulates immunity.

    Science.gov (United States)

    Guven-Maiorov, Emine; Tsai, Chung-Jung; Nussinov, Ruth

    2016-10-01

    Signaling pathways shape and transmit the cell's reaction to its changing environment; however, pathogens can circumvent this response by manipulating host signaling. To subvert host defense, they beat it at its own game: they hijack host pathways by mimicking the binding surfaces of host-encoded proteins. For this, it is not necessary to achieve global protein homology; imitating merely the interaction surface is sufficient. Different protein folds often interact via similar protein-protein interface architectures. This similarity in binding surfaces permits the pathogenic protein to compete with a host target protein. Thus, rather than binding a host-encoded partner, the host protein hub binds the pathogenic surrogate. The outcome can be dire: rewiring or repurposing the host pathways, shifting the cell signaling landscape and consequently the immune response. They can also cause persistent infections as well as cancer by modulating key signaling pathways, such as those involving Ras. Mapping the rewired host-pathogen 'superorganism' interaction network - along with its structural details - is critical for in-depth understanding of pathogenic mechanisms and developing efficient therapeutics. Here, we overview the role of molecular mimicry in pathogen host evasion as well as types of molecular mimicry mechanisms that emerged during evolution.

  15. Genetic differentiation among sympatric cuckoo host races: males matter.

    Science.gov (United States)

    Fossøy, Frode; Antonov, Anton; Moksnes, Arne; Røskaft, Eivin; Vikan, Johan R; Møller, Anders P; Shykoff, Jacqui A; Stokke, Bård G

    2011-06-07

    Generalist parasites regularly evolve host-specific races that each specialize on one particular host species. Many host-specific races originate from geographically structured populations where local adaptations to different host species drive the differentiation of distinct races. However, in sympatric populations where several host races coexist, gene flow could potentially disrupt such host-specific adaptations. Here, we analyse genetic differentiation among three sympatrically breeding host races of the brood-parasitic common cuckoo, Cuculus canorus. In this species, host-specific adaptations are assumed to be controlled by females only, possibly via the female-specific W-chromosome, thereby avoiding that gene flow via males disrupts local adaptations. Although males were more likely to have offspring in two different host species (43% versus 7%), they did not have significantly more descendants being raised outside their putative foster species than females (9% versus 2%). We found significant genetic differentiation for both biparentally inherited microsatellite DNA markers and maternally inherited mitochondrial DNA markers. To our knowledge, this is the first study that finds significant genetic differentiation in biparentally inherited markers among cuckoo host-specific races. Our results imply that males also may contribute to the evolution and maintenance of the different races, and hence that the genes responsible for egg phenotype may be found on autosomal chromosomes rather than the female-specific W-chromosome as previously assumed.

  16. Host shift and speciation in a coral-feeding nudibranch

    Science.gov (United States)

    Faucci, Anuschka; Toonen, Robert J; Hadfield, Michael G

    2006-01-01

    While the role of host preference in ecological speciation has been investigated extensively in terrestrial systems, very little is known in marine environments. Host preference combined with mate choice on the preferred host can lead to population subdivision and adaptation leading to host shifts. We use a phylogenetic approach based on two mitochondrial genetic markers to disentangle the taxonomic status and to investigate the role of host specificity in the speciation of the nudibranch genus Phestilla (Gastropoda, Opisthobranchia) from Guam, Palau and Hawaii. Species of the genus Phestilla complete their life cycle almost entirely on their specific host coral (species of Porites, Goniopora and Tubastrea). They reproduce on their host coral and their planktonic larvae require a host-specific chemical cue to metamorphose and settle onto their host. The phylogenetic trees of the combined cytochrome oxidase I and ribosomal 16S gene sequences clarify the relationship among species of Phestilla identifying most of the nominal species as monophyletic clades. We found a possible case of host shift from Porites to Goniopora and Tubastrea in sympatric Phestilla spp. This represents one of the first documented cases of host shift as a mechanism underlying speciation in a marine invertebrate. Furthermore, we found highly divergent clades within Phestilla sp. 1 and Phestilla minor (8.1–11.1%), suggesting cryptic speciation. The presence of a strong phylogenetic signal for the coral host confirms that the tight link between species of Phestilla and their host coral probably played an important role in speciation within this genus. PMID:17134995

  17. Assimilating host model information into a limited area model

    Directory of Open Access Journals (Sweden)

    Nils Gustafsson

    2012-01-01

    Full Text Available We propose to add an extra source of information to the data-assimilation of the regional HIgh Resolution Limited Area Model (HIRLAM model, constraining larger scales to the host model providing the lateral boundary conditions. An extra term, Jk, measuring the distance to the large-scale vorticity of the host model, is added to the cost-function of the variational data-assimilation. Vorticity is chosen because it is a good representative of the large-scale flow and because vorticity is a basic control variable of the HIRLAM variational data-assimilation. Furthermore, by choosing only vorticity, the remaining model variables, divergence, temperature, surface pressure and specific humidity will be allowed to adapt to the modified vorticity field in accordance with the internal balance constraints of the regional model. The error characteristics of the Jk term are described by the horizontal spectral densities and the vertical eigenmodes (eigenvectors and eigenvalues of the host model vorticity forecast error fields, expressed in the regional model geometry. The vorticity field, provided by the European Centre for Medium-range Weather Forecasts (ECMWF operational model, was assimilated into the HIRLAM model during an experiment period of 33 d in winter with positive impact on forecast verification statistics for upper air variables and mean sea level pressure.The review process was handled by Editor-in-Cheif Harald Lejenäs

  18. Rate of resistance evolution and polymorphism in long- and short-lived hosts.

    Science.gov (United States)

    Bruns, Emily; Hood, Michael E; Antonovics, Janis

    2015-02-01

    Recent theoretical work has shown that long-lived hosts are expected to evolve higher equilibrium levels of disease resistance than shorter-lived hosts, but questions of how longevity affects the rate of resistance evolution and the maintenance of polymorphism remain unanswered. Conventional wisdom suggests that adaptive evolution should occur more slowly in long-lived organisms than in short-lived organisms. However, the opposite may be true for the evolution of disease-resistance traits where exposure to disease, and therefore the strength of selection for resistance increases with longevity. In a single locus model of innate resistance to a frequency-dependent, sterilizing disease, longer lived hosts evolved resistance more rapidly than short-lived hosts. Moreover, resistance in long-lived hosts could only be polymorphic for more costly and more extreme resistance levels than short-lived hosts. The increased rate of evolution occurred in spite of longer generation times because longer-lived hosts had both a longer period of exposure to disease as well as higher disease prevalence. Qualitatively similar results were found when the model was extended to mortality-inducing diseases, or to density-dependent transmission modes. Our study shows that the evolutionary dynamics of host resistance is determined by more than just levels of resistance and cost, but is highly sensitive to the life-history traits of the host.

  19. Parasitoid Diaeretiella rapae (Hymenoptera: Braconidae) Adjusts Reproductive Strategy When Competing for Hosts.

    Science.gov (United States)

    Kant, Rashmi; Minor, Maria A

    2017-06-01

    Parasitoid fitness depends on its ability to manipulate reproductive strategies when in competition. This study investigated the parasitism and sex allocation strategies of the parasitic wasp Diaeretiella rapae McIntosh at a range of host (Brevicoryne brassicae L.) and conspecific densities. The results suggest that D. rapae females adjust their progeny production and progeny sex ratio with changing competition. When foraging alone, female D. rapae parasitize larger number of B. brassicae nymphs when the number of available hosts is increased, but the overall proportion of parasitized hosts decreases with increase in host density. The proportion of female offspring also decreases with elevated host density. Increase in the number of female D. rapae foraging together increased total parasitism, but reduced relative contribution of each individual female. The number of female progeny decreased when multiple females competed for the same host. However, foraging experience in the presence of one or more conspecifics increased the parasitism rate and proportion of female progeny. Competing females were more active during oviposition and had shorter lives. The study suggests that both host and foundress (female parasitoid) densities have significant effect on progeny production, sex allocation, and longevity of foraging females. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  20. Identification of two lineages of host-associated eriophyoid mites predisposed to different levels of host diversification.

    Science.gov (United States)

    Li, Hao-Sen; Hoffmann, Ary A; Guo, Jing-Feng; Zuo, Yun; Xue, Xiao-Feng; Pang, Hong; Hong, Xiao-Yue

    2016-12-01

    Herbivorous arthropods can diversify as a consequence of evolutionary changes in response to their plant hosts. Current patterns of host association of herbivores are likely to reflect a long evolutionary history of herbivore-plant co-evolution. Here, we used molecular phylogenetics to track the evolutionary history of host shifts and diversification of 66 eriophyoid mites (Acari, Eriophyoidea), and linked past patterns of evolutionary diversification to more recent patterns of divergence by tracking population genetic variation in 13 of the eriophyoid mite species feeding on different gymnosperm hosts. This allowed us to explore the relationship between a past history of diversification and the current potential of mites to undergo host range shifts. We found that population-level diversity across gymnosperm hosts as measured by 28S rRNA markers was greater in species from the mite clade that had radiated across evolutionary time to utilize a variety of hosts including angiosperms, compared to species from the clade that has remained restricted to ancestral gymnosperm hosts. Species from the radiated clade exhibited higher variation in host use. Lineages of mites that have in the past been able to radiate and adapt to diverse plants may therefore be predisposed to continue their expansion on new hosts, although additional clades need to be tested.

  1. Pattern mimicry of host eggs by the common cuckoo, as seen through a bird's eye

    National Research Council Canada - National Science Library

    Mary Caswell Stoddard; Martin Stevens

    2010-01-01

    Cuckoo—host interactions provide classical examples of coevolution. Cuckoos place hosts under selection to detect and reject foreign eggs, while host defences result in the evolution of host-egg mimicry in cuckoos...

  2. How pathogens use linear motifs to perturb host cell networks

    KAUST Repository

    Via, Allegra

    2015-01-01

    Molecular mimicry is one of the powerful stratagems that pathogens employ to colonise their hosts and take advantage of host cell functions to guarantee their replication and dissemination. In particular, several viruses have evolved the ability to interact with host cell components through protein short linear motifs (SLiMs) that mimic host SLiMs, thus facilitating their internalisation and the manipulation of a wide range of cellular networks. Here we present convincing evidence from the literature that motif mimicry also represents an effective, widespread hijacking strategy in prokaryotic and eukaryotic parasites. Further insights into host motif mimicry would be of great help in the elucidation of the molecular mechanisms behind host cell invasion and the development of anti-infective therapeutic strategies.

  3. Predictors of Host Specificity among Behavior-Manipulating Parasites

    DEFF Research Database (Denmark)

    Fredensborg, B. L.

    2014-01-01

    -specialist that has a restricted ecological niche that it masters. Parasites that manipulate hosts’ behavior are often thought to represent resource-specialists based on a few spectacular examples of manipulation of the host’s behavior. However, the determinants of which, and how many, hosts a manipulating parasite...... can exploit (i.e., niche breadth) are basically unknown. Here, I present an analysis based on published records of the use of hosts by 67 species from 38 genera of helminths inducing parasite increased trophic transmission, a widespread strategy of parasites that has been reported from many taxa...... of parasites and hosts. Using individual and multivariate analyses, I examined the effect of the host’s and parasite’s taxonomy, location of the parasite in the host, type of behavioral change, and the effect of debilitation on host-specificity, measured as the mean taxonomic relatedness of hosts...

  4. Varroa destructor changes its cuticular hydrocarbons to mimic new hosts.

    Science.gov (United States)

    Le Conte, Y; Huang, Z Y; Roux, M; Zeng, Z J; Christidès, J-P; Bagnères, A-G

    2015-06-01

    Varroa destructor (Vd) is a honeybee ectoparasite. Its original host is the Asian honeybee, Apis cerana, but it has also become a severe, global threat to the European honeybee, Apis mellifera. Previous studies have shown that Varroa can mimic a host's cuticular hydrocarbons (HC), enabling the parasite to escape the hygienic behaviour of the host honeybees. By transferring mites between the two honeybee species, we further demonstrate that Vd is able to mimic the cuticular HC of a novel host species when artificially transferred to this new host. Mites originally from A. cerana are more efficient than mites from A. mellifera in mimicking HC of both A. cerana and A. mellifera. This remarkable adaptability may explain their relatively recent host-shift from A. cerana to A. mellifera.

  5. Coral host cells acidify symbiotic algal microenvironment to promote photosynthesis.

    Science.gov (United States)

    Barott, Katie L; Venn, Alexander A; Perez, Sidney O; Tambutté, Sylvie; Tresguerres, Martin

    2015-01-13

    Symbiotic dinoflagellate algae residing inside coral tissues supply the host with the majority of their energy requirements through the translocation of photosynthetically fixed carbon. The algae, in turn, rely on the host for the supply of inorganic carbon. Carbon must be concentrated as CO2 in order for photosynthesis to proceed, and here we show that the coral host plays an active role in this process. The host-derived symbiosome membrane surrounding the algae abundantly expresses vacuolar H(+)-ATPase (VHA), which acidifies the symbiosome space down to pH ∼ 4. Inhibition of VHA results in a significant decrease in average H(+) activity in the symbiosome of up to 75% and a significant reduction in O2 production rate, a measure of photosynthetic activity. These results suggest that host VHA is part of a previously unidentified carbon concentrating mechanism for algal photosynthesis and provide mechanistic evidence that coral host cells can actively modulate the physiology of their symbionts.

  6. JIM CORGEL GM, e-business Hosting Services, IBMGlobal Services

    Institute of Scientific and Technical Information of China (English)

    JANKOT

    2004-01-01

    To many Chinese enterprises, e-business hosting services - IT resource consolidation and automation - are still a relatively new concept. The general concern is one related to the security of data as companies outsource the manage-ment of their IT environment. Jim Corgel,general manager of IBM Global Services'e-business hosting services, admits that it takes education to convince the potential users of the value of hosting services. Here he shares his thoughts on this latest innovation with CIB.

  7. Recombinant hosts suitable for simultaneous saccharification and fermentation

    Science.gov (United States)

    Ingram, Lonnie O'Neal; Zhou, Shengde

    2007-06-05

    The invention provides recombinant host cells containing at least one heterologous polynucleotide encoding a polysaccharase under the transcriptional control of a surrogate promoter capable of increasing the expression of the polysaccharase. In addition, the invention further provides such hosts with genes encoding secretory protein/s to facilitate the secretion of the expressed polysaccharase. Preferred hosts of the invention are ethanologenic and capable of carrying out simultaneous saccharification fermentation resulting in the production of ethanol from complex cellulose substrates.

  8. Vibrational relaxation of guest and host in mixed molecular crystals

    Science.gov (United States)

    Hill, Jeffrey R.; Chronister, Eric L.; Chang, Ta-Chau; Kim, Hackjin; Postlewaite, Jay C.; Dlott, Dana D.

    1988-02-01

    Vibrational relaxation (VR) of dilute impurity molecules (naphthalene, anthracene) in crystalline host matrices (durene, naphthalene) is studied with the ps photon echo technique. The results obtained by echoes on vibrations in the electronically excited state are compared to previous ps time delayed coherent Raman studies of ground state vibrations of the pure host matrix. The relaxation channels for guest and host, and the effects of molecular and crystal structure on VR rates are determined.

  9. Interplay between Candida albicans and the Mammalian Innate Host Defense

    Science.gov (United States)

    Cheng, Shih-Chin; Joosten, Leo A. B.; Kullberg, Bart-Jan

    2012-01-01

    Candida albicans is both the most common fungal commensal microorganism in healthy individuals and the major fungal pathogen causing high mortality in at-risk populations, especially immunocompromised patients. In this review, we summarize the interplay between the host innate system and C. albicans, ranging from how the host recognizes, responds, and clears C. albicans infection to how C. albicans evades, dampens, and escapes from host innate immunity. PMID:22252867

  10. Host Microbiota Contributes to Health and Response to Disease.

    Science.gov (United States)

    Aurora, Rajeev; Sanford, Thomas

    2015-01-01

    Recent studies have revealed that normal microbiota interacts with the host through four mechanisms: the normal microbiome acts as a barrier against pathogens; second, as modulators of the permeability of host mucosa; third, as modulators of energy extraction from, and metabolic utilization of ingested food; and lastly, as modulators of the immune system. An alteration of the normal microbiota increases predisposition of the host to diseases through these four mechanisms.

  11. Host plant use by competing Acacia-ants: mutualists monopolize while parasites share hosts

    OpenAIRE

    Stefanie Kautz; Ballhorn, Daniel J.; Johannes Kroiss; Pauls, Steffen U.; Moreau, Corrie S.; Sascha Eilmus; Erhard Strohm; Martin Heil

    2012-01-01

    Protective ant-plant mutualisms that are exploited by non-defending parasitic ants represent prominent model systems for ecology and evolutionary biology. The mutualist Pseudomyrmex ferrugineus is an obligate plant-ant and fully depends on acacias for nesting space and food. The parasite Pseudomyrmex gracilis facultatively nests on acacias and uses host-derived food rewards but also external food sources. Integrative analyses of genetic microsatellite data, cuticular hydrocarbons and behavior...

  12. Host-selective toxins of Pyrenophora tritici-repentis induce common responses associated with host susceptibility.

    Directory of Open Access Journals (Sweden)

    Iovanna Pandelova

    Full Text Available Pyrenophora tritici-repentis (Ptr, a necrotrophic fungus and the causal agent of tan spot of wheat, produces one or a combination of host-selective toxins (HSTs necessary for disease development. The two most studied toxins produced by Ptr, Ptr ToxA (ToxA and Ptr ToxB (ToxB, are proteins that cause necrotic or chlorotic symptoms respectively. Investigation of host responses induced by HSTs provides better insight into the nature of the host susceptibility. Microarray analysis of ToxA has provided evidence that it can elicit responses similar to those associated with defense. In order to evaluate whether there are consistent host responses associated with susceptibility, a similar analysis of ToxB-induced changes in the same sensitive cultivar was conducted. Comparative analysis of ToxA- and ToxB-induced transcriptional changes showed that similar groups of genes encoding WRKY transcription factors, RLKs, PRs, components of the phenylpropanoid and jasmonic acid pathways are activated. ROS accumulation and photosystem dysfunction proved to be common mechanism-of-action for these toxins. Despite similarities in defense responses, transcriptional and biochemical responses as well as symptom development occur more rapidly for ToxA compared to ToxB, which could be explained by differences in perception as well as by differences in activation of a specific process, for example, ethylene biosynthesis in ToxA treatment. Results of this study suggest that perception of HSTs will result in activation of defense responses as part of a susceptible interaction and further supports the hypothesis that necrotrophic fungi exploit defense responses in order to induce cell death.

  13. Geographical Distribution of Phacellaria Benth.(Santalaceae)and its Hosts

    Institute of Scientific and Technical Information of China (English)

    Li Dognxue; Ding Yulong

    2006-01-01

    Based on the geographical distribution of the species of Phacellaria and its host plants in the world,we speculated on the possible time,sites,and migration of the origin of Phacellaria.The host plants of Phacellaria mainly belong to Loranthaceae.Plants of Phacellaria and their hosts are mainly distributed in tropical and subtropical areas.The plants of Phacellaria might have originated from a tropical area in the south of China before the Tertiary.Their ancestors were parasitic on the ancestors of some plants of Loranthaceae by chance during the Tertiary.It possibly took them millions of years to form a sturdy relationship with their hosts.

  14. OHS students: reaching a decision about hosting placements.

    Science.gov (United States)

    Boucaut, Rose

    2008-01-01

    Physiotherapists have an established role in occupational health, and their undergraduate education is important in preparation for such practice. At the University of South Australia students undertake small occupational health and safety projects on-site in industry. These industry placements are a challenge to secure, and the supervising industry hosts are generally not physiotherapists. This study sought to uncover influences involved when organisations consider hosting students. A qualitative approach was taken where semistructured interviews were conducted with a purposeful sample of nine industry hosts to explore their views about placements. Seven hosts were managers and two were physiotherapists. Three main themes came from the data analysis. The first and overriding theme was the "mutual benefit" in hosting students, where students gained valuable experience from working in industry on real problems, and hosts gained from the students' activities. The second theme related to what the host organisation gained - "the transfer and acquisition of resources, knowledge and skills" provided by the students, the nature and quality of which were important to hosts. The last theme had two components of "timing and time." The timing of student activities and how that fits with other activities simultaneously happening within the organisation was an important factor. Finally, participants reported consideration of the time taken to supervise the students in relation to time saved through student activities which assisted the host organization. Knowldege about influencing factors gained from this study may assist physiotherapy educators in securing student placements in industry.

  15. Chemically modified tetracyclines: The novel host modulating agents

    Directory of Open Access Journals (Sweden)

    Devulapalli Narasimha Swamy

    2015-01-01

    Full Text Available Periodontal pathogens and destructive host responses are involved in the initiation and progression of periodontitis. The emergence of host response modulation as a treatment concept has resulted from our improved understanding of the pathogenesis of periodontal disease. A variety of drugs have been evaluated as host modulation agents (HMA, including Non Steroidal Anti Inflammatory Drugs (NSAIDS, bisphosphonates, tetracyclines, enamel matrix proteins and bone morphogenetic proteins. Chemically modified tetracyclines (CMTs are one such group of drugs which have been viewed as potential host modulating agents by their anticollagenolytic property. The CMTs are designed to be more potent inhibitors of pro inflammatory mediators and can increase the levels of anti inflammatory mediators.

  16. Manipulation of Host Cholesterol by Obligate Intracellular Bacteria

    Directory of Open Access Journals (Sweden)

    Dhritiman Samanta

    2017-05-01

    Full Text Available Cholesterol is a multifunctional lipid that plays important metabolic and structural roles in the eukaryotic cell. Despite having diverse lifestyles, the obligate intracellular bacterial pathogens Chlamydia, Coxiella, Anaplasma, Ehrlichia, and Rickettsia all target cholesterol during host cell colonization as a potential source of membrane, as well as a means to manipulate host cell signaling and trafficking. To promote host cell entry, these pathogens utilize cholesterol-rich microdomains known as lipid rafts, which serve as organizational and functional platforms for host signaling pathways involved in phagocytosis. Once a pathogen gains entrance to the intracellular space, it can manipulate host cholesterol trafficking pathways to access nutrient-rich vesicles or acquire membrane components for the bacteria or bacteria-containing vacuole. To acquire cholesterol, these pathogens specifically target host cholesterol metabolism, uptake, efflux, and storage. In this review, we examine the strategies obligate intracellular bacterial pathogens employ to manipulate cholesterol during host cell colonization. Understanding how obligate intracellular pathogens target and use host cholesterol provides critical insight into the host-pathogen relationship.

  17. Host defense peptides: an alternative as antiinfective and immunomodulatory therapeutics.

    Science.gov (United States)

    Alba, Annia; López-Abarrategui, Carlos; Otero-González, Anselmo J

    2012-01-01

    Host defense peptides are conserved components of innate immune response present among all classes of life. These peptides are potent, broad spectrum antimicrobial agents with potential as novel therapeutic compounds. Also, the ability of host defense peptides to modulate immunity is an emerging therapeutic concept since its selective modulation is a novel antiinfective strategy. Their mechanisms of action and the fundamental differences between pathogens and host cells surfaces mostly lead to a not widely extended microbial resistance and to a lower toxicity toward host cells. Biological libraries and rational design are novel tools for developing such molecules with promising applications as therapeutic drugs.

  18. Cross-kingdom host shifts of phytomyxid parasites.

    Science.gov (United States)

    Neuhauser, Sigrid; Kirchmair, Martin; Bulman, Simon; Bass, David

    2014-02-23

    Phytomyxids (plasmodiophorids and phagomyxids) are cosmopolitan, obligate biotrophic protist parasites of plants, diatoms, oomycetes and brown algae. Plasmodiophorids are best known as pathogens or vectors for viruses of arable crops (e.g. clubroot in brassicas, powdery potato scab, and rhizomania in sugar beet). Some phytomyxid parasites are of considerable economic and ecologic importance globally, and their hosts include important species in marine and terrestrial environments. However most phytomyxid diversity remains uncharacterised and knowledge of their relationships with host taxa is very fragmentary. Our molecular and morphological analyses of phytomyxid isolates-including for the first time oomycete and sea-grass parasites-demonstrate two cross-kingdom host shifts between closely related parasite species: between angiosperms and oomycetes, and from diatoms/brown algae to angiosperms. Switching between such phylogenetically distant hosts is generally unknown in host-dependent eukaryote parasites. We reveal novel plasmodiophorid lineages in soils, suggesting a much higher diversity than previously known, and also present the most comprehensive phytomyxid phylogeny to date. Such large-scale host shifts between closely related obligate biotrophic eukaryote parasites is to our knowledge unique to phytomyxids. Phytomyxids may readily adapt to a wide diversity of new hosts because they have retained the ability to covertly infect alternative hosts. A high cryptic diversity and ubiquitous distribution in agricultural and natural habitats implies that in a changing environment phytomyxids could threaten the productivity of key species in marine and terrestrial environments alike via host shift speciation.

  19. Host-directed therapeutics as novel angle for tuberculosis treatment.

    Science.gov (United States)

    Kim, Ye-Ram; Yang, Chul-Su

    2017-07-07

    Despite significant efforts to improve tuberculosis (TB) treatment, it remains a worldwide infectious disease due to the limitations of current TB regimens. Recent work on novel TB treatment strategies has suggested that directly targeting host factors is beneficial for TB treatment. Such strategies, termed host-directed therapeutics (HDTs), focus on host-pathogen interactions. HDTs are more beneficial than existed TB drugs, which are limited the long durations of treatment and the emergence of drug-resistant strains. Targets of HDTs include host factors such as cytokines, immune check points, immune cell functions, and essential enzyme activities. This article includes examples of potentially applicable HDTs and introduces novel approaches for their development.

  20. On Distributed PV Hosting Capacity Estimation, Sensitivity Study, and Improvement

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Fei; Mather, Barry

    2017-07-01

    This paper first studies the estimated distributed PV hosting capacities of seventeen utility distribution feeders using the Monte Carlo simulation based stochastic analysis, and then analyzes the sensitivity of PV hosting capacity to both feeder and photovoltaic system characteristics. Furthermore, an active distribution network management approach is proposed to maximize PV hosting capacity by optimally switching capacitors, adjusting voltage regulator taps, managing controllable branch switches and controlling smart PV inverters. The approach is formulated as a mixed-integer nonlinear optimization problem and a genetic algorithm is developed to obtain the solution. Multiple simulation cases are studied and the effectiveness of the proposed approach on increasing PV hosting capacity is demonstrated.

  1. Expanding the Entamoeba Universe: New Hosts Yield Novel Ribosomal Lineages.

    Science.gov (United States)

    Jacob, Alison S; Busby, Eloise J; Levy, Abigail D; Komm, Natasha; Clark, C Graham

    2016-01-01

    Removing the requirement for cell culture has led to a substantial increase in the number of lineages of Entamoeba recognized as distinct. Surveying the range of potential host species for this parasite genus has barely been started and it is clear that additional sampling of the same host in different locations often identifies additional diversity. In this study, using small subunit ribosomal RNA gene sequencing, we identify four new lineages of Entamoeba, including the first report of Entamoeba from an elephant, and extend the host range of some previously described lineages. In addition, examination of microbiome data from a number of host animals suggests that substantial Entamoeba diversity remains to be uncovered.

  2. Using host response modifiers in the treatment of periodontal disease.

    Science.gov (United States)

    Novak, M John; Donley, Timothy G

    2002-01-01

    Periodontal disease is the result of a complex interaction between microbial plaque, the host's inflammatory response to the plaque, and host modifying factors (e.g., smoking, diabetes, genetics) that may have an impact on the disease process. It is known that plaque initiates periodontal disease but that the host response is responsible for the destruction of periodontal tissues. This article describes why host response modifiers may be used to help control inflammation and tissue destruction as part of the initial phase of periodontal therapy in selected patient groups.

  3. Effects of rearing host species on the host-feeding capacity and parasitism of the whitefly parasitoid Encarsia formosa.

    Science.gov (United States)

    Dai, Peng; Ruan, Changchun; Zang, Liansheng; Wan, Fanghao; Liu, Linzhou

    2014-01-01

    Parasitoids of the Encarsia genus (Hymenoptera: Aphelinidae) are important biological control agents against whiteflies. Some of the species in this genus not only parasitize their hosts, but also kill them through host feeding. The whitefly parasitoid, Encarsia formosa Gahan, was examined to determine whether the rearing host species affects its subsequent host-feeding capacity and parasitism. E. formosa wasps were reared on Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) and Bemisia tabaci (Gennadius) 'Q', and their subsequent host-feeding capacity and parasitism of T. vaporariorum and B. tabaci were examined. E. formosa reared on T. vaporariorum were significantly larger in body size than those reared on B. tabaci, but these wasps killed a similar number of whitefly nymphs by host feeding when they attacked the same host species on which they were reared. Regardless of the species on which it was reared, E. formosa fed significantly more on the B. tabaci nymphs than on the T. vaporariorum nymphs. The number of whitefly nymphs parasitized by E. formosa differed between the wasps reared on T. vaporariorum and those reared on B. tabaci depending on which whitefly species was offered as a host. In addition, the wasps reared on T. vaporariorum parasitized significantly more on T. vaporariorum than those reared on B. tabaci. The wasps reared on B. tabaci, however, parasitized similar numbers of whiteflies of both host species. The results indicated that the host-feeding capacity of E. formosa was affected more by the host species attacked than by the rearing host species, but the parasitism was affected by the host species attacked and the rearing host species. Generally, E. formosa reared on T. vaporariorum killed more T. vaporariorum nymphs by parasitism and host feeding than those reared on B. tabaci. Additionally, a similar number of B. tabaci nymphs were killed by parasitism and host feeding regardless of the rearing host species. Currently

  4. Mechanisms of Salmonella Typhi Host Restriction.

    Science.gov (United States)

    Spanò, Stefania

    2016-01-01

    Salmonella enterica serovar Typhi (S. Typhi) is the cause of typhoid fever, a life-threatening bacterial infection that is very common in the developing world. Recent spread of antimicrobial resistant isolates of S. Typhi makes typhoid fever, a global public health risk. Despite being a common disease, still very little is known about the molecular mechanisms underlying typhoid fever and S. Typhi pathogenesis. In contrast to other Salmonellae, S. Typhi can only infect humans. The molecular bases of this human restriction are mostly unknown. Recent studies identified a novel pathway that contributes to S. Typhi human restriction and is required for killing S. Typhi in macrophages of nonsusceptible species. The small Rab GTPase Rab32 and its guanine nucleotide exchange factor BLOC-3 are the critical components of this pathway. These proteins were already well known as important regulators of intracellular membrane transport. In particular, they are central for the transport of enzymes that synthetize melanin in pigment cells. The recent findings that Rab32 and BLOC-3 are required for S. Typhi host restriction point out to a novel mechanism restricting the growth of bacterial pathogen, dependent on the transport of still unknown molecule(s) to the S. Typhi vacuole. The identification of this novel antimicrobial pathway constitutes a critical starting point to study molecular mechanisms killing bacterial pathogens and possibly identify novel antimicrobial molecules.

  5. Plant cell proliferation inside an inorganic host.

    Science.gov (United States)

    Perullini, Mercedes; Rivero, María Mercedes; Jobbágy, Matías; Mentaberry, Alejandro; Bilmes, Sara A

    2007-01-10

    In recent years, much attention has been paid to plant cell culture as a tool for the production of secondary metabolites and the expression of recombinant proteins. Plant cell immobilization offers many advantages for biotechnological processes. However, the most extended matrices employed, such as calcium-alginate, cannot fully protect entrapped cells. Sol-gel chemistry of silicates has emerged as an outstanding strategy to obtain biomaterials in which living cells are truly protected. This field of research is rapidly developing and a large number of bacteria and yeast-entrapping ceramics have already been designed for different applications. But even mild thermal and chemical conditions employed in sol-gel synthesis may result harmful to cells of higher organisms. Here we present a method for the immobilization of plant cells that allows cell growth at cavities created inside a silica matrix. Plant cell proliferation was monitored for a 6-month period, at the end of which plant calli of more than 1 mm in diameter were observed inside the inorganic host. The resulting hybrid device had good mechanical stability and proved to be an effective barrier against biological contamination, suggesting that it could be employed for long-term plant cell entrapment applications.

  6. Conducting polyheterocycle composites based on porous hosts

    Science.gov (United States)

    Park, J. S.; Ruckenstein, E.

    1992-02-01

    Conducting composites based on porous substrates (cotton fiber, non-woven polypropylene mat and porous crosslinked polystyrene) have been prepared by a two step imbibition technique. First, the substrate was imbibed with a solution of monomer (pyrrole or bithiophene) in acetonitrile, followed by partial drying. Subsequently, the substrate was again imbibed, this time with an oxidant dissolved in a suitable solvent. The polymerization of the monomer inside the host in the presence of the oxidant and the doping of the polymer with the oxidant leads to the conducting composite. The highly hydrophobic and porous crosslinked polystyrene, prepared by the concentrated emulsion polymerization method, is the most efficient. The solvent employed for the oxidant plays a major role. A FeCl3-methanol system and porous crosslinked polystyrene lead to conductivities of polythiophene and polypyrrole based composites of 3.63 and 0.65 S/cm, respectively. Copper perchlorate and iron perchlorate are also suitable oxidants. The environmental and thermal stabilities of polypyrrole based composites are lower than those of polythiophene based composites. The thermal stability of polypyrrole based composites can be enhanced by including a small amount of an organic antioxidant, such as amides or substituted phenols, in the composite.

  7. Orienteering World Cup hosted by CERN Club

    CERN Multimedia

    Katarina Anthony

    2010-01-01

    Elite runners took to the streets of Geneva for the last leg of the Orienteering World Cup, from 8-10 October. The Geneva finals were hosted by the CERN Orienteering Club and concluded months of competitions held across 5 countries.   Women's World-Cup winner, Simone Niggli (centre).  © Ilknur Colak The final events of the Orienteering World Cup took place in the Old Town of Geneva and Saint-Cergue, with runners following routes prepared by the CERN Orienteering Club. Orienteering is a sport of navigation, using only a compass, map and your sense of direction. The objective is to get to all the points on the map as quickly as possible, choosing your own paths as you run. This was the CERN club’s first successful participation in the World Cup, cementing its reputation as a fixture in the international orienteering world. Orienteering is not your typical Swiss pastime. Developed in Scandinavia, the sport has been gaining popularity internationally. “...

  8. Modulation of host immunity by beneficial microbes.

    Science.gov (United States)

    Zamioudis, Christos; Pieterse, Corné M J

    2012-02-01

    In nature, plants abundantly form beneficial associations with soilborne microbes that are important for plant survival and, as such, affect plant biodiversity and ecosystem functioning. Classical examples of symbiotic microbes are mycorrhizal fungi that aid in the uptake of water and minerals, and Rhizobium bacteria that fix atmospheric nitrogen for the plant. Several other types of beneficial soilborne microbes, such as plant-growth-promoting rhizobacteria and fungi with biological control activity, can stimulate plant growth by directly suppressing deleterious soilborne pathogens or by priming aboveground plant parts for enhanced defense against foliar pathogens or insect herbivores. The establishment of beneficial associations requires mutual recognition and substantial coordination of plant and microbial responses. A growing body of evidence suggests that beneficial microbes are initially recognized as potential invaders, after which an immune response is triggered, whereas, at later stages of the interaction, mutualists are able to short-circuit plant defense responses to enable successful colonization of host roots. Here, we review our current understanding of how symbiotic and nonsymbiotic beneficial soil microbes modulate the plant immune system and discuss the role of local and systemic defense responses in establishing the delicate balance between the two partners.

  9. Porous Silicon—A Versatile Host Material

    Directory of Open Access Journals (Sweden)

    Klemens Rumpf

    2010-02-01

    Full Text Available This work reviews the use of porous silicon (PS as a nanomaterial which is extensively investigated and utilized for various applications, e.g., in the fields of optics, sensor technology and biomedicine. Furthermore the combination of PS with one or more materials which are also nanostructured due to their deposition within the porous matrix is discussed. Such nanocompounds offer a broad avenue of new and interesting properties depending on the kind of involved materials as well as on their morphology. The filling of the pores performed by electroless or electrochemical deposition is described, whereas different morphologies, reaching from micro- to macro pores are utilized as host material which can be self-organized or fabricated by prestructuring. For metal-deposition within the porous structures, both ferromagnetic and non-magnetic metals are used. Emphasis will be put on self-arranged mesoporous silicon, offering a quasi-regular pore arrangement, employed as template for filling with ferromagnetic metals. By varying the deposition parameters the precipitation of the metal structures within the pores can be tuned in geometry and spatial distribution leading to samples with desired magnetic properties. The correlation between morphology and magnetic behaviour of such semiconducting/magnetic systems will be determined. Porous silicon and its combination with a variety of filling materials leads to nanocomposites with specific physical properties caused by the nanometric size and give rise to a multiplicity of potential applications in spintronics, magnetic and magneto-optic devices, nutritional food additives as well as drug delivery.

  10. Bartonella species and their ectoparasites: selective host adaptation or strain selection between the vector and the mammalian host?

    Science.gov (United States)

    Tsai, Yi-Lun; Chang, Chao-Chin; Chuang, Shih-Te; Chomel, Bruno B

    2011-07-01

    A wide range of blood-sucking arthropods have either been confirmed or are suspected as important vectors in Bartonella transmission to mammals, including humans. Overall, it appears that the diversity of Bartonella species DNA identified in ectoparasites is much broader than the species detected in their mammalian hosts, suggesting a mechanism of adaptation of Bartonella species to their host-vector ecosystem. However, these mechanisms leading to the fitness between the vectors and their hosts still need to be investigated.

  11. Identification of cotton fleahopper (Hemiptera: Miridae) host plants in central Texas and compendium of reported hosts in the United States.

    Science.gov (United States)

    Esquivel, J F; Esquivel, S V

    2009-06-01

    The cotton fleahopper, Pseudatomoscelis seriatus (Reuter), is an early-season pest of developing cotton in Central Texas and other regions of the Cotton Belt. Cotton fleahopper populations develop on spring weed hosts and move to cotton as weed hosts senesce or if other weed hosts are not readily available. To identify weed hosts that were seasonably available for the cotton fleahopper in Central Texas, blooming weed species were sampled during early-season (17 March-31 May), mid-season (1 June-14 August), late-season (15 August-30 November), and overwintering (1 December-16 March) periods. The leading hosts for cotton fleahopper adults and nymphs were evening primrose (Oenothera speciosa T. Nuttall) and Mexican hat [Ratibida columnifera (T. Nuttall) E. Wooton and P. Standley], respectively, during the early season. During the mid-season, silver-leaf nightshade (Solanum elaeagnifolium A. Cavanilles) was consistently a host for fleahopper nymphs and adults. Woolly croton (Croton capitatus A. Michaux) was a leading host during the late season. Cotton fleahoppers were not collected during the overwintering period. Other suitable hosts were available before previously reported leading hosts became available. Eight previously unreported weed species were documented as temporary hosts. A compendium of reported hosts, which includes >160 plant species representing 35 families, for the cotton fleahopper is provided for future research addressing insect-host plant associations. Leading plant families were Asteraceae, Lamiaceae, and Onagraceae. Results presented here indicate a strong argument for assessing weed species diversity and abundance for the control of the cotton fleahopper in the Cotton Belt.

  12. Invasion success of a scarab beetle within its native range: host range expansion versus host-shift

    Directory of Open Access Journals (Sweden)

    Marie-Caroline Lefort

    2014-02-01

    Full Text Available Only recently has it been formally acknowledged that native species can occasionally reach the status of ‘pest’ or ‘invasive species’ within their own native range. The study of such species has potential to help unravel fundamental aspects of biological invasions. A good model for such a study is the New Zealand native scarab beetle, Costelytra zealandica (White, which even in the presence of its natural enemies has become invasive in exotic pastures throughout the country. Because C. zealandica still occurs widely within its native habitat, we hypothesised that this species has only undergone a host range expansion (ability to use equally both an ancestral and new host onto exotic hosts rather than a host shift (loss of fitness on the ancestral host in comparison to the new host. Moreover, this host range expansion could be one of the main drivers of its invasion success. In this study, we investigated the fitness response of populations of C. zealandica from native and exotic flora, to several feeding treatments comprising its main exotic host plant as well as one of its ancestral hosts. Our results suggest that our initial hypothesis was incorrect and that C. zealandica populations occurring in exotic pastures have experienced a host-shift rather than simply a host-range expansion. This finding suggests that an exotic plant introduction can facilitate the evolution of a distinct native host-race, a phenomenon often used as evidence for speciation in phytophagous insects and which may have been instrumental to the invasion success of C. zealandica.

  13. Observation on the host parasitoid interaction between Periplaneta americana, the American cockroach and Tetrastichus hagenowii, an oothecal parasitoid

    Directory of Open Access Journals (Sweden)

    R. Srinivasan

    1994-09-01

    Full Text Available Investigations were carried out on the host parasitoid interaction between Periplaneta americana, the American cockroach and Tetrastichus hagenowii, an oothecal parasitoid. This gregarious female parasitoid infected and or oviposited in only one host and caused 100 por cento mortality of the infected host. However, increase in parasitoid density decreased the progeny production and influenced the sex ratio. The progenies produced were male biased. When host preference was tested by offering oothecae of different species of cockroaches, T. hagenowii showed a predilection towards the oothecae of P. americana, suggestings its host specificity.

  14. Observation on the host parasitoid interaction between Periplaneta americana, the American cockroach and Tetrastichus hagenowii, an oothecal parasitoid.

    Science.gov (United States)

    Srinivasan, R; Panicker, K N

    1994-01-01

    Investigations were carried out on the host parasitoid interaction between Periplaneta americana, the American cockroach and Tetrastichus hagenowii, an oothecal parasitoid. This gregarious female parasitoid infected and or oviposited in only one host and caused 100% mortality of the infected host. However, increase in parasitoid density decreased the progeny production and influenced the sex ratio. The progenies produced were male biased. When host preference was tested by offering oothecae of different species of cockroaches. T. hagenowii showed a predilection towards the oothecae of P. americana, suggesting its host specificity.

  15. Age consistency between exoplanet hosts and field stars

    Science.gov (United States)

    Bonfanti, A.; Ortolani, S.; Nascimbeni, V.

    2016-01-01

    Context. Transiting planets around stars are discovered mostly through photometric surveys. Unlike radial velocity surveys, photometric surveys do not tend to target slow rotators, inactive or metal-rich stars. Nevertheless, we suspect that observational biases could also impact transiting-planet hosts. Aims: This paper aims to evaluate how selection effects reflect on the evolutionary stage of both a limited sample of transiting-planet host stars (TPH) and a wider sample of planet-hosting stars detected through radial velocity analysis. Then, thanks to uniform derivation of stellar ages, a homogeneous comparison between exoplanet hosts and field star age distributions is developed. Methods: Stellar parameters have been computed through our custom-developed isochrone placement algorithm, according to Padova evolutionary models. The notable aspects of our algorithm include the treatment of element diffusion, activity checks in terms of log{R'HK} and vsini, and the evaluation of the stellar evolutionary speed in the Hertzsprung-Russel diagram in order to better constrain age. Working with TPH, the observational stellar mean density ρ⋆ allows us to compute stellar luminosity even if the distance is not available, by combining ρ⋆ with the spectroscopic log g. Results: The median value of the TPH ages is 5 Gyr. Even if this sample is not very large, however the result is very similar to what we found for the sample of spectroscopic hosts, whose modal and median values are [3, 3.5) Gyr and 4.8 Gyr, respectively. Thus, these stellar samples suffer almost the same selection effects. An analysis of MS stars of the solar neighbourhood belonging to the same spectral types bring to an age distribution similar to the previous ones and centered around solar age value. Therefore, the age of our Sun is consistent with the age distribution of solar neighbourhood stars with spectral types from late F to early K, regardless of whether they harbour planets or not. We considered

  16. Genetic Analogy Between Sediment—Hosted Gold Deposits and Sediment—Hosted Copper Deposits in Southwest China

    Institute of Scientific and Technical Information of China (English)

    肖荣阁; 陈卉泉; 等

    1996-01-01

    The sediment-hosted copper deposits according to the authors' study were formed from connate formation water during the post-sedimentary or diagenetic stage while the sediment-hosted disseminated gold deposits are unanimously considered to be of post-sedimentary hydrothermal origin.Therefore,apart from their own individulities.These two types of deposits must share some characters in common.Comparisons are attempted,in this paper,between the sediment-hosted copper deposits in southwest China and the Triassic sediment-hosted disseminated gold deposits in the Yunnan-Guizhou-Guangxi Triangle in terms of geological and geochemical features.

  17. Different host exploitation strategies in two zebra mussel-trematode systems: adjustments of host life history traits.

    Science.gov (United States)

    Minguez, Laëtitia; Buronfosse, Thierry; Giambérini, Laure

    2012-01-01

    The zebra mussel is the intermediate host for two digenean trematodes, Phyllodistomum folium and Bucephalus polymorphus, infecting gills and the gonad respectively. Many gray areas exist relating to the host physiological disturbances associated with these infections, and the strategies used by these parasites to exploit their host without killing it. The aim of this study was to examine the host exploitation strategies of these trematodes and the associated host physiological disturbances. We hypothesized that these two parasite species, by infecting two different organs (gills or gonads), do not induce the same physiological changes. Four cellular responses (lysosomal and peroxisomal defence systems, lipidic peroxidation and lipidic reserves) in the host digestive gland were studied by histochemistry and stereology, as well as the energetic reserves available in gonads. Moreover, two indices were calculated related to the reproductive status and the physiological condition of the organisms. Both parasites induced adjustments of zebra mussel life history traits. The host-exploitation strategy adopted by P. folium would occur during a short-term period due to gill deformation, and could be defined as "virulent." Moreover, this parasite had significant host gender-dependent effects: infected males displayed a slowed-down metabolism and energetic reserves more allocated to growth, whereas females displayed better defences and would allocate more energy to reproduction and maintenance. In contrast, B. polymorphus would be a more "prudent" parasite, exploiting its host during a long-term period through the consumption of reserves allocated to reproduction.

  18. Different host exploitation strategies in two zebra mussel-trematode systems: adjustments of host life history traits.

    Directory of Open Access Journals (Sweden)

    Laëtitia Minguez

    Full Text Available The zebra mussel is the intermediate host for two digenean trematodes, Phyllodistomum folium and Bucephalus polymorphus, infecting gills and the gonad respectively. Many gray areas exist relating to the host physiological disturbances associated with these infections, and the strategies used by these parasites to exploit their host without killing it. The aim of this study was to examine the host exploitation strategies of these trematodes and the associated host physiological disturbances. We hypothesized that these two parasite species, by infecting two different organs (gills or gonads, do not induce the same physiological changes. Four cellular responses (lysosomal and peroxisomal defence systems, lipidic peroxidation and lipidic reserves in the host digestive gland were studied by histochemistry and stereology, as well as the energetic reserves available in gonads. Moreover, two indices were calculated related to the reproductive status and the physiological condition of the organisms. Both parasites induced adjustments of zebra mussel life history traits. The host-exploitation strategy adopted by P. folium would occur during a short-term period due to gill deformation, and could be defined as "virulent." Moreover, this parasite had significant host gender-dependent effects: infected males displayed a slowed-down metabolism and energetic reserves more allocated to growth, whereas females displayed better defences and would allocate more energy to reproduction and maintenance. In contrast, B. polymorphus would be a more "prudent" parasite, exploiting its host during a long-term period through the consumption of reserves allocated to reproduction.

  19. Toxoplasma exports dense granule proteins beyond the vacuole to the host cell nucleus and rewires the host genome expression.

    Science.gov (United States)

    Bougdour, Alexandre; Tardieux, Isabelle; Hakimi, Mohamed-Ali

    2014-03-01

    Toxoplasma gondii is the most widespread apicomplexan parasite and occupies a large spectrum of niches by infecting virtually any warm-blooded animals. As an obligate intracellular parasite, Toxoplasma has evolved a repertoire of strategies to fine-tune the cellular environment in an optimal way to promote growth and persistence in host tissues hence increasing the chance to be transmitted to new hosts. Short and long-term intracellular survival is associated with Toxoplasma ability to both evade the host deleterious immune defences and to stimulate a beneficial immune balance by governing host cell gene expression. It is only recently that parasite proteins responsible for driving these transcriptional changes have been identified. While proteins contained in the apical secretory Rhoptry organelle have already been identified as bona fide secreted effectors that divert host signalling pathways, recent findings revealed that dense granule proteins should be added to the growing list of effectors as they reach the host cell cytoplasm and nucleus and target various host cell pathways in the course of cell infection. Herein, we emphasize on a novel subfamily of dense granule residentproteins, exemplified with the GRA16 and GRA24 members we recently discovered as both are exported beyond the vacuole-containing parasites and reach the host cell nucleus to reshape the host genome expression.

  20. Quantitative evaluation of the host-colonizing capabilities of the enteric bacterium Pantoea using plant and insect hosts.

    Science.gov (United States)

    Nadarasah, Geetanchaly; Stavrinides, John

    2014-03-01

    The genus Pantoea is a highly diverse group comprising free-living, and both pathogenic and non-pathogenic host-associating species. Pathogenic isolates have been found to infect insects, plants and humans, yet it is unclear whether these isolates have similar pathogenic potential to the free-living environmental populations. Using MLSA of six housekeeping genes, we evaluated the phylogenetic relationships among 115 environmental and clinical (human) isolates representing 11 Pantoea species. An overlay of the location of isolation onto the resulting tree revealed that clinical and environmental isolates are interspersed, and do not form distinctive groups. We then conducted quantitative growth assays of our isolates using maize, onion and fruit flies as hosts. Notably, most clinical isolates were able to grow in both plant hosts often comparably or even better than the environmental isolates. There were no obvious growth or host colonization patterns that could distinguish those isolates with clinical potential. Growth of an isolate in one host could not be predicted based on its performance in another host, nor could host growth be predicted by phylogeny or source of isolation. This work demonstrates that the host-colonizing capabilities of all Pantoea species groups is unpredictable, indicating a broader host range and pathogenic potential than currently assumed.

  1. Cryptic diversity and patterns of host specificity in trematode flatworms.

    Science.gov (United States)

    Hayward, Alexander

    2010-07-01

    The widespread utilization of molecular markers has revealed that a broad spectrum of taxa contain sets of morphologically cryptic, but genetically distinct lineages (Bickford et al. 2007). The identification of cryptic taxa is important as an accurate appreciation of diversity is crucial for a proper understanding of evolutionary and ecological processes. An example is the study of host specificity in parasitic taxa, where an apparent generalist may be found to contain a complex of several more specific species (Smith et al. 2006). Host specificity is a key life history trait that varies greatly among parasites (Poulin & Keeney 2007). While some can exploit a wide range of hosts, others are confined to just a single species. Access to additional hosts increases the resources available to a parasite. However, physiological or ecological constraints can restrict the extension of host range. Furthermore, there may be a trade-off between relaxed specificity and performance: generalism can decrease a parasites ability to adapt to each individual host species, and increase exposure to competition from other parasites (Poulin 1998). Despite the central role that host specificity plays in parasite life history, relatively little is known about how host range is determined in natural systems, and data from field studies are required to evaluate among competing ideas. In this issue, an exciting paper by Locke et al. (2010) makes a valuable contribution toward the understanding of host specificity in an important group of trematode flatworms. Using molecular methods, Locke et al. reveal an almost four-fold increase in the appreciated diversity of their focal group. In combination with a large and elegant sampling design this allows them to accurately assess host specificity for each taxon, and thus draw key insights into the factors that control host range in a dominant parasite group.

  2. Host Antimicrobial Peptides in Bacterial Homeostasis and Pathogenesis of Disease

    Directory of Open Access Journals (Sweden)

    Derek R. Heimlich

    2014-11-01

    Full Text Available Innate immune responses function as a first line of host defense against the development of bacterial infection, and in some cases to preserve the sterility of privileged sites in the human host. Bacteria that enter these sites must counter host responses for colonization. From the host’s perspective, the innate immune system works expeditiously to minimize the bacterial threat before colonization and subsequent dysbiosis. The multifactorial nature of disease further challenges predictions of how each independent variable influences bacterial pathogenesis. From bacterial colonization to infection and through disease, the microenvironments of the host are in constant flux as bacterial and host factors contribute to changes at the host-pathogen interface, with the host attempting to eradicate bacteria and the bacteria fighting to maintain residency. A key component of this innate host response towards bacterial infection is the production of antimicrobial peptides (AMPs. As an early component of the host response, AMPs modulate bacterial load and prevent establishment of infection. Under quiescent conditions, some AMPs are constitutively expressed by the epithelium. Bacterial infection can subsequently induce production of other AMPs in an effort to maintain sterility, or to restrict colonization. As demonstrated in various studies, the absence of a single AMP can influence pathogenesis, highlighting the importance of AMP concentration in maintaining homeostasis. Yet, AMPs can increase bacterial virulence through the co-opting of the peptides or alteration of bacterial virulence gene expression. Further, bacterial factors used to subvert AMPs can modify host microenvironments and alter colonization of the residential flora that principally maintain homeostasis. Thus, the dynamic interplay between host defense peptides and bacterial factors produced to quell peptide activity play a critical role in the progression and outcome of disease.

  3. Host-specific functional significance of Caenorhabditis gut commensals

    Directory of Open Access Journals (Sweden)

    Maureen Berg

    2016-10-01

    Full Text Available The gut microbiota is an important contributor to host health and fitness. Given its importance, microbiota composition should not be left to chance. However, what determines this composition is far from clear, with results supporting contributions of both environmental factors and host genetics. To gauge the relative contributions of host genetics and environment, specifically the microbial diversity, we characterized the gut microbiotas of Caenorhabditis species spanning 200-300 million years of evolution, and raised on different composted soil environments. Comparisons were based on 16S rDNA deep sequencing data, as well as on functional evaluation of gut isolates. Worm microbiotas were distinct from those in their respective soil environment, and included bacteria previously identified as part of the C. elegans core microbiota. Microbiotas differed between experiments initiated with different soil communities, but within each experiment, worm microbiotas clustered according to host identity, demonstrating a dominant contribution of environmental diversity, but also a contribution of host genetics. The dominance of environmental contributions hindered identification of host-associated microbial taxa from 16S data. Characterization of gut isolates from C. elegans and C. briggsae, focusing on the core family Enterobacteriaceae, were also unable to expose phylogenetic distinctions between microbiotas of the two species. However, functional evaluation of the isolates revealed host-specific contributions, wherein gut commensals protected their own host from infection, but not a non-host. Identification of commensal host-specificity at the functional level, otherwise overlooked in standard sequence-based analyses, suggests that the contribution of host genetics to shaping of gut microbiotas may be greater than previously realized.

  4. Host-Specific Functional Significance of Caenorhabditis Gut Commensals

    Science.gov (United States)

    Berg, Maureen; Zhou, Xiao Ying; Shapira, Michael

    2016-01-01

    The gut microbiota is an important contributor to host health and fitness. Given its importance, microbiota composition should not be left to chance. However, what determines this composition is far from clear, with results supporting contributions of both environmental factors and host genetics. To gauge the relative contributions of host genetics and environment, specifically the microbial diversity, we characterized the gut microbiotas of Caenorhabditis species spanning 200–300 million years of evolution, and raised on different composted soil environments. Comparisons were based on 16S rDNA deep sequencing data, as well as on functional evaluation of gut isolates. Worm microbiotas were distinct from those in their respective soil environment, and included bacteria previously identified as part of the C. elegans core microbiota. Microbiotas differed between experiments initiated with different soil communities, but within each experiment, worm microbiotas clustered according to host identity, demonstrating a dominant contribution of environmental diversity, but also a significant contribution of host genetics. The dominance of environmental contributions hindered identification of host-associated microbial taxa from 16S data. Characterization of gut isolates from C. elegans and C. briggsae, focusing on the core family Enterobacteriaceae, were also unable to expose phylogenetic distinctions between microbiotas of the two species. However, functional evaluation of the isolates revealed host-specific contributions, wherein gut commensals protected their own host from infection, but not a non-host. Identification of commensal host-specificity at the functional level, otherwise overlooked in standard sequence-based analyses, suggests that the contribution of host genetics to shaping of gut microbiotas may be greater than previously realized.

  5. Does reservoir host mortality enhance transmission of West Nile virus?

    Directory of Open Access Journals (Sweden)

    Foppa Ivo M

    2007-05-01

    Full Text Available Abstract Background Since its 1999 emergence in New York City, West Nile virus (WNV has become the most important and widespread cause of mosquito-transmitted disease in North America. Its sweeping spread from the Atlantic to the Pacific coast was accompanied by widespread mortality among wild birds, especially corvids. Only sporadic avian mortality had previously been associated with this infection in the Old World. Here, we examine the possibility that reservoir host mortality may intensify transmission, both by concentrating vector mosquitoes on remaining hosts and by preventing the accumulation of "herd immunity". Results Inspection of the Ross-Macdonald expression of the basic reproductive number (R0 suggests that this quantity may increase with reservoir host mortality. Computer simulation confirms this finding and indicates that the level of virulence is positively associated with the numbers of infectious mosquitoes by the end of the epizootic. The presence of reservoir incompetent hosts in even moderate numbers largely eliminated the transmission-enhancing effect of host mortality. Local host die-off may prevent mosquitoes to "waste" infectious blood meals on immune host and may thus facilitate perpetuation and spread of transmission. Conclusion Under certain conditions, host mortality may enhance transmission of WNV and similarly maintained arboviruses and thus facilitate their emergence and spread. The validity of the assumptions upon which this argument is built need to be empirically examined.

  6. Parasitology: Parasite survives predation on its host

    DEFF Research Database (Denmark)

    Ponton, Fleur; Lebarbenchon, Camille; Lefèvre, Thierry

    2006-01-01

    As prisoners in their living habitat, parasites should be vulnerable to destruction by the predators of their hosts. But we show here that the parasitic gordian worm Paragordius tricuspidatus is able to escape not only from its insect host after ingestion by a fish or frog but also from the diges...

  7. Host ant independent oviposition in the parasitic butterfly Maculinea alcon

    DEFF Research Database (Denmark)

    Fürst, Matthias A; Nash, David Richard

    2010-01-01

    Parasitic Maculinea alcon butterflies can only develop in nests of a subset of available Myrmica ant species, so female butterflies have been hypothesized to preferentially lay eggs on plants close to colonies of the correct host ants. Previous correlational investigations of host...... is necessary for conservation of this endangered butterfly....

  8. Ectoparasite infestation and sex-biased local recruitment of hosts

    NARCIS (Netherlands)

    Heeb, P.; Werner, I.; Mateman, A.C.; Kolliker, M.; Brinkhof, M.W.G.; Lessells, C.M.; Richner, H.

    1999-01-01

    Dispersal patterns of organisms are a fundamental aspect of their ecology, modifying the genetic and social structure of local populations(1-4). Parasites reduce the reproductive success and survival of hosts and thereby exert selection pressure on host life-history traits(4-6), possibly affecting h

  9. Fire blight: applied genomic insights of the pathogen and host

    Science.gov (United States)

    The enterobacterial phytopathogen, Erwinia amylovora, causes fire blight, an invasive disease that threatens a wide range of commercial and ornamental Rosaceae host plants. The response elicited by E. amylovora in its host during disease development is similar to the hypersensitive reaction that ty...

  10. Host genes involved in Agrobacterium-mediated transformation

    NARCIS (Netherlands)

    Soltani, Jalal

    2009-01-01

    Agrobacterium is the nature’s genetic engineer that can transfer genes across the kingdom barriers to both prokaryotic and eukaryotic host cells. The host genes which are involved in Agrobacterium-mediated transformatiom (AMT) are not well known. Here, I studied in a systematic way to identify the

  11. Molecular mechanisms of epithelial host defense in the airways

    NARCIS (Netherlands)

    Vos, Joost Bastiaan

    2007-01-01

    Airway epithelial cells are indispensable for the host defense system in the lungs. Various strategies by which epithelial cells protect the lungs against inhaled pathogens have been described. In spite of that, the molecular mechanisms by which epithelial cells initiate and control the host defense

  12. Fungal strategies for overcoming host innate immune response.

    NARCIS (Netherlands)

    Chai, L.; Netea, M.G.; Vonk, A.G.; Kullberg, B.J.

    2009-01-01

    A successful pathogen is one that is able to effectively survive and evade detection by the host innate immune defense. Fungal pathogens have adopted strategies which evade host defense and eventually cause disease in at-risk patients. Shielding of stimulatory surface recognition molecules, shedding

  13. Host preference and suitability of grasses for Oebalus pugnax

    Science.gov (United States)

    Awuni, GA; Gore, J; Cook, D; Bond, JA; Musser, FR; Adams, CA

    2014-01-01

    The rice stink bug, Oebalus pugnax (Fabricius) (Hemiptera: Pentatomidae: Carpocorini), though graminaceous, discriminates among its numerous host grass species. This could represent a feeding preference, it could be related to host suitability for growth and development. To clarify the role of host grass discrimination, two laboratory studies were conducted: (1) free-choice tests to evaluate preferences of O. pugnax among 11 wild host grass species found in three rice-producing counties of the central Mississippi Delta (MS, USA), and (2) no-choice tests to evaluate the impact of rice (Oryza sativa L.), junglerice [Echinochloa colona (L.) Link], and dallisgrass (Paspalum dilatatum Poir.) (all Poaceae), on the development of O. pugnax from second instar to adult. In the free-choice test, four experiments were conducted, each with four sets of host grass species and observed 1, 2, 4, 8, and 16 h after release in cages. Approximately 4 h was necessary for O. pugnax to settle on preferred host grasses. Oebalus pugnax showed a feeding preference for junglerice over all 10 other grass species. Bahiagrass, Paspalum notatum Flueggé, was the least preferred. The no-choice tests showed significant effect of host grass species on O. pugnax mean development time of nymphal survival to adults. Survival of nymphs was lower and mean development time was longer on dallisgrass compared to rice and junglerice. Knowledge of O. pugnax rate of growth and development on host grasses could be useful in the future development of rice integrated pest management strategies. PMID:25635144

  14. Anion effects on the cyclobis(paraquat-p-phenylene) host

    DEFF Research Database (Denmark)

    Andersen, Sissel Stenbæk; Jensen, Morten; Sørensen, Anne;

    2012-01-01

    Binding studies between the electron accepting host cyclobis(paraquat-p-phenylene) and a series of electron donors in the presence of differently sized counteranions reveal that both the nature and the concentration of the anion have a large impact on the association strength of the resulting host...

  15. Host-pathogen interactions: A cholera surveillance system

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Aaron T.

    2016-02-22

    Bacterial pathogen-secreted proteases may play a key role in inhibiting a potentially widespread host-pathogen interaction. Activity-based protein profiling enabled the identification of a major Vibrio cholerae serine protease that limits the ability of a host-derived intestinal lectin to bind to the bacterial pathogen in vivo.

  16. Transfer of genetic information between parasite and its host

    OpenAIRE

    Soukal, Petr

    2011-01-01

    Horizontal gene transfer (HGT) is considered a rare evolutionary event. It can take place between unrelated organisms that coexist in an intimate symbiotic relationship. Such relationship have some parasites with its host. HGT between eukaryotic parasite and its host was identified in some holoparazitic and hemiparazitic plants, the most important human protozoan parasites, microsporidias, human blood-flukes, parasitoids and fruit flies.

  17. Chemoattraction of Ichthyophthirius multifiliis (Ciliophora) theronts to host molecules

    DEFF Research Database (Denmark)

    Buchmann, Kurt; Nielsen, Michael Engelbrecht

    1999-01-01

    to be present in fractions with host immunoglobulin and some still undetermined proteins. No clear association between enzyme activity and chemotactic potential was seen. The high chemoattractive effect of serum from various unrelated teleosts corresponds to the low host specificity of I. multifiliis...

  18. Evolution of host range in the follicle mite Demodex kutzeri.

    Science.gov (United States)

    Palopoli, Michael F; Tra, VAN; Matoin, Kassey; Mac, Phuong D

    2016-11-29

    The sequences of four mitochondrial genes were determined for Demodex mites isolated from two distantly related species within the family Cervidae, and identified morphologically as belonging to the species Demodex kutzeri. The sequences were used to test the hypothesis that Demodex are strictly host-specific, and hence cospeciate with their hosts: (1) The estimated divergence time between mites found on elk vs humans agreed closely with a previous estimate of the time that these host species last shared a common ancestor, suggesting cospeciation of mites and hosts, at least over long evolutionary timescales. (2) The extremely low levels of sequence divergence between the mites found on elk vs mule deer hosts indicated that these mites belong to the same species, which suggests that Demodex are able to move across host species boundaries over shorter timescales. Together, the results are consistent with the model that Demodex mites are not strict host-specialists, but instead lose the ability to move between host lineages gradually.

  19. Does reservoir host mortality enhance transmission of West Nile virus?

    Science.gov (United States)

    Foppa, Ivo M; Spielman, Andrew

    2007-05-11

    Since its 1999 emergence in New York City, West Nile virus (WNV) has become the most important and widespread cause of mosquito-transmitted disease in North America. Its sweeping spread from the Atlantic to the Pacific coast was accompanied by widespread mortality among wild birds, especially corvids. Only sporadic avian mortality had previously been associated with this infection in the Old World. Here, we examine the possibility that reservoir host mortality may intensify transmission, both by concentrating vector mosquitoes on remaining hosts and by preventing the accumulation of "herd immunity". Inspection of the Ross-Macdonald expression of the basic reproductive number (R0) suggests that this quantity may increase with reservoir host mortality. Computer simulation confirms this finding and indicates that the level of virulence is positively associated with the numbers of infectious mosquitoes by the end of the epizootic. The presence of reservoir incompetent hosts in even moderate numbers largely eliminated the transmission-enhancing effect of host mortality. Local host die-off may prevent mosquitoes to "waste" infectious blood meals on immune host and may thus facilitate perpetuation and spread of transmission. Under certain conditions, host mortality may enhance transmission of WNV and similarly maintained arboviruses and thus facilitate their emergence and spread. The validity of the assumptions upon which this argument is built need to be empirically examined.

  20. Begging and cowbirds : brood parasites make hosts scream louder

    NARCIS (Netherlands)

    Boncoraglio, Giuseppe; Saino, Nicola; Garamszegi, Laszlo Z.

    2009-01-01

    Avian brood parasites have evolved striking begging ability that often allows them to prevail over the host progeny in competition for parental resources. Host young are therefore selected by brood parasites to evolve behavioral strategies that reduce the cost of parasitism. We tested the prediction

  1. Prospects for altering host range for baculovirus bioinsecticides.

    Science.gov (United States)

    Thiem, S M

    1997-06-01

    Advances in the understanding of baculovirus replication and the identification of genes that affect host range set the stage for constructing recombinant baculoviruses for specific past insects. The modification of baculovirus host specificity has recently been achieved by inserting or deleting genes that affect virus replication or cellular defenses.

  2. Is parasitoid acceptance of different host species dynamic?

    Science.gov (United States)

    Choice of host individuals by parasitoids is dynamic, varying with physiological state and experience. In particular, female parasitoids with high egg loads and low life expectancy are more willing to accept low quality hosts than females with low egg loads and high life expectancy. However, studi...

  3. Host cells and methods for production of isobutanol

    Energy Technology Data Exchange (ETDEWEB)

    Anthony, Larry Cameron; He, Hongxian; Huang, Lixuan Lisa; Okeefe, Daniel P.; Kruckeberg, Arthur Leo; Li, Yougen; Maggio-Hall, Lori Ann; McElvain, Jessica; Nelson, Mark J.; Patnaik, Ranjan; Rothman, Steven Cary

    2016-08-23

    Provided herein are recombinant yeast host cells and methods for their use for production of isobutanol. Yeast host cells provided comprise an isobutanol biosynthetic pathway and at least one of reduced or eliminated aldehyde dehydrogenase activity, reduced or eliminated acetolactate reductase activity; or a heterologous polynucleotide encoding a polypeptide having ketol-acid reductoisomerase activity.

  4. Host genes involved in Agrobacterium-mediated transformation

    NARCIS (Netherlands)

    Soltani, Jalal

    2009-01-01

    Agrobacterium is the nature’s genetic engineer that can transfer genes across the kingdom barriers to both prokaryotic and eukaryotic host cells. The host genes which are involved in Agrobacterium-mediated transformatiom (AMT) are not well known. Here, I studied in a systematic way to identify the w

  5. Cytokines in lethal graft-versus-host disease

    NARCIS (Netherlands)

    Knulst, A.C.; Bril-Bazuin, C.; Tibbe, G.J.M.; Oudenaren, van A.; Savelkoul, H.F.J.; Benner, R.

    1992-01-01

    Graft-versus-host disease (GVHD) is caused by donor T lymphocytes that recognize foreign antigens on host tissues. This leads to T cell activation, which involves a cascade of events including the transcription of genes for cytokines and their receptors and the production of cytokines. One of the fi

  6. Aspects of host-plant relationship of the Colorado beetle

    NARCIS (Netherlands)

    Bongers, W.

    1970-01-01

    Host plant choice, suitability of and conditioning to the host in Leptinotarsa decemlineata SAY were studied under controlled conditions.

    The literature on historical and geographical distribution of the Colorado beetle has been reviewed and an extensive survey is given of the

  7. Pattern Recognition Receptors in Innate Immunity, Host Defense, and Immunopathology

    Science.gov (United States)

    Suresh, Rahul; Mosser, David M.

    2013-01-01

    Infection by pathogenic microbes initiates a set of complex interactions between the pathogen and the host mediated by pattern recognition receptors. Innate immune responses play direct roles in host defense during the early stages of infection, and they also exert a profound influence on the generation of the adaptive immune responses that ensue.…

  8. Host response mechanisms in periodontal diseases

    Science.gov (United States)

    SILVA, Nora; ABUSLEME, Loreto; BRAVO, Denisse; DUTZAN, Nicolás; GARCIA-SESNICH, Jocelyn; VERNAL, Rolando; HERNÁNDEZ, Marcela; GAMONAL, Jorge

    2015-01-01

    presents a significantly host immune and inflammatory response to the microbial challenge that determine of susceptibility to develop the destructive/progressive periodontitis under the influence of multiple behavioral, environmental and genetic factors. PMID:26221929

  9. The Circumstellar Environments of Exoplanet Host Stars

    Science.gov (United States)

    Chen, Christine

    The WFIRST-AFTA mission currently includes the provision for a high contrast imaging instrument with a primary goal of discovering new, low mass exoplanets and characterizing their atmospheres. To date, eight exoplanetary systems have been discovered via direct imaging using the current generation of ground-based high-contrast facilities. Five of those systems, including the iconic beta Pictoris and HR 8799 systems, possess infrared excesses, indicative of the presence of circumstellar dust. Detailed studies of dust and gas morphology in the beta Pictoris disk provided the impetus for searching for, and eventually imaging the planet. These studies further suggest that additional planets orbit the star, but are below current detection thresholds. Such systems will be prime targets for WFIRST-AFTA, which will obtain visual spectroscopy of several spectral features from molecules in the exoplanet atmospheres including CH4, H2O, and CO2. We propose to: (1) model the dust in exoplanetary systems with well characterized planets and infrared excesses to better constrain the dust geometry and particle properties; (2) generate synthetic WFIRST-AFTA images of these disks with embedded known and putative planets using point-spread-functions generated by JPL, and run our simulations though a WFIRST-AFTA pipeline; and (3) evaluate the sensitivity of WFIRST-AFTA to known and putative planets that have a range of masses and distances from their host stars. The proposed simulations will also assist the community in understanding how WFIRST-AFTA will contribute to our knowledge of debris disks and the role that minor bodies play in the delivery of water into the terrestrial planet zone. The proposed project is complementary to the efforts currently being carried out by the Science Definition Team (SDT), which focus on simulating planets embedded in tenuous disks, analogous to the Zodiacal dust system in our Solar System, the Earth s resonant dust ring, and the HR 4796 dust ring

  10. Host response mechanisms in periodontal diseases

    Directory of Open Access Journals (Sweden)

    Nora SILVA

    2015-06-01

    a stage that presents a significantly host immune and inflammatory response to the microbial challenge that determine of susceptibility to develop the destructive/progressive periodontitis under the influence of multiple behavioral, environmental and genetic factors.

  11. Can shale safely host US nuclear waste?

    Science.gov (United States)

    Neuzil, C.E.

    2013-01-01

    "Even as cleanup efforts after Japan’s Fukushima disaster offer a stark reminder of the spent nuclear fuel (SNF) stored at nuclear plants worldwide, the decision in 2009 to scrap Yucca Mountain as a permanent disposal site has dimmed hope for a repository for SNF and other high-level nuclear waste (HLW) in the United States anytime soon. About 70,000 metric tons of SNF are now in pool or dry cask storage at 75 sites across the United States [Government Accountability Office, 2012], and uncertainty about its fate is hobbling future development of nuclear power, increasing costs for utilities, and creating a liability for American taxpayers [Blue Ribbon Commission on America’s Nuclear Future, 2012].However, abandoning Yucca Mountain could also result in broadening geologic options for hosting America’s nuclear waste. Shales and other argillaceous formations (mudrocks, clays, and similar clay-rich media) have been absent from the U.S. repository program. In contrast, France, Switzerland, and Belgium are now planning repositories in argillaceous formations after extensive research in underground laboratories on the safety and feasibility of such an approach [Blue Ribbon Commission on America’s Nuclear Future, 2012; Nationale Genossenschaft für die Lagerung radioaktiver Abfälle (NAGRA), 2010; Organisme national des déchets radioactifs et des matières fissiles enrichies, 2011]. Other nations, notably Japan, Canada, and the United Kingdom, are studying argillaceous formations or may consider them in their siting programs [Japan Atomic Energy Agency, 2012; Nuclear Waste Management Organization (NWMO), (2011a); Powell et al., 2010]."

  12. Host niches and defensive extended phenotypes structure parasitoid wasp communities.

    Directory of Open Access Journals (Sweden)

    Richard Bailey

    2009-08-01

    Full Text Available Oak galls are spectacular extended phenotypes of gallwasp genes in host oak tissues and have evolved complex morphologies that serve, in part, to exclude parasitoid natural enemies.Parasitoids and their insect herbivore hosts have coevolved to produce diverse communities comprising about a third of all animal species. The factors structuring these communities, however, remain poorly understood. An emerging theme in community ecology is the need to consider the effects of host traits, shaped by both natural selection and phylogenetic history, on associated communities of natural enemies. Here we examine the impact of host traits and phylogenetic relatedness on 48 ecologically closed and species-rich communities of parasitoids attacking gall-inducing wasps on oaks. Gallwasps induce the development of spectacular and structurally complex galls whose species- and generation-specific morphologies are the extended phenotypes of gallwasp genes. All the associated natural enemies attack their concealed hosts through gall tissues, and several structural gall traits have been shown to enhance defence against parasitoid attack. Here we explore the significance of these and other host traits in predicting variation in parasitoid community structure across gallwasp species. In particular, we test the "Enemy Hypothesis," which predicts that galls with similar morphology will exclude similar sets of parasitoids and therefore have similar parasitoid communities. Having controlled for phylogenetic patterning in host traits and communities, we found significant correlations between parasitoid community structure and several gall structural traits (toughness, hairiness, stickiness, supporting the Enemy Hypothesis. Parasitoid community structure was also consistently predicted by components of the hosts' spatiotemporal niche, particularly host oak taxonomy and gall location (e.g., leaf versus bud versus seed. The combined explanatory power of structural and

  13. Selective Degradation of Host RNA Polymerase II Transcripts by Influenza A Virus PA-X Host Shutoff Protein.

    Science.gov (United States)

    Khaperskyy, Denys A; Schmaling, Summer; Larkins-Ford, Jonah; McCormick, Craig; Gaglia, Marta M

    2016-02-01

    Influenza A viruses (IAVs) inhibit host gene expression by a process known as host shutoff. Host shutoff limits host innate immune responses and may also redirect the translation apparatus to the production of viral proteins. Multiple IAV proteins regulate host shutoff, including PA-X, a ribonuclease that remains incompletely characterized. We report that PA-X selectively targets host RNA polymerase II (Pol II) transcribed mRNAs, while sparing products of Pol I and Pol III. Interestingly, we show that PA-X can also target Pol II-transcribed RNAs in the nucleus, including non-coding RNAs that are not destined to be translated, and reporter transcripts with RNA hairpin structures that block ribosome loading. Transcript degradation likely occurs in the nucleus, as PA-X is enriched in the nucleus and its nuclear localization correlates with reduction in target RNA levels. Complete degradation of host mRNAs following PA-X-mediated endonucleolytic cleavage is dependent on the host 5'->3'-exonuclease Xrn1. IAV mRNAs are structurally similar to host mRNAs, but are synthesized and modified at the 3' end by the action of the viral RNA-dependent RNA polymerase complex. Infection of cells with wild-type IAV or a recombinant PA-X-deficient virus revealed that IAV mRNAs resist PA-X-mediated degradation during infection. At the same time, loss of PA-X resulted in changes in the synthesis of select viral mRNAs and a decrease in viral protein accumulation. Collectively, these results significantly advance our understanding of IAV host shutoff, and suggest that the PA-X causes selective degradation of host mRNAs by discriminating some aspect of Pol II-dependent RNA biogenesis in the nucleus.

  14. Selective Degradation of Host RNA Polymerase II Transcripts by Influenza A Virus PA-X Host Shutoff Protein.

    Directory of Open Access Journals (Sweden)

    Denys A Khaperskyy

    2016-02-01

    Full Text Available Influenza A viruses (IAVs inhibit host gene expression by a process known as host shutoff. Host shutoff limits host innate immune responses and may also redirect the translation apparatus to the production of viral proteins. Multiple IAV proteins regulate host shutoff, including PA-X, a ribonuclease that remains incompletely characterized. We report that PA-X selectively targets host RNA polymerase II (Pol II transcribed mRNAs, while sparing products of Pol I and Pol III. Interestingly, we show that PA-X can also target Pol II-transcribed RNAs in the nucleus, including non-coding RNAs that are not destined to be translated, and reporter transcripts with RNA hairpin structures that block ribosome loading. Transcript degradation likely occurs in the nucleus, as PA-X is enriched in the nucleus and its nuclear localization correlates with reduction in target RNA levels. Complete degradation of host mRNAs following PA-X-mediated endonucleolytic cleavage is dependent on the host 5'->3'-exonuclease Xrn1. IAV mRNAs are structurally similar to host mRNAs, but are synthesized and modified at the 3' end by the action of the viral RNA-dependent RNA polymerase complex. Infection of cells with wild-type IAV or a recombinant PA-X-deficient virus revealed that IAV mRNAs resist PA-X-mediated degradation during infection. At the same time, loss of PA-X resulted in changes in the synthesis of select viral mRNAs and a decrease in viral protein accumulation. Collectively, these results significantly advance our understanding of IAV host shutoff, and suggest that the PA-X causes selective degradation of host mRNAs by discriminating some aspect of Pol II-dependent RNA biogenesis in the nucleus.

  15. Testing local host adaptation and phenotypic plasticity in a herbivore when alternative related host plants occur sympatrically.

    Science.gov (United States)

    Ruiz-Montoya, Lorena; Núñez-Farfán, Juan

    2013-01-01

    Host race formation in phytophagous insects can be an early stage of adaptive speciation. However, the evolution of phenotypic plasticity in host use is another possible outcome. Using a reciprocal transplant experiment we tested the hypothesis of local adaptation in the aphid Brevicoryne brassicae. Aphid genotypes derived from two sympatric host plants, Brassica oleracea and B. campestris, were assessed in order to measure the extent of phenotypic plasticity in morphological and life history traits in relation to the host plants. We obtained an index of phenotypic plasticity for each genotype. Morphological variation of aphids was summarized by principal components analysis. Significant effects of recipient host on morphological variation and life history traits (establishment, age at first reproduction, number of nymphs, and intrinsic growth rate) were detected. We did not detected genotype × host plant interaction; in general the genotypes developed better on B. campestris, independent of the host plant species from which they were collected. Therefore, there was no evidence to suggest local adaptation. Regarding plasticity, significant differences among genotypes in the index of plasticity were detected. Furthermore, significant selection on PC1 (general aphid body size) on B. campestris, and on PC1 and PC2 (body length relative to body size) on B. oleracea was detected. The elevation of the reaction norm of PC1 and the slope of the reaction norm for PC2 (i.e., plasticity) were under directional selection. Thus, host plant species constitute distinct selective environments for B. brassicae. Aphid genotypes expressed different phenotypes in response to the host plant with low or nil fitness costs. Phenotypic plasticity and gene flow limits natural selection for host specialization promoting the maintenance of genetic variation in host exploitation.

  16. Three regimes of extrasolar planets inferred from host star metallicities

    CERN Document Server

    Buchhave, Lars A; Latham, David W; Sasselov, Dimitar; Cochran, William D; Endl, Michael; Isaacson, Howard; Juncher, Diana; Marcy, Geoffrey W

    2014-01-01

    Approximately half of the extrasolar planets (exoplanets) with radii less than four Earth radii are in orbits with short periods. Despite their sheer abundance, the compositions of such planets are largely unknown. The available evidence suggests that they range in composition from small, high-density rocky planets to low-density planets consisting of rocky cores surrounded by thick hydrogen and helium gas envelopes. Understanding the transition from the gaseous planets to Earth-like rocky worlds is important to estimate the number of potentially habitable planets in our Galaxy and provide constraints on planet formation theories. Here we report the abundances of heavy elements (that is, the metallicities) of more than 400 stars hosting 600 exoplanet candidates, and find that the exoplanets can be categorized into three populations defined by statistically distinct (~ 4.5{\\sigma}) metallicity regions. We interpret these regions as reflecting the formation regimes of terrestrial-like planets (radii less than 1...

  17. Distribution of the intermediate hosts of Echinococcus multilocularis in Shiqu County, Sichuan, China

    Institute of Scientific and Technical Information of China (English)

    XU Xiang; GUAN Ya-yi; TIAN Tian; WU Wei-ping; WANG Qian; HUANG Yan; LI Guang-qing; WANG Li-ying

    2011-01-01

    Background The rodentia and lagomorpha animals are the intermediate hosts of Echinococcus multilocularis, their distribution and infection of this parasite may facilitate the infection of definitive hosts such as dogs. The aim of this study was to determine the distribution of the intermediate hosts of Echinococcus multilocularis in Shiqu County, Sichuan, China.Methods A systematic sampling method was used to investigate the density of burrows of rodents and lagomorphs at 97 pasture sites in winter and summer pastureland and remote sensing (RS) technology was used to correlate their densities to the distribution of these animals in different landscape types.Results Based on the densities of Ochotona curzoniae, Microtus fuscus (dependent variable) and their burrow densities (independent variable) in survey points, regression equations were fitted respectively (Ochotona curzoniae, P<0.0001, R2=0.8705; Microtus fuscus, P <0.0001, R2=0.9736). Their burrow density in summer pastureland was higher than in winter pastureland (F=36.65, P <0.0001). The burrow densities of Ochotona curzoniae and Microtus fuscus in bareland and half-bareland are higher than in grassland (F=7.73, P <0.001).Conclusions The regression relationship between the densities of Ochotona curzoniae and Microtus fuscus and their burrow densities indicate that the burrow densities could reflect the animal densities and that the burrow density was greater in summer pastureland than in winter pastureland. The main distribution areas of the intermediate hosts were in bareland and half-bareland.

  18. Host manipulation by cancer cells: Expectations, facts, and therapeutic implications.

    Science.gov (United States)

    Tissot, Tazzio; Arnal, Audrey; Jacqueline, Camille; Poulin, Robert; Lefèvre, Thierry; Mery, Frédéric; Renaud, François; Roche, Benjamin; Massol, François; Salzet, Michel; Ewald, Paul; Tasiemski, Aurélie; Ujvari, Beata; Thomas, Frédéric

    2016-03-01

    Similar to parasites, cancer cells depend on their hosts for sustenance, proliferation and reproduction, exploiting the hosts for energy and resources, and thereby impairing their health and fitness. Because of this lifestyle similarity, it is predicted that cancer cells could, like numerous parasitic organisms, evolve the capacity to manipulate the phenotype of their hosts to increase their own fitness. We claim that the extent of this phenomenon and its therapeutic implications are, however, underappreciated. Here, we review and discuss what can be regarded as cases of host manipulation in the context of cancer development and progression. We elaborate on how acknowledging the applicability of these principles can offer novel therapeutic and preventive strategies. The manipulation of host phenotype by cancer cells is one more reason to adopt a Darwinian approach in cancer research. © 2016 WILEY Periodicals, Inc.

  19. Design stars: how small DNA viruses remodel the host nucleus.

    Science.gov (United States)

    Jiang, Mengxi; Imperiale, Michael J

    2012-05-01

    Numerous host components are encountered by viruses during the infection process. While some of these host structures are left unchanged, others may go through dramatic remodeling processes. In this review, we summarize these host changes that occur during small DNA virus infections, with a focus on host nuclear components and pathways. Although these viruses differ significantly in their genome structures and infectious pathways, there are common nuclear targets that are altered by various viral factors. Accumulating evidence suggests that these nuclear remodeling processes are often essential for productive viral infections and/or viral-induced transformation. Understanding the complex interactions between viruses and these host structures and pathways will help to build a more integrated network of how the virus completes its life cycle and point toward the design of novel therapeutic regimens that either prevent harmful viral infections or employ viruses as nontraditional treatment options or molecular tools.

  20. Scale insect host ranges are broader in the tropics.

    Science.gov (United States)

    Hardy, Nate B; Peterson, Daniel A; Normark, Benjamin B

    2015-12-01

    The specificity of the interactions between plants and their consumers varies considerably. The evolutionary and ecological factors underlying this variation are unclear. Several potential explanatory factors vary with latitude, for example plant species richness and the intensity of herbivory. Here, we use comparative phylogenetic methods to test the effect of latitude on host range in scale insects. We find that, on average, scale insects that occur in lower latitudes are more polyphagous. This result is at odds with the general pattern of greater host-plant specificity of insects in the tropics. We propose that this disparity reflects a high cost for host specificity in scale insects, stemming from unusual aspects of scale insect life history, for example, passive wind-driven dispersal. More broadly, the strong evidence for pervasive effects of geography on host range across insect groups stands in stark contrast to the weak evidence for constraints on host range due to genetic trade-offs.

  1. Patterns of host adaptation in fly infecting Entomophthora species

    DEFF Research Database (Denmark)

    de Fine Licht, Henrik Hjarvard; Jensen, Annette Bruun; Eilenberg, Jørgen

    .g. Entomophthora, Strongwellsea and Entomophaga). Species diversification of the obligate IPF within Entomophthoromycota thus seems to be primarily driven by co-evolutionary host adaptation to specific insect families, genera or species-complexes, but the underlying genetic factors of host adaptation......Insect pathogenic fungi (IPF) differ widely in their capability to infect different hosts. Some are generalists and will, given a sufficient number of infectious spores are present, infect almost any species of insect (e.g. Hypocrealean Metarhizium and Beauveria). Members of a different main IPF...... phylum Entomophthoromycota generally have more narrow host-ranges where some species for example only infect aphids or only locusts. Certain species (or strains) are even more host specific and are only known to infect a single or very few taxonomically related insect species under natural conditions (e...

  2. Legionella metaeffector exploits host proteasome to temporally regulate cognate effector.

    Directory of Open Access Journals (Sweden)

    Tomoko Kubori

    Full Text Available Pathogen-associated secretion systems translocate numerous effector proteins into eukaryotic host cells to coordinate cellular processes important for infection. Spatiotemporal regulation is therefore important for modulating distinct activities of effectors at different stages of infection. Here we provide the first evidence of "metaeffector," a designation for an effector protein that regulates the function of another effector within the host cell. Legionella LubX protein functions as an E3 ubiquitin ligase that hijacks the host proteasome to specifically target the bacterial effector protein SidH for degradation. Delayed delivery of LubX to the host cytoplasm leads to the shutdown of SidH within the host cells at later stages of infection. This demonstrates a sophisticated level of coevolution between eukaryotic cells and L. pneumophila involving an effector that functions as a key regulator to temporally coordinate the function of a cognate effector protein.

  3. Lactobacilli-Host mutualism: "learning on the fly".

    Science.gov (United States)

    Matos, Renata C; Leulier, François

    2014-08-29

    Metazoans establish with microorganisms complex interactions for their mutual benefits. Drosophila, which has already proven useful host model to study several aspects of innate immunity and host-bacteria pathogenic associations has become a powerful model to dissect the mechanisms behind mutualistic host-microbe interactions. Drosophila microbiota is composed of simple and aerotolerant bacterial communities mostly composed of Lactobacillaceae and Acetobactereaceae. Drosophila mono- or poly-associated with lactobacilli strains constitutes a powerful model to dissect the complex interplay between lactobacilli and host biologic traits. Thanks to the genetic tractability of both Drosophila and lactobacilli this association model offers a great opportunity to reveal the underlying molecular mechanisms. Here, we review our current knowledge about how the Drosophila model is helping our understanding of how lactobacilli shapes host biology.

  4. Spodoptera frugiperda (Lepidoptera: Noctuidae) host-plant variants: two host strains or two distinct species?

    Science.gov (United States)

    Dumas, Pascaline; Legeai, Fabrice; Lemaitre, Claire; Scaon, Erwan; Orsucci, Marion; Labadie, Karine; Gimenez, Sylvie; Clamens, Anne-Laure; Henri, Hélène; Vavre, Fabrice; Aury, Jean-Marc; Fournier, Philippe; Kergoat, Gael J; d'Alençon, Emmanuelle

    2015-06-01

    The moth Spodoptera frugiperda is a well-known pest of crops throughout the Americas, which consists of two strains adapted to different host-plants: the first feeds preferentially on corn, cotton and sorghum whereas the second is more associated with rice and several pasture grasses. Though morphologically indistinguishable, they exhibit differences in their mating behavior, pheromone compositions, and show development variability according to the host-plant. Though the latter suggest that both strains are different species, this issue is still highly controversial because hybrids naturally occur in the wild, not to mention the discrepancies among published results concerning mating success between the two strains. In order to clarify the status of the two host-plant strains of S. frugiperda, we analyze features that possibly reflect the level of post-zygotic isolation: (1) first generation (F1) hybrid lethality and sterility; (2) patterns of meiotic segregation of hybrids in reciprocal second generation (F2), as compared to the meiosis of the two parental strains. We found a significant reduction of mating success in F1 in one direction of the cross and a high level of microsatellite markers showing transmission ratio distortion in the F2 progeny. Our results support the existence of post-zygotic reproductive isolation between the two laboratory strains and are in accordance with the marked level of genetic differentiation that was recovered between individuals of the two strains collected from the field. Altogether these results provide additional evidence in favor of a sibling species status for the two strains.

  5. Occurrence and host specificity of a neogregarine protozoan in four milkweed butterfly hosts (Danaus spp.).

    Science.gov (United States)

    Barriga, Paola A; Sternberg, Eleanore D; Lefèvre, Thierry; de Roode, Jacobus C; Altizer, Sonia

    2016-10-01

    Throughout their global range, wild monarch butterflies (Danaus plexippus) are infected with the protozoan Ophryocystis elektroscirrha (OE). In monarchs, OE infection reduces pupal eclosion, adult lifespan, adult body size and flight ability. Infection of other butterfly hosts with OE is rare or unknown, and the only previously published records of OE infection were on monarch and queen butterflies (D. gilippus). Here we explored the occurrence and specificity of OE and OE-like parasites in four Danaus butterfly species. We surveyed wild D. eresimus (soldier), D. gilippus (queen), D. petilia (lesser wanderer), and D. plexippus (monarch) from five countries to determine the presence of infection. We conducted five cross-infection experiments, on monarchs and queen butterflies and their OE and OE-like parasites, to determine infection probability and the impact of infection on their hosts. Our field survey showed that OE-like parasites were present in D. gilippus, D. petilia, and D. plexippus, but were absent in D. eresimus. Infection probability varied geographically such that D. gilippus and D. plexippus populations in Puerto Rico and Trinidad were not infected or had low prevalence of infection, whereas D. plexippus from S. Florida and Australia had high prevalence. Cross-infection experiments showed evidence for host specificity, in that OE strains from monarchs were more effective at infecting monarchs than queens, and monarchs were less likely to be infected by OE-like strains from queens and lesser wanderers relative to their own natal strains. Our study showed that queens are less susceptible to OE and OE-like infection than monarchs, and that the reduction in adult lifespan following infection is more severe in monarchs than in queens.

  6. Hatching strategies in monogenean (platyhelminth) parasites that facilitate host infection.

    Science.gov (United States)

    Whittington, Ian D; Kearn, Graham C

    2011-07-01

    In parasites, environmental cues may influence hatching of eggs and enhance the success of infections. The two major endoparasitic groups of parasitic platyhelminths, cestodes (tapeworms) and digeneans (flukes), typically have high fecundity, infect more than one host species, and transmit trophically. Monogeneans are parasitic flatworms that are among the most host specific of all parasites. Most are ectoparasites with relatively low fecundity and direct life cycles tied to water. They infect a single host species, usually a fish, although some are endoparasites of amphibians and aquatic chelonian reptiles. Monogenean eggs have strong shells and mostly release ciliated larvae, which, against all odds, must find, identify, and infect a suitable specific host. Some monogeneans increase their chances of finding a host by greatly extending the hatching period (possible bet-hedging). Others respond to cues for hatching such as shadows, chemicals, mechanical disturbance, and osmotic changes, most of which may be generated by the host. Hatching may be rhythmical, larvae emerging at times when the host is more vulnerable to invasion, and this may be combined with responses to other environmental cues. Different monogenean species that infect the same host species may adopt different strategies of hatching, indicating that tactics may be more complex than first thought. Control of egg assembly and egg-laying, possibly by host hormones, has permitted colonization of frogs and toads by polystomatid monogeneans. Some monogeneans further improve the chances of infection by attaching eggs to the host or by retaining eggs on, or in, the body of the parasite. The latter adaptation has led ultimately to viviparity in gyrodactylid monogeneans.

  7. Fundamental factors determining the nature of parasite aggregation in hosts.

    Directory of Open Access Journals (Sweden)

    Sébastien Gourbière

    Full Text Available The distribution of parasites in hosts is typically aggregated: a few hosts harbour many parasites, while the remainder of hosts are virtually parasite free. The origin of this almost universal pattern is central to our understanding of host-parasite interactions; it affects many facets of their ecology and evolution. Despite this, the standard statistical framework used to characterize parasite aggregation does not describe the processes generating such a pattern. In this work, we have developed a mathematical framework for the distribution of parasites in hosts, starting from a simple statistical description in terms of two fundamental processes: the exposure of hosts to parasites and the infection success of parasites. This description allows the level of aggregation of parasites in hosts to be related to the random variation in these two processes and to true host heterogeneity. We show that random variation can generate an aggregated distribution and that the common view, that encounters and success are two equivalent filters, applies to the average parasite burden under neutral assumptions but it does not apply to the variance of the parasite burden, and it is not true when heterogeneity between hosts is incorporated in the model. We find that aggregation decreases linearly with the number of encounters, but it depends non-linearly on parasite success. We also find additional terms in the variance of the parasite burden which contribute to the actual level of aggregation in specific biological systems. We have derived the formal expressions of these contributions, and these provide new opportunities to analyse empirical data and tackle the complexity of the origin of aggregation in various host-parasite associations.

  8. Contact and voter processes on the infinite percolation cluster as models of host-symbiont interactions

    CERN Document Server

    Bertacchi, Daniela; Zucca, Fabio

    2009-01-01

    We introduce spatially explicit stochastic processes to model multispecies hostsymbiont interactions. The host environment is static, modeled by the infinite percolation cluster of site percolation. Symbionts evolve on the infinite cluster through contact or voter type interactions, where each host may be infected by a colony of symbionts. In the presence of a single symbiont species, the condition for invasion as a function of the density of the habitat of hosts and the maximal size of the colonies is investigated in details. In the presence of multiple symbiont species, it is proved that the community of symbionts clusters in two dimensions whereas symbiont species may coexist in higher dimensions.

  9. Dynamical friction and scratches of orbiting satellite galaxies on host systems

    CERN Document Server

    Ogiya, Go

    2015-01-01

    We study the dynamical response of extended systems, hosts, to smaller systems, satellites, orbiting around the hosts using extremely high-resolution N-body simulations with up to one billion particles. This situation corresponds to minor mergers which are ubiquitous in the scenario of hierarchical structure formation in the universe. According to Chandrasekhar (1943), satellites create density wakes along the orbit and the wakes cause a deceleration force on satellites, i.e. dynamical friction. This study proposes an analytical model to predict the dynamical response of hosts in the density distribution and finds not only traditional wakes but also mirror images of over- and underdensities centered on the host. Controlled N-body simulations with high resolutions verify the predictions of the analytical model directly. We apply our analytical model to the expected dynamical response of nearby interacting galaxy pairs, the Milky Way - Large Magellanic Cloud system and the M31 - M33 system.

  10. Dynamical friction and scratches of orbiting satellite galaxies on host systems

    Science.gov (United States)

    Ogiya, Go; Burkert, Andreas

    2016-04-01

    We study the dynamical response of extended systems, hosts, to smaller systems, satellites, orbiting around the hosts using extremely high-resolution N-body simulations with up to one billion particles. This situation corresponds to minor mergers which are ubiquitous in the scenario of hierarchical structure formation in the universe. According to Chandrasekhar, satellites create density wakes along the orbit and the wakes cause a deceleration force on satellites, i.e. dynamical friction. This study proposes an analytical model to predict the dynamical response of hosts as reflected in their density distribution and finds not only traditional wakes but also mirror images of over- and underdensities centred on the host. Our controlled N-body simulations with high resolutions verify the predictions of the analytical model. We apply our analytical model to the expected dynamical response of nearby interacting galaxy pairs, the Milky Way-Large Magellanic Cloud system and the M31-M33 system.

  11. Lichenicolous fungi show population subdivision by host species but do not share population history with their hosts.

    Science.gov (United States)

    Werth, Silke; Millanes, Ana María; Wedin, Mats; Scheidegger, Christoph

    2013-01-01

    Lichenicolous fungi are a species-rich biological group growing on lichen thalli. Here, we analyze the genetic structure of the lichenicolous basidiomycete Tremella lobariacearum and three host species (Lobaria pulmonaria, Lobaria macaronesica, and Lobaria immixta) in Macaronesia. We used ordination and analysis of molecular variance to investigate the structuring of genetic variation, and a simulation test to investigate whether rDNA haplotypes of T. lobariacearum were significantly associated with host species. To investigate the evolutionary and demographic history of the lichenicolous fungus and its hosts, we used coalescent samplers to generate trees, and Bayesian skyline plots. We found that the hosts were most important in structuring populations of the lichenicolous species. Despite their wide geographic distribution, the same haplotypes of T. lobariacearum consistently associated with a given host species. Our results suggest that the Lobaria hosts create a selective environment for the lichenicolous fungus. Both the pathogen and the host populations exhibited substantial genetic structure. However, evolutionary and demographic histories differed between the parasite and its hosts, as evidenced by different divergence times and tree topologies.

  12. Host specificity and temporal and seasonal shifts in host preference of a web-spider parasitoid Zatypota percontatoria.

    Science.gov (United States)

    Korenko, Stanislav; Michalková, Veronika; Zwakhals, Kees; Pekár, Stano

    2011-01-01

    Current knowledge about polysphinctine parasite wasps' interactions with their spider hosts is very fragmented and incomplete. This study presents the host specificity of Zatypota percontatoria (Müller) (Hymenoptera: Ichneumonidae) and its adaptation to varying host availability. Two years of field observations show that Z. percontatoria is a stenophagous parasitoid that parasitizes only five closely related web-building spiders of the family Theridiidae (Araneae). Within the Theridiidae it attacks only species belonging to a small group of species, here called the "Theridion" group. These hosts have a similar biology, but are available at different levels of abundance and at different sizes over the season. Laboratory experiments showed that this wasp species ignores linyphiid, araneid or dictynid spiders and accepts only theridiid spiders of the "Theridion" group. In the field study, wasp females preferred older juvenile and sub-adult female spider instars with intermediate body size. Only 5% of the parasitized spiders were males. Parasitism in the natural population of theridiid spiders was on average 1.3%. Parasitism was most frequent on two species, Theridion varians Hahn in 2007 and Neottiura bimaculata Linnaeus in 2008. The parasitization rate was positively correlated with spider abundance. The wasp responded adaptively to seasonal changes in host abundance and host body size and shifted host preference according to the availability of suitable hosts during, as well as between, seasons. In spring and summer the highest percentage of parasitism was on T. varians and in autumn it was on N. bimaculata.

  13. Influence of host age and host deprivation on longevity,egg load dynamics and oviposition rate in Microplitis rufiventris

    Institute of Scientific and Technical Information of China (English)

    ESMAT MOHAMED HEGAZI; GEHAN MOHAMED ABD EL-AZIZ; AHMED YOUSEF EL-SHAZLY; WEDAD EMAM KHAFAGI

    2007-01-01

    Adult size, longevity, egg load dynamics and oviposition of Microplitis rufiventris Kok. which began their development in the first, second, third (preferred hosts) or fourth (non-preferred hosts) instar larvae of Spodoptera littoralis (Boisd.) were studied. The parasitoid size was largely determined by the initial host size at parasitism. Non-ovipositing females derived from older hosts lived for longer periods than those derived from younger ones. However, the ovipositing females, irrespective of their size, lived for almost the same periods. At emergence, the oviducts of adult females contain a significant amount of mature eggs available for oviposition for a few hours on eclosion day. Egg load increases during the early phase of adult life. The amount of additional mature eggs and rate of egg maturation per hour was greater for wasps derived from preferred hosts compared with those in females derived from non-preferred hosts. The pattern of egg production in M. rufiventris females depended on the availability of hosts for parasitization. Host-deprived females depleted the egg complement with aging; the longer the host deprivation, the lower the oviduct egg load.Marked reduction in both realized or potential fecundity of host-deprived females was observed following host availability. Host privation for more than 3 days induced a marked deficit fecundity pattern through the female's life. The realized fecundity was determined by the interaction among host availability, the number of eggs that are matured over the female's life span, oviposition rate and host size from which the female was derived. These results suggest that: (i) M. rufiventris wasp is a weak synovigenic species; (ii) the maturation of additional eggs is inhibited once the maximum oviduct egg load is reached; (iii) the egg load of the newly emerged female is significantly less than the realized fecundity; and (iv)because M. rufiventris females oviposit fewer eggs when they begin depleting their

  14. Diversifying selection and host adaptation in two endosymbiont genomes

    Directory of Open Access Journals (Sweden)

    Slatko Barton

    2007-04-01

    Full Text Available Abstract Background The endosymbiont Wolbachia pipientis infects a broad range of arthropod and filarial nematode hosts. These diverse associations form an attractive model for understanding host:symbiont coevolution. Wolbachia's ubiquity and ability to dramatically alter host reproductive biology also form the foundation of research strategies aimed at controlling insect pests and vector-borne disease. The Wolbachia strains that infect nematodes are phylogenetically distinct, strictly vertically transmitted, and required by their hosts for growth and reproduction. Insects in contrast form more fluid associations with Wolbachia. In these taxa, host populations are most often polymorphic for infection, horizontal transmission occurs between distantly related hosts, and direct fitness effects on hosts are mild. Despite extensive interest in the Wolbachia system for many years, relatively little is known about the molecular mechanisms that mediate its varied interactions with different hosts. We have compared the genomes of the Wolbachia that infect Drosophila melanogaster, wMel and the nematode Brugia malayi, wBm to that of an outgroup Anaplasma marginale to identify genes that have experienced diversifying selection in the Wolbachia lineages. The goal of the study was to identify likely molecular mechanisms of the symbiosis and to understand the nature of the diverse association across different hosts. Results The prevalence of selection was far greater in wMel than wBm. Genes contributing to DNA metabolism, cofactor biosynthesis, and secretion were positively selected in both lineages. In wMel there was a greater emphasis on DNA repair, cell division, protein stability, and cell envelope synthesis. Conclusion Secretion pathways and outer surface protein encoding genes are highly affected by selection in keeping with host:parasite theory. If evidence of selection on various cofactor molecules reflects possible provisioning, then both insect as

  15. Host habitat assessment by a parasitoid using fungal volatiles

    Directory of Open Access Journals (Sweden)

    Steidle Johannes LM

    2007-02-01

    Full Text Available Abstract Background The preference – performance hypothesis predicts that oviposition preference of insects should correlate with host suitability for offspring development. Therefore, insect females have to be able to assess not only the quality of a given host but also the environmental conditions of the respective host habitat. Chemical cues are a major source of information used by insects for this purpose. Primary infestation of stored grain by stored product pests often favors the intense growth of mold. This can lead to distinct sites of extreme environmental conditions (hot-spots with increased insect mortality. We studied the influence of mold on chemical orientation, host recognition, and fitness of Lariophagus distinguendus, a parasitoid of beetle larvae developing in stored grain. Results Volatiles of wheat infested by Aspergillus sydowii and A. versicolor repelled female parasitoids in an olfactometer. Foraging L. distinguendus females are known to be strongly attracted to the odor of larval host feces from the granary weevil Sitophilus granarius, which may adhere in remarkable amounts to the surface of the grains. Feces from moldy weevil cultures elicited neutral responses but parasitoids clearly avoided moldy feces when non-moldy feces were offered simultaneously. The common fungal volatile 1-octen-3-ol was the major component of the odor of larval feces from moldy weevil cultures and repelled female parasitoids at naturally occurring doses. In bioassays investigating host recognition behavior of L. distinguendus, females spent less time on grains containing hosts from moldy weevil cultures and showed less drumming and drilling behavior than on non-moldy controls. L. distinguendus had a clearly reduced fitness on hosts from moldy weevil cultures. Conclusion We conclude that L. distinguendus females use 1-octen-3-ol for host habitat assessment to avoid negative fitness consequences due to secondary mold infestation of host

  16. Use of Host-like Peptide Motifs in Viral Proteins Is a Prevalent Strategy in Host-Virus Interactions

    Directory of Open Access Journals (Sweden)

    Tzachi Hagai

    2014-06-01

    Full Text Available Viruses interact extensively with host proteins, but the mechanisms controlling these interactions are not well understood. We present a comprehensive analysis of eukaryotic linear motifs (ELMs in 2,208 viral genomes and reveal that viruses exploit molecular mimicry of host-like ELMs to possibly assist in host-virus interactions. Using a statistical genomics approach, we identify a large number of potentially functional ELMs and observe that the occurrence of ELMs is often evolutionarily conserved but not uniform across virus families. Some viral proteins contain multiple types of ELMs, in striking similarity to complex regulatory modules in host proteins, suggesting that ELMs may act combinatorially to assist viral replication. Furthermore, a simple evolutionary model suggests that the inherent structural simplicity of ELMs often enables them to tolerate mutations and evolve quickly. Our findings suggest that ELMs may allow fast rewiring of host-virus interactions, which likely assists rapid viral evolution and adaptation to diverse environments.

  17. Constitutive modeling for isotropic materials (HOST)

    Science.gov (United States)

    Chan, Kwai S.; Lindholm, Ulric S.; Bodner, S. R.; Hill, Jeff T.; Weber, R. M.; Meyer, T. G.

    1986-01-01

    The results of the third year of work on a program which is part of the NASA Hot Section Technology program (HOST) are presented. The goals of this program are: (1) the development of unified constitutive models for rate dependent isotropic materials; and (2) the demonstration of the use of unified models in structural analyses of hot section components of gas turbine engines. The unified models selected for development and evaluation are those of Bodner-Partom and of Walker. A test procedure was developed for assisting the generation of a data base for the Bodner-Partom model using a relatively small number of specimens. This test procedure involved performing a tensile test at a temperature of interest that involves a succession of strain-rate changes. The results for B1900+Hf indicate that material constants related to hardening and thermal recovery can be obtained on the basis of such a procedure. Strain aging, thermal recovery, and unexpected material variations, however, preluded an accurate determination of the strain-rate sensitivity parameter is this exercise. The effects of casting grain size on the constitutive behavior of B1900+Hf were studied and no particular grain size effect was observed. A systematic procedure was also developed for determining the material constants in the Bodner-Partom model. Both the new test procedure and the method for determining material constants were applied to the alternate material, Mar-M247 . Test data including tensile, creep, cyclic and nonproportional biaxial (tension/torsion) loading were collected. Good correlations were obtained between the Bodner-Partom model and experiments. A literature survey was conducted to assess the effects of thermal history on the constitutive behavior of metals. Thermal history effects are expected to be present at temperature regimes where strain aging and change of microstructure are important. Possible modifications to the Bodner-Partom model to account for these effects are outlined

  18. Reservoir host competence and the role of domestic and commensal hosts in the transmission of Trypanosoma cruzi.

    Science.gov (United States)

    Gürtler, Ricardo E; Cardinal, M V

    2015-11-01

    We review the epidemiological role of domestic and commensal hosts of Trypanosoma cruzi using a quantitative approach, and compiled >400 reports on their natural infection. We link the theory underlying simple mathematical models of vector-borne parasite transmission to the types of evidence used for reservoir host identification: mean duration of infectious life; host infection and infectiousness; and host-vector contact. The infectiousness of dogs or cats most frequently exceeded that of humans. The host-feeding patterns of major vectors showed wide variability among and within triatomine species related to their opportunistic behavior and variable ecological, biological and social contexts. The evidence shows that dogs, cats, commensal rodents and domesticated guinea pigs are able to maintain T. cruzi in the absence of any other host species. They play key roles as amplifying hosts and sources of T. cruzi in many (peri)domestic transmission cycles covering a broad diversity of ecoregions, ecotopes and triatomine species: no other domestic animal plays that role. Dogs comply with the desirable attributes of natural sentinels and sometimes were a point of entry of sylvatic parasite strains. The controversies on the role of cats and other hosts illustrate the issues that hamper assessing the relative importance of reservoir hosts on the basis of fragmentary evidence. We provide various study cases of how eco-epidemiological and genetic-marker evidence helped to unravel transmission cycles and identify the implicated hosts. Keeping dogs, cats and rodents out of human sleeping quarters and reducing their exposure to triatomine bugs are predicted to strongly reduce transmission risks.

  19. Molecular systematics of pinniped hookworms (Nematoda: Uncinaria): species delimitation, host associations and host-induced morphometric variation.

    Science.gov (United States)

    Nadler, Steven A; Lyons, Eugene T; Pagan, Christopher; Hyman, Derek; Lewis, Edwin E; Beckmen, Kimberlee; Bell, Cameron M; Castinel, Aurelie; Delong, Robert L; Duignan, Padraig J; Farinpour, Cher; Huntington, Kathy Burek; Kuiken, Thijs; Morgades, Diana; Naem, Soraya; Norman, Richard; Parker, Corwin; Ramos, Paul; Spraker, Terry R; Berón-Vera, Bárbara

    2013-12-01

    Hookworms of the genus Uncinaria have been widely reported from juvenile pinnipeds, however investigations of their systematics has been limited, with only two species described, Uncinaria lucasi from northern fur seals (Callorhinus ursinus) and Uncinaria hamiltoni from South American sea lions (Otaria flavescens). Hookworms were sampled from these hosts and seven additional species including Steller sea lions (Eumetopias jubatus), California sea lions (Zalophus californianus), South American fur seals (Arctocephalus australis), Australian fur seals (Arctocephalus pusillus), New Zealand sea lions (Phocarctos hookeri), southern elephant seals (Mirounga leonina), and the Mediterranean monk seal (Monachus monachus). One hundred and thirteen individual hookworms, including an outgroup species, were sequenced for four genes representing two loci (nuclear ribosomal DNA and mitochondrial DNA). Phylogenetic analyses of these sequences recovered seven independent evolutionary lineages or species, including the described species and five undescribed species. The molecular evidence shows that U. lucasi parasitises both C. ursinus and E. jubatus, whereas U. hamiltoni parasitises O. flavescens and A. australis. The five undescribed hookworm species were each associated with single host species (Z. californianus, A. pusillus, P. hookeri, M. leonina and M. monachus). For parasites of otarids, patterns of Uncinaria host-sharing and phylogenetic relationships had a strong biogeographic component with separate clades of parasites from northern versus southern hemisphere hosts. Comparison of phylogenies for these hookworms and their hosts suggests that the association of U. lucasi with northern fur seals results from a host-switch from Steller sea lions. Morphometric data for U. lucasi shows marked host-associated size differences for both sexes, with U. lucasi individuals from E. jubatus significantly larger. This result suggests that adult growth of U. lucasi is reduced within the

  20. Deep-Sea Hydrothermal Vent Viruses Compensate for Microbial Metabolism in Virus-Host Interactions.

    Science.gov (United States)

    He, Tianliang; Li, Hongyun; Zhang, Xiaobo

    2017-07-11

    Viruses are believed to be responsible for the mortality of host organisms. However, some recent investigations reveal that viruses may be essential for host survival. To date, it remains unclear whether viruses are beneficial or harmful to their hosts. To reveal the roles of viruses in the virus-host interactions, viromes and microbiomes of sediment samples from three deep-sea hydrothermal vents were explored in this study. To exclude the influence of exogenous DNAs on viromes, the virus particles were purified with nuclease (DNase I and RNase A) treatments and cesium chloride density gradient centrifugation. The metagenomic analysis of viromes without exogenous DNA contamination and microbiomes of vent samples indicated that viruses had compensation effects on the metabolisms of their host microorganisms. Viral genes not only participated in most of the microbial metabolic pathways but also formed branched pathways in microbial metabolisms, including pyrimidine metabolism; alanine, aspartate, and glutamate metabolism; nitrogen metabolism and assimilation pathways of the two-component system; selenocompound metabolism; aminoacyl-tRNA biosynthesis; and amino sugar and nucleotide sugar metabolism. As is well known, deep-sea hydrothermal vent ecosystems exist in relatively isolated environments which are barely influenced by other ecosystems. The metabolic compensation of hosts mediated by viruses might represent a very important aspect of virus-host interactions.IMPORTANCE Viruses are the most abundant biological entities in the oceans and have very important roles in regulating microbial community structure and biogeochemical cycles. The relationship between virus and host microbes is broadly thought to be that of predator and prey. Viruses can lyse host cells to control microbial population sizes and affect community structures of hosts by killing specific microbes. However, viruses also influence their hosts through manipulation of bacterial metabolism. We found

  1. The ecology of infectious disease: effects of host diversity and community composition on Lyme disease risk.

    Science.gov (United States)

    LoGiudice, Kathleen; Ostfeld, Richard S; Schmidt, Kenneth A; Keesing, Felicia

    2003-01-21

    The extent to which the biodiversity and community composition of ecosystems affect their functions is an issue that grows ever more compelling as human impacts on ecosystems increase. We present evidence that supports a novel function of vertebrate biodiversity, the buffering of human risk of exposure to Lyme-disease-bearing ticks. We tested the Dilution Effect model, which predicts that high species diversity in the community of tick hosts reduces vector infection prevalence by diluting the effects of the most competent disease reservoir, the ubiquitous white-footed mouse (Peromyscus leucopus). As habitats are degraded by fragmentation or other anthropogenic forces, some members of the host community disappear. Thus, species-poor communities tend to have mice, but few other hosts, whereas species-rich communities have mice, plus many other potential hosts. We demonstrate that the most common nonmouse hosts are relatively poor reservoirs for the Lyme spirochete and should reduce the prevalence of the disease by feeding, but rarely infecting, ticks. By accounting for nearly every host species' contribution to the number of larval ticks fed and infected, we show that as new host species are added to a depauperate community, the nymphal infection prevalence, a key risk factor, declines. We identify important "dilution hosts" (e.g., squirrels), characterized by high tick burdens, low reservoir competence, and high population density, as well as "rescue hosts" (e.g., shrews), which are capable of maintaining high disease risk when mouse density is low. Our study suggests that the preservation of vertebrate biodiversity and community composition can reduce the incidence of Lyme disease.

  2. Diverse host-seeking behaviors of skin-penetrating nematodes.

    Directory of Open Access Journals (Sweden)

    Michelle L Castelletto

    2014-08-01

    Full Text Available Skin-penetrating parasitic nematodes infect approximately one billion people worldwide and are responsible for some of the most common neglected tropical diseases. The infective larvae of skin-penetrating nematodes are thought to search for hosts using sensory cues, yet their host-seeking behavior is poorly understood. We conducted an in-depth analysis of host seeking in the skin-penetrating human parasite Strongyloides stercoralis, and compared its behavior to that of other parasitic nematodes. We found that Str. stercoralis is highly mobile relative to other parasitic nematodes and uses a cruising strategy for finding hosts. Str. stercoralis shows robust attraction to a diverse array of human skin and sweat odorants, most of which are known mosquito attractants. Olfactory preferences of Str. stercoralis vary across life stages, suggesting a mechanism by which host seeking is limited to infective larvae. A comparison of odor-driven behavior in Str. stercoralis and six other nematode species revealed that parasite olfactory preferences reflect host specificity rather than phylogeny, suggesting an important role for olfaction in host selection. Our results may enable the development of new strategies for combating harmful nematode infections.

  3. Differential impact of simultaneous migration on coevolving hosts and parasites

    Directory of Open Access Journals (Sweden)

    Lopez-Pascua Laura DC

    2007-01-01

    Full Text Available Abstract Background The dynamics of antagonistic host-parasite coevolution are believed to be crucially dependent on the rate of migration between populations. We addressed how the rate of simultaneous migration of host and parasite affected resistance and infectivity evolution of coevolving meta-populations of the bacterium Pseudomonas fluorescens and a viral parasite (bacteriophage. The increase in genetic variation resulting from small amounts of migration is expected to increase rates of adaptation of both host and parasite. However, previous studies suggest phages should benefit more from migration than bacteria; because in the absence of migration, phages are more genetically limited and have a lower evolutionary potential compared to the bacteria. Results The results supported the hypothesis: migration increased the resistance of bacteria to their local (sympatric hosts. Moreover, migration benefited phages more than hosts with respect to 'global' (measured with respect to the whole range of migration regimes patterns of resistance and infectivity, because of the differential evolutionary responses of bacteria and phage to different migration regimes. Specifically, we found bacterial global resistance peaked at intermediate rates of migration, whereas phage global infectivity plateaued when migration rates were greater than zero. Conclusion These results suggest that simultaneous migration of hosts and parasites can dramatically affect the interaction of host and parasite. More specifically, the organism with the lower evolutionary potential may gain the greater evolutionary advantage from migration.

  4. Characterization of the Sulfolobus host-SSV2 virus interaction

    DEFF Research Database (Denmark)

    Contursi, P.; Jensen, S.; Aucelli, T.

    2006-01-01

    The Sulfolobus spindle virus, SSV2, encodes a tyrosine integrase which furthers provirus formation in host chromosomes. Consistently with the prediction made during sequence analysis, integration was found to occur in the downstream half of the tRNAGly (CCC) gene. In this paper we report the find......The Sulfolobus spindle virus, SSV2, encodes a tyrosine integrase which furthers provirus formation in host chromosomes. Consistently with the prediction made during sequence analysis, integration was found to occur in the downstream half of the tRNAGly (CCC) gene. In this paper we report...... during the growth of the natural host REY15/4, the cellular content of SSV2 DNA remains fairly low throughout the incubation of the foreign host. The accumulation of episomal DNA in the former case cannot be traced to decreased packaging activity because of a simultaneous increase in the virus titre...... in the medium. In addition, the interaction between SSV2 and its natural host is characterized by the concurrence of host growth inhibition and the induction of viral DNA replication. When this virus-host interaction was investigated using S. islandicus REY15A, a strain which is closely related to the natural...

  5. Microbiota and host immune responses: a love-hate relationship.

    Science.gov (United States)

    Tomkovich, Sarah; Jobin, Christian

    2016-01-01

    A complex relationship between the microbiota and the host emerges early at birth and continues throughout life. The microbiota includes the prokaryotes, viruses and eukaryotes living among us, all of which interact to different extents with various organs and tissues in the body, including the immune system. Although the microbiota is most dense in the lower intestine, its influence on host immunity extends beyond the gastrointestinal tract. These interactions with the immune system operate through the actions of various microbial structures and metabolites, with outcomes ranging from beneficial to deleterious for the host. These differential outcomes are dictated by host factors, environment, and the type of microbes or products present in a specific ecosystem. It is also becoming clear that the microbes are in turn affected and respond to the host immune system. Disruption of this complex dialogue between host and microbiota can lead to immune pathologies such as inflammatory bowel diseases, diabetes and obesity. This review will discuss recent advances regarding the ways in which the host immune system and microbiota interact and communicate with one another.

  6. What Can Phages Tell Us about Host-Pathogen Coevolution?

    Directory of Open Access Journals (Sweden)

    John J. Dennehy

    2012-01-01

    Full Text Available The outcomes of host-parasite interactions depend on the coevolutionary forces acting upon them, but because every host-parasite relation is enmeshed in a web of biotic and abiotic interactions across a heterogeneous landscape, host-parasite coevolution has proven difficult to study. Simple laboratory phage-bacteria microcosms can ameliorate this difficulty by allowing controlled, well-replicated experiments with a limited number of interactors. Genetic, population, and life history data obtained from these studies permit a closer examination of the fundamental correlates of host-parasite coevolution. In this paper, I describe the results of phage-bacteria coevolutionary studies and their implications for the study of host-parasite coevolution. Recent experimental studies have confirmed phage-host coevolutionary dynamics in the laboratory and have shown that coevolution can increase parasite virulence, specialization, adaptation, and diversity. Genetically, coevolution frequently proceeds in a manner best described by the Gene for Gene model, typified by arms race dynamics, but certain contexts can result in Red Queen dynamics according to the Matching Alleles model. Although some features appear to apply only to phage-bacteria systems, other results are broadly generalizable and apply to all instances of antagonistic coevolution. With laboratory host-parasite coevolutionary studies, we can better understand the perplexing array of interactions that characterize organismal diversity in the wild.

  7. Host Diet Affects the Morphology of Monarch Butterfly Parasites.

    Science.gov (United States)

    Hoang, Kevin; Tao, Leiling; Hunter, Mark D; de Roode, Jacobus C

    2017-06-01

    Understanding host-parasite interactions is essential for ecological research, wildlife conservation, and health management. While most studies focus on numerical traits of parasite groups, such as changes in parasite load, less focus is placed on the traits of individual parasites such as parasite size and shape (parasite morphology). Parasite morphology has significant effects on parasite fitness such as initial colonization of hosts, avoidance of host immune defenses, and the availability of resources for parasite replication. As such, understanding factors that affect parasite morphology is important in predicting the consequences of host-parasite interactions. Here, we studied how host diet affected the spore morphology of a protozoan parasite ( Ophryocystis elektroscirrha ), a specialist parasite of the monarch butterfly ( Danaus plexippus ). We found that different host plant species (milkweeds; Asclepias spp.) significantly affected parasite spore size. Previous studies have found that cardenolides, secondary chemicals in host plants of monarchs, can reduce parasite loads and increase the lifespan of infected butterflies. Adding to this benefit of high cardenolide milkweeds, we found that infected monarchs reared on milkweeds of higher cardenolide concentrations yielded smaller parasites, a potentially hidden characteristic of cardenolides that may have important implications for monarch-parasite interactions.

  8. The distribution of Symbiodinium diversity within individual host foraminifera

    Science.gov (United States)

    Fay, S. A.; Weber, M. X.; Lipps, J. H.

    2009-09-01

    While one-to-one specificity between reef-dwelling hosts and symbiotic dinoflagellates of the genus Symbiodinium may occur, detailed examination of some hosts reveals that they contain multiple symbiont types. Individuals of the foraminifer Amphisorus hemprichii living in Papua New Guinea contained mixed communities of Symbiodinium dominated by symbiont types in clades C and F. Moreover, the types showed a distinct pattern in their distribution across the radius of the foraminifer, with clade F Symbiodinium more prevalent in the center of the host cell. The mixed community of symbionts and their pattern of distribution within the foraminifer is likely the result of processes happening both inside the foraminifer and in its external environment. Persistent mixed symbiont communities in foraminifera may be stabilized through benefits conferred by maintaining multiple symbiont lineages for symbiont shuffling. Alternatively they may be stabilized through a heterogeneous internal host environment, partitioning of symbiont functional roles or limitation of symbiont reproduction by the host. Six factors generally determine the presence of any particular symbiont type within a foraminifer: mode of transmission, availability from the environment, recognition by the host, regulation by the host, competition between lineages, and fitness of the holobiont.

  9. Knowing your enemies: seasonal dynamics of host social parasite recognition

    Science.gov (United States)

    D'Ettorre, Patrizia; Brunner, Elisabeth; Wenseleers, Tom; Heinze, Jürgen

    2004-12-01

    Despite its evolutionary significance, behavioural flexibility of social response has rarely been investigated in insects. We studied a host social parasite system: the slave-making ant Polyergus rufescens and its host Formica rufibarbis. Free-living host workers from parasitized and from unparasitized areas were compared in their level of aggression against the parasite and alien conspecifics. We expected that a seasonal change would occur in the acceptance threshold of F. rufibarbis workers from a parasitized area towards the parasite, whereas F. rufibarbis workers from an unparasitized area would not show substantial changes connected with the parasite’s peak in activity (raiding and colony-founding season). The results showed a significant adaptive behavioural flexibility of host species workers and are consistent with the acceptance threshold model’s (Reeve 1989) prediction that recognition systems are not fixed but context-dependent. In particular, host workers from the unparasitized area were highly aggressive towards the parasite regardless of the season, whereas host workers from the parasitized area significantly increased their aggression towards the parasite during its raiding and colony-founding season. Being able to detect and possibly kill a Polyergus scout searching for host nests can be an effective strategy for a Formica colony to avoid being raided or usurped by a parasite queen.

  10. A slowly evolving host moves first in symbiotic interactions

    Science.gov (United States)

    Damore, James; Gore, Jeff

    2011-03-01

    Symbiotic relationships, both parasitic and mutualistic, are ubiquitous in nature. Understanding how these symbioses evolve, from bacteria and their phages to humans and our gut microflora, is crucial in understanding how life operates. Often, symbioses consist of a slowly evolving host species with each host only interacting with its own sub-population of symbionts. The Red Queen hypothesis describes coevolutionary relationships as constant arms races with each species rushing to evolve an advantage over the other, suggesting that faster evolution is favored. Here, we use a simple game theoretic model of host- symbiont coevolution that includes population structure to show that if the symbionts evolve much faster than the host, the equilibrium distribution is the same as it would be if it were a sequential game where the host moves first against its symbionts. For the slowly evolving host, this will prove to be advantageous in mutualisms and a handicap in antagonisms. The model allows for symbiont adaptation to its host, a result that is robust to changes in the parameters and generalizes to continuous and multiplayer games. Our findings provide insight into a wide range of symbiotic phenomena and help to unify the field of coevolutionary theory.

  11. Brood parasites lay eggs matching the appearance of host clutches.

    Science.gov (United States)

    Honza, Marcel; Šulc, Michal; Jelínek, Václav; Požgayová, Milica; Procházka, Petr

    2014-01-07

    Interspecific brood parasitism represents a prime example of the coevolutionary arms race where each party has evolved strategies in response to the other. Here, we investigated whether common cuckoos (Cuculus canorus) actively select nests within a host population to match the egg appearance of a particular host clutch. To achieve this goal, we quantified the degree of egg matching using the avian vision modelling approach. Randomization tests revealed that cuckoo eggs in naturally parasitized nests showed lower chromatic contrast to host eggs than those assigned randomly to other nests with egg-laying date similar to naturally parasitized clutches. Moreover, egg matching in terms of chromaticity was better in naturally parasitized nests than it would be in the nests of the nearest active non-parasitized neighbour. However, there was no indication of matching in achromatic spectral characteristics whatsoever. Thus, our results clearly indicate that cuckoos select certain host nests to increase matching of their own eggs with host clutches, but only in chromatic characteristics. Our results suggest that the ability of cuckoos to actively choose host nests based on the eggshell appearance imposes a strong selection pressure on host egg recognition.

  12. What Can Phages Tell Us about Host-Pathogen Coevolution?

    Science.gov (United States)

    Dennehy, John J

    2012-01-01

    The outcomes of host-parasite interactions depend on the coevolutionary forces acting upon them, but because every host-parasite relation is enmeshed in a web of biotic and abiotic interactions across a heterogeneous landscape, host-parasite coevolution has proven difficult to study. Simple laboratory phage-bacteria microcosms can ameliorate this difficulty by allowing controlled, well-replicated experiments with a limited number of interactors. Genetic, population, and life history data obtained from these studies permit a closer examination of the fundamental correlates of host-parasite coevolution. In this paper, I describe the results of phage-bacteria coevolutionary studies and their implications for the study of host-parasite coevolution. Recent experimental studies have confirmed phage-host coevolutionary dynamics in the laboratory and have shown that coevolution can increase parasite virulence, specialization, adaptation, and diversity. Genetically, coevolution frequently proceeds in a manner best described by the Gene for Gene model, typified by arms race dynamics, but certain contexts can result in Red Queen dynamics according to the Matching Alleles model. Although some features appear to apply only to phage-bacteria systems, other results are broadly generalizable and apply to all instances of antagonistic coevolution. With laboratory host-parasite coevolutionary studies, we can better understand the perplexing array of interactions that characterize organismal diversity in the wild.

  13. Simultaneous transcriptional profiling of bacteria and their host cells.

    Directory of Open Access Journals (Sweden)

    Michael S Humphrys

    Full Text Available We developed an RNA-Seq-based method to simultaneously capture prokaryotic and eukaryotic expression profiles of cells infected with intracellular bacteria. As proof of principle, this method was applied to Chlamydia trachomatis-infected epithelial cell monolayers in vitro, successfully obtaining transcriptomes of both C. trachomatis and the host cells at 1 and 24 hours post-infection. Chlamydiae are obligate intracellular bacterial pathogens that cause a range of mammalian diseases. In humans chlamydiae are responsible for the most common sexually transmitted bacterial infections and trachoma (infectious blindness. Disease arises by adverse host inflammatory reactions that induce tissue damage & scarring. However, little is known about the mechanisms underlying these outcomes. Chlamydia are genetically intractable as replication outside of the host cell is not yet possible and there are no practical tools for routine genetic manipulation, making genome-scale approaches critical. The early timeframe of infection is poorly understood and the host transcriptional response to chlamydial infection is not well defined. Our simultaneous RNA-Seq method was applied to a simplified in vitro model of chlamydial infection. We discovered a possible chlamydial strategy for early iron acquisition, putative immune dampening effects of chlamydial infection on the host cell, and present a hypothesis for Chlamydia-induced fibrotic scarring through runaway positive feedback loops. In general, simultaneous RNA-Seq helps to reveal the complex interplay between invading bacterial pathogens and their host mammalian cells and is immediately applicable to any bacteria/host cell interaction.

  14. Invasion and Persistence of Infectious Agents in Fragmented Host Populations

    Science.gov (United States)

    Jesse, Marieke; Mazzucco, Rupert; Dieckmann, Ulf; Heesterbeek, Hans; Metz, Johan A. J.

    2011-01-01

    One of the important questions in understanding infectious diseases and their prevention and control is how infectious agents can invade and become endemic in a host population. A ubiquitous feature of natural populations is that they are spatially fragmented, resulting in relatively homogeneous local populations inhabiting patches connected by the migration of hosts. Such fragmented population structures are studied extensively with metapopulation models. Being able to define and calculate an indicator for the success of invasion and persistence of an infectious agent is essential for obtaining general qualitative insights into infection dynamics, for the comparison of prevention and control scenarios, and for quantitative insights into specific systems. For homogeneous populations, the basic reproduction ratio plays this role. For metapopulations, defining such an ‘invasion indicator’ is not straightforward. Some indicators have been defined for specific situations, e.g., the household reproduction number . However, these existing indicators often fail to account for host demography and especially host migration. Here we show how to calculate a more broadly applicable indicator for the invasion and persistence of infectious agents in a host metapopulation of equally connected patches, for a wide range of possible epidemiological models. A strong feature of our method is that it explicitly accounts for host demography and host migration. Using a simple compartmental system as an example, we illustrate how can be calculated and expressed in terms of the key determinants of epidemiological dynamics. PMID:21980339

  15. Characterization of the Sulfolobus host-SSV2 virus interaction

    DEFF Research Database (Denmark)

    Contursi, P.; Jensen, S.; Aucelli, T.

    2006-01-01

    The Sulfolobus spindle virus, SSV2, encodes a tyrosine integrase which furthers provirus formation in host chromosomes. Consistently with the prediction made during sequence analysis, integration was found to occur in the downstream half of the tRNAGly (CCC) gene. In this paper we report the find......The Sulfolobus spindle virus, SSV2, encodes a tyrosine integrase which furthers provirus formation in host chromosomes. Consistently with the prediction made during sequence analysis, integration was found to occur in the downstream half of the tRNAGly (CCC) gene. In this paper we report...... during the growth of the natural host REY15/4, the cellular content of SSV2 DNA remains fairly low throughout the incubation of the foreign host. The accumulation of episomal DNA in the former case cannot be traced to decreased packaging activity because of a simultaneous increase in the virus titre...... in the medium. In addition, the interaction between SSV2 and its natural host is characterized by the concurrence of host growth inhibition and the induction of viral DNA replication. When this virus-host interaction was investigated using S. islandicus REY15A, a strain which is closely related to the natural...

  16. A host as an ecosystem: Wolbachia coping with environmental constraints.

    Science.gov (United States)

    Sicard, Mathieu; Dittmer, Jessica; Grève, Pierre; Bouchon, Didier; Braquart-Varnier, Christine

    2014-12-01

    The Wolbachia are intracellular endosymbionts widely distributed among invertebrates. These primarily vertically transmitted α-proteobacteria have been intensively studied during the last decades because of their intriguing interactions with hosts, ranging from reproductive manipulations to mutualism. To optimize their vertical transmission from mother to offspring, the Wolbachia have developed fine-tuned strategies. However, the Wolbachia are not restricted to the female gonads and frequently exhibit wide intra-host distributions. This extensive colonization of somatic organs might be necessary for Wolbachia to develop their diverse extended phenotypes. From an endosymbiont's perspective, the within-host environment potentially presents different environmental constraints. Hence, the Wolbachia have to face different intracellular habitats, their host's immune system as well as other microorganisms co-occurring in the same host individual and sometimes even in the same cell. A means for the Wolbachia to protect themselves from these environmental constraints may be to live 'hidden' in vacuoles within host cells. In this review, we summarize the current knowledge regarding the extent of the Wolbachia pandemic and discuss the various environmental constraints these bacteria may have to face within their 'host ecosystem'. Finally, we identify new avenues for future research to better understand the complexity of Wolbachia's interactions with their intracellular environment.

  17. Host Response of Ornamental Palms to Rotylenchulus reniformis.

    Science.gov (United States)

    Inserra, R N; Dunn, R A; Vovlas, N

    1994-12-01

    The responses of 20 species of ornamental palms and one cycad (Cycas revoluta) to two populations of the reniform nematode, Rotylenchulus reniformis, from southern Florida were studied in two greenhouse experiments conducted in 1989-1991 and 1991-92. Ornamental palms in pots were exposed to initial population densities of 400 and 1,500 R. reniformis/l00 cm(3) soil for 16 and 15 months, respectively. Nematode reproduction occurred on Acoelorrhaphe wrightii and Washingtonia robusta, but not on the other palms or the cycad. In both experiments, nematode numbers on A. wrightii and W. robusta were significantly smaller than those on cowpea (Vigna unguiculata), a susceptible host of the nematode used as a control in these experiments. Nematodes surviving in pots containing nonhost palms for 16 months retained infectivity and were able to reproduce on susceptible cowpea in a bioassay. Sections from Washingtonia robusta roots infected by R. reniformis females showed the nematode feeding on syncytia formed by endodermal, pericyclic, and vascular parenchyma cells in a manner similar to that reported for other monocot hosts of the reniform nematode.

  18. Epidemiological Implications of Host Biodiversity and Vector Biology: Key Insights from Simple Models.

    Science.gov (United States)

    Dobson, Andrew D M; Auld, Stuart K J R

    2016-04-01

    Models used to investigate the relationship between biodiversity change and vector-borne disease risk often do not explicitly include the vector; they instead rely on a frequency-dependent transmission function to represent vector dynamics. However, differences between classes of vector (e.g., ticks and insects) can cause discrepancies in epidemiological responses to environmental change. Using a pair of disease models (mosquito- and tick-borne), we simulated substitutive and additive biodiversity change (where noncompetent hosts replaced or were added to competent hosts, respectively), while considering different relationships between vector and host densities. We found important differences between classes of vector, including an increased likelihood of amplified disease risk under additive biodiversity change in mosquito models, driven by higher vector biting rates. We also draw attention to more general phenomena, such as a negative relationship between initial infection prevalence in vectors and likelihood of dilution, and the potential for a rise in density of infected vectors to occur simultaneously with a decline in proportion of infected hosts. This has important implications; the density of infected vectors is the most valid metric for primarily zoonotic infections, while the proportion of infected hosts is more relevant for infections where humans are a primary host.

  19. Breeding matters: Natal experience influences population state-dependent host acceptance by an eruptive insect herbivore

    Science.gov (United States)

    2017-01-01

    Eruptive forest insects are highly influential agents of change in forest ecosystems, and their effects have increased with recent climate change. State-dependent life histories contribute significantly to the population dynamics of eruptive forest insect herbivores; however, the proximate mechanisms by which these species shift between states is poorly understood. Laboratory bioassays were conducted using the mountain pine beetle (Dendroctonus ponderosae) to determine the effect of maternal host selection on offspring host preferences, as they apply to population state-dependent behaviors. Female mountain pine beetles exhibited state-dependent preference for artificial host material amended with monoterpenes in the absence of other cues, such that individuals reared in high-density epidemic-state simulations rejected low monoterpene conditions, while low-density endemic-state beetles accepted low monoterpene conditions. State-specific behavior in offspring was dependent on rearing conditions, as a function of maternal host selection, and these effects were observed within one generation. Density-dependent host selection behaviors exhibited by female mountain pine beetle offspring is reinforced by context-dependent maternal effects arising from parental host selection, and in situ exposure to conspecifics. These results demonstrate potential proximate mechanisms that control population dynamics in eruptive forest insects, and will allow for more accurate predictions of continued impact and spread of these species. PMID:28207862

  20. Pepper weevil attraction to volatiles from host and nonhost plants.

    Science.gov (United States)

    Addesso, Karla M; McAuslane, Heather J

    2009-02-01

    The location of wild and cultivated host plants by pepper weevil (Anthonomus eugenii Cano) may be aided by visual cues, the male-produced aggregation pheromone, herbivore-induced, or constitutive host plant volatiles. The attractiveness of constitutive plant volatiles to pioneer weevils is important in understanding, and perhaps controlling, dispersal of this insect between wild and cultivated hosts. Ten-day-old male and 2- and 10-day-old female weevils were tested in short-range Y-tube assays. Ten-day-old male and female weevils were attracted to the volatiles released by whole plants of three known oviposition hosts, 'Jalapeno' pepper, American black nightshade, and eggplant, as well as tomato, a congener, which supports feeding but not oviposition. Two-day-old females were attracted to all plants tested, including lima bean, an unrelated, nonhost plant. Fruit volatiles from all three hosts and flower volatiles from nightshade and eggplant were also attractive. In choice tests, weevils showed different preferences for the oviposition hosts, depending on age and sex. Upwind response of 10-day-old male and female weevils to host plant volatiles was also tested in long-range wind tunnel assays. Weevils responded to pepper, nightshade, and eggplant volatiles by moving upwind. There was no difference in the observed upwind response of the weevils to the three host plants under no-choice conditions. Reproductively mature pepper weevils can detect, orient to, and discriminate between the volatile plumes of host plants in the absence of visual cues, conspecific feeding damage, or the presence of their aggregation pheromone.

  1. Host Specialization in the Charcoal Rot Fungus, Macrophomina phaseolina.

    Science.gov (United States)

    Su, G; Suh, S O; Schneider, R W; Russin, J S

    2001-02-01

    ABSTRACT To investigate host specialization in Macrophomina phaseolina, the fungus was isolated from soybean, corn, sorghum, and cotton root tissue and soil from fields cropped continuously to these species for 15 years in St. Joseph, LA. Chlorate phenotype of each isolate was determined after growing on a minimal medium containing 120 mM potassium chlorate. Consistent differences in chlorate sensitivity were detected among isolates from different hosts and from soil versus root. To further explore genetic differentiation among fungal isolates from each host, these isolates were examined by restriction fragment length polymorphism and random amplified polymorphic DNA (RAPD) analysis. No variations were observed among isolates in restriction patterns of DNA fragments amplified by polymerase chain reaction covering the internal transcribed spacer region, 5.8S rRNA and part of 25S rRNA, suggesting that M. phaseolina constitutes a single species. Ten random primers were used to amplify the total DNA of 45 isolates, and banding patterns resulting from RAPD analysis were compared with the neighbor-joining method. Isolates from a given host were genetically similar to each other but distinctly different from those from other hosts. Chlorate-sensitive isolates were distinct from chlorate-resistant isolates within a given host. In greenhouse tests, soybean, sorghum, corn, and cotton were grown separately in soil infested with individual isolates of M. phaseolina that were chosen based on their host of origin and chlorate phenotype. Root colonization and plant weight were measured after harvesting. More colonization of corn roots occurred when corn was grown in soil containing corn isolates compared with isolates from other hosts. However, there was no host specialization in isolates from soybean, sorghum, or cotton. More root colonization in soybean occurred with chlorate-sensitive than with chlorate-resistant isolates.

  2. Modulation of host immunity and reproduction by horizontally acquired Wolbachia.

    Science.gov (United States)

    Pigeault, Romain; Braquart-Varnier, Christine; Marcadé, Isabelle; Mappa, Gaëtan; Mottin, Elmina; Sicard, Mathieu

    2014-11-01

    The Wolbachia are symbiotic bacteria vertically transmitted from one host generation to another. However, a growing amount of data shows that horizontal transfers of Wolbachia also frequently occur within and between host species. The consequences of the arrival of new symbionts on host physiology can be studied by their experimental introduction in asymbiotic hosts. After experimental transfers of the eight major isopod Wolbachia strains in the isopod Porcellio dilatatus only two of them (wCon and wDil) were found to (1) have no pathogenic effect on the host and (2) be able to pass vertically to the host offspring. In the present work, we studied the influence of these two strains, able to complete an horizontal transfer, on immunity and reproduction of P. dilatatus at two stages of the transfer: (1) in recipient hosts that encounter the symbionts: to test the influence of symbiont when acquired during host life and (2) in vertically infected offspring: to test the influence of a symbiotic interaction occurring all lifelong. The impact of Wolbachia varied depending on the stage: there were clearer effects in vertically infected individuals than in those that acquired the symbionts during their lives. Moreover, the two Wolbachia strains showed contrasted effects: the strain wCon tended to reduce the reproductive investment but to maintain or increase immune parameters whilst wDil had positive effects on reproductive investment but decreased the investment in some immune parameters. These results suggest that horizontally acquisition of Wolbachia can influence the balance between host immune and reproductive traits.

  3. Parasite fitness traits under environmental variation: disentangling the roles of a chytrid's immediate host and external environment.

    Science.gov (United States)

    Van den Wyngaert, Silke; Vanholsbeeck, Olivier; Spaak, Piet; Ibelings, Bas W

    2014-10-01

    Parasite environments are heterogeneous at different levels. The first level of variability is the host itself. The second level represents the external environment for the hosts, to which parasites may be exposed during part of their life cycle. Both levels are expected to affect parasite fitness traits. We disentangle the main and interaction effects of variation in the immediate host environment, here the diatom Asterionella formosa (variables host cell volume and host condition through herbicide pre-exposure) and variation in the external environment (variables host density and acute herbicide exposure) on three fitness traits (infection success, development time and reproductive output) of a chytrid parasite. Herbicide exposure only decreased infection success in a low host density environment. This result reinforces the hypothesis that chytrid zoospores use photosynthesis-dependent chemical cues to locate its host. At high host densities, chemotaxis becomes less relevant due to increasing chance contact rates between host and parasite, thereby following the mass-action principle in epidemiology. Theoretical support for this finding is provided by an agent-based simulation model. The immediate host environment (cell volume) substantially affected parasite reproductive output and also interacted with the external herbicide exposed environment. On the contrary, changes in the immediate host environment through herbicide pre-exposure did not increase infection success, though it had subtle effects on zoospore development time and reproductive output. This study shows that both immediate host and external environment as well as their interaction have significant effects on parasite fitness. Disentangling these effects improves our understanding of the processes underlying parasite spread and disease dynamics.

  4. Technologies to Increase PV Hosting Capacity in Distribution Feeders: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Fei; Mather, Barry; Gotseff, Peter

    2016-08-01

    This paper studies the distributed photovoltaic (PV) hosting capacity in distribution feeders by using the stochastic analysis approach. Multiple scenario simulations are conducted to analyze several factors that affect PV hosting capacity, including the existence of voltage regulator, PV location, the power factor of PV inverter and Volt/VAR control. Based on the conclusions obtained from simulation results, three approaches are then proposed to increase distributed PV hosting capacity, which can be formulated as the optimization problem to obtain the optimal solution. All technologies investigated in this paper utilize only existing assets in the feeder and therefore are implementable for a low cost. Additionally, the tool developed for these studies is described.

  5. Statistical Properties of Gamma-Ray Burst Host Galaxies

    Indian Academy of Sciences (India)

    Jie-Min Chen; Jin Zhang; Lan-Wei Jia; En-Wei Liang

    2014-09-01

    A statistical analysis of gamma-ray burst host galaxies is presented and a clear metallicity-stellar mass relation is found in our sample. A trend that a more massive host galaxy tends to have a higher star-formation rate is also found. No correlation is found between V and H. GRB host galaxies at a higher redshift also tend to have a higher star formation rate, however, even in the same redshift, the star formation rate may vary for three orders of magnitude.

  6. Structural insights into bacterial modulation of the host cytoskeleton.

    Science.gov (United States)

    Stebbins, C Erec

    2004-12-01

    Many bacterial pathogens manipulate the host cell cytoskeleton during infection. Such cytoskeletal modulation can occur at several points of contact between the pathogen and the host, and involves extracellular receptors, intracellular signal transduction and cytoskeletal proteins themselves. The field of bacterial pathogenesis has progressed dramatically over the past decade, such that structural knowledge is both timely and essential for a full appreciation of the biology at the pathogen-host interface. Several recent examples involving bacterial proteins that target actin, Rho family GTPases and extracellular receptors have contributed to a structural understanding of eukaryotic cytoskeletal modulation by pathogens.

  7. Host-parasite interactions between whiteflies and their parasitoids.

    Science.gov (United States)

    Gelman, Dale B; Gerling, Dan; Blackburn, Michael B; Hu, Jing S

    2005-12-01

    There is relatively little information available concerning the physiological and biochemical interactions between whiteflies and their parasitoids. In this report, we describe interactions between aphelinid parasitoids and their aleyrodid hosts that we have observed in four host-parasite systems: Bemisia tabaci/Encarsia formosa, Trialeurodes vaporariorum/E. formosa, B. tabaci/Eretmocerus mundus, and T. lauri/Encarsia scapeata. In the absence of reported polydnavirus and teratocytes, these parasitoids probably inject and/or produce compounds that interfere with the host immune response and also manipulate host development to suit their own needs. In addition, parasitoids must coordinate their own development with that of their host. Although eggs are deposited under all four instars of B. tabaci, Eretmocerus larvae only penetrate 4th instar B. tabaci nymphs. A pre-penetrating E. mundus first instar was capable of inducing permanent developmental arrest in its host, and upon penetration stimulated its host to produce a capsule (epidermal in origin) in which the parasitoid larva developed. T. vaporariorum and B. tabaci parasitized by E. formosa initiated adult development, and, on occasion, produced abnormal adult wings and eyes. In these systems, the site of parasitoid oviposition depended on the host species, occurring within or pressing into the ventral ganglion in T. vaporariorum and at various locations in B. tabaci. E. formosa's final larval molt is cued by the initiation of adult development in its host. In the T. lauri-E. scapeata system, both the host whitefly and the female parasitoid diapause during most of the year, i.e., from June until the middle of February (T. lauri) or from May until the end of December (E. scapeata). It appears that the growth and development of the insects are directed by the appearance of new, young foliage on Arbutus andrachne, the host tree. When adult female parasitoids emerged in the spring, they laid unfertilized male

  8. Asteroseismology of Exoplanet-Host Stars in the TESS Era

    DEFF Research Database (Denmark)

    Campante, Tiago L.; Schofield, Mathew; Chaplin, William J.

    2015-01-01

    in the characterization of host stars and their planetary systems. Examples include the precise estimation of the fundamental properties of stellar hosts, the obliquity determination of planetary systems, or the orbital eccentricity determination via asterodensity profiling. The Transiting Exoplanet Survey Satellite...... and planetary populations, we investigate the asteroseismic yield of the mission, placing particular emphasis on the yield of exoplanet-host stars for which we expect to detect solar-like oscillations. This is done both for the cohort of target stars (observed at a 2-min cadence), which will mainly involve low...

  9. Natural Host Relationships of Hantaviruses Native to Western Venezuela

    Science.gov (United States)

    Milazzo, Mary L.; Duno, Gloria; Utrera, Antonio; Richter, Martin H.; Duno, Freddy; de Manzione, Nuris

    2010-01-01

    Abstract Strains of Caño Delgadito virus (CADV) and Maporal virus (MAPV) were isolated from 25 (8.9%) of the 280 rodents captured on farms in 1997 in western Venezuela. The results of analyses of laboratory and zoographic data indicated that Alston's cotton rat (Sigmodon alstoni) is the principal host of CADV, horizontal virus transmission is the dominant mode of CADV transmission in Alston's cotton rat in nature, a pygmy rice rat (Oligoryzomys sp.) is the principal host of MAPV, and the natural host relationships of CADV and MAPV are highly specific. PMID:20055578

  10. The bigger, the better? Volume measurements of parasites and hosts

    DEFF Research Database (Denmark)

    Nagler, Christina; Hörnig, Marie K.; Haug, Joachim T.

    2017-01-01

    . Using advanced imaging methods (micro-CT in conjunction with 3D modeling), we measured the volume of parasitic structures (externa, interna, egg mass, egg number, visceral mass) and the volume of the entire host. Our results show positive correlations between the volume of (1) entire rhizocephalan...... (externa + interna) and host body, (2) rhizocephalan externa and host body, (3) rhizocephalan visceral mass and rhizocephalan body, (4) egg mass and rhizocephalan externa, (5) rhizocephalan egg mass and their egg number. Comparing the rhizocephalan Sylon hippolytes, a parasite of caridean shrimps...

  11. Cooperation of Adhesin Alleles in Salmonella-Host Tropism

    Science.gov (United States)

    De Masi, Leon; Yue, Min; Hu, Changmin; Rakov, Alexey V.; Rankin, Shelley C.

    2017-01-01

    ABSTRACT Allelic combinations and host specificities for three fimbrial adhesins, FimH, BcfD, and StfH, were compared for 262 strains of Salmonella enterica serovar Newport, a frequent human and livestock pathogen. Like FimH, BcfD had two major alleles (designated A and B), whereas StfH had two allelic groups, each with two alleles (subgroup A1 and A2 and subgroup B1 and B2). The most prevalent combinations of FimH/BcfD/StfH alleles in S. Newport were A/A/A1 and B/B/B1. The former set was most frequently found in bovine and porcine strains, whereas the latter combination was most frequently found in environmental and human isolates. Bacteria genetically engineered to express Fim, Bcf, or Stf fimbriae on their surface were tested with the different alleles for binding to human, porcine, and bovine intestinal epithelial cells. The major allelic combinations with bovine and porcine strains (A/A/A1) or with human isolates (B/B/B1) provided at least two alleles capable of binding significantly better than the other alleles to an intestinal epithelial cell line from the respective host(s). However, each combination of alleles kept at least one allele mediating binding to an intestinal epithelial cell from another host. These findings indicated that allelic variation in multiple adhesins of S. Newport contributes to bacterial adaptation to certain preferential hosts without losing the capacity to maintain a broad host range. IMPORTANCE Salmonella enterica remains a leading foodborne bacterial pathogen in the United States; infected livestock serve often as the source of contaminated food products. A study estimated that over a billion Salmonella gastroenteritis cases and up to 33 million typhoid cases occur annually worldwide, with 3.5 million deaths. Although many Salmonella strains with a broad host range present preferential associations with certain host species, it is not clear what determines the various levels of host adaptation. Here, causal properties of host

  12. Fish, fans and hydroids: host species of pygmy seahorses

    Science.gov (United States)

    Reijnen, Bastian T.; van der Meij, Sancia E.T.; van Ofwegen, Leen P.

    2011-01-01

    Abstract An overview of the octocoral and hydrozoan host species of pygmy seahorses is provided based on literature records and recently collected field data for Hippocampus bargibanti, Hippocampus denise and Hippocampus pontohi. Seven new associations are recognized and an overview of the so far documented host species is given. A detailed re-examination of octocoral type material and a review of the taxonomic history of the alcyonacean genera Annella (Subergorgiidae) and Muricella (Acanthogorgiidae) are included as baseline for future revisions. The host specificity and colour morphs of pygmy seahorses are discussed, as well as the reliability of (previous) identifications and conservation issues. PMID:21747677

  13. Asteroseismology of Exoplanet-Host Stars in the TESS Era

    DEFF Research Database (Denmark)

    Campante, Tiago L.; Schofield, Mathew; Chaplin, William J.;

    2015-01-01

    in the characterization of host stars and their planetary systems. Examples include the precise estimation of the fundamental properties of stellar hosts, the obliquity determination of planetary systems, or the orbital eccentricity determination via asterodensity profiling. The Transiting Exoplanet Survey Satellite...... and planetary populations, we investigate the asteroseismic yield of the mission, placing particular emphasis on the yield of exoplanet-host stars for which we expect to detect solar-like oscillations. This is done both for the cohort of target stars (observed at a 2-min cadence), which will mainly involve low...

  14. Technologies to Increase PV Hosting Capacity in Distribution Feeders

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Fei; Mather, Barry; Gotseff, Peter

    2016-11-14

    This paper studies the distributed photovoltaic (PV) hosting capacity in distribution feeders by using the stochastic analysis approach. Multiple scenario simulations are conducted to analyze several factors that affect PV hosting capacity, including the existence of voltage regulator, PV location, the power factor of PV inverter and Volt/VAR control. Based on the conclusions obtained from simulation results, three approaches are then proposed to increase distributed PV hosting capacity, which can be formulated as the optimization problem to obtain the optimal solution. All technologies investigated in this paper utilize only existing assets in the feeder and therefore are implementable for a low cost. Additionally, the tool developed for these studies is described.

  15. Galling Aphids (Hemiptera: Aphidoidea in China: Diversity and Host Specificity

    Directory of Open Access Journals (Sweden)

    Jing Chen

    2012-01-01

    Full Text Available Gall formation is an interesting plant response to aphid feeding. This paper presents a review of galling aphids in China. Altogether, 157 species and subspecies in ten families and subfamilies are found to induce galls on their host plants. As many as 39% species are endemic to China. The Eriosomatinae include the highest percentage of gall-inducing species. The great diversity of gall morphology may be described in terms of five characteristics: type, site, size, shape, and structure. The host association and host specificity of galling aphids are also discussed.

  16. Studies of archaeal virus-host systems in thermal environments

    DEFF Research Database (Denmark)

    Erdmann, Susanne

    of the host. Biochemical characterizations of viral proteins were performed to gain a better understanding of the persistence of these viruses under the harsh conditions of their habitats and the relationship with their hosts. In particular proteins of ATV (Acidianus two-tailed virus) were investigated...... system of Sulfolobus species was investigated when challenged by different genetic elements. This adaptive immune system has a major impact on virus-host interactions. The adaptation mechanism, involving the uptake of fragments of genetic elements as spacer regions in CRISPR arrays was induced using...

  17. Host defense peptides and their antimicrobial-immunomodulatory duality.

    Science.gov (United States)

    Steinstraesser, Lars; Kraneburg, Ursula; Jacobsen, Frank; Al-Benna, Sammy

    2011-03-01

    Host defence peptides (HDPs) are short cationic molecules produced by the immune systems of most multicellular organisms and play a central role as effector molecules of innate immunity. Host defence peptides have a wide range of biological activities from direct killing of invading pathogens to modulation of immunity and other biological responses of the host. HDPs have important functions in multiple, clinically relevant disease processes and their imbalanced expression is associated with pathology in different organ systems and cell types. Furthermore, HDPs are now evaluated as model molecules for the development of novel natural antibiotics and immunoregulatory compounds. This review provides an overview of HDPs focused on their antimicrobial-immunomodulatory duality.

  18. Soilborne fungi have strong host-affinity and host-specific effects on seed germination and survival in a lowland tropical forest

    Science.gov (United States)

    The Janzen-Connell (JC) hypothesis provides a powerful framework for explaining the maintenance of tree diversity in tropical forests. Its central tenet -- that recruits experience high mortality near conspecifics and at high densities -- assumes a degree of host specialization in interactions betwe...

  19. Determining virus-host interactions and glycerol metabolism profiles in geographically diverse solar salterns with metagenomics

    Science.gov (United States)

    Moller, Abraham G.

    2017-01-01

    Solar salterns are excellent model ecosystems for studying virus-microbial interactions because of their low microbial diversity, environmental stability, and high viral density. By using the power of CRISPR spacers to link viruses to their prokaryotic hosts, we explored virus-host interactions in geographically diverse salterns. Using taxonomic profiling, we identified hosts such as archaeal Haloquadratum, Halorubrum, and Haloarcula and bacterial Salinibacter, and we found that community composition related to not only salinity but also local environmental dynamics. Characterizing glycerol metabolism genes in these metagenomes suggested Halorubrum and Haloquadratum possess most dihydroxyacetone kinase genes while Salinibacter possesses most glycerol-3-phosphate dehydrogenase genes. Using two different methods, we detected fewer CRISPR spacers in Haloquadratum-dominated compared with Halobacteriaceae-dominated saltern metagenomes. After CRISPR detection, spacers were aligned against haloviral genomes to map virus to host. While most alignments for each saltern metagenome linked viruses to Haloquadratum walsbyi, there were also alignments indicating interactions with the low abundance taxa Haloarcula and Haloferax. Further examination of the dinucleotide and trinucleotide usage differences between paired viruses and their hosts confirmed viruses and hosts had similar nucleotide usage signatures. Detection of cas genes in the salterns supported the possibility of CRISPR activity. Taken together, our studies suggest similar virus-host interactions exist in different solar salterns and that the glycerol metabolism gene dihydroxyacetone kinase is associated with Haloquadratum and Halorubrum. PMID:28097058

  20. Alternative mechanisms of increased eggshell hardness of avian brood parasites relative to host species

    Science.gov (United States)

    Igic, Branislav; Braganza, Kim; Hyland, Margaret M.; Silyn-Roberts, Heather; Cassey, Phillip; Grim, Tomas; Rutila, Jarkko; Moskát, Csaba; Hauber, Mark E.

    2011-01-01

    Obligate brood parasitic birds lay their eggs in nests of other species and parasite eggs typically have evolved greater structural strength relative to host eggs. Increased mechanical strength of the parasite eggshell is an adaptation that can interfere with puncture ejection behaviours of discriminating hosts. We investigated whether hardness of eggshells is related to differences between physical and chemical traits from three different races of the parasitic common cuckoo Cuculus canorus, and their respective hosts. Using tools developed for materials science, we discovered a novel correlate of increased strength of parasite eggs: the common cuckoo's egg exhibits a greater microhardness, especially in the inner region of the shell matrix, relative to its host and sympatric non-host species. We then tested predictions of four potential mechanisms of shell strength: (i) increased relative thickness overall, (ii) greater proportion of the structurally harder shell layers, (iii) higher concentration of inorganic components in the shell matrix, and (iv) elevated deposition of a high density compound, MgCO3, in the shell matrix. We confirmed support only for hypothesis (i). Eggshell characteristics did not differ between parasite eggs sampled from different host nests in distant geographical sites, suggesting an evolutionarily shared microstructural mechanism of stronger parasite eggshells across diverse host-races of brood parasitic cuckoos. PMID:21561966

  1. Energy-cascade organic photovoltaic devices incorporating a host-guest architecture.

    Science.gov (United States)

    Menke, S Matthew; Holmes, Russell J

    2015-02-04

    In planar heterojunction organic photovoltaic devices (OPVs), broad spectral coverage can be realized by incorporating multiple molecular absorbers in an energy-cascade architecture. Here, this approach is combined with a host-guest donor layer architecture previously shown to optimize exciton transport for the fluorescent organic semiconductor boron subphthalocyanine chloride (SubPc) when diluted in an optically transparent host. In order to maximize the absorption efficiency, energy-cascade OPVs that utilize both photoactive host and guest donor materials are examined using the pairing of SubPc and boron subnaphthalocyanine chloride (SubNc), respectively. In a planar heterojunction architecture, excitons generated on the SubPc host rapidly energy transfer to the SubNc guest, where they may migrate toward the dissociating, donor-acceptor interface. Overall, the incorporation of a photoactive host leads to a 13% enhancement in the short-circuit current density and a 20% enhancement in the power conversion efficiency relative to an optimized host-guest OPV combining SubNc with a nonabsorbing host. This work underscores the potential for further design refinements in planar heterojunction OPVs and demonstrates progress toward the effective separation of functionality between constituent OPV materials.

  2. Determining virus-host interactions and glycerol metabolism profiles in geographically diverse solar salterns with metagenomics

    Directory of Open Access Journals (Sweden)

    Abraham G. Moller

    2017-01-01

    Full Text Available Solar salterns are excellent model ecosystems for studying virus-microbial interactions because of their low microbial diversity, environmental stability, and high viral density. By using the power of CRISPR spacers to link viruses to their prokaryotic hosts, we explored virus-host interactions in geographically diverse salterns. Using taxonomic profiling, we identified hosts such as archaeal Haloquadratum, Halorubrum, and Haloarcula and bacterial Salinibacter, and we found that community composition related to not only salinity but also local environmental dynamics. Characterizing glycerol metabolism genes in these metagenomes suggested Halorubrum and Haloquadratum possess most dihydroxyacetone kinase genes while Salinibacter possesses most glycerol-3-phosphate dehydrogenase genes. Using two different methods, we detected fewer CRISPR spacers in Haloquadratum-dominated compared with Halobacteriaceae-dominated saltern metagenomes. After CRISPR detection, spacers were aligned against haloviral genomes to map virus to host. While most alignments for each saltern metagenome linked viruses to Haloquadratum walsbyi, there were also alignments indicating interactions with the low abundance taxa Haloarcula and Haloferax. Further examination of the dinucleotide and trinucleotide usage differences between paired viruses and their hosts confirmed viruses and hosts had similar nucleotide usage signatures. Detection of cas genes in the salterns supported the possibility of CRISPR activity. Taken together, our studies suggest similar virus-host interactions exist in different solar salterns and that the glycerol metabolism gene dihydroxyacetone kinase is associated with Haloquadratum and Halorubrum.

  3. Filamentous phages prevalent in Pseudoalteromonas spp. confer properties advantageous to host survival in Arctic sea ice.

    Science.gov (United States)

    Yu, Zi-Chao; Chen, Xiu-Lan; Shen, Qing-Tao; Zhao, Dian-Li; Tang, Bai-Lu; Su, Hai-Nan; Wu, Zhao-Yu; Qin, Qi-Long; Xie, Bin-Bin; Zhang, Xi-Ying; Yu, Yong; Zhou, Bai-Cheng; Chen, Bo; Zhang, Yu-Zhong

    2015-03-17

    Sea ice is one of the most frigid environments for marine microbes. In contrast to other ocean ecosystems, microbes in permanent sea ice are space confined and subject to many extreme conditions, which change on a seasonal basis. How these microbial communities are regulated to survive the extreme sea ice environment is largely unknown. Here, we show that filamentous phages regulate the host bacterial community to improve survival of the host in permanent Arctic sea ice. We isolated a filamentous phage, f327, from an Arctic sea ice Pseudoalteromonas strain, and we demonstrated that this type of phage is widely distributed in Arctic sea ice. Growth experiments and transcriptome analysis indicated that this phage decreases the host growth rate, cell density and tolerance to NaCl and H2O2, but enhances its motility and chemotaxis. Our results suggest that the presence of the filamentous phage may be beneficial for survival of the host community in sea ice in winter, which is characterized by polar night, nutrient deficiency and high salinity, and that the filamentous phage may help avoid over blooming of the host in sea ice in summer, which is characterized by polar day, rich nutrient availability, intense radiation and high concentration of H2O2. Thus, while they cannot kill the host cells by lysing them, filamentous phages confer properties advantageous to host survival in the Arctic sea ice environment. Our study provides a foremost insight into the ecological role of filamentous phages in the Arctic sea ice ecosystem.

  4. Compensation for risks: host community benefits in siting locally unwanted facilities

    Science.gov (United States)

    Himmelberger, Jeffery J.; Ratick, Samuel J.; White, Allen L.

    1991-09-01

    This article analyzes the recent negotiations connected with siting 24 solid-waste landfills in Wisconsin. We examine the association between the type and amount of compensation paid to host communities by facility developers and the size of facilities, certain facility characteristics, the timing of negotiated agreements, the size of the host community, and the socioeconomic status of the host area. Our findings suggest that the level of compensation after adjusting for landfill capacity is positively associated with the percentage of total facility capacity dedicated to host community use, positively associated with the percentage of people of the host area who are in poverty, and larger for public facilities that accept municipal wastes. Other explanatory variables we examined, whose association with levels of compensation proved statistically insignificant, were facility size, facility status (new vs expansion), facility use (countyonly vs multicounty), timing of negotiation, host community size, and the host area education level, population density, and per capita income. We discuss the policy implications of our principal findings and future research questions in light of the persistent opposition surrounding the siting of solid-waste and other waste-management facilities.

  5. Flexible host choice and common host switches in the evolution of generalist and specialist cuckoo bees (Anthophila: Sphecodes).

    Science.gov (United States)

    Habermannová, Jana; Bogusch, Petr; Straka, Jakub

    2013-01-01

    Specialization makes resource use more efficient and should therefore be a common process in animal evolution. However, this process is not as universal in nature as one might expect. Our study shows that Sphecodes (Halictidae) cuckoo bees frequently change their host over the course of their evolution. To test the evolutionary scenario of host specialization in cuckoo bees, we constructed well-supported phylogenetic trees based on partial sequences of five genes for subtribe Sphecodina (Halictini). We detected up to 17 host switches during Sphecodes evolution based on 37 ingroup species subject to mapping analysis of the hosts associated with the cuckoo bee species. We also examine the direction of evolution of host specialization in Sphecodes using the likelihood ratio test and obtain results to support the bidirectional evolutionary scenario in which specialists can arise from generalists, and vice versa. We explain the existence of generalist species in Sphecodes based on their specialization at the individual level, which is recently known in two species. Our findings suggest flexible host choice and frequent host switches in the evolution of Sphecodes cuckoo bees. This scenario leads us to propose an individual choice constancy hypothesis based on the individual specialization strategy in cuckoo bees. Choice constancy has a close relationship to flower constancy in bees and might be an extension of the latter. Our analysis also shows relationships among the genera Microsphecodes, Eupetersia, Sphecodes and Austrosphecodes, a formerly proposed Sphecodes subgenus. Austrosphecodes species form a basal lineage of the subtribe, and Microsphecodes makes it paraphyletic.

  6. VirHostNet 2.0: surfing on the web of virus/host molecular interactions data.

    Science.gov (United States)

    Guirimand, Thibaut; Delmotte, Stéphane; Navratil, Vincent

    2015-01-01

    VirHostNet release 2.0 (http://virhostnet.prabi.fr) is a knowledgebase dedicated to the network-based exploration of virus-host protein-protein interactions. Since the previous VirhostNet release (2009), a second run of manual curation was performed to annotate the new torrent of high-throughput protein-protein interactions data from the literature. This resource is shared publicly, in PSI-MI TAB 2.5 format, using a PSICQUIC web service. The new interface of VirHostNet 2.0 is based on Cytoscape web library and provides a user-friendly access to the most complete and accurate resource of virus-virus and virus-host protein-protein interactions as well as their projection onto their corresponding host cell protein interaction networks. We hope that the VirHostNet 2.0 system will facilitate systems biology and gene-centered analysis of infectious diseases and will help to identify new molecular targets for antiviral drugs design. This resource will also continue to help worldwide scientists to improve our knowledge on molecular mechanisms involved in the antiviral response mediated by the cell and in the viral strategies selected by viruses to hijack the host immune system.

  7. Chemostats and epidemics: competition for nutrients/hosts.

    Science.gov (United States)

    Smith, Hal L; Thieme, Horst R

    2013-01-01

    In a chemostat, several species compete for the same nutrient, while in an epidemic, several strains of the same pathogen may compete for the same susceptible hosts. As winner, chemostat models predict the species with the lowest break-even concentration, while epidemic models predict the strain with the largest basic reproduction number. We show that these predictions amount to the same if the per capita functional responses of consumer species to the nutrient concentration or of infective individuals to the density of susceptibles are proportional to each other but that they are different if the functional responses are nonproportional. In the second case, the correct prediction is given by the break-even concentrations. In the case of nonproportional functional responses, we add a class for which the prediction does not only rely on local stability and instability of one-species (strain) equilibria but on the global outcome of the competition. We also review some results for nonautonomous models.

  8. Lectin Activation in Giardia lamblia by Host Protease: A Novel Host-Parasite Interaction

    Science.gov (United States)

    Lev, Boaz; Ward, Honorine; Keusch, Gerald T.; Pereira, Miercio E. A.

    1986-04-01

    A lectin in Giardia lamblia was activated by secretions from the human duodenum, the environment where the parasite lives. Incubation of the secretions with trypsin inhibitors prevented the appearance of lectin activity, implicating proteases as the activating agent. Accordingly, lectin activation was also produced by crystalline trypsin and Pronase; other proteases tested were ineffective. When activated, the lectin agglutinated intestinal cells to which the parasite adheres in vivo. The lectin was most specific to mannose-6-phosphate and apparently was bound to the plasma membrane. Activation of a parasite lectin by a host protease represents a novel mechanism of hostparasite interaction and may contribute to the affinity of Giardia lamblia to the infection site.

  9. Generous hosts: What makes Madagascar periwinkle (Catharanthus roseus) the perfect experimental host plant for fastidious bacteria?

    Science.gov (United States)

    Killiny, Nabil

    2016-12-01

    Although much attention has been paid to the metabolism and biosynthesis of monoterpene alkaloids in Catharanthus roseus, its value as an experimental host for a variety of agriculturally and economically important phytopathogenic bacteria warrants further study. In the present study, we evaluated the chemical composition of the phloem and xylem saps of C. roseus to infer the nutritional requirements of phloem- and xylem-limited phytopathogens. Periwinkle phloem sap consisted of a rich mixture of sugars, organic acids, amino acids, amines, fatty acids, sugar acids and sugar alcohols while xylem contained similar compounds in lesser concentrations. Plant sap analysis may lead to a better understanding of the biology of fastidious Mollicutes and their complex nutritional requirements, and to successful culture of phytoplasmas and other uncultured phloem-restricted bacteria such as Candidatus Liberibacter asiaticus, the causal agent of huanglongbing in citrus. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  10. Cucumis melo endornavirus: Genome organization, host range and co-divergence with the host.

    Science.gov (United States)

    Sabanadzovic, Sead; Wintermantel, William M; Valverde, Rodrigo A; McCreight, James D; Aboughanem-Sabanadzovic, Nina

    2016-03-02

    A high molecular weight dsRNA was isolated from a Cucumis melo L. plant (referred to as 'CL01') of an unknown cultivar and completely sequenced. Sequence analyses showed that dsRNA is associated with an endornavirus for which a name Cucumis melo endornavirus (CmEV) is proposed. The genome of CmEV-CL01 consists of 15,078 nt, contains a single, 4939 codons-long ORF and terminates with a stretch of 10 cytosine residues. Comparisons of the putative CmEV-encoded polyprotein with available references in protein databases revealed a unique genome organization characterized by the presence of the following domains: viral helicase Superfamily 1 (Hel-1), three glucosyltransferases (doublet of putative capsular polysaccharide synthesis proteins and a putative C_28_Glycosyltransferase), and an RNA-dependent RNA polymerase (RdRp). The presence of three glycome-related domains of different origin makes the genome organization of CmEV unique among endornaviruses. Phylogenetic analyses of viral RdRp domains showed that CmEV belongs to a specific lineage within the family Endornaviridae made exclusively of plant-infecting endornaviruses. An RT-PCR based survey demonstrated high incidence of CmEV among melon germplasm accession (>87% of tested samples). Analyses of partial genome sequences of CmEV isolates from 26 different melon genotypes suggest fine-tuned virus adaptation and co-divergence with the host. Finally, results of the present study revealed that CmEV is present in plants belonging to three different genera in the family Cucurbitaceae. Such diverse host range is unreported for known endornaviruses and suggests a long history of CmEV association with cucurbits predating their speciation.

  11. Second intermediate host land snails and definitive host animals of Brachylaima cribbi in southern Australia

    Directory of Open Access Journals (Sweden)

    Butcher A.R.

    2005-03-01

    Full Text Available This study of infection of southern Australian land snails with Brachylaima cribbi metacercariae has shown that all commonly encountered native and introduced snails are susceptible second intermediate hosts. The range of infected snails is extensive with metacercariae-infected snails being present in all districts across southern Australia. C. virgata has the highest average natural metacercarial infection intensity of 6.1 metacercariae per infected snail. The susceptibility of birds, mammals and reptiles to B. cribbi infection was studied in South Australia by capturing, dissecting and examining the intestinal tract contents of animals which commonly eat land snails as a food source. Indigenous Australian little ravens (Corvus mellori, which are a common scavenger bird, and two other passeriform birds, the black bird (Turdus merula and the starling (Sturnus vulgaris, which are both introduced European birds, were found to have the highest infection rates of all animals examined. Other birds found infected with B. cribbi were an emu (Dromaius novaehollandiae, chickens (Gallus gallus and a pigeon (Columba livia. Natural infections were also detected in field mice (Mus domesticus and shingleback lizards (Tiliqua rugosa although the intensity of infection was lower than that observed in birds. Susceptibility studies of laboratory mice, rats and ducks showed that mice developed patent infections which persisted for several weeks, rats developed a short-lived infection of three weeks’ duration and ducks did not support infection. This study has shown for the first time that a brachylaimid can infect a wide host range of birds, mammals and reptiles in nature.

  12. New mechanisms of disease and parasite-host interactions.

    Science.gov (United States)

    de Souza, Tiago Alves Jorge; de Carli, Gabriel Jose; Pereira, Tiago Campos

    2016-09-01

    An unconventional interaction between a patient and parasites was recently reported, in which parasitic cells invaded host's tissues, establishing several tumors. This finding raises various intriguing hypotheses on unpredicted forms of interplay between a patient and infecting parasites. Here we present four unusual hypothetical host-parasite scenarios with intriguing medical consequences. Relatively simple experimental designs are described in order to evaluate such hypotheses. The first one refers to the possibility of metabolic disorders in parasites intoxicating the host. The second one is on possibility of patients with inborn errors of metabolism (IEM) being more resistant to parasites (due to accumulation of toxic compounds in the bloodstream). The third one refers to a mirrored scenario: development of tumors in parasites due to ingestion of host's circulating cancer cells. The last one describes a complex relationship between parasites accumulating a metabolite and supplying it to a patient with an IEM. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. The listeriosis triangle: Pathogen, host and the environment

    Directory of Open Access Journals (Sweden)

    Abram Maja

    2012-03-01

    Full Text Available Listeria monocytogenes is a foodborne pathogen well known for its adaptability to diverse environment and host niches and its high fatality rate among infected immunocompromised populations. Infection in the immunocompetent host occurs but risk factors for the disease primarily points to abnormalities in cell-mediated and innate immunity as major predispositions to listeriosis. After ingestion of contaminated food, this pathogen is able to cross the intestinal, blood-brain and placental barrier and leads to gastroenteritis, meningitis and maternofetal infections which may result in abortion and spontaneous stillbirth. Despite the extensive use of this bacterium in the study of cell-mediated immunity and intracellular growth, our understanding of the host, pathogen and environmental factors that impact the pathogenesis of listeriosis is still incomplete. This review will summarize current knowledge, including our own efforts, about pathogen, host and environmental factors that influence, and contribute to the pathogenesis of Listeria monocytogenes infection.

  14. The Design of Molecular Hosts, Guests, and Their Complexes.

    Science.gov (United States)

    Cram, Donald J.

    1988-01-01

    Describes the origins, definitions, tools, and principles of host-guest chemistry. Gives examples of chiral recognition in complexation, of partial transacylase mimics, of caviplexes, and of a synthetic molecular cell. (Author/RT)

  15. Dopamine drives Drosophila sechellia adaptation to its toxic host.

    Science.gov (United States)

    Lavista-Llanos, Sofía; Svatoš, Aleš; Kai, Marco; Riemensperger, Thomas; Birman, Serge; Stensmyr, Marcus C; Hansson, Bill S

    2014-12-09

    Many insect species are host-obligate specialists. The evolutionary mechanism driving the adaptation of a species to a toxic host is, however, intriguing. We analyzed the tight association of Drosophila sechellia to its sole host, the fruit of Morinda citrifolia, which is toxic to other members of the melanogaster species group. Molecular polymorphisms in the dopamine regulatory protein Catsup cause infertility in D. sechellia due to maternal arrest of oogenesis. In its natural host, the fruit compensates for the impaired maternal dopamine metabolism with the precursor l-DOPA, resuming oogenesis and stimulating egg production. l-DOPA present in morinda additionally increases the size of D. sechellia eggs, what in turn enhances early fitness. We argue that the need of l-DOPA for successful reproduction has driven D. sechellia to become an M. citrifolia obligate specialist. This study illustrates how an insect's dopaminergic system can sustain ecological adaptations by modulating ontogenesis and development.

  16. The effect of floral resources on parasitoid and host longevity

    DEFF Research Database (Denmark)

    Sigsgaard, Lene; Betzer, Cathrine; Naulin, Cyril

    2013-01-01

    to increase functional biodiversity, the longevity of C. aretas and its host A. comariana was assessed on 5 flowering species: buckwheat, Fagopyrum esculentum Moench (Caryophyllales: Polygonaceae); borage, Borago officinalis L. (Boraginaceae); strawberry, Fragaria x ananassa Duchesne (Rosales: Rosaceae...

  17. Ibrutinib Effective against Graft-Versus-Host Disease

    Science.gov (United States)

    A Cancer Currents blog post on results from a small clinical trial showing that ibrutinib can effectively treat graft-versus-host-disease, a common and serious complication of allogeneic stem cell transplants.

  18. Interactions between Streptococcus pneumoniae and the human host

    NARCIS (Netherlands)

    Mens, S.P. van

    2014-01-01

    Streptococcus pneumoniae, the pneumococcus, is an important human pathogen causing considerable morbidity and mortality worldwide. This thesis addresses several interactions between pneumococcus and man. The first part of the thesis deals with the host immune response against pneumococci. We studied

  19. Effects of host heterogeneity on pathogen diversity and evolution

    DEFF Research Database (Denmark)

    Fleming-Davies, Arietta E; Dukic, Vanja; Andreasen, Viggo;

    2015-01-01

    Phenotypic variation is common in most pathogens, yet the mechanisms that maintain this diversity are still poorly understood. We asked whether continuous host variation in susceptibility helps maintain phenotypic variation, using experiments conducted with a baculovirus that infects gypsy moth...

  20. Age consistency between exoplanet hosts and field stars

    CERN Document Server

    Bonfanti, Andrea; Nascimbeni, Valerio

    2015-01-01

    Transiting planets around stars are discovered mostly through photometric surveys. Unlike radial velocity surveys, photometric surveys do not tend to target slow rotators, inactive and metal-rich stars. Nevertheless, we suspect that observational biases could impact also transiting-planet hosts. This paper aims at evaluating how selection effects reflect on the evolutionary stage of both a limited sample of transiting-planet host stars (TPH) and a wider sample of planet-hosting stars detected through radial velocity analysis. Then, thanks to uniform derivation of stellar ages, a homogeneous comparison between exoplanet hosts and field star age distributions is developed. Stellar parameters have been computed through our custom-developed isochrone placement algorithm, according to Padova evolutionary models. The notable aspects of our algorithm include the treatment of element diffusion, activity checks in terms of $\\log{R'_{HK}}$ and $v\\sin{i}$ and the evaluation of the stellar evolutionary speed in the Hertz...