Control of cyclin C levels during development of Dictyostelium.

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David M Greene

2010-05-01

Full Text Available Cdk8 and its partner cyclin C form part of the mediator complex which links the basal transcription machinery to regulatory proteins. The pair are required for correct regulation of a subset of genes and have been implicated in control of development in a number of organisms including the social amoeba Dictyostelium discoideum. When feeding, Dictyostelium amoebae are unicellular but upon starvation they aggregate to form a multicellular structure which develops into a fruiting body containing spores. Cells in which the gene encoding Cdk8 has been deleted fail to enter aggregates due to a failure of early gene expression.We have monitored the expression levels of cyclin C protein during development and find levels decrease after the multicellular mound is formed. This decrease is triggered by extracellular cAMP that, in turn, is working in part through an increase in intracellular cAMP. The loss of cyclin C is coincident with a reduction in the association of Cdk8 with a high molecular weight complex in the nucleus. Overexpression of cyclin C and Cdk8 lead to an increased rate of early development, consistent with the levels being rate limiting.Overall these results show that both cyclin C and Cdk8 are regulated during development in response to extracellular signals and the levels of these proteins are important in controlling the timing of developmental processes. These findings have important implications for the role of these proteins in controlling development, suggesting that they are targets for developmental signals to regulate gene expression.

Comparing the Dictyostelium and Entamoeba genomes reveals an ancient split in the Conosa lineage.

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Jie Song

2005-12-01

Full Text Available The Amoebozoa are a sister clade to the fungi and the animals, but are poorly sampled for completely sequenced genomes. The social amoeba Dictyostelium discoideum and amitochondriate pathogen Entamoeba histolytica are the first Amoebozoa with genomes completely sequenced. Both organisms are classified under the Conosa subphylum. To identify Amoebozoa-specific genomic elements, we compared these two genomes to each other and to other eukaryotic genomes. An expanded phylogenetic tree built from the complete predicted proteomes of 23 eukaryotes places the two amoebae in the same lineage, although the divergence is estimated to be greater than that between animals and fungi, and probably happened shortly after the Amoebozoa split from the opisthokont lineage. Most of the 1,500 orthologous gene families shared between the two amoebae are also shared with plant, animal, and fungal genomes. We found that only 42 gene families are distinct to the amoeba lineage; among these are a large number of proteins that contain repeats of the FNIP domain, and a putative transcription factor essential for proper cell type differentiation in D. discoideum. These Amoebozoa-specific genes may be useful in the design of novel diagnostics and therapies for amoebal pathologies.

Kin discrimination increases with genetic distance in a social amoeba.

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Ostrowski, Elizabeth A; Katoh, Mariko; Shaulsky, Gad; Queller, David C; Strassmann, Joan E

2008-11-25

In the social amoeba Dictyostelium discoideum, thousands of cells aggregate upon starvation to form a multicellular fruiting body, and approximately 20% of them die to form a stalk that benefits the others. The aggregative nature of multicellular development makes the cells vulnerable to exploitation by cheaters, and the potential for cheating is indeed high. Cells might avoid being victimized if they can discriminate among individuals and avoid those that are genetically different. We tested how widely social amoebae cooperate by mixing isolates from different localities that cover most of their natural range. We show here that different isolates partially exclude one another during aggregation, and there is a positive relationship between the extent of this exclusion and the genetic distance between strains. Our findings demonstrate that D. discoideum cells co-aggregate more with genetically similar than dissimilar individuals, suggesting the existence of a mechanism that discerns the degree of genetic similarity between individuals in this social microorganism.

The Beneficial Effect of Equisetum giganteum L. against Candida Biofilm Formation: New Approaches to Denture Stomatitis

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Rafaela A. S. Alavarce

2015-01-01

Full Text Available Equisetum giganteum L. (E. giganteum, Equisetaceae, commonly called “giant horsetail,” is an endemic plant of Central and South America and is used in traditional medicine as diuretic and hemostatic in urinary disorders and in inflammatory conditions among other applications. The chemical composition of the extract EtOH 70% of E. giganteum has shown a clear presence of phenolic compounds derived from caffeic and ferulic acids and flavonoid heterosides derived from quercitin and kaempferol, in addition to styrylpyrones. E. giganteum, mainly at the highest concentrations, showed antimicrobial activity against the relevant microorganisms tested: Escherichia coli, Staphylococcus aureus, and Candida albicans. It also demonstrated antiadherent activity on C. albicans biofilms in an experimental model that is similar to dentures. Moreover, all concentrations tested showed anti-inflammatory activity. The extract did not show cytotoxicity in contact with human cells. These properties might qualify E. giganteum extract to be a promising alternative for the topic treatment and prevention of oral candidiasis and denture stomatitis.

An evolutionarily significant unicellular strategy in response to starvation stress in Dictyostelium social amoebae [v1; ref status: indexed, http://f1000r.es/3hg

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Darja Dubravcic

2014-06-01

Full Text Available The social amoeba Dictyostelium discoideum is widely studied for its multicellular development program as a response to starvation and constitutes a model of choice in microbial cooperation studies. Aggregates of up to 106 cells form fruiting bodies containing two cell types: (i dormant spores (~80% that can persist for months in the absence of nutrients, and (ii dead stalk cells (~20% that promote the dispersion of the spores towards nutrient-rich areas. It is often overlooked that not all cells aggregate upon starvation. Using a new quantitative approach based on time-lapse fluorescence microscopy and a low ratio of reporting cells, we have quantified this fraction of non-aggregating cells. In realistic starvation conditions, up to 15% of cells do not aggregate, which makes this third cell fate a significant component of the population-level response of social amoebae to starvation. Non-aggregating cells have an advantage over cells in aggregates since they resume growth earlier upon arrival of new nutrients, but have a shorter lifespan under prolonged starvation. We find that phenotypic heterogeneities linked to cell nutritional state bias the representation of cells in the aggregating vs. non-aggregating fractions, and thus regulate population partitioning. Next, we report that the fraction of non-aggregating cells depends on genetic factors that regulate the timing of starvation, signal sensing efficiency and aggregation efficiency. In addition, interactions between clones in mixtures of non-isogenic cells affect the partitioning of each clone into both fractions. We further test the evolutionary significance of the non-aggregating cell fraction. The partitioning of cells into aggregating and non-aggregating fractions is optimal in fluctuating environments with an unpredictable duration of starvation periods. D. discoideum thus constitutes a model system lying at the intersection of microbial cooperation and bet hedging, defining a new

Whole genome sequencing of mutation accumulation lines reveals a low mutation rate in the social amoeba Dictyostelium discoideum.

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Gerda Saxer

Full Text Available Spontaneous mutations play a central role in evolution. Despite their importance, mutation rates are some of the most elusive parameters to measure in evolutionary biology. The combination of mutation accumulation (MA experiments and whole-genome sequencing now makes it possible to estimate mutation rates by directly observing new mutations at the molecular level across the whole genome. We performed an MA experiment with the social amoeba Dictyostelium discoideum and sequenced the genomes of three randomly chosen lines using high-throughput sequencing to estimate the spontaneous mutation rate in this model organism. The mitochondrial mutation rate of 6.76×10(-9, with a Poisson confidence interval of 4.1×10(-9 - 9.5×10(-9, per nucleotide per generation is slightly lower than estimates for other taxa. The mutation rate estimate for the nuclear DNA of 2.9×10(-11, with a Poisson confidence interval ranging from 7.4×10(-13 to 1.6×10(-10, is the lowest reported for any eukaryote. These results are consistent with low microsatellite mutation rates previously observed in D. discoideum and low levels of genetic variation observed in wild D. discoideum populations. In addition, D. discoideum has been shown to be quite resistant to DNA damage, which suggests an efficient DNA-repair mechanism that could be an adaptation to life in soil and frequent exposure to intracellular and extracellular mutagenic compounds. The social aspect of the life cycle of D. discoideum and a large portion of the genome under relaxed selection during vegetative growth could also select for a low mutation rate. This hypothesis is supported by a significantly lower mutation rate per cell division in multicellular eukaryotes compared with unicellular eukaryotes.

Gene discovery by chemical mutagenesis and whole-genome sequencing in Dictyostelium.

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Li, Cheng-Lin Frank; Santhanam, Balaji; Webb, Amanda Nicole; Zupan, Blaž; Shaulsky, Gad

2016-09-01

Whole-genome sequencing is a useful approach for identification of chemical-induced lesions, but previous applications involved tedious genetic mapping to pinpoint the causative mutations. We propose that saturation mutagenesis under low mutagenic loads, followed by whole-genome sequencing, should allow direct implication of genes by identifying multiple independent alleles of each relevant gene. We tested the hypothesis by performing three genetic screens with chemical mutagenesis in the social soil amoeba Dictyostelium discoideum Through genome sequencing, we successfully identified mutant genes with multiple alleles in near-saturation screens, including resistance to intense illumination and strong suppressors of defects in an allorecognition pathway. We tested the causality of the mutations by comparison to published data and by direct complementation tests, finding both dominant and recessive causative mutations. Therefore, our strategy provides a cost- and time-efficient approach to gene discovery by integrating chemical mutagenesis and whole-genome sequencing. The method should be applicable to many microbial systems, and it is expected to revolutionize the field of functional genomics in Dictyostelium by greatly expanding the mutation spectrum relative to other common mutagenesis methods. © 2016 Li et al.; Published by Cold Spring Harbor Laboratory Press.

Cheating by exploitation of developmental prestalk patterning in Dictyostelium discoideum.

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Anupama Khare

2010-02-01

Full Text Available The cooperative developmental system of the social amoeba Dictyostelium discoideum is susceptible to exploitation by cheaters-strains that make more than their fair share of spores in chimerae. Laboratory screens in Dictyostelium have shown that the genetic potential for facultative cheating is high, and field surveys have shown that cheaters are abundant in nature, but the cheating mechanisms are largely unknown. Here we describe cheater C (chtC, a strong facultative cheater mutant that cheats by affecting prestalk differentiation. The chtC gene is developmentally regulated and its mRNA becomes stalk-enriched at the end of development. chtC mutants are defective in maintaining the prestalk cell fate as some of their prestalk cells transdifferentiate into prespore cells, but that defect does not affect gross developmental morphology or sporulation efficiency. In chimerae between wild-type and chtC mutant cells, the wild-type cells preferentially give rise to prestalk cells, and the chtC mutants increase their representation in the spore mass. Mixing chtC mutants with other cell-type proportioning mutants revealed that the cheating is directly related to the prestalk-differentiation propensity of the victim. These findings illustrate that a cheater can victimize cooperative strains by exploiting an established developmental pathway.

Cheating by Exploitation of Developmental Prestalk Patterning in Dictyostelium discoideum

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Khare, Anupama; Shaulsky, Gad

2010-01-01

The cooperative developmental system of the social amoeba Dictyostelium discoideum is susceptible to exploitation by cheaters—strains that make more than their fair share of spores in chimerae. Laboratory screens in Dictyostelium have shown that the genetic potential for facultative cheating is high, and field surveys have shown that cheaters are abundant in nature, but the cheating mechanisms are largely unknown. Here we describe cheater C (chtC), a strong facultative cheater mutant that cheats by affecting prestalk differentiation. The chtC gene is developmentally regulated and its mRNA becomes stalk-enriched at the end of development. chtC mutants are defective in maintaining the prestalk cell fate as some of their prestalk cells transdifferentiate into prespore cells, but that defect does not affect gross developmental morphology or sporulation efficiency. In chimerae between wild-type and chtC mutant cells, the wild-type cells preferentially give rise to prestalk cells, and the chtC mutants increase their representation in the spore mass. Mixing chtC mutants with other cell-type proportioning mutants revealed that the cheating is directly related to the prestalk-differentiation propensity of the victim. These findings illustrate that a cheater can victimize cooperative strains by exploiting an established developmental pathway. PMID:20195510

dictyExpress: a web-based platform for sequence data management and analytics in Dictyostelium and beyond.

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Stajdohar, Miha; Rosengarten, Rafael D; Kokosar, Janez; Jeran, Luka; Blenkus, Domen; Shaulsky, Gad; Zupan, Blaz

2017-06-02

Dictyostelium discoideum, a soil-dwelling social amoeba, is a model for the study of numerous biological processes. Research in the field has benefited mightily from the adoption of next-generation sequencing for genomics and transcriptomics. Dictyostelium biologists now face the widespread challenges of analyzing and exploring high dimensional data sets to generate hypotheses and discovering novel insights. We present dictyExpress (2.0), a web application designed for exploratory analysis of gene expression data, as well as data from related experiments such as Chromatin Immunoprecipitation sequencing (ChIP-Seq). The application features visualization modules that include time course expression profiles, clustering, gene ontology enrichment analysis, differential expression analysis and comparison of experiments. All visualizations are interactive and interconnected, such that the selection of genes in one module propagates instantly to visualizations in other modules. dictyExpress currently stores the data from over 800 Dictyostelium experiments and is embedded within a general-purpose software framework for management of next-generation sequencing data. dictyExpress allows users to explore their data in a broader context by reciprocal linking with dictyBase-a repository of Dictyostelium genomic data. In addition, we introduce a companion application called GenBoard, an intuitive graphic user interface for data management and bioinformatics analysis. dictyExpress and GenBoard enable broad adoption of next generation sequencing based inquiries by the Dictyostelium research community. Labs without the means to undertake deep sequencing projects can mine the data available to the public. The entire information flow, from raw sequence data to hypothesis testing, can be accomplished in an efficient workspace. The software framework is generalizable and represents a useful approach for any research community. To encourage more wide usage, the backend is open

Yersinia outer protein YopE affects the actin cytoskeleton in Dictyostelium discoideum through targeting of multiple Rho family GTPases

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Vlahou, Georgia

2009-07-14

Abstract Background All human pathogenic Yersinia species share a virulence-associated type III secretion system that translocates Yersinia effector proteins into host cells to counteract infection-induced signaling responses and prevent phagocytosis. Dictyostelium discoideum has been recently used to study the effects of bacterial virulence factors produced by internalized pathogens. In this study we explored the potential of Dictyostelium as model organism for analyzing the effects of ectopically expressed Yersinia outer proteins (Yops). Results The Yersinia pseudotuberculosis virulence factors YopE, YopH, YopM and YopJ were expressed de novo within Dictyostelium and their effects on growth in axenic medium and on bacterial lawns were analyzed. No severe effect was observed for YopH, YopJ and YopM, but expression of YopE, which is a GTPase activating protein for Rho GTPases, was found to be highly detrimental. GFP-tagged YopE expressing cells had less conspicuous cortical actin accumulation and decreased amounts of F-actin. The actin polymerization response upon cAMP stimulation was impaired, although chemotaxis was unaffected. YopE also caused reduced uptake of yeast particles. These alterations are probably due to impaired Rac1 activation. We also found that YopE predominantly associates with intracellular membranes including the Golgi apparatus and inhibits the function of moderately overexpressed RacH. Conclusion The phenotype elicited by YopE in Dictyostelium can be explained, at least in part, by inactivation of one or more Rho family GTPases. It further demonstrates that the social amoeba Dictyostelium discoideum can be used as an efficient and easy-to-handle model organism in order to analyze the function of a translocated GAP protein of a human pathogen.

Inorganic Polyphosphate Is Essential for Salmonella Typhimurium Virulence and Survival in Dictyostelium discoideum

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Macarena A. Varas

2018-01-01

Full Text Available Inorganic polyphosphate (polyP deficiency in enteric bacterial pathogens reduces their ability to invade and establish systemic infections in different hosts. For instance, inactivation of the polyP kinase gene (ppk encoding the enzyme responsible for polyP biosynthesis reduces invasiveness and intracellular survival of Salmonella enterica serovar Typhimurium (S. Typhimurium in epithelial cells and macrophages in vitro. In addition, the virulence in vivo of a S. Typhimurium Δppk mutant is significantly reduced in a murine infection model. In spite of these observations, the role played by polyP during the Salmonella-host interaction is not well understood. The social amoeba Dictyostelium discoideum has proven to be a useful model for studying relevant aspects of the host-pathogen interaction. In fact, many intracellular pathogens can survive within D. discoideum cells using molecular mechanisms also required to survive within macrophages. Recently, we established that S. Typhimurium is able to survive intracellularly in D. discoideum and identified relevant genes linked to virulence that are crucial for this process. The aim of this study was to determine the effect of a polyP deficiency in S. Typhimurium during its interaction with D. discoideum. To do this, we evaluated the intracellular survival of wild-type and Δppk strains of S. Typhimurium in D. discoideum and the ability of these strains to delay the social development of the amoeba. In contrast to the wild-type strain, the Δppk mutant was unable to survive intracellularly in D. discoideum and enabled the social development of the amoeba. Both phenotypes were complemented using a plasmid carrying a copy of the ppk gene. Next, we simultaneously evaluated the proteomic response of both S. Typhimurium and D. discoideum during host-pathogen interaction via global proteomic profiling. The analysis of our results allowed the identification of novel molecular signatures that give insight into

Spontaneous emergence of large-scale cell cycle synchronization in amoeba colonies

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Segota, Igor; Boulet, Laurent; Franck, David; Franck, Carl

2014-01-01

Unicellular eukaryotic amoebae Dictyostelium discoideum are generally believed to grow in their vegetative state as single cells until starvation, when their collective aspect emerges and they differentiate to form a multicellular slime mold. While major efforts continue to be aimed at their starvation-induced social aspect, our understanding of population dynamics and cell cycle in the vegetative growth phase has remained incomplete. Here we show that cell populations grown on a substrate spontaneously synchronize their cell cycles within several hours. These collective population-wide cell cycle oscillations span millimeter length scales and can be completely suppressed by washing away putative cell-secreted signals, implying signaling by means of a diffusible growth factor or mitogen. These observations give strong evidence for collective proliferation behavior in the vegetative state. (paper)

Clues to γ-secretase, huntingtin and Hirano body normal function using the model organism Dictyostelium discoideum

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Myre Michael A

2012-04-01

Full Text Available Abstract Many neurodegenerative disorders, although related by their destruction of brain function, display remarkable cellular and/or regional pathogenic specificity likely due to a deregulated functionality of the mutant protein. However, neurodegenerative disease genes, for example huntingtin (HTT, the ataxins, the presenilins (PSEN1/PSEN2 are not simply localized to neurons but are ubiquitously expressed throughout peripheral tissues; it is therefore paramount to properly understand the earliest precipitating events leading to neuronal pathogenesis to develop effective long-term therapies. This means, in no unequivocal terms, it is crucial to understand the gene's normal function. Unfortunately, many genes are often essential for embryogenesis which precludes their study in whole organisms. This is true for HTT, the β-amyloid precursor protein (APP and presenilins, responsible for early onset Alzheimer's disease (AD. To better understand neurological disease in humans, many lower and higher eukaryotic models have been established. So the question arises: how reasonable is the use of organisms to study neurological disorders when the model of choice does not contain neurons? Here we will review the surprising, and novel emerging use of the model organism Dictyostelium discoideum, a species of soil-living amoeba, as a valuable biomedical tool to study the normal function of neurodegenerative genes. Historically, the evidence on the usefulness of simple organisms to understand the etiology of cellular pathology cannot be denied. But using an organism without a central nervous system to understand diseases of the brain? We will first introduce the life cycle of Dictyostelium, the presence of many disease genes in the genome and how it has provided unique opportunities to identify mechanisms of disease involving actin pathologies, mitochondrial disease, human lysosomal and trafficking disorders and host-pathogen interactions. Secondly, I will

High fidelity information processing in folic acid chemotaxis of Dictyostelium amoebae.

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Segota, Igor; Mong, Surin; Neidich, Eitan; Rachakonda, Archana; Lussenhop, Catherine J; Franck, Carl

2013-11-06

Living cells depend upon the detection of chemical signals for their existence. Eukaryotic cells can sense a concentration difference as low as a few per cent across their bodies. This process was previously suggested to be limited by the receptor-ligand binding fluctuations. Here, we first determine the chemotaxis response of Dictyostelium cells to static folic acid gradients and show that they can significantly exceed this sensitivity, responding to gradients as shallow as 0.2% across the cell body. Second, using a previously developed information theory framework, we compare the total information gained about the gradient (based on the cell response) to its upper limit: the information gained at the receptor-ligand binding step. We find that the model originally applied to cAMP sensing fails as demonstrated by the violation of the data processing inequality, i.e. the total information exceeds the information at the receptor-ligand binding step. We propose an extended model with multiple known receptor types and with cells allowed to perform several independent measurements of receptor occupancy. This does not violate the data processing inequality and implies the receptor-ligand binding noise dominates both for low- and high-chemoattractant concentrations. We also speculate that the interplay between exploration and exploitation is used as a strategy for accurate sensing of otherwise unmeasurable levels of a chemoattractant.

Extracts of Equisetum giganteum L and Copaifera reticulate Ducke show strong antiviral activity against the sexually transmitted pathogen herpes simplex virus type 2.

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Churqui, Marianela Patzi; Lind, Liza; Thörn, Karolina; Svensson, Alexandra; Savolainen, Otto; Aranda, Katty Terrazas; Eriksson, Kristina

2018-01-10

Equisetum giganteum L and Copaifera reticulate Ducke have been traditionally used by women of the Tacana tribe in the Bolivian Amazonas for genital hygiene and for treatment of genital infection/inflammation. To assess the ability of extracts from Equisetum giganteum L and Copaifera reticulate Ducke to block genital viral infection by herpes simplex virus type 2. Equisetum giganteum L and Copaifera reticulate Ducke were collected from the Amazon region of La Paz, Bolivia. Extracts were prepared and screened for anti-viral activity against herpes simplex virus type 2 (HSV-2) using both in vitro and in in vivo models of infection. Equisetum giganteum L and Copaifera reticulate Ducke efficiently blocked HSV-2 infection of cell cultures without major cell cytotoxic effects. Extracts of Equisetum giganteum L and Copaifera reticulate Ducke could prevent HSV-2 disease development when administered together with virus in a mouse model of genital HSV-2 infection. In vitro analyses revealed that both plant extracts exerted their anti-HSV-2 effects by interfering with viral cell attachment and entry, but could not block viral replication post entry. These studies show that extracts of Equisetum giganteum L and Copaifera reticulate Ducke have potent antiviral activities against HSV-2 comparable to those two previously identified plants, Croton lechleri Müll. Arg. and Uncaria tomentosa (Willd. ex Schult.) DC. These studies confirm that plants used by the Tacana tribe could be explored further for the development of novel topical antiviral microbicides. Copyright © 2017. Published by Elsevier B.V.

Folic acid is a potent chemoattractant of free-living amoebae in a new and amazing species of protist, Vahlkampfia sp.

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Maeda, Yasuo; Mayanagi, Taira; Amagai, Aiko

2009-03-01

Folic acid (folate; vitamin Bc) is well recognized as essential for the proper metabolism of the essential amino acid methionine as well as for the synthesis of adenine and thymine. A folate deficiency has been Implicated in a wide variety of disorders from Alzheimer's disease to depression and neural tube defects. In the cellular slime molds, including Dictyostelium, vegetative growth-phase cells are known to chemotactically move toward folate that is secreted by bacterial food sources such as Escherichia coli. Intracellular folate signal transductlon, including G proteins, Ca(2+)channels, and the PIP3 pathway, has been reported in D. discoideum. To our surprise, the genuine chemoattractant(s) of free-living protozoan amoebae have remained to be determined, possibly because of lack of a pertinent method for assaying chemotaxis. We recently isolated a primitive free-living amoeba from the soil of Costa Rica and identified it as a new species of the genus Vahlkampfia belonging to Subclass Gymnamoebia, which includes Entamoeba and Acanthamoeba. The amoebae can grow and multiply quite rapidly, engulfing nearby bacteria such as E. coli. Importantly, we have demonstrated here using a quite simple but finely designed chemotaxis assay that the Vahlkampfia amoebae exhibit chemotaxis toward higher folate concentrations. Riboflavin and cyanocobalamin were also found to serve as positive chemoattractants. Among these chemoattractants, folate is of particular importance because its function seems to be evolutionarily conserved as a potent chemoattractant of amoeboid cells in a wide range of organisms as well as in the Protista and cellular slime molds.

An autoregulatory circuit for long-range self-organization in Dictyostelium cell populations.

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Sawai, Satoshi; Thomason, Peter A; Cox, Edward C

2005-01-20

Nutrient-deprived Dictyostelium amoebae aggregate to form a multicellular structure by chemotaxis, moving towards propagating waves of cyclic AMP that are relayed from cell to cell. Organizing centres are not formed by founder cells, but are dynamic entities consisting of cores of outwardly rotating spiral waves that self-organize in a homogeneous cell population. Spiral waves are ubiquitously observed in chemical reactions as well as in biological systems. Although feedback control of spiral waves in spatially extended chemical reactions has been demonstrated in recent years, the mechanism by which control is achieved in living systems is unknown. Here we show that mutants of the cyclic AMP/protein kinase A pathway show periodic signalling, but fail to organize coherent long-range wave territories, owing to the appearance of numerous spiral cores. A theoretical model suggests that autoregulation of cell excitability mediated by protein kinase A acts to optimize the number of signalling centres.

TM9/Phg1 and SadA proteins control surface expression and stability of SibA adhesion molecules in Dictyostelium.

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Froquet, Romain; le Coadic, Marion; Perrin, Jackie; Cherix, Nathalie; Cornillon, Sophie; Cosson, Pierre

2012-02-01

TM9 proteins form a family of conserved proteins with nine transmembrane domains essential for cellular adhesion in many biological systems, but their exact role in this process remains unknown. In this study, we found that genetic inactivation of the TM9 protein Phg1A dramatically decreases the surface levels of the SibA adhesion molecule in Dictyostelium amoebae. This is due to a decrease in sibA mRNA levels, in SibA protein stability, and in SibA targeting to the cell surface. A similar phenotype was observed in cells devoid of SadA, a protein that does not belong to the TM9 family but also exhibits nine transmembrane domains and is essential for cellular adhesion. A contact site A (csA)-SibA chimeric protein comprising only the transmembrane and cytosolic domains of SibA and the extracellular domain of the Dictyostelium surface protein csA also showed reduced stability and relocalization to endocytic compartments in phg1A knockout cells. These results indicate that TM9 proteins participate in cell adhesion by controlling the levels of adhesion proteins present at the cell surface.

A comparative sequence analysis reveals a common GBD/FH3-FH1-FH2-DAD architecture in formins from Dictyostelium, fungi and metazoa

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Uyeda Taro QP

2005-03-01

Full Text Available Abstract Background Formins are multidomain proteins defined by a conserved FH2 (formin homology 2 domain with actin nucleation activity preceded by a proline-rich FH1 (formin homology 1 domain. Formins act as profilin-modulated processive actin nucleators conserved throughout a wide range of eukaryotes. Results We present a detailed sequence analysis of the 10 formins (ForA to J identified in the genome of the social amoeba Dictyostelium discoideum. With the exception of ForI and ForC all other formins conform to the domain structure GBD/FH3-FH1-FH2-DAD, where DAD is the Diaphanous autoinhibition domain and GBD/FH3 is the Rho GTPase-binding domain/formin homology 3 domain that we propose to represent a single domain. ForC lacks a FH1 domain, ForI lacks recognizable GBD/FH3 and DAD domains and ForA, E and J have additional unique domains. To establish the relationship between formins of Dictyostelium and other organisms we constructed a phylogenetic tree based on the alignment of FH2 domains. Real-time PCR was used to study the expression pattern of formin genes. Expression of forC, D, I and J increased during transition to multi-cellular stages, while the rest of genes displayed less marked developmental variations. During sexual development, expression of forH and forI displayed a significant increase in fusion competent cells. Conclusion Our analysis allows some preliminary insight into the functionality of Dictyostelium formins: all isoforms might display actin nucleation activity and, with the exception of ForI, might also be susceptible to autoinhibition and to regulation by Rho GTPases. The architecture GBD/FH3-FH1-FH2-DAD appears common to almost all Dictyostelium, fungal and metazoan formins, for which we propose the denomination of conventional formins, and implies a common regulatory mechanism.

A comparative sequence analysis reveals a common GBD/FH3-FH1-FH2-DAD architecture in formins from Dictyostelium, fungi and metazoa.

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Rivero, Francisco; Muramoto, Tetsuya; Meyer, Ann-Kathrin; Urushihara, Hideko; Uyeda, Taro Q P; Kitayama, Chikako

2005-03-01

Formins are multidomain proteins defined by a conserved FH2 (formin homology 2) domain with actin nucleation activity preceded by a proline-rich FH1 (formin homology 1) domain. Formins act as profilin-modulated processive actin nucleators conserved throughout a wide range of eukaryotes. We present a detailed sequence analysis of the 10 formins (ForA to J) identified in the genome of the social amoeba Dictyostelium discoideum. With the exception of ForI and ForC all other formins conform to the domain structure GBD/FH3-FH1-FH2-DAD, where DAD is the Diaphanous autoinhibition domain and GBD/FH3 is the Rho GTPase-binding domain/formin homology 3 domain that we propose to represent a single domain. ForC lacks a FH1 domain, ForI lacks recognizable GBD/FH3 and DAD domains and ForA, E and J have additional unique domains. To establish the relationship between formins of Dictyostelium and other organisms we constructed a phylogenetic tree based on the alignment of FH2 domains. Real-time PCR was used to study the expression pattern of formin genes. Expression of forC, D, I and J increased during transition to multi-cellular stages, while the rest of genes displayed less marked developmental variations. During sexual development, expression of forH and forI displayed a significant increase in fusion competent cells. Our analysis allows some preliminary insight into the functionality of Dictyostelium formins: all isoforms might display actin nucleation activity and, with the exception of ForI, might also be susceptible to autoinhibition and to regulation by Rho GTPases. The architecture GBD/FH3-FH1-FH2-DAD appears common to almost all Dictyostelium, fungal and metazoan formins, for which we propose the denomination of conventional formins, and implies a common regulatory mechanism.

A flavin-dependent halogenase catalyzes the chlorination step in the biosynthesis of Dictyostelium differentiation-inducing factor 1.

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Neumann, Christopher S; Walsh, Christopher T; Kay, Robert R

2010-03-30

Differentiation-inducing factor 1 (DIF-1) is a polyketide-derived morphogen which drives stalk cell formation in the developmental cycle of Dictyostelium discoideum. Previous experiments demonstrated that the biosynthetic pathway proceeds via dichlorination of the precursor molecule THPH, but the enzyme responsible for this transformation has eluded characterization. Our recent studies on prokaryotic flavin-dependent halogenases and insights from the sequenced Dd genome led us to a candidate gene for this transformation. In this work, we present in vivo and in vitro evidence that chlA from Dd encodes a flavin-dependent halogenase capable of catalyzing both chlorinations in the biosynthesis of DIF-1. The results provide in vitro characterization of a eukaryotic oxygen-dependent halogenase and demonstrate a broad reach in biology for this molecular tailoring strategy, notably its involvement in the differentiation program of a social amoeba.

Lack of Ecological and Life History Context Can Create the Illusion of Social Interactions in Dictyostelium discoideum.

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Martínez-García, Ricardo; Tarnita, Corina E

2016-12-01

Studies of social microbes often focus on one fitness component (reproductive success within the social complex), with little information about or attention to other stages of the life cycle or the ecological context. This can lead to paradoxical results. The life cycle of the social amoeba Dictyostelium discoideum includes a multicellular stage in which not necessarily clonal amoebae aggregate upon starvation to form a possibly chimeric (genetically heterogeneous) fruiting body made of dead stalk cells and spores. The lab-measured reproductive skew in the spores of chimeras indicates strong social antagonism that should result in low genotypic diversity, which is inconsistent with observations from nature. Two studies have suggested that this inconsistency stems from the one-dimensional assessment of fitness (spore production) and that the solution lies in tradeoffs between multiple life-history traits, e.g.: spore size versus viability; and spore-formation (via aggregation) versus staying vegetative (as non-aggregated cells). We develop an ecologically-grounded, socially-neutral model (i.e. no social interactions between genotypes) for the life cycle of social amoebae in which we theoretically explore multiple non-social life-history traits, tradeoffs and tradeoff-implementing mechanisms. We find that spore production comes at the expense of time to complete aggregation, and, depending on the experimental setup, spore size and viability. Furthermore, experimental results regarding apparent social interactions within chimeric mixes can be qualitatively recapitulated under this neutral hypothesis, without needing to invoke social interactions. This allows for simple potential resolutions to the previously paradoxical results. We conclude that the complexities of life histories, including social behavior and multicellularity, can only be understood in the appropriate multidimensional ecological context, when considering all stages of the life cycle.

Identification and recombinant expression of anandamide hydrolyzing enzyme from Dictyostelium discoideum

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Neelamegan Dhamodharan

2012-06-01

Full Text Available Abstract Background Anandamide (Arachidonoyl ethanolamide is a potent bioactive lipid studied extensively in humans, which regulates several neurobehavioral processes including pain, feeding and memory. Bioactivity is terminated when hydrolyzed into free arachidonic acid and ethanolamine by the enzyme fatty acid amide hydrolase (FAAH. In this study we report the identification of a FAAH homolog from Dictyostelium discoideum and its function to hydrolyze anandamide. Results A putative FAAH DNA sequence coding for a conserved amidase signature motif was identified in the Dictyostelium genome database and the corresponding cDNA was isolated and expressed as an epitope tagged fusion protein in either E.coli or Dictyostelium. Wild type Dictyostelium cells express FAAH throughout their development life cycle and the protein was found to be predominantly membrane associated. Production of recombinant HIS tagged FAAH protein was not supported in E.coli host, but homologous Dictyostelium host was able to produce the same successfully. Recombinant FAAH protein isolated from Dictyostelium was shown to hydrolyze anandamide and related synthetic fatty acid amide substrates. Conclusions This study describes the first identification and characterisation of an anandamide hydrolyzing enzyme from Dictyostelium discoideum, suggesting the potential of Dictyostelium as a simple eukaryotic model system for studying mechanisms of action of any FAAH inhibitors as drug targets.

Survival of the fattest

DEFF Research Database (Denmark)

Morgani, Sophie M; Brickman, Joshua M

2013-01-01

Experiments on the social amoeba Dictyostelium discoideum show that the origins of lineage bias in this system lie in the nutritional history of individual cells. Clues to the molecular basis for this process suggest similar forces may be at work in early mammalian development.......Experiments on the social amoeba Dictyostelium discoideum show that the origins of lineage bias in this system lie in the nutritional history of individual cells. Clues to the molecular basis for this process suggest similar forces may be at work in early mammalian development....

Characterization of PEBBLEs as a Tool for Real-Time Measurement of Dictyostelium discoideum Endosomal pH

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Everett Moding

2009-01-01

Full Text Available The measurement of intracellular ion concentration change is important for understanding the cellular mechanisms for communication. Recently developed nanosensors, (Photonic Explorers for Biomedical use with Biologically Localized Embedding PEBBLEs, have a number of advantages for measuring ions in cells over established methods using microelectrodes, unbound fluorescent dyes, or NMR. PEBBLE sensors have been shown to work in principle for measuring dynamic ion changes, but few in vivo applications have been demonstrated. We modified the protocol for the fabrication of pH sensing PEBBLEs and developed a protocol for the utilization of these sensors for the monitoring of dynamic pH changes in the endosomes of slime mold Dictyostelium discoideum (D. discoideum. Oregon Green 514-CdSe Quantum Dot PEBBLEs were used to measure real-time pH inside D. discoideum endosomes during cAMP stimulation. Endosomal pH was shown to decrease during cAMP signaling, demonstrating a movement of protons into the endosomes of D. discoideum amoebae.

Arachidonic acid is a chemoattractant for Dictyostelium discoideum ...

Indian Academy of Sciences (India)

SEARCHU

binding proteins and calmodulin-dependent phosphorylation linked to calmodulin-dependent chemotaxis to folic and cAMP in Dictyostelium; Cell Signal 13 575–584. Gerisch G and Hess B 1974 Cyclic-AMP-controlled oscillations in suspended Dictyostelium cells: Their relation to morphogenetic cell interactions; Proc. Natl.

Partial genetic suppression of a loss-of-function mutant of the neuronal ceroid lipofuscinosis-associated protease TPP1 in Dictyostelium discoideum

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Jonathan E. Phillips

2015-02-01

Full Text Available Neuronal ceroid lipofuscinosis (NCL is the most common childhood-onset neurodegenerative disease. NCL is inevitably fatal, and there is currently no treatment available. Children with NCL show a progressive decline in movement, vision and mental abilities, and an accumulation of autofluorescent deposits in neurons and other cell types. Late-infantile NCL is caused by mutations in the lysosomal protease tripeptidyl peptidase 1 (TPP1. TPP1 cleaves tripeptides from the N-terminus of proteins in vitro, but little is known about the physiological function of TPP1. TPP1 shows wide conservation in vertebrates but it is not found in Drosophila, Caenorhabditis elegans or Saccharomyces cerevisiae. Here, we characterize ddTpp1, a TPP1 ortholog present in the social amoeba Dictyostelium discoideum. Lysates from cells lacking ddTpp1 show a reduced but not abolished ability to cleave a TPP1 substrate, suggesting that other Dictyostelium enzymes can perform this cleavage. ddTpp1 and human TPP1 localize to the lysosome in Dictyostelium, indicating conserved function and trafficking. Cells that lack ddTpp1 show precocious multicellular development and a reduced ability to form spores during development. When cultured in autophagy-stimulating conditions, cells lacking ddTpp1 rapidly decrease in size and are less viable than wild-type cells, suggesting that one function of ddTpp1 could be to limit autophagy. Cells that lack ddTpp1 exhibit strongly impaired development in the presence of the lysosome-perturbing drug chloroquine, and this phenotype can be suppressed through a secondary mutation in the gene that we name suppressor of tpp1− A (stpA, which encodes a protein with some similarity to mammalian oxysterol-binding proteins (OSBPs. Taken together, these results suggest that targeting specific proteins could be a viable way to suppress the effects of loss of TPP1 function.

Infection and Proliferation of Giant Viruses in Amoeba Cells.

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Takemura, Masaharu

2016-01-01

Acanthamoeba polyphaga mimivirus, the first discovered giant virus with genome size and particle size much larger than previously discovered viruses, possesses several genes for translation and CRISPER Cas system-like defense mechanism against virophages, which co-infect amoeba cells with the giant virus and which inhibit giant virus proliferation. Mimiviruses infect amoeba cells by phagocytosis and release their DNA into amoeba cytoplasm through their stargate structure. After infection, giant virion factories (VFs) form in amoeba cytoplasm, followed by DNA replication and particle formation at peripheral regions of VF. Marseilleviruses, the smallest giant viruses, infect amoeba cells by phagocytosis or endocytosis, form larger VF than Mimivirus's VF in amoeba cytoplasm, and replicate their particles. Pandoraviruses found in 2013 have the largest genome size and particle size among all viruses ever found. Pandoraviruses infect amoeba cells by phagocytosis and release their DNA into amoeba cytoplasm through their mouth-like apical pores. The proliferation of Pandoraviruses occurs along with nucleus disruption. New virions form at the periphery of the region formerly occupied by the amoeba cell nucleus.

Evidence for nucleolar subcompartments in Dictyostelium

International Nuclear Information System (INIS)

Catalano, Andrew; O’Day, Danton H.

2015-01-01

Highlights: • Two nucleolar subcompartments (NoSC1, NoSC2) were found in Dictyostelium. • Specific nucleolar proteins localize to different nucleolar subcompartments. • Specific proteins exit NoSC1 and NoSC2 differently upon Actinomycin D treatment. • KRKR appears to function as an NoSC2 nucleolar subcompartment localization signal. - Abstract: The nucleolus is a multifunctional nuclear compartment usually consisting of two to three subcompartments which represent stages of ribosomal biogenesis. It is linked to several human diseases including viral infections, cancer, and neurodegeneration. Dictyostelium is a model eukaryote for the study of fundamental biological processes as well as several human diseases however comparatively little is known about its nucleolus. Unlike most nucleoli it does not possess visible subcompartments at the ultrastructural level. Several recently identified nucleolar proteins in Dictyostelium leave the nucleolus after treatment with the rDNA transcription inhibitor actinomycin-D (AM-D). Different proteins exit in different ways, suggesting that previously unidentified nucleolar subcompartments may exist. The identification of nucleolar subcompartments would help to better understand the nucleolus in this model eukaryote. Here, we show that Dictyostelium nucleolar proteins nucleomorphin isoform NumA1 and Bud31 localize throughout the entire nucleolus while calcium-binding protein 4a localizes to only a portion, representing nucleolar subcompartment 1 (NoSC1). SWI/SNF complex member Snf12 localizes to a smaller area within NoSC1 representing a second nucleolar subcompartment, NoSC2. The nuclear/nucleolar localization signal KRKR from Snf12 localized GFP to NoSC2, and thus also appears to function as a nucleolar subcompartment localization signal. FhkA localizes to the nucleolar periphery displaying a similar pattern to that of Hsp32. Similarities between the redistribution patterns of Dictyostelium nucleolar proteins during

Evidence for nucleolar subcompartments in Dictyostelium

Energy Technology Data Exchange (ETDEWEB)

Catalano, Andrew, E-mail: acatalano@ccny.cuny.edu [Department of Biology, University of Toronto at Mississauga, 3359 Mississauga Rd. N., Mississauga, Ontario L5L 1C6 (Canada); O’Day, Danton H., E-mail: danton.oday@utoronto.ca [Department of Biology, University of Toronto at Mississauga, 3359 Mississauga Rd. N., Mississauga, Ontario L5L 1C6 (Canada); Department of Cell and Systems Biology, University of Toronto, 25 Harbord St., Toronto, Ontario M5S 3G5 (Canada)

2015-01-24

Highlights: • Two nucleolar subcompartments (NoSC1, NoSC2) were found in Dictyostelium. • Specific nucleolar proteins localize to different nucleolar subcompartments. • Specific proteins exit NoSC1 and NoSC2 differently upon Actinomycin D treatment. • KRKR appears to function as an NoSC2 nucleolar subcompartment localization signal. - Abstract: The nucleolus is a multifunctional nuclear compartment usually consisting of two to three subcompartments which represent stages of ribosomal biogenesis. It is linked to several human diseases including viral infections, cancer, and neurodegeneration. Dictyostelium is a model eukaryote for the study of fundamental biological processes as well as several human diseases however comparatively little is known about its nucleolus. Unlike most nucleoli it does not possess visible subcompartments at the ultrastructural level. Several recently identified nucleolar proteins in Dictyostelium leave the nucleolus after treatment with the rDNA transcription inhibitor actinomycin-D (AM-D). Different proteins exit in different ways, suggesting that previously unidentified nucleolar subcompartments may exist. The identification of nucleolar subcompartments would help to better understand the nucleolus in this model eukaryote. Here, we show that Dictyostelium nucleolar proteins nucleomorphin isoform NumA1 and Bud31 localize throughout the entire nucleolus while calcium-binding protein 4a localizes to only a portion, representing nucleolar subcompartment 1 (NoSC1). SWI/SNF complex member Snf12 localizes to a smaller area within NoSC1 representing a second nucleolar subcompartment, NoSC2. The nuclear/nucleolar localization signal KRKR from Snf12 localized GFP to NoSC2, and thus also appears to function as a nucleolar subcompartment localization signal. FhkA localizes to the nucleolar periphery displaying a similar pattern to that of Hsp32. Similarities between the redistribution patterns of Dictyostelium nucleolar proteins during

Mechano-chemical signaling maintains the rapid movement of Dictyostelium cells

International Nuclear Information System (INIS)

Lombardi, M.L.; Knecht, D.A.; Lee, J.

2008-01-01

The survival of Dictyostelium cells depends on their ability to efficiently chemotax, either towards food or to form multicellular aggregates. Although the involvement of Ca 2+ signaling during chemotaxis is well known, it is not clear how this regulates cell movement. Previously, fish epithelial keratocytes have been shown to display transient increases in intracellular calcium ([Ca 2+ ] i ) that are mediated by stretch-activated calcium channels (SACs), which play a role in retraction of the cell body [J. Lee, A. Ishihara, G. Oxford, B. Johnson, and K. Jacobson, Regulation of cell movement is mediated by stretch-activated calcium channels. Nature, 1999. 400(6742): p. 382-6.]. To investigate the involvement of SACs in Dictyostelium movement we performed high resolution calcium imaging in wild-type (NC4A2) Dictyostelium cells to detect changes in [Ca 2+ ] i . We observed small, brief, Ca 2+ transients in randomly moving wild-type cells that were dependent on both intracellular and extracellular sources of calcium. Treatment of cells with the SAC blocker gadolinium (Gd 3+ ) inhibited transients and decreased cell speed, consistent with the involvement of SACs in regulating Dictyostelium motility. Additional support for SAC activity was given by the increase in frequency of Ca 2+ transients when Dictyostelium cells were moving on a more adhesive substratum or when they were mechanically stretched. We conclude that mechano-chemical signaling via SACs plays a major role in maintaining the rapid movement of Dictyostelium cells

Amoeba/amoebal symbiont genetic transfers: lessons from giant virus neighbours.

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Thomas, Vincent; Greub, Gilbert

2010-01-01

Free-living amoebae serve as hosts for a variety of amoebae-resisting microorganisms, including giant viruses and certain bacteria. The latter include symbiotic bacteria as well as bacteria exhibiting a pathogenic phenotype towards amoebae. Amoebae-resisting bacteria have been shown to be widespread in water and to use the amoebae as a reservoir, a replication niche, a protective armour as well as a training ground to select virulence traits allowing survival in the face of microbicidal effects of macrophages, the first line of defense against invading pathogens. More importantly, amoebae play a significant role as a melting pot for genetic exchanges. These ecological and evolutionary roles of amoebae might also be at play for giant viruses and knowledge derived from the study of amoebae-resisting bacteria is useful for the study and understanding of interactions between amoebae and giant viruses. This is especially important since some genes have spread in all domains of life and the exponential availability of eukaryotic genomes and metagenomic sequences will allow researchers to explore these genetic exchanges in a more comprehensive way, thus completely changing our perception of the evolutionary history of organisms. Thus, a large part of this review is dedicated to report current known gene exchanges between the different amoebae-resisting organisms and between amoebae and the internalized bacteria. Copyright 2010 S. Karger AG, Basel.

Lack of incorporation of tritiated uridine by nuclei of mature sieve elements in Metasequoia glyptostroboides and Sequoiadendron giganteum.

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Hébant, C

1975-01-01

The majority of nuclei which persist in "mature" sieve elements of Metasequoia glyptostroboides Hu and Chen and Sequoiadendron giganteum Buchholz fail to incorporate tritiated uridine (10 μCi/ml; 7 hours incubation of stem fragments). This is interpreted as further evidence for the degenerated condition of these nuclei.

Culture growth of testate amoebae under different silicon concentrations.

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Wanner, Manfred; Seidl-Lampa, Barbara; Höhn, Axel; Puppe, Daniel; Meisterfeld, Ralf; Sommer, Michael

2016-10-01

Testate amoebae with self-secreted siliceous shell platelets ("idiosomes") play an important role in terrestrial silicon (Si) cycles. In this context, Si-dependent culture growth dynamics of idiosomic testate amoebae are of interest. Clonal cultures of idiosomic testate amoebae were analyzed under three different Si concentrations: low (50μmolL -1 ), moderate/site-specific (150μmolL -1 ) and high Si supply (500μmolL -1 ). Food (Saccharomyces cerevisiae) was provided in surplus. (i) Shell size of four different clones of idiosomic testate amoebae either decreased (Trinema galeata, Euglypha filifera cf.), increased (E. rotunda cf.), or did not change (E. rotunda) under the lowest Si concentration (50μmolSiL -1 ). (ii) Culture growth of idiosomic Euglypha rotunda was dependent on Si concentration. The more Si available in the culture medium, the earlier the entry into exponential growth phase. (iii) Culture growth of idiosomic Euglypha rotunda was dependent on origin of inoculum. Amoebae previously cultured under a moderate Si concentration revealed highest sustainability in consecutive cultures. Amoebae derived from cultures with high Si concentrations showed rapid culture growth which finished early in consecutive cultures. (iv) Si (diluted in the culture medium) was absorbed by amoebae and fixed in the amoeba shells resulting in decreased Si concentrations. Copyright © 2016 Elsevier GmbH. All rights reserved.

Variation, sex, and social cooperation: molecular population genetics of the social amoeba Dictyostelium discoideum.

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Jonathan M Flowers

2010-07-01

Full Text Available Dictyostelium discoideum is a eukaryotic microbial model system for multicellular development, cell-cell signaling, and social behavior. Key models of social evolution require an understanding of genetic relationships between individuals across the genome or possibly at specific genes, but the nature of variation within D. discoideum is largely unknown. We re-sequenced 137 gene fragments in wild North American strains of D. discoideum and examined the levels and patterns of nucleotide variation in this social microbial species. We observe surprisingly low levels of nucleotide variation in D. discoideum across these strains, with a mean nucleotide diversity (pi of 0.08%, and no strong population stratification among North American strains. We also do not find any clear relationship between nucleotide divergence between strains and levels of social dominance and kin discrimination. Kin discrimination experiments, however, show that strains collected from the same location show greater ability to distinguish self from non-self than do strains from different geographic areas. This suggests that a greater ability to recognize self versus non-self may arise among strains that are more likely to encounter each other in nature, which would lead to preferential formation of fruiting bodies with clonemates and may prevent the evolution of cheating behaviors within D. discoideum populations. Finally, despite the fact that sex has rarely been observed in this species, we document a rapid decay of linkage disequilibrium between SNPs, the presence of recombinant genotypes among natural strains, and high estimates of the population recombination parameter rho. The SNP data indicate that recombination is widespread within D. discoideum and that sex as a form of social interaction is likely to be an important aspect of the life cycle.

Revised Parameters for the AMOEBA Polarizable Atomic Multipole Water Model

Science.gov (United States)

Pande, Vijay S.; Head-Gordon, Teresa; Ponder, Jay W.

2016-01-01

A set of improved parameters for the AMOEBA polarizable atomic multipole water model is developed. The protocol uses an automated procedure, ForceBalance, to adjust model parameters to enforce agreement with ab initio-derived results for water clusters and experimentally obtained data for a variety of liquid phase properties across a broad temperature range. The values reported here for the new AMOEBA14 water model represent a substantial improvement over the previous AMOEBA03 model. The new AMOEBA14 water model accurately predicts the temperature of maximum density and qualitatively matches the experimental density curve across temperatures ranging from 249 K to 373 K. Excellent agreement is observed for the AMOEBA14 model in comparison to a variety of experimental properties as a function of temperature, including the 2nd virial coefficient, enthalpy of vaporization, isothermal compressibility, thermal expansion coefficient and dielectric constant. The viscosity, self-diffusion constant and surface tension are also well reproduced. In comparison to high-level ab initio results for clusters of 2 to 20 water molecules, the AMOEBA14 model yields results similar to the AMOEBA03 and the direct polarization iAMOEBA models. With advances in computing power, calibration data, and optimization techniques, we recommend the use of the AMOEBA14 water model for future studies employing a polarizable water model. PMID:25683601

Palaeoecology of testate amoebae in a tropical peatland.

Science.gov (United States)

Swindles, Graeme T; Lamentowicz, Mariusz; Reczuga, Monika; Galloway, Jennifer M

2016-09-01

We present the first detailed analysis of subfossil testate amoebae from a tropical peatland. Testate amoebae were analysed in a 4-m peat core from western Amazonia (Peru) and a transfer function developed from the site was applied to reconstruct changes in water table over the past ca. 8,000 years. Testate amoebae were in very low abundance in the core, especially in the lower 125cm, due to a combination of poor preservation and obscuration by other organic matter. A modified preparation method enabled at least 50 testate amoebae to be counted in each core sample. The most abundant taxa preserved include Centropyxis aculeata, Hyalosphenia subflava, Phryganella acropodia and Trigonopyxis arcula. Centropyxis aculeata, an unambiguous wet indicator, is variably present and indicates several phases of near-surface water table. Our work shows that even degraded, low-abundance assemblages of testate amoebae can provide useful information regarding the long-term ecohydrological developmental history of tropical peatlands. Copyright © 2015 Elsevier GmbH. All rights reserved.

Evaluating Different Virulence Traits of Klebsiella pneumoniae Using Dictyostelium discoideum and Zebrafish Larvae as Host Models

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Andrés E. Marcoleta

2018-02-01

Full Text Available Multiresistant and invasive hypervirulent Klebsiella pneumoniae strains have become one of the most urgent bacterial pathogen threats. Recent analyses revealed a high genomic plasticity of this species, harboring a variety of mobile genetic elements associated with virulent strains, encoding proteins of unknown function whose possible role in pathogenesis have not been addressed. K. pneumoniae virulence has been studied mainly in animal models such as mice and pigs, however, practical, financial, ethical and methodological issues limit the use of mammal hosts. Consequently, the development of simple and cost-effective experimental approaches with alternative host models is needed. In this work we described the use of both, the social amoeba and professional phagocyte Dictyostelium discoideum and the fish Danio rerio (zebrafish as surrogate host models to study K. pneumoniae virulence. We compared three K. pneumoniae clinical isolates evaluating their resistance to phagocytosis, intracellular survival, lethality, intestinal colonization, and innate immune cells recruitment. Optical transparency of both host models permitted studying the infective process in vivo, following the Klebsiella-host interactions through live-cell imaging. We demonstrated that K. pneumoniae RYC492, but not the multiresistant strains 700603 and BAA-1705, is virulent to both host models and elicits a strong immune response. Moreover, this strain showed a high resistance to phagocytosis by D. discoideum, an increased ability to form biofilms and a more prominent and irregular capsule. Besides, the strain 700603 showed the unique ability to replicate inside amoeba cells. Genomic comparison of the K. pneumoniae strains showed that the RYC492 strain has a higher overall content of virulence factors although no specific genes could be linked to its phagocytosis resistance, nor to the intracellular survival observed for the 700603 strain. Our results indicate that both zebrafish

Myosin-II sets the optimal response time scale of chemotactic amoeba

Science.gov (United States)

Hsu, Hsin-Fang; Westendorf, Christian; Tarantola, Marco; Bodenschatz, Eberhard; Beta, Carsten

2014-03-01

The response dynamics of the actin cytoskeleton to external chemical stimuli plays a fundamental role in numerous cellular functions. One of the key players that governs the dynamics of the actin network is the motor protein myosin-II. Here we investigate the role of myosin-II in the response of the actin system to external stimuli. We used a microfluidic device in combination with a photoactivatable chemoattractant to apply stimuli to individual cells with high temporal resolution. We directly compare the actin dynamics in Dictyostelium discodelium wild type (WT) cells to a knockout mutant that is deficient in myosin-II (MNL). Similar to the WT a small population of MNL cells showed self-sustained oscillations even in absence of external stimuli. The actin response of MNL cells to a short pulse of chemoattractant resembles WT during the first 15 sec but is significantly delayed afterward. The amplitude of the dominant peak in the power spectrum from the response time series of MNL cells to periodic stimuli with varying period showed a clear resonance peak at a forcing period of 36 sec, which is significantly delayed as compared to the resonance at 20 sec found for the WT. This shift indicates an important role of myosin-II in setting the response time scale of motile amoeba. Institute of Physics und Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany.

Structural and functional studies of a family of Dictyostelium discoideum developmentally regulated, prestalk genes coding for small proteins

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Escalante Ricardo

2008-01-01

Full Text Available Abstract Background The social amoeba Dictyostelium discoideum executes a multicellular development program upon starvation. This morphogenetic process requires the differential regulation of a large number of genes and is coordinated by extracellular signals. The MADS-box transcription factor SrfA is required for several stages of development, including slug migration and spore terminal differentiation. Results Subtractive hybridization allowed the isolation of a gene, sigN (SrfA-induced gene N, that was dependent on the transcription factor SrfA for expression at the slug stage of development. Homology searches detected the existence of a large family of sigN-related genes in the Dictyostelium discoideum genome. The 13 most similar genes are grouped in two regions of chromosome 2 and have been named Group1 and Group2 sigN genes. The putative encoded proteins are 87–89 amino acids long. All these genes have a similar structure, composed of a first exon containing a 13 nucleotides long open reading frame and a second exon comprising the remaining of the putative coding region. The expression of these genes is induced at10 hours of development. Analyses of their promoter regions indicate that these genes are expressed in the prestalk region of developing structures. The addition of antibodies raised against SigN Group 2 proteins induced disintegration of multi-cellular structures at the mound stage of development. Conclusion A large family of genes coding for small proteins has been identified in D. discoideum. Two groups of very similar genes from this family have been shown to be specifically expressed in prestalk cells during development. Functional studies using antibodies raised against Group 2 SigN proteins indicate that these genes could play a role during multicellular development.

Effects of Nickel, Chlorpyrifos and Their Mixture on the Dictyostelium discoideum Proteome

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Boatti, Lara; Robotti, Elisa; Marengo, Emilio; Viarengo, Aldo; Marsano, Francesco

2012-01-01

Mixtures of chemicals can have additive, synergistic or antagonistic interactions. We investigated the effects of the exposure to nickel, the organophosphate insecticide chlorpyrifos at effect concentrations (EC) of 25% and 50% and their binary mixture (Ec25 + EC25) on Dictyostelium discoideum amoebae based on lysosomal membrane stability (LMS). We treated D. discoideum with these compounds under controlled laboratory conditions and evaluated the changes in protein levels using a two-dimensional gel electrophoresis (2DE) proteomic approach. Nickel treatment at EC25 induced changes in 14 protein spots, 12 of which were down-regulated. Treatment with nickel at EC50 resulted in changes in 15 spots, 10 of which were down-regulated. Treatment with chlorpyrifos at EC25 induced changes in six spots, all of which were down-regulated; treatment with chlorpyrifos at EC50 induced changes in 13 spots, five of which were down-regulated. The mixture corresponding to EC25 of each compound induced changes in 19 spots, 13 of which were down-regulated. The data together reveal that a different protein expression signature exists for each treatment, and that only a few proteins are modulated in multiple different treatments. For a simple binary mixture, the proteomic response does not allow for the identification of each toxicant. The protein spots that showed significant differences were identified by mass spectrometry, which revealed modulations of proteins involved in metal detoxification, stress adaptation, the oxidative stress response and other cellular processes. PMID:23443088

Surveillance of parasitic Legionella in surface waters by using immunomagnetic separation and amoebae enrichment.

Science.gov (United States)

Hsu, Tsui-Kang; Wu, Shu-Fen; Hsu, Bing-Mu; Kao, Po-Min; Tao, Chi-Wei; Shen, Shu-Min; Ji, Wen-Tsai; Huang, Wen-Chien; Fan, Cheng-Wei

2015-01-01

Free-living amoebae (FLA) are potential reservoirs of Legionella in aquatic environments. However, the parasitic relationship between various Legionella and amoebae remains unclear. In this study, surface water samples were gathered from two rivers for evaluating parasitic Legionella. Warmer water temperature is critical to the existence of Legionella. This result suggests that amoebae may be helpful in maintaining Legionella in natural environments because warmer temperatures could enhance parasitisation of Legionella in amoebae. We next used immunomagnetic separation (IMS) to identify extracellular Legionella and remove most free Legionella before detecting the parasitic ones in selectively enriched amoebae. Legionella pneumophila was detected in all the approaches, confirming that the pathogen is a facultative amoebae parasite. By contrast, two obligate amoebae parasites, Legionella-like amoebal pathogens (LLAPs) 8 and 9, were detected only in enriched amoebae. However, several uncultured Legionella were detected only in the extracellular samples. Because the presence of potential hosts, namely Vermamoeba vermiformis, Acanthamoeba spp. and Naegleria gruberi, was confirmed in the samples that contained intracellular Legionella, uncultured Legionella may survive independently of amoebae. Immunomagnetic separation and amoebae enrichment may have referential value for detecting parasitic Legionella in surface waters.

A new social gene in Dictyostelium discoideum, chtB

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Santorelli Lorenzo A

2013-01-01

Full Text Available Abstract Background Competitive social interactions are ubiquitous in nature, but their genetic basis is difficult to determine. Much can be learned from single gene knockouts in a eukaryote microbe. The mutants can be competed with the parent to discern the social impact of that specific gene. Dictyostelium discoideum is a social amoeba that exhibits cooperative behavior in the construction of a multicellular fruiting body. It is a good model organism to study the genetic basis of cooperation since it has a sequenced genome and it is amenable to genetic manipulation. When two strains of D. discoideum are mixed, a cheater strain can exploit its social partner by differentiating more spore than its fair share relative to stalk cells. Cheater strains can be generated in the lab or found in the wild and genetic analyses have shown that cheating behavior can be achieved through many pathways. Results We have characterized the knockout mutant chtB, which was isolated from a screen for cheater mutants that were also able to form normal fruiting bodies on their own. When mixed in equal proportions with parental strain cells, chtB mutants contributed almost 60% of the total number of spores. To do so, chtB cells inhibit wild type cells from becoming spores, as indicated by counts and by the wild type cells’ reduced expression of the prespore gene, cotB. We found no obvious fitness costs (morphology, doubling time in liquid medium, spore production, and germination efficiency associated with the cheating ability of the chtB knockout. Conclusions In this study we describe a new gene in D. discoideum, chtB, which when knocked out inhibits the parental strain from producing spores. Moreover, under lab conditions, we did not detect any fitness costs associated with this behavior.

Amoeba: a distributed operating system for the 1990s

NARCIS (Netherlands)

Mullender, Sape J.; van Rossum, Guido; Tanenbaum, Andrew S.; van Renesse, Robbert; van Staveren, Hans

A description is given of the Amoeba distributed operating system, which appears to users as a centralized system but has the speed, fault tolerance, security safeguards, and flexibility required for the 1990s. The Amoeba software is based on objects. Objects are managed by server processes and

Amoeba: A Distributed Operating System for the 1990s

NARCIS (Netherlands)

Mullender, S.J.; van Rossum, G.; Tanenbaum, A.S.; van Renesse, R.; van Staveren, H.

1990-01-01

A description is given of the Amoeba distributed operating system, which appears to users as a centralized system but has the speed, fault tolerance, security safeguards, and flexibility required for the 1990s. The Amoeba software is based on objects. Objects are managed by server processes and

Phospholipase Cδ regulates germination of Dictyostelium spores

NARCIS (Netherlands)

Dijken, Peter van; Haastert, Peter J.M. van

2001-01-01

Background: Many eukaryotes, including plants and fungi make spores that resist severe environmental stress. The micro-organism Dictyostelium contains a single phospholipase C gene (PLC); deletion of the gene has no effect on growth, cell movement and differentiation. In this report we show that PLC

Dispatch. Dictyostelium chemotaxis: fascism through the back door?

Science.gov (United States)

Insall, Robert

2003-04-29

Aggregating Dictyostelium cells secrete cyclic AMP to attract their neighbours by chemotaxis. It has now been shown that adenylyl cyclase is enriched in the rear of cells, and this localisation is required for normal aggregation.

Chemotaxis of Dictyostelium discoideum: Collective Oscillation of Cellular Contacts

Science.gov (United States)

Schäfer, Edith; Tarantola, Marco; Polo, Elena; Westendorf, Christian; Oikawa, Noriko; Bodenschatz, Eberhard; Geil, Burkhard; Janshoff, Andreas

2013-01-01

Chemotactic responses of Dictyostelium discoideum cells to periodic self-generated signals of extracellular cAMP comprise a large number of intricate morphological changes on different length scales. Here, we scrutinized chemotaxis of single Dictyostelium discoideum cells under conditions of starvation using a variety of optical, electrical and acoustic methods. Amebas were seeded on gold electrodes displaying impedance oscillations that were simultaneously analyzed by optical video microscopy to relate synchronous changes in cell density, morphology, and distance from the surface to the transient impedance signal. We found that starved amebas periodically reduce their overall distance from the surface producing a larger impedance and higher total fluorescence intensity in total internal reflection fluorescence microscopy. Therefore, we propose that the dominant sources of the observed impedance oscillations observed on electric cell-substrate impedance sensing electrodes are periodic changes of the overall cell-substrate distance of a cell. These synchronous changes of the cell-electrode distance were also observed in the oscillating signal of acoustic resonators covered with amebas. We also found that periodic cell-cell aggregation into transient clusters correlates with changes in the cell-substrate distance and might also contribute to the impedance signal. It turned out that cell-cell contacts as well as cell-substrate contacts form synchronously during chemotaxis of Dictyostelium discoideum cells. PMID:23349816

Diversity and community ecology of forest epiphyte testate amoebae from European Russia.

Science.gov (United States)

Payne, Richard J; Belyakova, Olga; Mazei, Yuri

2015-10-01

Testate amoebae are an abundant group of microorganisms which make a significant contribution to the diversity of protist life. Most of the world's potential habitats for testate amoebae have been barely studied and when such places are investigated they frequently reveal novel communities and species. Here we consider the testate amoeba communities associated with boreal forest epiphytes (mosses and lichens); an environment which we argue has been under-researched. We present a dataset of 165 samples from four regions of western Russia and analyse these data in relation to micro-habitat position and selected environmental data. The testate amoebae of epiphytes are abundant but dominated by ubiquitous species. We show that there are trends toward a lower species richness and test concentration with greater elevation on the trunk and in lichens compared to mosses. There are considerable differences in community composition between sampling regions. Of all measured environmental variables only moisture content showed a significant relationship with testate amoeba community structure. Our data highlight how little is known about testate amoeba communities of this habitat and call for greater research efforts, particularly in less-studied regions and biomes. Copyright © 2015 Elsevier GmbH. All rights reserved.

Amoeba-related health risk in drinking water systems: could monitoring of amoebae be a complementary approach to current quality control strategies?

Science.gov (United States)

Codony, Francesc; Pérez, Leonardo Martín; Adrados, Bárbara; Agustí, Gemma; Fittipaldi, Mariana; Morató, Jordi

2012-01-01

Culture-based methods for fecal indicator microorganisms are the standard protocol to assess potential health risk from drinking water systems. However, these traditional fecal indicators are inappropriate surrogates for disinfection-resistant fecal pathogens and the indigenous pathogens that grow in drinking water systems. There is now a range of molecular-based methods, such as quantitative PCR, which allow detection of a variety of pathogens and alternative indicators. Hence, in addition to targeting total Escherichia coli (i.e., dead and alive) for the detection of fecal pollution, various amoebae may be suitable to indicate the potential presence of pathogenic amoeba-resisting microorganisms, such as Legionellae. Therefore, monitoring amoeba levels by quantitative PCR could be a useful tool for directly and indirectly evaluating health risk and could also be a complementary approach to current microbial quality control strategies for drinking water systems.

Chemotaxis of Dictyostelium discoideum: collective oscillation of cellular contacts.

Directory of Open Access Journals (Sweden)

Edith Schäfer

Full Text Available Chemotactic responses of Dictyostelium discoideum cells to periodic self-generated signals of extracellular cAMP comprise a large number of intricate morphological changes on different length scales. Here, we scrutinized chemotaxis of single Dictyostelium discoideum cells under conditions of starvation using a variety of optical, electrical and acoustic methods. Amebas were seeded on gold electrodes displaying impedance oscillations that were simultaneously analyzed by optical video microscopy to relate synchronous changes in cell density, morphology, and distance from the surface to the transient impedance signal. We found that starved amebas periodically reduce their overall distance from the surface producing a larger impedance and higher total fluorescence intensity in total internal reflection fluorescence microscopy. Therefore, we propose that the dominant sources of the observed impedance oscillations observed on electric cell-substrate impedance sensing electrodes are periodic changes of the overall cell-substrate distance of a cell. These synchronous changes of the cell-electrode distance were also observed in the oscillating signal of acoustic resonators covered with amebas. We also found that periodic cell-cell aggregation into transient clusters correlates with changes in the cell-substrate distance and might also contribute to the impedance signal. It turned out that cell-cell contacts as well as cell-substrate contacts form synchronously during chemotaxis of Dictyostelium discoideum cells.

Detection and identification of free-living amoeba from aquatic environment in Taiwan

Science.gov (United States)

Jiun Tzeng, Kai; Che Tung, Min; Hsu, Bing Mu; Tsai, Hsiu Feng; Huang, Po Hsiang; Hao Huang, Kuan; Kao, Po Min; Shen, Shu Min; Chen, Jung Sheng

2013-04-01

Free-living amoebae including Acanthamoeba, Naegleria, Balamuthia and Hartmannella are widely distributed in water, soil, and air. They can infect humans and can lead to serious illness even death. The aim of this study is to investigate the presence of free-living amoebae from aquatic environment in Taiwan, and to compare the differences between Acanthamoeba and Naegleria in different cultivation methods and conditions. In this study, we used molecular method with specific primers by Polymerase Chain Reaction (PCR) to amplify and to analyze the occurrence of free-living amoebae in aquatic environment. We collected 92 samples from environmental water in Taiwan. The results show that 33 water samples (35.9%) and 11 water samples (12.0%) were detected positive for Acanthamoeba and Naegleria, respectively. Furthermore, both Acanthamoeba and Naegleria can be cultured by PYG in 30° C, but not all free-living amoebae can be enriched and isolated by using storage-cultivation method. Due to the presence of Acanthamoeba and Naegleria in aquatic environment, the water quality monitoring should be more conscious. Keywords: free-living amoebae; Acanthamoeba; Naegleria; Balamuthia; Hartmannella; PCR

Raman spectroscopic study on the excystation process in a single unicellular organism amoeba (Acanthamoeba polyphaga)

Science.gov (United States)

Lin, Yu-Chung; Perevedentseva, Elena; Cheng, Chia-Liang

2015-05-01

An in vivo Raman spectroscopic study of amoeba (Acanthamoeba polyphaga) is presented. The changes of the spectra during the amoeba cyst activation and excystation are analyzed. The spectra show the changes of the relative intensities of bands corresponding to protein, lipid, and carotenoid components during cyst activation. The presence of carotenoids in the amoeba is observed via characteristic Raman bands. These signals in the Raman spectra are intense in cysts but decrease in intensity with cyst activation and exhibit a correlation with the life cycle of amoeba. This work demonstrates the feasibility of using Raman spectroscopy for the detection of single amoeba microorganisms in vivo and for the analysis of the amoeba life activity. The information obtained may have implications for the estimation of epidemiological situations and for the diagnostics and prognosis of the development of amoebic inflammations.

Checklist, diversity and distribution of testate amoebae in Chile.

Science.gov (United States)

Fernández, Leonardo D; Lara, Enrique; Mitchell, Edward A D

2015-10-01

Bringing together more than 170 years of data, this study represents the first attempt to construct a species checklist and analyze the diversity and distribution of testate amoebae in Chile, a country that encompasses the southwestern region of South America, countless islands and part of the Antarctic. In Chile, known diversity includes 416 testate amoeba taxa (64 genera, 352 infrageneric taxa), 24 of which are here reported for the first time. Species-accumulation plots show that in Chile, the number of testate amoeba species reported has been continually increasing since the mid-19th century without leveling off. Testate amoebae have been recorded in 37 different habitats, though they are more diverse in peatlands and rainforest soils. Only 11% of species are widespread in continental Chile, while the remaining 89% of the species exhibit medium or short latitudinal distribution ranges. Also, species composition of insular Chile and the Chilean Antarctic territory is a depauperated subset of that found in continental Chile. Nearly, the 10% of the species reported here are endemic to Chile and many of them are distributed only within the so-called Chilean biodiversity hotspot (ca. 25° S-47° S). These findings are here thoroughly discussed in a biogeographical and evolutionary context. Copyright © 2015 Elsevier GmbH. All rights reserved.

Amoebae and other protozoa in material samples from moisture-damaged buildings

International Nuclear Information System (INIS)

Yli-Pirilae, T.; Kusnetsov, Jaana; Haatainen, Susanna; Haenninen, Marja; Jalava, Pasi; Reiman, Marjut; Seuri, Markku; Hirvonen, Maija-Riitta; Nevalainen, Aino

2004-01-01

Mold growth in buildings has been shown to be associated with adverse health effects. The fungal and bacterial growth on moistened building materials has been studied, but little attention has been paid to the other organisms spawning in the damaged materials. We examined moist building materials for protozoa, concentrating on amoebae. Material samples (n=124) from moisture-damaged buildings were analyzed for amoebae, fungi, and bacteria. Amoebae were detected in 22% of the samples, and they were found to favor cooccurrence with bacteria and the fungi Acremonium spp., Aspergillus versicolor, Chaetomium spp., and Trichoderma spp. In addition, 11 seriously damaged samples were screened for other protozoa. Ciliates and flagellates were found in almost every sample analyzed. Amoebae are known to host pathogenic bacteria, such as chlamydiae, legionellae, and mycobacteria and they may have a role in the complex of exposure that contributes to the health effects associated with moisture damage in buildings

Characterization of two unusual guanylyl cyclases from Dictyostelium

NARCIS (Netherlands)

Roelofs, Jeroen; Haastert, Peter J.M. van

2002-01-01

Guanylyl cyclase A (GCA) and soluble guanylyl cyclase (sGC) encode GCs in Dictyostelium and have a topology similar to 12-transmembrane and soluble adenylyl cyclase, respectively. We demonstrate that all detectable GC activity is lost in a cell line in which both genes have been inactivated. Cell

Arachidonic acid is a chemoattractant for Dictyostelium discoideum

Indian Academy of Sciences (India)

Arachidonic acid is a chemoattractant for Dictyostelium discoideum cells ... Arachidonic acid; chemotaxis; fatty acids; iplA ... Previously, we have shown that arachidonic acid (AA) induces an increase in the cytosolic Ca2+ concentration by causing the release of Ca2+ from intracellular stores and activating influx of ...

Occurrence of Infected Free-Living Amoebae in Cooling Towers of Southern Brazil.

Science.gov (United States)

Soares, Scheila S; Souza, Thamires K; Berté, Francisco K; Cantarelli, Vlademir V; Rott, Marilise B

2017-12-01

This study determined the occurrence of potentially pathogenic free-living amoebae (FLA) and bacteria associated with amoebae in air-conditioning cooling towers in southern Brazil. Water samples were collected from 36 cooling systems from air-conditioning in the state of Rio Grande do Sul, Brazil. The organisms were identified using polymerase chain reaction (PCR) and sequencing automated. The results showed that these aquatic environments, with variable temperature, are potential "hot spots" for emerging human pathogens like free-living amoebae and bacteria associated. In total, 92% of the cooling-tower samples analyzed were positive for FLA, and Acanthamoeba was the dominant genus by culture and PCR. Amoebal isolates revealed intracellular bacteria in 39.3% of them and all were confirmed as members of the genus Pseudomonas. The results obtained show the important role of cooling towers as a source of amoebae-associated pathogens.

Calcium regulates the expression of a Dictyostelium discoideum ...

Indian Academy of Sciences (India)

In a screen for calcium-regulated gene expression during growth and development of Dictyostelium discoideum we have identified an asparaginyl tRNA synthetase (ddAsnRS) gene, the second tRNA synthetase gene identified in this organism. The ddAsnRS gene shows many unique features. One, it is repressed by ...

Parasitic amoebae found in water bodies of Ukraine.

Science.gov (United States)

Patsyuk, Marina

2017-12-01

Two parasitic amoebian species are found in mollusks of the water bodies of Ukraine. Vahlkampfia sp. is found in hepatopankreas of Unio conus Spengler, 1793, and Acanthamoeba sp. is observed in mantle cavity of Viviparus viviparus Linnaeus, 1758. For these protist species, the mollusks are shown to be intermediate hosts where amoebae feed and reproduce. An experimental infection with Vahlkampfia sp. and Acanthamoeba sp. was not successful, no pathological changes in mollusks were observed. These amoebae are successfully cultured in fresh water and agar medium, hence we can safely consider them free-living. Copyright © 2017 Elsevier Inc. All rights reserved.

Contrasting species-environment relationships in communities of testate amoebae, bryophytes and vascular plants along the fen-bog gradient.

Science.gov (United States)

Lamentowicz, Mariusz; Lamentowicz, Lukasz; van der Knaap, Willem O; Gabka, Maciej; Mitchell, Edward A D

2010-04-01

We studied the vegetation, testate amoebae and abiotic variables (depth of the water table, pH, electrical conductivity, Ca and Mg concentrations of water extracted from mosses) along the bog to extremely rich fen gradient in sub-alpine peatlands of the Upper Engadine (Swiss Alps). Testate amoeba diversity was correlated to that of mosses but not of vascular plants. Diversity peaked in rich fen for testate amoebae and in extremely rich fen for mosses, while for testate amoebae and mosses it was lowest in bog but for vascular plants in extremely rich fen. Multiple factor and redundancy analyses (RDA) revealed a stronger correlation of testate amoebae than of vegetation to water table and hydrochemical variables and relatively strong correlation between testate amoeba and moss community data. In RDA, hydrochemical variables explained a higher proportion of the testate amoeba and moss data than water table depth. Abiotic variables explained a higher percentage of the species data for testate amoebae (30.3% or 19.5% for binary data) than for mosses (13.4%) and vascular plants (10%). These results show that (1) vascular plant, moss and testate amoeba communities respond differently to ecological gradients in peatlands and (2) testate amoebae are more strongly related than vascular plants to the abiotic factors at the mire surface. These differences are related to vertical trophic gradients and associated niche differentiation.

Targets downstream of Cdk8 in Dictyostelium development

Directory of Open Access Journals (Sweden)

Skelton Jason

2011-01-01

Full Text Available Abstract Background Cdk8 is a component of the mediator complex which facilitates transcription by RNA polymerase II and has been shown to play an important role in development of Dictyostelium discoideum. This eukaryote feeds as single cells but starvation triggers the formation of a multicellular organism in response to extracellular pulses of cAMP and the eventual generation of spores. Strains in which the gene encoding Cdk8 have been disrupted fail to form multicellular aggregates unless supplied with exogenous pulses of cAMP and later in development, cdk8- cells show a defect in spore production. Results Microarray analysis revealed that the cdk8- strain previously described (cdk8-HL contained genome duplications. Regeneration of the strain in a background lacking detectable gene duplication generated strains (cdk8-2 with identical defects in growth and early development, but a milder defect in spore generation, suggesting that the severity of this defect depends on the genetic background. The failure of cdk8- cells to aggregate unless rescued by exogenous pulses of cAMP is consistent with a failure to express the catalytic subunit of protein kinase A. However, overexpression of the gene encoding this protein was not sufficient to rescue the defect, suggesting that this is not the only important target for Cdk8 at this stage of development. Proteomic analysis revealed two potential targets for Cdk8 regulation, one regulated post-transcriptionally (4-hydroxyphenylpyruvate dioxygenase (HPD and one transcriptionally (short chain dehydrogenase/reductase (SDR1. Conclusions This analysis has confirmed the importance of Cdk8 at multiple stages of Dictyostelium development, although the severity of the defect in spore production depends on the genetic background. Potential targets of Cdk8-mediated gene regulation have been identified in Dictyostelium which will allow the mechanism of Cdk8 action and its role in development to be determined.

A secreted factor represses cell proliferation in Dictyostelium.

Science.gov (United States)

Brock, Debra A; Gomer, Richard H

2005-10-01

Many cells appear to secrete factors called chalones that limit their proliferation, but in most cases the factors have not been identified. We found that growing Dictyostelium cells secrete a 60 kDa protein called AprA for autocrine proliferation repressor. AprA has similarity to putative bacterial proteins of unknown function. Compared with wild-type cells, aprA-null cells proliferate faster, while AprA overexpressing cells proliferate slower. Growing wild-type cells secrete a factor that inhibits the proliferation of wild-type and aprA- cells; this activity is not secreted by aprA- cells. AprA purified by immunoprecipitation also slows the proliferation of wild-type and aprA- cells. Compared with wild type, there is a higher percentage of multinucleate cells in the aprA- population, and when starved, aprA- cells form abnormal structures that contain fewer spores. AprA may thus decrease the number of multinucleate cells and increase spore production. Together, the data suggest that AprA functions as part of a Dictyostelium chalone.

Giant Viruses of Amoebae: A Journey Through Innovative Research and Paradigm Changes.

Science.gov (United States)

Colson, Philippe; La Scola, Bernard; Raoult, Didier

2017-09-29

Giant viruses of amoebae were discovered serendipitously in 2003; they are visible via optical microscopy, making them bona fide microbes. Their lifestyle, structure, and genomes break the mold of classical viruses. Giant viruses of amoebae are complex microorganisms. Their genomes harbor between 444 and 2,544 genes, including many that are unique to viruses, and encode translation components; their virions contain >100 proteins as well as mRNAs. Mimiviruses have a specific mobilome, including virophages, provirophages, and transpovirons, and can resist virophages through a system known as MIMIVIRE (mimivirus virophage resistance element). Giant viruses of amoebae bring upheaval to the definition of viruses and tend to separate the current virosphere into two categories: very simple viruses and viruses with complexity similar to that of other microbes. This new paradigm is propitious for enhanced detection and characterization of giant viruses of amoebae, and a particular focus on their role in humans is warranted.

Radiation effects on the species-specific cell sorting-out of the cellular slime molds

International Nuclear Information System (INIS)

Satow, Takashi

1976-01-01

The effects of gamma-rays irradiation on the development and the species-specific cell sorting-out of the cellular slime mold, Dictyostelium discoideum, were investigated. The interphase amoebae of the organism showed extremely resistant to 60 Co gamma-rays. The percentage of non-stained cells estimated by dye staining method was more than 90% at the dose of 270 kR. The amoebae irradiated at 270 kR performed the development similar in the most respects to that of the un-irradiated amoebae except that a little portion of the fruiting bodies were abnormal and that the appearance of aggregates and slugs delayed 3 hrs. The ability of the species-specific cell sorting-out was not affected by gamma-rays irradiation at 270 kR. (auth.)

Analysis of Rheb in the cellular slime mold Dictyostelium discoideum

Indian Academy of Sciences (India)

2014-01-27

Jan 27, 2014 ... lyse the caspase-independent cell death mechanism. It is a ..... we observed exclusive expression in the prespore region. (figure 5A). There were ..... disc formation in Dictyostelium discoideum is an early event in culmination.

Excitable signal relay in Dictyostelium discoideum

Science.gov (United States)

Mestler, Troy; Schwab, David; Mehta, Pankaj; Gregor, Thomas

2011-03-01

The social amoeba D. discoideum transitions when starved from a collection of individual cells into a multicellular spore-complex. During this process, amoebae display several interesting phenomena including intercellular signaling, pattern formation, and cell differentiation. At the heart of these phenomena is the exchange of the signaling molecule cyclic-AMP, which has previously been extensively studied using a variety of indirect methods. Here we employ a sensor that uses a compound fluorescent protein whose emission spectrum changes in the presence of bound cyclic AMP to directly monitor, in real time and in vivo, intracellular cAMP concentrations. We use cells expressing this sensor in microchemostats to study intracellular cAMP concentrations at the single-cell level in response to precise, dynamically-controlled external cAMP stimulation. Specifically, we show that these cells display excitability much like that found in neurons and agree experimentally quite well with a modified FitzHugh-Nagumo dynamical systems model. This single-cell model sets groundwork for a comprehensive multicellular model that promises to explain emergent behavior in D. discoideum.

Biochemistry and genetics of inositol phosphate metabolism in Dictyostelium

NARCIS (Netherlands)

vanHaastert, PJM; van Dijken, P.

1997-01-01

Biochemical and genetic data on the metabolism of inositol phosphates in the microorganism Dictyostelium are combined in a scheme composed of in five subroutes. The first subroute is the inositol cycle as found in other organisms:inositol is incorporated into phospholipids that are hydrolysed by PLC

A secreted protein is an endogenous chemorepellant in Dictyostelium discoideum.

Science.gov (United States)

Phillips, Jonathan E; Gomer, Richard H

2012-07-03

Chemorepellants may play multiple roles in physiological and pathological processes. However, few endogenous chemorepellants have been identified, and how they function is unclear. We found that the autocrine signal AprA, which is produced by growing Dictyostelium discoideum cells and inhibits their proliferation, also functions as a chemorepellant. Wild-type cells at the edge of a colony show directed movement outward from the colony, whereas cells lacking AprA do not. Cells show directed movement away from a source of recombinant AprA and dialyzed conditioned media from wild-type cells, but not dialyzed conditioned media from aprA(-) cells. The secreted protein CfaD, the G protein Gα8, and the kinase QkgA are necessary for the chemorepellant activity of AprA as well as its proliferation-inhibiting activity, whereas the putative transcription factor BzpN is dispensable for the chemorepellant activity of AprA but necessary for inhibition of proliferation. Phospholipase C and PI3 kinases 1 and 2, which are necessary for the activity of at least one other chemorepellant in Dictyostelium, are not necessary for recombinant AprA chemorepellant activity. Starved cells are not repelled by recombinant AprA, suggesting that aggregation-phase cells are not sensitive to the chemorepellant effect. Cell tracking indicates that AprA affects the directional bias of cell movement, but not cell velocity or the persistence of cell movement. Together, our data indicate that the endogenous signal AprA acts as an autocrine chemorepellant for Dictyostelium cells.

Autonomous and non-autonomous traits mediate social cooperation ...

Indian Academy of Sciences (India)

2011-07-08

Jul 8, 2011 ... In the trishanku (triA−) mutant of the social amoeba Dictyostelium discoideum, aggregates are smaller than usual and the spore mass is located mid-way up the stalk, not at the apex. We have monitored aggregate territory size, spore allocation and fruiting body morphology in chimaeric groups of ...

Detection and Identification of Free-living Amoeba from Environmental Water in Taiwan by PCR Method

Science.gov (United States)

Tsai, H. F.; Hsu, B. M.; Huang, K. H.; She, C. Y.; Kao, P. M.; Shen, S. M.; Tseng, S. F.; Chen, J. S.

2012-04-01

Acanthamoeba, Naegleria, Balamuthia and Hartmannella all belong to free-living amoebae that are present ubiquitously in the environment including water, soil, and air. Free-living amoebae are parasites which can infect humans and can lead to serious illness and even death. The aim of this study is to investigate the presence of free-living amoebae in aquatic environment in Taiwan, and to compare the differences between Acanthamoeba and Naegleria in diverse cultivation methods and conditions. In this study, we used molecular method by PCR amplification with specific primers to analyze the occurrence of free-living amoebae. We collected 176 samples from environmental water including drinking water treatment plants, stream water, and hot spring recreational areas in Taiwan. Based on the results of PCR, 43 water samples (24.4%) were detected positive for free-living amoebae. The most common Acanthamoeba genotype isolated from samples including T2, T4, T5, T12, and T15. N. australiensis and N. lovaniensis were also identified by molecular biology techniques. Furthermore, we found that both Acanthamoeba and Naegleria can be cultured by PYG in 30° C, but not all free-living amoebae can be isolated and enriched by using storage-cultivation method. Because of the widespread presence of Acanthamoeba and Naegleria in aquatic environments, the water quality and safety of aquatic environments should be more conscious in Taiwan and worldwide. Keywords: free-living amoebae; Acanthamoeba; Naegleria; Balamuthia; Hartmannella; PCR

Behavioural differentiation induced by environmental variation when crossing a toxic zone in an amoeba

International Nuclear Information System (INIS)

Kunita, Itsuki; Kuroda, Shigeru; Nakagaki, Toshiyuki; Ueda, Kei-Ichi; Akita, Dai

2017-01-01

Organisms choose from among various courses of action in response to a wide variety of environmental conditions and the mechanism by which various behaviours are induced is an open question. Interesting behaviour was recently reported: that a unicellular organism of slime mold Physarum polycephalum known as an amoeba had multiple responses (crossing, returning, etc) when the amoeba encounters a zone with toxic levels of quinine, even under carefully controlled conditions. We here examined this elegant example in more detail to obtain insight into behavioural differentiation. We found that the statistical distribution of passage times across a quinine zone switch from unimodal to bimodal (with peaks corresponding to fast crossing and no crossing) when a periodic light stimulation to modulate a biorhythm in amoeba is applied homogeneously across the space, even under the same level of chemical stimuli. Based on a mathematical model for cell movement in amoeba, we successfully reproduced the stimulation-induced differentiation, which was observed experimentally. These dynamics may be explained by a saddle structure around a canard solution. Our results imply that the differentiation of behavioural types in amoeba is modified step-by-step via the compounding of stimulation inputs. The complex behaviour like the differentiation in amoeba may provide a basis for understanding the mechanism of behaviour selection in higher animals from an ethological perspective. (paper)

Behavioural differentiation induced by environmental variation when crossing a toxic zone in an amoeba

Science.gov (United States)

Kunita, Itsuki; Ueda, Kei-Ichi; Akita, Dai; Kuroda, Shigeru; Nakagaki, Toshiyuki

2017-09-01

Organisms choose from among various courses of action in response to a wide variety of environmental conditions and the mechanism by which various behaviours are induced is an open question. Interesting behaviour was recently reported: that a unicellular organism of slime mold Physarum polycephalum known as an amoeba had multiple responses (crossing, returning, etc) when the amoeba encounters a zone with toxic levels of quinine, even under carefully controlled conditions. We here examined this elegant example in more detail to obtain insight into behavioural differentiation. We found that the statistical distribution of passage times across a quinine zone switch from unimodal to bimodal (with peaks corresponding to fast crossing and no crossing) when a periodic light stimulation to modulate a biorhythm in amoeba is applied homogeneously across the space, even under the same level of chemical stimuli. Based on a mathematical model for cell movement in amoeba, we successfully reproduced the stimulation-induced differentiation, which was observed experimentally. These dynamics may be explained by a saddle structure around a canard solution. Our results imply that the differentiation of behavioural types in amoeba is modified step-by-step via the compounding of stimulation inputs. The complex behaviour like the differentiation in amoeba may provide a basis for understanding the mechanism of behaviour selection in higher animals from an ethological perspective.

RNAi silenced Dd-grp94 (Dictyostelium discoideum glucose-regulated protein 94 kDa) cell lines in Dictyostelium exhibit marked reduction in growth rate and delay in development.

Science.gov (United States)

Baviskar, Sandhya N; Shields, Malcolm S

2010-01-01

Glucose-regulated 94 kDa protein (Grp94) is a resident of the endoplasmic reticulum (ER) of multicellular eukaryotes. It is a constitutively expressed protein that is overexpressed in certain abnormal conditions of the cell such as depletion of glucose and calcium, and low oxygen and pH. The protein is also implicated in diseased conditions like cancer and Alzheimer's disease. In this study, the consequences of downregulation of Grp94 were investigated at both unicellular and multicellular stages of Dictyostelium discoideum. Previous studies have shown the expression of Dd-Grp94 (Dictyostelium discoideum glucose-regulated 94 kDa protein) in wild-type cells varies during development, and overexpression of Dd-Grp94 leads to abnormal cell shape and inhibition of development (i.e., formation of fruiting bodies). Grp94 is a known calcium binding protein and an efficient calcium buffer. Therefore, in the present study we hypothesized that downregulation of Dd-Grp94 protein would affect Dictyostelium cell structure, growth, and development. We found that Dd-grp94 RNAi recombinants exhibited reduced growth rate, cell size, and a subtle change in cell motility compared to the parental cells. The recombinants also exhibited a delay in development and small fruiting bodies. These results establish that Dd-grp94 plays a crucial role in determining normal cell structure, growth and differentiation.

Mimivirus: leading the way in the discovery of giant viruses of amoebae.

Science.gov (United States)

Colson, Philippe; La Scola, Bernard; Levasseur, Anthony; Caetano-Anollés, Gustavo; Raoult, Didier

2017-04-01

The accidental discovery of the giant virus of amoeba - Acanthamoeba polyphaga mimivirus (APMV; more commonly known as mimivirus) - in 2003 changed the field of virology. Viruses were previously defined by their submicroscopic size, which probably prevented the search for giant viruses, which are visible by light microscopy. Extended studies of giant viruses of amoebae revealed that they have genetic, proteomic and structural complexities that were not thought to exist among viruses and that are comparable to those of bacteria, archaea and small eukaryotes. The giant virus particles contain mRNA and more than 100 proteins, they have gene repertoires that are broader than those of other viruses and, notably, some encode translation components. The infection cycles of giant viruses of amoebae involve virus entry by amoebal phagocytosis and replication in viral factories. In addition, mimiviruses are infected by virophages, defend against them through the mimivirus virophage resistance element (MIMIVIRE) system and have a unique mobilome. Overall, giant viruses of amoebae, including mimiviruses, marseilleviruses, pandoraviruses, pithoviruses, faustoviruses and molliviruses, challenge the definition and classification of viruses, and have increasingly been detected in humans.

Crystallization and preliminary X-ray crystallographic analysis of the NmrA-like DDB-G0286605 protein from the social amoeba Dictyostelium discoideum

International Nuclear Information System (INIS)

Kim, Min-Kyu; Yim, Hyung-Soon; Kang, Sa-Ouk

2010-01-01

In order to investigate its structure and function, the NmrA-like domain-containing DDB-G0286605 protein from D. discoideum was expressed, purified and crystallized. X-ray diffraction analysis is reported to a resolution of 1.64 Å. The DDB-G0286605 gene product from Dictyostelium discoideum, an NmrA-like protein that belongs to the short-chain dehydrogenase/reductase family, has been crystallized by the hanging-drop vapour-diffusion method at 295 K. A 1.64 Å resolution data set was collected using synchrotron radiation. The DDB-G0286605 protein crystals belonged to space group P2 1 , with unit-cell parameters a = 67.598, b = 54.935, c = 84.219 Å, β = 109.620°. Assuming the presence of two molecules in the asymmetric unit, the solvent content was estimated to be about 43.25% with 99% probability. Molecular-replacement trials were attempted with three NmrA-like proteins, NmrA, HSCARG and QOR2, as search models, but failed. This may be a consequence of the low sequence identity between the DDB-G0286605 protein and the search models (DDB-G0286605 has a primary-sequence identity of 28, 32 and 19% to NmrA, HCARG and QOR2, respectively)

Amoeba Management System Transformation in the Light of Organisational Change Literature

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Urban Wieslaw

2017-03-01

Full Text Available The object of this study is the system of amoebas founded originally in Japanese Kyocera. The study aims to identify milestones of the transformation in a company organisational system to the Amoeba Management System (AMS. The study takes a conceptual research approach. It starts from the analysis of available sources on the AMS, identifies the most challenging points of this system, and afterwards, based on organisational change literature, formulates the main steps of transformation towards AMS. The following milestones of AMS implementation emerge from organisational change theories: (1 the preparation for AMS, (2 the change of organisational structure, (3 the design and introduction of a new accounting system, (4 the introduction of inner prices between amoebas, and (5 the transformation of the organisational culture. At the end of the study, the most important issues for future research are listed.

Eukaryotic cell flattening

Science.gov (United States)

Bae, Albert; Westendorf, Christian; Erlenkamper, Christoph; Galland, Edouard; Franck, Carl; Bodenschatz, Eberhard; Beta, Carsten

2010-03-01

Eukaryotic cell flattening is valuable for improving microscopic observations, ranging from bright field to total internal reflection fluorescence microscopy. In this talk, we will discuss traditional overlay techniques, and more modern, microfluidic based flattening, which provides a greater level of control. We demonstrate these techniques on the social amoebae Dictyostelium discoideum, comparing the advantages and disadvantages of each method.

Subcellular localization of ammonium transporters in Dictyostelium discoideum

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Davis Carter T

2008-12-01

Full Text Available Abstract Background With the exception of vertebrates, most organisms have plasma membrane associated ammonium transporters which primarily serve to import a source of nitrogen for nutritional purposes. Dictyostelium discoideum has three ammonium transporters, Amts A, B and C. Our present work used fluorescent fusion proteins to determine the cellular localization of the Amts and tested the hypothesis that the transporters mediate removal of ammonia generated endogenously from the elevated protein catabolism common to many protists. Results Using RFP and YFP fusion constructs driven by the actin 15 promoter, we found that the three ammonium transporters were localized on the plasma membrane and on the membranes of subcellular organelles. AmtA and AmtB were localized on the membranes of endolysosomes and phagosomes, with AmtB further localized on the membranes of contractile vacuoles. AmtC also was localized on subcellular organelles when it was stabilized by coexpression with either the AmtA or AmtB fusion transporter. The three ammonium transporters exported ammonia linearly with regard to time during the first 18 hours of the developmental program as revealed by reduced export in the null strains. The fluorescently tagged transporters rescued export when expressed in the null strains, and thus they were functional transporters. Conclusion Unlike ammonium transporters in most organisms, which import NH3/NH4+ as a nitrogen source, those of Dictyostelium export ammonia/ammonium as a waste product from extensive catabolism of exogenously derived and endogenous proteins. Localization on proteolytic organelles and on the neutral contractile vacuole suggests that Dictyostelium ammonium transporters may have unique subcellular functions and play a role in the maintenance of intracellular ammonium distribution. A lack of correlation between the null strain phenotypes and ammonia excretion properties of the ammonium transporters suggests that it is not

Xpf and not the Fanconi anaemia proteins or Rev3 accounts for the extreme resistance to cisplatin in Dictyostelium discoideum.

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Xiao-Yin Zhang

2009-09-01

Full Text Available Organisms like Dictyostelium discoideum, often referred to as DNA damage "extremophiles", can survive exposure to extremely high doses of radiation and DNA crosslinking agents. These agents form highly toxic DNA crosslinks that cause extensive DNA damage. However, little is known about how Dictyostelium and the other "extremophiles" can tolerate and repair such large numbers of DNA crosslinks. Here we describe a comprehensive genetic analysis of crosslink repair in Dictyostelium discoideum. We analyse three gene groups that are crucial for a replication-coupled repair process that removes DNA crosslinks in higher eukarya: The Fanconi anaemia pathway (FA, translesion synthesis (TLS, and nucleotide excision repair. Gene disruption studies unexpectedly reveal that the FA genes and the TLS enzyme Rev3 play minor roles in tolerance to crosslinks in Dictyostelium. However, disruption of the Xpf nuclease subcomponent results in striking hypersensitivity to crosslinks. Genetic interaction studies reveal that although Xpf functions with FA and TLS gene products, most Xpf mediated repair is independent of these two gene groups. These results suggest that Dictyostelium utilises a distinct Xpf nuclease-mediated repair process to remove crosslinked DNA. Other DNA damage-resistant organisms and chemoresistant cancer cells might adopt a similar strategy to develop resistance to DNA crosslinking agents.

AMOEBA Polarizable Force Field Parameters of the Heme Cofactor in Its Ferrous and Ferric Forms.

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Wu, Xiaojing; Clavaguera, Carine; Lagardère, Louis; Piquemal, Jean-Philip; de la Lande, Aurélien

2018-04-16

We report the first parameters of the heme redox cofactors for the polarizable AMOEBA force field in both the ferric and ferrous forms. We consider two types of complexes, one with two histidine side chains as axial ligands and one with a histidine and a methionine side chain as ligands. We have derived permanent multipoles from second-order Møller-Plesset perturbation theory (MP2). The sets of parameters have been validated in a first step by comparison of AMOEBA interaction energies of heme and a collection of biologically relevant molecules with MP2 and Density Functional Theory (DFT) calculations. In a second validation step, we consider interaction energies with large aggregates comprising around 80 H 2 O molecules. These calculations are repeated for 30 structures extracted from semiempirical PM7 DM simulations. Very encouraging agreement is found between DFT and the AMOEBA force field, which results from an accurate treatment of electrostatic interactions. We finally report long (10 ns) MD simulations of cytochromes in two redox states with AMOEBA testing both the 2003 and 2014 AMOEBA water models. These simulations have been carried out with the TINKER-HP (High Performance) program. In conclusion, owing to their ubiquity in biology, we think the present work opens a wide array of applications of the polarizable AMOEBA force field on hemeproteins.

Seasonal changes in Sphagnum peatland testate amoeba communities along a hydrological gradient.

Science.gov (United States)

Marcisz, Katarzyna; Lamentowicz, Lukasz; Słowińska, Sandra; Słowiński, Michał; Muszak, Witold; Lamentowicz, Mariusz

2014-10-01

Testate amoebae are an abundant and functionally important group of protists in peatlands, but little is known about the seasonal patterns of their communities. We investigated the relationships between testate amoeba diversity and community structure and water table depth and light conditions (shading vs. insolation) in a Sphagnum peatland in Northern Poland (Linje mire) in spring and summer 2010. We monitored the water table at five sites across the peatland and collected Sphagnum samples in lawn and hummock micro-sites around each piezometer, in spring (3 May) and mid-summer (6 August) 2010. Water table differed significantly between micro-sites and seasons (Kruskal-Wallis test, p=0.001). The community structure of testate amoebae differed significantly between spring and summer in both hummock and lawn micro-sites. We recorded a small, but significant drop in Shannon diversity, between spring and summer (1.76 vs. 1.72). Strongest correlations were found between testate amoeba communities and water table lowering and light conditions. The relative abundance of mixotrophic species Hyalosphenia papilio, Archerella flavum and of Euglypha ciliata was higher in the summer. Copyright © 2014 Elsevier GmbH. All rights reserved.

A study of nucleo-cytoplasmic large DNA viruses: detection and characterization of viruses in environmental amoeba

OpenAIRE

Fugas, Mariana Costa

2012-01-01

Tese de mestrado. Biologia (Biologia Molecular e Genética). Universidade de Lisboa, Faculdade de Ciências, 2012 Amoeba associated microorganisms (ARMs) are bacteria or viruses that share a symbiotic relationship with amoebas. Many ARMs are associated with human diseases and it has been reported the acquisition of resistance inside their host. These facts highlight the importance of finding and characterizing ARMs in a public health’s perspective. In the present work, amoebas from environme...

Quadruplexes in 'Dicty': crystal structure of a four-quartet G-quadruplex formed by G-rich motif found in the Dictyostelium discoideum genome.

Science.gov (United States)

Guédin, Aurore; Lin, Linda Yingqi; Armane, Samir; Lacroix, Laurent; Mergny, Jean-Louis; Thore, Stéphane; Yatsunyk, Liliya A

2018-06-01

Guanine-rich DNA has the potential to fold into non-canonical G-quadruplex (G4) structures. Analysis of the genome of the social amoeba Dictyostelium discoideum indicates a low number of sequences with G4-forming potential (249-1055). Therefore, D. discoideum is a perfect model organism to investigate the relationship between the presence of G4s and their biological functions. As a first step in this investigation, we crystallized the dGGGGGAGGGGTACAGGGGTACAGGGG sequence from the putative promoter region of two divergent genes in D. discoideum. According to the crystal structure, this sequence folds into a four-quartet intramolecular antiparallel G4 with two lateral and one diagonal loops. The G-quadruplex core is further stabilized by a G-C Watson-Crick base pair and a A-T-A triad and displays high thermal stability (Tm > 90°C at 100 mM KCl). Biophysical characterization of the native sequence and loop mutants suggests that the DNA adopts the same structure in solution and in crystalline form, and that loop interactions are important for the G4 stability but not for its folding. Four-tetrad G4 structures are sparse. Thus, our work advances understanding of the structural diversity of G-quadruplexes and yields coordinates for in silico drug screening programs and G4 predictive tools.

Buse_Francisella and free-living amoebae data sets

Data.gov (United States)

U.S. Environmental Protection Agency — Co-infection data in the form of colony forming units and amoeba cell counts. This dataset is associated with the following publication: Buse , H., F. Schaefer, and...

Role of phospholipase C in Dictyostelium : Formation of inositol 1,4,5-trisphosphate and normal development in cells lacking phospholipase C activity

NARCIS (Netherlands)

Drayer, A. Lyndsay; Kaay, Jeroen van der; Mayr, Georg W.; Haastert, Peter J.M. van

1994-01-01

The micro-organism Dictyostelium uses extracellular cAMP to induce chemotaxis and cell differentiation. Signals are transduced via surface receptors, which activate G proteins, to effector enzymes. The deduced protein sequence of Dictyostelium discoideum phosphabidylinositol-specific phospholipase C

The actinome of Dictyostelium discoideum in comparison to actins and actin-related proteins from other organisms.

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Jayabalan M Joseph

Full Text Available Actin belongs to the most abundant proteins in eukaryotic cells which harbor usually many conventional actin isoforms as well as actin-related proteins (Arps. To get an overview over the sometimes confusing multitude of actins and Arps, we analyzed the Dictyostelium discoideum actinome in detail and compared it with the genomes from other model organisms. The D. discoideum actinome comprises 41 actins and actin-related proteins. The genome contains 17 actin genes which most likely arose from consecutive gene duplications, are all active, in some cases developmentally regulated and coding for identical proteins (Act8-group. According to published data, the actin fraction in a D. discoideum cell consists of more than 95% of these Act8-type proteins. The other 16 actin isoforms contain a conventional actin motif profile as well but differ in their protein sequences. Seven actin genes are potential pseudogenes. A homology search of the human genome using the most typical D. discoideum actin (Act8 as query sequence finds the major actin isoforms such as cytoplasmic beta-actin as best hit. This suggests that the Act8-group represents a nearly perfect actin throughout evolution. Interestingly, limited data from D. fasciculatum, a more ancient member among the social amoebae, show different relationships between conventional actins. The Act8-type isoform is most conserved throughout evolution. Modeling of the putative structures suggests that the majority of the actin-related proteins is functionally unrelated to canonical actin. The data suggest that the other actin variants are not necessary for the cytoskeleton itself but rather regulators of its dynamical features or subunits in larger protein complexes.

Long-Term Hydrological Reconstruction From a Beaver Meadow Using Testate Amoebae

Science.gov (United States)

Von Ness, K.; Loisel, J.; Karran, D. J.; Westbrook, C.; Kohlmeyer, C.

2016-12-01

Beaver ponds contribute up to 0.8 Tg/yr of atmospheric methane (CH4) globally (Whitfield et al., 2014) and were found to be the largest CH4 emitters among all the wetland types in boreal environments (Roulet et al., 1992). However, the sources and underlying mechanisms of carbon emission and sequestration in beaver ponds requires further elucidation. Here we present the historical development of a beaver meadow located in the Sibbald Research Wetland in the Rocky Mountains of Kananaskis Provincial Park, Alberta, Canada. We use a combination of testate amoebae, plant macrofossils, and other geochemical proxies to provide high-resolution reconstructions along three peat cores extracted in hydrologically distinct portions of the meadow. To our knowledge, this is the first attempt at reconstructing long-term hydrological conditions in these systems. Testate amoebae (Protozoa: Rhizopoda) are single-celled organisms that inhabit moist substrates and produce a decay-resistant test. As each taxon generally occupies a discrete ecological niche related to soil moisture and pH, testate amoebae are good indicators of past and ongoing hydrological change. Preliminary analysis of testate amoebae assemblages downcore suggests that this proxy is suitable to reconstruct hydrological changes in meadows, with wetter and drier communities being in good agreement with wetter and drier plant macrofossil assemblages. The nitrogen isotopic signature of peat samples (ongoing) will be used as a proxy for changes in nutrient input; it could become a proxy for past beaver activity.

Multiple Degradation Pathways of Chemoattractant Mediated Cyclic GMP Accumulation in Dictyostelium

NARCIS (Netherlands)

Haastert, Peter J.M. van; Lookeren Campagne, Michiel M. van; Kesbeke, Fanja

1983-01-01

Chemoattractants induce a transient accumulation of cGMP levels in Dictyostelium. Intracellular cGMP levels reach a peak at 10 s and prestimulated cGMP levels are recovered at about 30 s. Intracellular and extracellular cGMP levels were detected simultaneously after stimulation of D. lacteum cells

Evaluating the use of testate amoebae for palaeohydrological reconstruction in permafrost peatlands

OpenAIRE

Swindles, Graeme T.; Amesbury, Matthew J.; Turner, T. Edward; Carrivick, Jonathan L.; Woulds, Clare; Raby, Cassandra; Mullan, Donal; Roland, Thomas P.; Galloway, Jennifer M.; Parry, Lauren; Kokfelt, Ulla; Garneau, Michelle; Charman, Dan J.; Holden, Joseph

2015-01-01

The melting of high-latitude permafrost peatlands is a major concern due to a potential positive feedback on global climate change. We examine the ecology of testate amoebae in permafrost peatlands, based on sites in Sweden (~ 200 km north of the Arctic Circle). Multivariate statistical analysis confirms that water-table depth and moisture content are the dominant controls on the distribution of testate amoebae, corroborating the results from studies in mid-latitude peatlands. We present a ne...

A secreted factor represses cell proliferation in Dictyostelium

OpenAIRE

Brock, Debra A.; Gomer, Richard H.

2005-01-01

Many cells appear to secrete factors called chalones that limit their proliferation, but in most cases the factors have not been identified. We found that growing Dictyostelium cells secrete a 60 kDa protein called AprA for autocrine proliferation repressor. AprA has similarity to putative bacterial proteins of unknown function. Compared with wild-type cells, aprA-null cells proliferate faster, while AprA overexpressing cells proliferate slower. Growing wild-type cells secrete a factor that i...

Counting Legionella cells within single amoeba host cells

Science.gov (United States)

Here we present the first attempt to quantify L. pneumophila cell numbers within individual amoebae hosts that may be released into engineered water systems. The maximum numbers of culturable L. pneumophila cells grown within Acanthamoeba polyphaga and Naegleria fowleri were 134...

Overexpression of the cAMP Receptor 1 in Growing Dictyostelium Cells

NARCIS (Netherlands)

Johnson, Ronald L.; Vaughan, Roxanne A.; Caterina, Michael J.; Haastert, Peter J.M. van; Devreotes, Peter N.

1991-01-01

cAR1, the cAMP receptor expressed normally during the early aggregation stage of the Dictyostelium developmental program, has been expressed during the growth stage, when only low amounts of endogenous receptors are present. Transformants expressing cAR1 have 7-40 times over growth stage and

Amoebae as potential environmental hosts for Mycobacterium ulcerans and other mycobacteria, but doubtful actors in Buruli ulcer epidemiology.

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Sophie Gryseels

Full Text Available The reservoir and mode of transmission of Mycobacterium ulcerans, the causative agent of Buruli ulcer, remain unknown. Ecological, genetic and epidemiological information nonetheless suggests that M. ulcerans may reside in aquatic protozoa.We experimentally infected Acanthamoeba polyphaga with M. ulcerans and found that the bacilli were phagocytised, not digested and remained viable for the duration of the experiment. Furthermore, we collected 13 water, 90 biofilm and 45 detritus samples in both Buruli ulcer endemic and non-endemic communities in Ghana, from which we cultivated amoeboid protozoa and mycobacteria. M. ulcerans was not isolated, but other mycobacteria were as frequently isolated from intracellular as from extracellular sources, suggesting that they commonly infect amoebae in nature. We screened the samples as well as the amoeba cultures for the M. ulcerans markers IS2404, IS2606 and KR-B. IS2404 was detected in 2% of the environmental samples and in 4% of the amoeba cultures. The IS2404 positive amoeba cultures included up to 5 different protozoan species, and originated both from Buruli ulcer endemic and non-endemic communities.This is the first report of experimental infection of amoebae with M. ulcerans and of the detection of the marker IS2404 in amoeba cultures isolated from the environment. We conclude that amoeba are potential natural hosts for M. ulcerans, yet remain sceptical about their implication in the transmission of M. ulcerans to humans and their importance in the epidemiology of Buruli ulcer.

eIF2α Kinases Control Chalone Production in Dictyostelium discoideum ▿

Science.gov (United States)

Bowman, Robert L.; Xiong, Yanhua; Kirsten, Janet H.; Singleton, Charles K.

2011-01-01

Growing Dictyostelium cells secrete CfaD and AprA, two proteins that have been characterized as chalones. They exist within a high-molecular-weight complex that reversibly inhibits cell proliferation, but not growth, via cell surface receptors and a signaling pathway that includes G proteins. How the production of these two proteins is regulated is unknown. Dictyostelium cells possess three GCN2-type eukaryotic initiation factor 2 α subunit (eIF2α) kinases, proteins that phosphorylate the translational initiation factor eIF2α and possess a tRNA binding domain involved in their regulation. The Dictyostelium kinases have been shown to function during development in regulating several processes. We show here that expression of an unregulated, activated kinase domain greatly inhibits cell proliferation. The inhibitory effect on proliferation is not due to a general inhibition of translation. Instead, it is due to enhanced production of a secreted factor(s). Indeed, extracellular CfaD and AprA proteins, but not their mRNAs, are overproduced in cells expressing the activated kinase domain. The inhibition of proliferation is not seen when the activated kinase domain is expressed in cells lacking CfaD or AprA or in cells that contain a nonphosphorylatable eIF2α. We conclude that production of the chalones CfaD and AprA is translationally regulated by eIF2α phosphorylation. Both proteins are upregulated at the culmination of development, and this enhanced production is lacking in a strain that possesses a nonphosphorylatable eIF2α. PMID:21278229

Normal chemotaxis in Dictyostelium discoideum cells with a depolarized plasma membrane potential

NARCIS (Netherlands)

Duijn, Bert van; Vogelzang, Sake A.; Ypey, Dirk L.; Molen, Loek G. van der; Haastert, Peter J.M. van

1990-01-01

We examined a possible role for the plasma membrane potential in signal transduction during cyclic AMP-induced chemotaxis in the cellular slime mold Dictyostelium discoideum. Chemotaxis, cyclic GMP and cyclic AMP responses in cells with a depolarized membrane potential were measured. Cells can be

Origin and diversity of testate amoebae shell composition: Example of Bullinularia indica living in Sphagnum capillifolium.

Science.gov (United States)

Delaine, Maxence; Bernard, Nadine; Gilbert, Daniel; Recourt, Philippe; Armynot du Châtelet, Eric

2017-06-01

Testate amoebae are free-living shelled protists that build a wide range of shells with various sizes, shapes, and compositions. Recent studies showed that xenosomic testate amoebae shells could be indicators of atmospheric particulate matter (PM) deposition. However, no study has yet been conducted to assess the intra-specific mineral, organic, and biologic grain diversity of a single xenosomic species in a natural undisturbed environment. This study aims at providing new information about grain selection to develop the potential use of xenosomic testate amoebae shells as bioindicators of the multiple-origin mineral/organic diversity of their proximal environment. To fulfil these objectives, we analysed the shell content of 38 Bullinularia indica individuals, a single xenosomic testate amoeba species living in Sphagnum capillifolium, by scanning electron microscope (SEM) coupled with X-ray spectroscopy. The shells exhibited high diversities of mineral, organic, and biomineral grains, which confirms their capability to recycle xenosomes. Mineral grain diversity and size of B. indica matched those of the atmospheric natural mineral PM deposited in the peatbog. Calculation of grain size sorting revealed a discrete selection of grains agglutinated by B. indica. These results are a first step towards understanding the mechanisms of particle selection by xenosomic testate amoebae in natural conditions. Copyright © 2017 Elsevier GmbH. All rights reserved.

Platyamoeba pseudovannellida n. sp., a naked amoeba with wide salt tolerance isolated from the Salton Sea, California.

Science.gov (United States)

Hauer, G; Rogerson, A; Anderson, O R

2001-01-01

A new species of naked amoeba, Platyamoeba pseudovannellida n.sp., is described on the basis of light microscopic and fine structural features. The amoeba was isolated from the Salton Sea, California, from water at a salinity of ca. 44%. Locomotive amoebae occasionally had a spatulate outline and floating cells had radiating pseudopodia, sometimes with pointed tips. Both these features are reminiscent of the genus Vannella. However, the surface coat (glycocalyx) as revealed by TEM indicates that this is a species of Platyamoeba. Although salinity was not used as a diagnostic feature, this species was found to have remarkable tolerance to fluctuating salinity levels, even when changes were rapid. Amoebae survived over the range 0 per thousand to 150 per thousand salt and grew within the range 0 per thousand to 138 per thousand salt. The generation time of cells averaged 29 h and was not markedly affected by salt concentration. This is longer than expected for an amoeba of this size and suggests a high energetic cost of coping with salinity changes. The morphology of cells changed with increasing salinity: at 0 per thousand cells were flattened and active and at the other extreme (138 per thousand) amoebae were wrinkled and domed and cell movement was very slow. At the ultrastructural level, the cytoplasm of cells grown at high salinity (98 per thousand was considerably denser than that of cells reared at 0 per thousand.

Pleckstrin Homology Domain Diffusion in Dictyostelium Cytoplasm Studied Using Fluorescence Correlation Spectroscopy

NARCIS (Netherlands)

Engel, Ruchira; Hink, Mark A.; Bosgraaf, Leonard; Haastert, Peter J.M. van; Visser, Antonie J.W.G.

2004-01-01

The translocation of pleckstrin homology (PH) domain-containing proteins from the cytoplasm to the plasma membrane plays an important role in the chemotaxis mechanism of Dictyostelium cells. The diffusion of three PH domain-green fluorescent protein (GFP) fusions (PH2-GFP, PH10-GFP, and PH-CRAC

Pleckstrin homology domain diffusion in Dictyostelium cytoplasm studied using fluorescence correlation spectroscopy

NARCIS (Netherlands)

Ruchira, A.; Hink, M.A.; Bosgraaf, L.; Haastert, van P.J.M.; Visser, A.J.W.G.

2004-01-01

The translocation of pleckstrin homology (PH) domain-containing proteins from the cytoplasm to the plasma membrane plays an important role in the chemotaxis mechanism of Dictyostelium cells. The diffusion of three PH domain-green fluorescent protein (GFP) fusions (PH2-GFP, PH10-GFP, and PH-CRAC

[Nitrogen input altered testate amoebae community in peatland of Sanjiang Plain, Northeast China].

Science.gov (United States)

Song, Li-hong; Yan, Xiu-min; Wang, Ke-hong; Zhu, Xiao-yan; Wu, Dong-hu

2015-02-01

In the present study, an in situ control experiment was carried out to explore the response of testate amoebae to exogenous nitrogen addition in peatland of Sanjiang Plain. The results showed that nitrogen addition increased the biomass of testate amoebae at lower levels (6 g N · m(-2)), while decreased it at higher levels (> 12 g N · m(-2)). At genus level, nitrogen addition significantly increased the biomass of Arcella and Phryganella, decreased the biomass of Euglypha. Only lower nitrogen addition significantly increased the biomass of Centropyxis. At species level, nitrogen addition significantly decreased the biomass of Euglypha rotunda, while the biomass of either Centropyxis cassis or Phryganella acropodia was increased by a lower nitrogen addition treatment. This study suggested that the response of peatland testate amoebae to nitrogen addition was species specific, which could potentially be used as an indicator for the environment of peatlands.

Sensitization of Dictyostelium chemotaxis by phosphoinositide-3-kinase-mediated self-organizing signalling patches

NARCIS (Netherlands)

Postma, M.; Roelofs, J.; Goedhart, J.; Loovers, H.M.; Visser, A.J.W.G.; Haastert, van P.J.M.

2004-01-01

The leading edge of Dictyostelium cells in chemoattractant gradients can be visualized using green fluorescent protein (GFP) tagged to the pleckstrin-homology (PH) domain of cytosolic regulator of adenylyl cyclase (CRAC), which presumable binds phosphatidylinositol-(3,4,5)triphosphate

Sensitization of Dictyostelium chemotaxis by phosphoinositide-3-kinase-mediated self-organizing signalling patches.

NARCIS (Netherlands)

Postma, M.; Roelofs, J.; Goedhart, J.; Loovers, H.M.; Visser, A.J.; van Haastert, P.J.

2004-01-01

The leading edge of Dictyostelium cells in chemoattractant gradients can be visualized using green fluorescent protein (GFP) tagged to the pleckstrin-homology (PH) domain of cytosolic regulator of adenylyl cyclase (CRAC), which presumable binds phosphatidylinositol-(3,4,5)triphosphate

The carboxy-terminal domain of Dictyostelium C-module-binding factor is an independent gene regulatory entity.

Directory of Open Access Journals (Sweden)

Jörg Lucas

Full Text Available The C-module-binding factor (CbfA is a multidomain protein that belongs to the family of jumonji-type (JmjC transcription regulators. In the social amoeba Dictyostelium discoideum, CbfA regulates gene expression during the unicellular growth phase and multicellular development. CbfA and a related D. discoideum CbfA-like protein, CbfB, share a paralogous domain arrangement that includes the JmjC domain, presumably a chromatin-remodeling activity, and two zinc finger-like (ZF motifs. On the other hand, the CbfA and CbfB proteins have completely different carboxy-terminal domains, suggesting that the plasticity of such domains may have contributed to the adaptation of the CbfA-like transcription factors to the rapid genome evolution in the dictyostelid clade. To support this hypothesis we performed DNA microarray and real-time RT-PCR measurements and found that CbfA regulates at least 160 genes during the vegetative growth of D. discoideum cells. Functional annotation of these genes revealed that CbfA predominantly controls the expression of gene products involved in housekeeping functions, such as carbohydrate, purine nucleoside/nucleotide, and amino acid metabolism. The CbfA protein displays two different mechanisms of gene regulation. The expression of one set of CbfA-dependent genes requires at least the JmjC/ZF domain of the CbfA protein and thus may depend on chromatin modulation. Regulation of the larger group of genes, however, does not depend on the entire CbfA protein and requires only the carboxy-terminal domain of CbfA (CbfA-CTD. An AT-hook motif located in CbfA-CTD, which is known to mediate DNA binding to A+T-rich sequences in vitro, contributed to CbfA-CTD-dependent gene regulatory functions in vivo.

Potential influence of birds on soil testate amoebae in the Arctic

Science.gov (United States)

Mazei, Yuri A.; Lebedeva, Natalia V.; Taskaeva, Anastasia A.; Ivanovsky, Alexander A.; Chernyshov, Viktor A.; Tsyganov, Andrey N.; Payne, Richard J.

2018-06-01

Birds can be an important agent of environmental change in High Arctic ecosystems, particularly due to the role of seabirds as a vector transferring nutrients from the marine to terrestrial realms. The soils of bird nesting sites are known to host distinct plant communities but the consequences of bird modification for microorganisms are much less clear. Our focus here is testate amoebae: a widely-distributed group of protists with significant roles in many aspects of ecosystem functioning. We compared the testate amoeba assemblages of a site on Spitsbergen (Svalbard archipelago) affected by nesting birds, with nearby control sites. We found differences in assemblage between sites, typified by reduced relative abundance of Phryganella acropodia and Centropyxis aerophila in bird-modified soils. These changes may reflect a reduced availability of fungal food sources. We found no evidence for differences in assemblage diversity or test concentration between bird-modified and control soils. Our dataset is small but results provide the first evidence for the potential effect of bird modification of soils on testate amoebae in the Arctic. Results show only limited similarity to experimental studies of nutrient addition, implying that response mechanisms may be more complicated than simply additional nutrient supply.

The potential influence of short-term environmental variability on the composition of testate amoeba communities in Sphagnum peatlands.

Science.gov (United States)

Sullivan, Maura E; Booth, Robert K

2011-07-01

Testate amoebae are a group of moisture-sensitive, shell-producing protozoa that have been widely used as indicators of changes in mean water-table depth within oligotrophic peatlands. However, short-term environmental variability (i.e., sub-annual) also probably influences community composition. The objective of this study was to assess the potential influence of short-term environmental variability on the composition of testate amoeba communities in Sphagnum-dominated peatlands. Testate amoebae and environmental conditions, including hourly measurements of relative humidity within the upper centimeter of the peatland surface, were examined throughout the 2008 growing season at 72 microsites within 11 peatlands of Pennsylvania and Wisconsin, USA. Relationships among testate amoeba communities, vegetation, depth to water table, pH, and an index of short-term environmental variability (EVI), were examined using nonmetric multidimensional scaling and correlation analysis. Results suggest that EVI influences testate amoeba communities, with some taxa more abundant under highly variable conditions (e.g., Arcella discoides, Difflugia pulex, and Hyalosphenia subflava) and others more abundant when environmental conditions at the peatland surface were relatively stable (e.g., Archerella flavum and Bullinularia indica). The magnitude of environmental variability experienced at the peatland surface appears to be primarily controlled by vegetation composition and density. In particular, sites with dense Sphagnum cover had lower EVI values than sites with loose-growing Sphagnum or vegetation dominated by vascular plants and/or non-Sphagnum bryophytes. Our results suggest that more environmental information may be inferred from testate amoebae than previously recognized. Knowledge of relationships between testate amoebae and short-term environmental variability should lead to more detailed and refined environmental inferences.

The Evolution of a distributed operating system (Amoeba)

NARCIS (Netherlands)

van Renesse, Robbert; Tanenbaum, Andrew S.; Mullender, Sape J.

1989-01-01

AMOEBA is a research project to build a true distributed operating system using the object model. Under the COST11-ter MANDIS project this work was extended to cover wide-area networks. Besides describing the system, this paper discusses the successive versions in the implementation of its model,

Presence of rotavirus and free-living amoebae in the water supplies of Karachi, Pakistan

Science.gov (United States)

Yousuf, Farzana Abubakar; Siddiqui, Ruqaiyyah; Khan, Naveed Ahmed

2017-01-01

ABSTRACT Rotavirus and pathogenic free-living amoebae are causative agents of important health problems, especially for developing countries like Pakistan where the population has limited access to clean water supplies. Here, we evaluated the prevalence of rotavirus and free-living amoebae (Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri) in drinking water supplies of Karachi, Pakistan. Six water filtration plants that supply drinking water to the population of Karachi were investigated. Additionally, drinking water samples from households were analyzed for the presence of rotavirus and free-living amoebae. Rotavirus was present in 35% of the water samples collected from water filtration plants; however, domestic tap water samples had a prevalence of only 5%. Out of 20 water samples from filtration plants, 13 (65%) were positive for Acanthamoeba spp., and one (5%) was positive for B. mandrillaris. Out of 20 drinking water samples collected from different areas of Karachi, 35% were positive for Acanthamoeba spp. Rotavirus was detected in 5% of the drinking water samples tested. Overall, these findings showed for the first time the presence of rotavirus, in addition to pathogenic free-living amoebae in drinking water supplies of Karachi that could be an important public health risk for the affected population. PMID:28591260

Presence of rotavirus and free-living amoebae in the water supplies of Karachi, Pakistan

Directory of Open Access Journals (Sweden)

Farzana Abubakar Yousuf

Full Text Available ABSTRACT Rotavirus and pathogenic free-living amoebae are causative agents of important health problems, especially for developing countries like Pakistan where the population has limited access to clean water supplies. Here, we evaluated the prevalence of rotavirus and free-living amoebae (Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri in drinking water supplies of Karachi, Pakistan. Six water filtration plants that supply drinking water to the population of Karachi were investigated. Additionally, drinking water samples from households were analyzed for the presence of rotavirus and free-living amoebae. Rotavirus was present in 35% of the water samples collected from water filtration plants; however, domestic tap water samples had a prevalence of only 5%. Out of 20 water samples from filtration plants, 13 (65% were positive for Acanthamoeba spp., and one (5% was positive for B. mandrillaris. Out of 20 drinking water samples collected from different areas of Karachi, 35% were positive for Acanthamoeba spp. Rotavirus was detected in 5% of the drinking water samples tested. Overall, these findings showed for the first time the presence of rotavirus, in addition to pathogenic free-living amoebae in drinking water supplies of Karachi that could be an important public health risk for the affected population.

The Dictyostelium discoideum cellulose synthase: Structure/function analysis and identification of interacting proteins

Energy Technology Data Exchange (ETDEWEB)

Richard L. Blanton

2004-02-19

OAK-B135 The major accomplishments of this project were: (1) the initial characterization of dcsA, the gene for the putative catalytic subunit of cellulose synthase in the cellular slime mold Dictyostelium discoideum; (2) the detection of a developmentally regulated event (unidentified, but perhaps a protein modification or association with a protein partner) that is required for cellulose synthase activity (i.e., the dcsA product is necessary, but not sufficient for cellulose synthesis); (3) the continued exploration of the developmental context of cellulose synthesis and DcsA; (4) the isolation of a GFP-DcsA-expressing strain (work in progress); and (5) the identification of Dictyostelium homologues for plant genes whose products play roles in cellulose biosynthesis. Although our progress was slow and many of our results negative, we did develop a number of promising avenues of investigation that can serve as the foundation for future projects.

The Amoebal MAP Kinase Response to Legionella pneumophila Is Regulated by DupA

OpenAIRE

Li, Zhiru; Dugan, Aisling S.; Bloomfield, Gareth; Skelton, Jason; Ivens, Alasdair; Losick, Vicki; Isberg, Ralph R.

2009-01-01

The amoeba Dictyostelium discoideum can support replication of Legionella pneumophila. Here we identify the dupA gene, encoding a putative tyrosine kinase/dual-specificity phosphatase, in a screen for D. discoideum mutants altered in allowing L. pneumophila intracellular replication. Inactivation of dupA resulted in depressed L. pneumophila growth and sustained hyperphosphorylation of the amoebal MAP kinase ERK1, consistent with loss of a phosphatase activity. Bacterial challenge of wild-type...

Cytoplasmic pH and the regulation of the dictyostelium cell cycle

NARCIS (Netherlands)

Aerts, R.J.; Durston, A.J.; Moolenaar, W.H.

1985-01-01

Cytoplasmic pH (pHl) was monitored during the cell cycle of synchronous populations of Dictyostelium discoideum by means of a pH “null point” method. There is a cycle of pHl that closely corresponds to the DNA replication cycle, with a minimum of pH 7.20 in interphase and a peak of pH 7.45 during S

Detection and identification of free-living amoeba from aquatic environment in different seasons in Taiwan

Science.gov (United States)

Tzeng, K.; Hsu, B.; Tsai, H.; Huang, P.; Tsai, J.; Kao, P.; Huang, K.; Chen, J.

2013-12-01

Free-living amoeba includes Acanthamoeba and Naegleria, which are widely distributed in water and soil. Human infection with free-living amoeba leads to serious illness, even lethal. For example, central nervous system infection will cause amoebic meningoencephalitis, and infections will cause amoebic keratitis. The presence of free-living amoeba in environment water can be used as a water quality indicator in ecosystem assessment. In Taiwan, reservoirs are indispensable because of the water source are limited by the steep terrain and the short river flow. Therefore, we need to pay more attention in the quality control of reservoirs water. The aims of this study are to investigate the presence of free-living amoeba in Taiwan reservoirs, and to compare the differences among seasons. At last, the identification and genotyping of Acanthamoeba and Naegleria are investigated. In this study, we use polymerase chain reaction with specific primers to analyze the presence of free-living amoeba in aquatic environment. We collected total 60 samples from reservoirs in Taiwan. The water samples are divided into two parts for both direct concentration method and culture method. The results show the different detection rates among seasons. For Acanthamoeba, the detection rates were 28.3% (17 of 60 water samples), 21.7% (13 of 60 water samples) and 8.3% (5 of 60 water samples) in autumn, winter and spring, respectively. For Naegleria, the detection rates were 6.7% (4 of 60 water samples), 0% (0 of 60 water samples) and 0% (0 of 60 water samples) were detected positive in autumn, winter and spring, respectively. Sequence analysis showed that the major genotypes in Acanthamoeba were T3, T4, T10 and T11 in autumn, T2, T4 and T10 in winter, T4 in spring. Due to the presences of Acanthamoeba and Naegleria in reservoirs, we should pay more attention in water quality monitoring to prevent the potential risks of diseases. Keywords: free-living amoeba, Acanthamoeba, Naegleria, polymerase

Evidence for a Messenger Function of Cyclic GMP During Phosphodiesterase Induction in Dictyostelium discoideum

NARCIS (Netherlands)

Haastert, Peter J.M. van; Pasveer, Frank J.; Meer, Rob C. van der; Heijden, Paul R. van der; Walsum, Hans van; Konijn, Theo M.

1982-01-01

Chemotactic stimulation of vegetative or aggregative Dictyostelium discoideum cells induced a transient elevation of cyclic GMP levels. The addition of chemoattractants to postvegetative cells by pulsing induced phosphodiesterase activity. The following lines of evidence suggest a messenger function

Engineering an artificial amoeba propelled by nanoparticle-triggered actin polymerization

Energy Technology Data Exchange (ETDEWEB)

Yi Jinsoo; Schmidt, Jacob; Chien Aichi; Montemagno, Carlo D [Department of Bioengineering, University of California Los Angeles, 420 Westwood Plaza, 7523 Boelter Hall, Los Angeles, CA 90095-1600 (United States)], E-mail: montemcd@ucmail.uc.edu

2009-02-25

We have engineered an amoeba system combining nanofabricated inorganic materials with biological components, capable of propelling itself via actin polymerization. The nanofabricated materials have a mechanism similar to the locomotion of the Listeria monocytogenes, food poisoning bacteria. The propulsive force generation utilizes nanoparticles made from nickel and gold functionalized with the Listeria monocytogenes transmembrane protein, ActA. These Listeria-mimic nanoparticles were in concert with actin, actin binding proteins, ATP (adenosine triphosphate) and encapsulated within a lipid vesicle. This system is an artificial cell, such as a vesicle, where artificial nanobacteria and actin polymerization machinery are used in driving force generators inside the cell. The assembled structure was observed to crawl on a glass surface analogously to an amoeba, with the speed of the movement dependent on the amount of actin monomers and ATP present.

The amoebal MAP kinase response to Legionella pneumophila is regulated by DupA.

Science.gov (United States)

Li, Zhiru; Dugan, Aisling S; Bloomfield, Gareth; Skelton, Jason; Ivens, Alasdair; Losick, Vicki; Isberg, Ralph R

2009-09-17

The amoeba Dictyostelium discoideum can support replication of Legionella pneumophila. Here we identify the dupA gene, encoding a putative tyrosine kinase/dual-specificity phosphatase, in a screen for D. discoideum mutants altered in allowing L. pneumophila intracellular replication. Inactivation of dupA resulted in depressed L. pneumophila growth and sustained hyperphosphorylation of the amoebal MAP kinase ERK1, consistent with loss of a phosphatase activity. Bacterial challenge of wild-type amoebae induced dupA expression and resulted in transiently increased ERK1 phosphorylation, suggesting that dupA and ERK1 are part of a response to bacteria. Indeed, over 500 of the genes misregulated in the dupA(-) mutant were regulated in response to L. pneumophila infection, including some thought to have immune-like functions. MAP kinase phosphatases are known to be highly upregulated in macrophages challenged with L. pneumophila. Thus, DupA may regulate a MAP kinase response to bacteria that is conserved from amoebae to mammals.

Free energy simulations with the AMOEBA polarizable force field and metadynamics on GPU platform.

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Peng, Xiangda; Zhang, Yuebin; Chu, Huiying; Li, Guohui

2016-03-05

The free energy calculation library PLUMED has been incorporated into the OpenMM simulation toolkit, with the purpose to perform enhanced sampling MD simulations using the AMOEBA polarizable force field on GPU platform. Two examples, (I) the free energy profile of water pair separation (II) alanine dipeptide dihedral angle free energy surface in explicit solvent, are provided here to demonstrate the accuracy and efficiency of our implementation. The converged free energy profiles could be obtained within an affordable MD simulation time when the AMOEBA polarizable force field is employed. Moreover, the free energy surfaces estimated using the AMOEBA polarizable force field are in agreement with those calculated from experimental data and ab initio methods. Hence, the implementation in this work is reliable and would be utilized to study more complicated biological phenomena in both an accurate and efficient way. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Extracellular calmodulin regulates growth and cAMP-mediated chemotaxis in Dictyostelium discoideum

International Nuclear Information System (INIS)

O’Day, Danton H.; Huber, Robert J.; Suarez, Andres

2012-01-01

Highlights: ► Extracellular calmodulin is present throughout growth and development in Dictyostelium. ► Extracellular calmodulin localizes within the ECM during development. ► Extracellular calmodulin inhibits cell proliferation and increases chemotaxis. ► Extracellular calmodulin exists in eukaryotic microbes. ► Extracellular calmodulin may be functionally as important as intracellular calmodulin. -- Abstract: The existence of extracellular calmodulin (CaM) has had a long and controversial history. CaM is a ubiquitous calcium-binding protein that has been found in every eukaryotic cell system. Calcium-free apo-CaM and Ca 2+ /CaM exert their effects by binding to and regulating the activity of CaM-binding proteins (CaMBPs). Most of the research done to date on CaM and its CaMBPs has focused on their intracellular functions. The presence of extracellular CaM is well established in a number of plants where it functions in proliferation, cell wall regeneration, gene regulation and germination. While CaM has been detected extracellularly in several animal species, including frog, rat, rabbit and human, its extracellular localization and functions are less well established. In contrast the study of extracellular CaM in eukaryotic microbes remains to be done. Here we show that CaM is constitutively expressed and secreted throughout asexual development in Dictyostelium where the presence of extracellular CaM dose-dependently inhibits cell proliferation but increases cAMP mediated chemotaxis. During development, extracellular CaM localizes within the slime sheath where it coexists with at least one CaMBP, the matricellular CaM-binding protein CyrA. Coupled with previous research, this work provides direct evidence for the existence of extracellular CaM in the Dictyostelium and provides insight into its functions in this model amoebozoan.

Nanovesicles released by Dictyostelium cells: a potential carrier for drug delivery.

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Lavialle, Françoise; Deshayes, Sophie; Gonnet, Florence; Larquet, Eric; Kruglik, Sergei G; Boisset, Nicolas; Daniel, Régis; Alfsen, Annette; Tatischeff, Irène

2009-10-01

Nanovesicles released by Dictyostelium discoideum cells grown in the presence of the DNA-specific dye Hoechst 33342 have been previously shown to mediate the transfer of the dye into the nuclei of Hoechst-resistant cells. The present investigation extends this work by conducting experiments in the presence of hypericin, a fluorescent therapeutic photosensitizer assayed for antitumoral photodynamic therapy. Nanovesicles released by Dictyostelium cells exhibit an averaged diameter between 50 and 150 nm, as measured by transmission cryoelectron microscopy. A proteomic analysis reveals a predominance of actin and actin-related proteins. The detection of a lysosomal membrane protein (LIMP II) indicates that these vesicles are likely generated in the late endosomal compartment. The use of the hypericin-containing nanovesicles as nanodevices for in vitro drug delivery was investigated by fluorescence microscopy. The observed signal was almost exclusively located in the perinuclear area of two human cell lines, skin fibroblasts (HS68) and cervix carcinoma (HeLa) cells. Studies by confocal microscopy with specific markers of cell organelles, provided evidence that hypericin was accumulated in the Golgi apparatus. All these data shed a new light on in vitro drug delivery by using cell-released vesicles as carriers.

A secreted protein is an endogenous chemorepellant in Dictyostelium discoideum

OpenAIRE

Phillips, Jonathan E.; Gomer, Richard H.

2012-01-01

Chemorepellants may play multiple roles in physiological and pathological processes. However, few endogenous chemorepellants have been identified, and how they function is unclear. We found that the autocrine signal AprA, which is produced by growing Dictyostelium discoideum cells and inhibits their proliferation, also functions as a chemorepellant. Wild-type cells at the edge of a colony show directed movement outward from the colony, whereas cells lacking AprA do not. Cells show directed mo...

Scanning the available Dictyostelium discoideum proteome for O-linked GlcNAc glycosylation sitesusing neural networks

DEFF Research Database (Denmark)

Gupta, Ramneek; Jung, Eva; Gooley, Andrew A

1999-01-01

Dictyostelium discoideum has been suggested as a eukaryotic model organism for glycobiology studies. Presently, the characteristics of acceptor sites for the N-acetylglucosaminyl-transferases in Dictyostelium discoideum, which link GlcNAc in an alpha linkage to hydroxyl residues, are largely...... unknown. This motivates the development of a species specific method for prediction of O-linked GlcNAc glycosylation sites in secreted and membrane proteins of D. discoideum. The method presented here employs a jury of artificial neural networks. These networks were trained to recognize the sequence...... context and protein surface accessibility in 39 experimentally determined O-alpha-GlcNAc sites found in D. discoideum glycoproteins expressed in vivo. Cross-validation of the data revealed a correlation in which 97% of the glycosylated and nonglycosylated sites were correctly identified. Based...

Advances in the knowledge of amphizoic amoebae infecting fish

Czech Academy of Sciences Publication Activity Database

Dyková, Iva; Lom, Jiří

2004-01-01

Roč. 51, 2/3 (2004), s. 81-97 ISSN 0015-5683 R&D Projects: GA AV ČR IAA6022202 Institutional research plan: CEZ:AV0Z6022909 Keywords : amphizoic amoebae * fish hosts * review Subject RIV: EA - Cell Biology Impact factor: 0.837, year: 2004

El extracto etanólico de las flores de Laccopetalum giganteum (pacra-pacra aumenta la fertilidad en ratas

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Jorge Arroyo

2007-09-01

Full Text Available Objetivos: Determinar si la administración por vía oral del extracto etanólico de flores de Laccopetalum giganteum (Pacra-pacra en ratas normales aumenta la fertilidad. Diseño: Estudio experimental. Lugar: Facultad de Medicina y Facultad de Farmacia y Bioquímica, Universidad Nacional Mayor de San Marcos. Material biológico: Ratas. Intervenciones: Cuarentiocho animales fueron divididos aleatoriamente en 2 grandes grupos, de 24 cada uno. El primero fue control, con solución salina fisiológica (SSF 5 mL/kg y el segundo con extracto vía oral, 300 mg/kg, durante 15 días. Cada grupo consideró 6 hembras y 6 machos juntos, y 6 hembras y 6 machos separados. Los animales que estuvieron juntos fueron sacrificados, para observar la presencia de fetos en el útero; y a los animales que estuvieron separados, se les extrajo muestra de sangre, para conocer el nivel de testosterona en machos y LH, FSH, estrógenos y progesterona en hembras, expresándose en µg/dL; el dosaje hormonal se realizó por el método de electroquimioluminiscencia. Asimismo, se determinó GOT, GPT, urea y creatinina, según las técnicas utilizadas en el laboratorio clínico. Principales medidas de resultados: Gravidez, FSH, LH, estrógenos y progesterona en ratas hembras; testosterona en ratas machos. Resultados: Los flavonoides, compuestos fenólicos y taninos estuvieron en mayor cantidad en el extracto etanólico. El 100% de ratas que recibió el extracto etanólico de la planta y estuvo junto a los machos resultó grávida; y, las separadas que recibieron el mismo extracto, presentaron incremento de FSH en las hembras y testosterona en los machos, comparativamente a los controles respectivos. Los niveles de GOT, GPT, urea y creatinina se encontraron dentro de los límites aceptados. Conclusiones: En condiciones experimentales, el extracto etanólico de las flores de Laccopetalum giganteum (pacra-pacra incrementó la fertilidad en ratas normales.

A retinoblastoma orthologue is required for the sensing of a chalone in Dictyostelium discoideum.

Science.gov (United States)

Bakthavatsalam, Deenadayalan; White, Michael J V; Herlihy, Sarah E; Phillips, Jonathan E; Gomer, Richard H

2014-03-01

Retinoblastoma-like proteins regulate cell differentiation and inhibit cell proliferation. The Dictyostelium discoideum retinoblastoma orthologue RblA affects the differentiation of cells during multicellular development, but it is unclear whether RblA has a significant effect on Dictyostelium cell proliferation, which is inhibited by the secreted proteins AprA and CfaD. We found that rblA⁻ cells in shaking culture proliferate to a higher density, die faster after reaching stationary density, and, after starvation, have a lower spore viability than wild-type cells, possibly because in shaking culture, rblA⁻ cells have both increased cytokinesis and lower extracellular accumulation of CfaD. However, rblA⁻ cells have abnormally slow proliferation on bacterial lawns. Recombinant AprA inhibits the proliferation of wild-type cells but not that of rblA⁻ cells, whereas CfaD inhibits the proliferation of both wild-type cells and rblA⁻ cells. Similar to aprA⁻ cells, rblA⁻ cells have a normal mass and protein accumulation rate on a per-nucleus basis, indicating that RblA affects cell proliferation but not cell growth. AprA also functions as a chemorepellent, and RblA is required for proper AprA chemorepellent activity despite the fact that RblA does not affect cell speed. Together, our data indicate that an autocrine proliferation-inhibiting factor acts through RblA to regulate cell density in Dictyostelium, suggesting that such factors may signal through retinoblastoma-like proteins to control the sizes of structures such as developing organs or tumors.

dictyBase 2015: Expanding data and annotations in a new software environment.

Science.gov (United States)

Basu, Siddhartha; Fey, Petra; Jimenez-Morales, David; Dodson, Robert J; Chisholm, Rex L

2015-08-01

dictyBase is the model organism database for the social amoeba Dictyostelium discoideum and related species. The primary mission of dictyBase is to provide the biomedical research community with well-integrated high quality data, and tools that enable original research. Data presented at dictyBase is obtained from sequencing centers, groups performing high throughput experiments such as large-scale mutagenesis studies, and RNAseq data, as well as a growing number of manually added functional gene annotations from the published literature, including Gene Ontology, strain, and phenotype annotations. Through the Dicty Stock Center we provide the community with an impressive amount of annotated strains and plasmids. Recently, dictyBase accomplished a major overhaul to adapt an outdated infrastructure to the current technological advances, thus facilitating the implementation of innovative tools and comparative genomics. It also provides new strategies for high quality annotations that enable bench researchers to benefit from the rapidly increasing volume of available data. dictyBase is highly responsive to its users needs, building a successful relationship that capitalizes on the vast efforts of the Dictyostelium research community. dictyBase has become the trusted data resource for Dictyostelium investigators, other investigators or organizations seeking information about Dictyostelium, as well as educators who use this model system. © 2015 Wiley Periodicals, Inc.

Transcriptional down-regulation and rRNA cleavage in Dictyostelium discoideum mitochondria during Legionella pneumophila infection.

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Chenyu Zhang

2009-05-01

Full Text Available Bacterial pathogens employ a variety of survival strategies when they invade eukaryotic cells. The amoeba Dictyostelium discoideum is used as a model host to study the pathogenic mechanisms that Legionella pneumophila, the causative agent of Legionnaire's disease, uses to kill eukaryotic cells. Here we show that the infection of D. discoideum by L. pneumophila results in a decrease in mitochondrial messenger RNAs, beginning more than 8 hours prior to detectable host cell death. These changes can be mimicked by hydrogen peroxide treatment, but not by other cytotoxic agents. The mitochondrial large subunit ribosomal RNA (LSU rRNA is also cleaved at three specific sites during the course of infection. Two LSU rRNA fragments appear first, followed by smaller fragments produced by additional cleavage events. The initial LSU rRNA cleavage site is predicted to be on the surface of the large subunit of the mitochondrial ribosome, while two secondary sites map to the predicted interface with the small subunit. No LSU rRNA cleavage was observed after exposure of D. discoideum to hydrogen peroxide, or other cytotoxic chemicals that kill cells in a variety of ways. Functional L. pneumophila type II and type IV secretion systems are required for the cleavage, establishing a correlation between the pathogenesis of L. pneumophila and D. discoideum LSU rRNA destruction. LSU rRNA cleavage was not observed in L. pneumophila infections of Acanthamoeba castellanii or human U937 cells, suggesting that L. pneumophila uses distinct mechanisms to interrupt metabolism in different hosts. Thus, L. pneumophila infection of D. discoideum results in dramatic decrease of mitochondrial RNAs, and in the specific cleavage of mitochondrial rRNA. The predicted location of the cleavage sites on the mitochondrial ribosome suggests that rRNA destruction is initiated by a specific sequence of events. These findings suggest that L. pneumophila specifically disrupts mitochondrial

Real-time PCR systems targeting giant viruses of amoebae and their virophages.

Science.gov (United States)

Ngounga, Tatsiana; Pagnier, Isabelle; Reteno, Dorine-Gaelle Ikanga; Raoult, Didier; La Scola, Bernard; Colson, Philippe

2013-01-01

Giant viruses that infect amoebae, including mimiviruses and marseilleviruses, were first described in 2003. Virophages were subsequently described that infect mimiviruses. Culture isolation with Acanthamoeba spp. and metagenomic studies have shown that these giant viruses are common inhabitants of our biosphere and have enabled the recent detection of these viruses in human samples. However, the genomes of these viruses display substantial genetic diversity, making it a challenge to examine their presence in environmental and clinical samples using conventional and real-time PCR. We designed and evaluated the performance of PCR systems capable of detecting all currently isolated mimiviruses, marseilleviruses and virophages to assess their prevalence in various samples. Our real-time PCR assays accurately detected all or most of the members of the currently delineated lineages of giant viruses infecting acanthamoebae as well as the mimivirus virophages, and enabled accurate classification of the mimiviruses of amoebae in lineages A, B or C. We were able to detect four new mimiviruses directly from environmental samples and correctly classified these viruses within mimivirus lineage C. This was subsequently confirmed by culture on amoebae followed by partial Sanger sequencing. PCR systems such as those implemented here may contribute to an improved understanding of the prevalence of mimiviruses, their virophages and marseilleviruses in humans.

Differentiation-inducing factor-1 and -2 function also as modulators for Dictyostelium chemotaxis.

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Hidekazu Kuwayama

Full Text Available BACKGROUND: In the early stages of development of the cellular slime mold Dictyostelium discoideum, chemotaxis toward cAMP plays a pivotal role in organizing discrete cells into a multicellular structure. In this process, a series of signaling molecules, such as G-protein-coupled cell surface receptors for cAMP, phosphatidylinositol metabolites, and cyclic nucleotides, function as the signal transducers for controlling dynamics of cytoskeleton. Differentiation-inducing factor-1 and -2 (DIF-1 and DIF-2 were originally identified as the factors (chlorinated alkylphenones that induce Dictyostelium stalk cell differentiation, but it remained unknown whether the DIFs had any other physiologic functions. METHODOLOGY/PRINCIPAL FINDINGS: To further elucidate the functions of DIFs, in the present study we investigated their effects on chemotaxis under various conditions. Quite interestingly, in shallow cAMP gradients, DIF-1 suppressed chemotaxis whereas DIF-2 promoted it greatly. Analyses with various mutants revealed that DIF-1 may inhibit chemotaxis, at least in part, via GbpB (a phosphodiesterase and a decrease in the intracellular cGMP concentration ([cGMP](i. DIF-2, by contrast, may enhance chemotaxis, at least in part, via RegA (another phosphodiesterase and an increase in [cGMP](i. Using null mutants for DimA and DimB, the transcription factors that are required for DIF-dependent prestalk differentiation, we also showed that the mechanisms for the modulation of chemotaxis by DIFs differ from those for the induction of cell differentiation by DIFs, at least in part. CONCLUSIONS/SIGNIFICANCE: Our findings indicate that DIF-1 and DIF-2 function as negative and positive modulators for Dictyostelium chemotaxis, respectively. To our knowledge, this is the first report in any organism of physiologic modulators (small molecules for chemotaxis having differentiation-inducing activity.

Response of testate amoebae to a late Holocene ecosystem shift in an Amazonian peatland.

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Swindles, Graeme T; Kelly, Thomas J; Roucoux, Katherine H; Lawson, Ian T

2018-03-15

To date there have only been two studies using testate amoebae as palaeoecological indicators in tropical peatlands. Here we present a new ∼500-year testate amoeba record from San Jorge, a domed peatland in Peruvian Amazonia, which has a well-constrained vegetation history based on pollen analysis. We observe a major shift from Hyalosphenia subflava to Cryptodifflugia oviformis-dominated communities at ∼50 cm depth (c. AD 1760), which suggests a change to drier conditions in the peatland. The application of a statistical transfer function also suggests a deepening of the water table at this time. The transition in the microbial assemblage occurs at a time when pollen and geochemical data indicate drier conditions (reduced influence of river flooding), leading to an ecosystem switch to more ombrotrophic-like conditions in the peatland. Our work illustrates the potential of testate amoebae as important tools in tropical peatland palaeoecology, and the power of multiproxy approaches for understanding the long-term development of tropical peatlands. Copyright © 2018 Elsevier GmbH. All rights reserved.

Potentially pathogenic free-living amoebae in some flood-affected areas during 2011 Chiang Mai flood.

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Wannasan, Anchalee; Uparanukraw, Pichart; Songsangchun, Apichart; Morakote, Nimit

2013-01-01

The survey was carried out to investigate the presence of potentially pathogenic free-living amoebae (FLA) during flood in Chiang Mai, Thailand in 2011. From different crisis flood areas, seven water samples were collected and tested for the presence of amoebae using culture and molecular methods. By monoxenic culture, FLA were detected from all samples at 37 °C incubation. The FLA growing at 37 °C were morphologically identified as Acanthamoeba spp., Naegleria spp. and some unidentified amoebae. Only three samples (42.8%), defined as thermotolerant FLA, continued to grow at 42 °C. By molecular methods, two non-thermotolerant FlA were shown to have 99% identity to Acanthamoeba sp. and 98% identity to Hartmannella vermiformis while the two thermotolerant FLA were identified as Echinamoeba exundans (100% identity) and Hartmannella sp. (99% identity). This first report of the occurrence of FLA in water during the flood disaster will provide information to the public to be aware of potentially pathogenic FLA.

Transient Kinetics of a cGMP-dependent cGMP-specific Phosphodiesterase from Dictyostelium discoideum

NARCIS (Netherlands)

Haastert, Peter J.M. van; Lookeren Campagne, Michiel M. van

1984-01-01

Chemotactic stimulation of Dictyostelium discoideum cells induces a fast transient increase of cGMP levels which reach a peak at 10 s. Prestimulation levels are recovered in ~30 s, which is achieved mainly by the action of a guanosine 3',5'-monophosphate cGMP-specific phosphodiesterase. This enzyme

A RabGAP regulates life-cycle duration via trimeric G-protein cascades in Dictyostelium discoideum.

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Hidekazu Kuwayama

Full Text Available BACKGROUND: The life-cycle of cellular slime molds comprises chronobiologically regulated processes. During the growth phase, the amoeboid cells proliferate at a definite rate. Upon starvation, they synthesize cAMP as both first and second messengers in signalling pathways and form aggregates, migrating slugs, and fruiting bodies, consisting of spores and stalk cells, within 24 h. In Dictyostelium discoideum, because most growth-specific events cease during development, proliferative and heterochronic mutations are not considered to be interrelated and no genetic factor governing the entire life-cycle duration has ever been identified. METHODOLOGY/PRINCIPAL FINDINGS: Using yeast 2-hybrid library screening, we isolated a Dictyostelium discoideum RabGAP, Dd Rbg-3, as a candidate molecule by which the Dictyostelium Gα2 subunit directs its effects. Rab GTPase-activating protein, RabGAP, acts as a negative regulator of Rab small GTPases, which orchestrate the intracellular membrane trafficking involved in cell proliferation. Deletion mutants of Dd rbg-3 exhibited an increased growth rate and a shortened developmental period, while an overexpression mutant demonstrated the opposite effects. We also show that Dd Rbg-3 interacts with 2 Gα subunits in an activity-dependent manner in vitro. Furthermore, both human and Caenorhabditis elegans rbg-3 homologs complemented the Dd rbg-3-deletion phenotype in D. discoideum, indicating that similar pathways may be generally conserved in multicellular organisms. CONCLUSIONS/SIGNIFICANCE: Our findings suggest that Dd Rbg-3 acts as a key element regulating the duration of D. discoideum life-span potentially via trimeric G-protein cascades.

Cyclic AMP signalling in Dictyostelium : G-proteins activate separate Ras pathways using specific RasGEFs

NARCIS (Netherlands)

Kae, Helmut; Kortholt, Arjan; Rehmann, Holger; Insall, RobertH.; Van Haastert, Peter J. M.; Spiegelman, George B.; Weeks, Gerald

In general, mammalian Ras guanine nucleotide exchange factors (RasGEFs) show little substrate specificity, although they are often thought to regulate specific pathways. Here, we provide in vitro and in vivo evidence that two RasGEFs can each act on specific Ras proteins. During Dictyostelium

Flourish or flush: effects of simulated extreme rainfall events on Sphagnum-dwelling testate amoebae in a subarctic bog (Abisko, Sweden).

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Tsyganov, Andrey N; Keuper, Frida; Aerts, Rien; Beyens, Louis

2013-01-01

Extreme precipitation events are recognised as important drivers of ecosystem responses to climate change and can considerably affect high-latitude ombrotrophic bogs. Therefore, understanding the relationships between increased rainfall and the biotic components of these ecosystems is necessary for an estimation of climate change impacts. We studied overall effects of increased magnitude, intensity and frequency of rainfall on assemblages of Sphagnum-dwelling testate amoebae in a field climate manipulation experiment located in a relatively dry subarctic bog (Abisko, Sweden). The effects of the treatment were estimated using abundance, species diversity and structure of living and empty shell assemblages of testate amoebae in living and decaying layers of Sphagnum. Our results show that increased rainfall reduced the mean abundance and species richness of living testate amoebae. Besides, the treatment affected species structure of both living and empty shell assemblages, reducing proportions of hydrophilous species. The effects are counterintuitive as increased precipitation-related substrate moisture was expected to have opposite effects on testate amoeba assemblages in relatively dry biotopes. Therefore, we conclude that other rainfall-related factors such as increased infiltration rates and frequency of environmental disturbances can also affect testate amoeba assemblages in Sphagnum and that hydrophilous species are particularly sensitive to variation in these environmental variables.

The Parkinson's disease-associated protein DJ-1 plays a positive nonmitochondrial role in endocytosis in Dictyostelium cells

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Suwei Chen

2017-10-01

Full Text Available The loss of function of DJ-1 caused by mutations in DJ1 causes a form of familial Parkinson's disease (PD. However, the role of DJ-1 in healthy and in PD cells is poorly understood. Even its subcellular localization in mammalian cells is uncertain, with both cytosolic and mitochondrial locations having been reported. We show here that DJ-1 is normally located in the cytoplasm in healthy Dictyostelium discoideum cells. With its unique life cycle, straightforward genotype-phenotype relationships, experimental accessibility and genetic tractability, D. discoideum offers an attractive model to investigate the roles of PD-associated genes. Furthermore, the study of mitochondrial biology, mitochondrial genome transcription and AMP-activated protein kinase-mediated cytopathologies in mitochondrial dysfunction have been well developed in this organism. Unlike mammalian systems, Dictyostelium mitochondrial dysfunction causes a reproducible and readily assayed array of aberrant phenotypes: defective phototaxis, impaired growth, normal rates of endocytosis and characteristic defects in multicellular morphogenesis. This makes it possible to study whether the underlying cytopathological mechanisms of familial PD involve mitochondrial dysfunction. DJ-1 has a single homologue in the Dictyostelium genome. By regulating the expression level of DJ-1 in D. discoideum, we show here that in unstressed cells, DJ-1 is required for normal rates of endocytic nutrient uptake (phagocytosis and, to a lesser extent, pinocytosis and thus growth. Reduced expression of DJ-1 had no effect on phototaxis in the multicellular migratory ‘slug’ stage of the life cycle, but resulted in thickened stalks in the final fruiting bodies. This pattern of phenotypes is distinct from that observed in Dictyostelium to result from mitochondrial dyfunction. Direct measurement of mitochondrial respiratory function in intact cells revealed that DJ-1 knockdown stimulates whereas DJ-1

Effect of UV irradiation (253.7 nm) on free Legionella and Legionella associated with its amoebae hosts.

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Cervero-Aragó, Sílvia; Sommer, Regina; Araujo, Rosa M

2014-12-15

Water systems are the primary reservoir for Legionella spp., where the bacteria live in association with other microorganisms, such as free-living amoebae. A wide range of disinfection treatments have been studied to control and prevent Legionella colonization but few of them were performed considering its relation with protozoa. In this study, the effectiveness of UV irradiation (253.7 nm) using low-pressure lamps was investigated as a disinfection method for Legionella and amoebae under controlled laboratory conditions. UV treatments were applied to 5 strains of Legionella spp., 4 strains of free-living amoeba of the genera Acanthamoeba and Vermamoeba, treating separately trophozoites and cysts, and to two different co-cultures of Legionella pneumophila with the Acanthamoeba strains. No significant differences in the UV inactivation behavior were observed among Legionella strains tested which were 3 logs reduced for fluences around 45 J/m(2). UV irradiation was less effective against free-living amoebae; which in some cases required up to 990 J/m(2) to obtain the same population reduction. UV treatment was more effective against trophozoites compared to cysts; moreover, inactivation patterns were clearly different between the genus Acanthamoeba and Vermamoeba. For the first time data about Vermamoeba vermiformis UV inactivation has been reported in a study. Finally, the results showed that the association of L. pneumophila with free-living amoebae decreases the effectiveness of UV irradiation against the bacteria in a range of 1.5-2 fold. That fact demonstrates that the relations established between different microorganisms in the water systems can modify the effectiveness of the UV treatments applied. Copyright © 2014 Elsevier Ltd. All rights reserved.

[The role of the floodplain gradient in structuring of testate amoebae communities in the Ilych River].

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Mazeĭ, Iu A; Malysheva, E A; Lapteva, E M; Komarov, A A; Taskaeva, A A

2012-01-01

Forty-two testate amoebae taxa were identified in alluvial soils of floodplain islands in the Ilych River. Among the pedo- and eurybionts, there were aquatic rhizopods. Along the floodplain transect (willow --> meadow --> deciduous forest --> coniferous forest), the testate amoebae community changed directly. There are spatially homogeneous (low beta-diversity) testacean communities but species rich on the local level (high alpha-diversity) within forests. Within willows and meadows, communities are characterized by low alpha-diversity and high heterogeneity that leads to high gamma-diversity.

Functional similarities between the dictyostelium protein AprA and the human protein dipeptidyl-peptidase IV.

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Herlihy, Sarah E; Tang, Yu; Phillips, Jonathan E; Gomer, Richard H

2017-03-01

Autocrine proliferation repressor protein A (AprA) is a protein secreted by Dictyostelium discoideum cells. Although there is very little sequence similarity between AprA and any human protein, AprA has a predicted structural similarity to the human protein dipeptidyl peptidase IV (DPPIV). AprA is a chemorepellent for Dictyostelium cells, and DPPIV is a chemorepellent for neutrophils. This led us to investigate if AprA and DPPIV have additional functional similarities. We find that like AprA, DPPIV is a chemorepellent for, and inhibits the proliferation of, D. discoideum cells, and that AprA binds some DPPIV binding partners such as fibronectin. Conversely, rAprA has DPPIV-like protease activity. These results indicate a functional similarity between two eukaryotic chemorepellent proteins with very little sequence similarity, and emphasize the usefulness of using a predicted protein structure to search a protein structure database, in addition to searching for proteins with similar sequences. © 2016 The Protein Society.

Functional similarities between the dictyostelium protein AprA and the human protein dipeptidyl‐peptidase IV

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Herlihy, Sarah E.; Tang, Yu; Phillips, Jonathan E.

2017-01-01

Abstract Autocrine proliferation repressor protein A (AprA) is a protein secreted by Dictyostelium discoideum cells. Although there is very little sequence similarity between AprA and any human protein, AprA has a predicted structural similarity to the human protein dipeptidyl peptidase IV (DPPIV). AprA is a chemorepellent for Dictyostelium cells, and DPPIV is a chemorepellent for neutrophils. This led us to investigate if AprA and DPPIV have additional functional similarities. We find that like AprA, DPPIV is a chemorepellent for, and inhibits the proliferation of, D. discoideum cells, and that AprA binds some DPPIV binding partners such as fibronectin. Conversely, rAprA has DPPIV‐like protease activity. These results indicate a functional similarity between two eukaryotic chemorepellent proteins with very little sequence similarity, and emphasize the usefulness of using a predicted protein structure to search a protein structure database, in addition to searching for proteins with similar sequences. PMID:28028841

Environmental Free-Living Amoebae Isolated from Soil in Khon Kaen, Thailand, Antagonize Burkholderia pseudomallei.

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Parumon Noinarin

Full Text Available Presence of Burkholderia pseudomallei in soil and water is correlated with endemicity of melioidosis in Southeast Asia and northern Australia. Several biological and physico-chemical factors have been shown to influence persistence of B. pseudomallei in the environment of endemic areas. This study was the first to evaluate the interaction of B. pseudomallei with soil amoebae isolated from B. pseudomallei-positive soil site in Khon Kaen, Thailand. Four species of amoebae, Paravahlkampfia ustiana, Acanthamoeba sp., Naegleria pagei, and isolate A-ST39-E1, were isolated, cultured and identified based on morphology, movement and 18S rRNA gene sequence. Co-cultivation combined with a kanamycin-protection assay of B. pseudomallei with these amoebae at MOI 20 at 30°C were evaluated during 0-6 h using the plate count technique on Ashdown's agar. The fate of intracellular B. pseudomallei in these amoebae was also monitored by confocal laser scanning microscopy (CLSM observation of the CellTracker™ Orange-B. pseudomallei stained cells. The results demonstrated the ability of P. ustiana, Acanthamoeba sp. and isolate A-ST39-E1 to graze B. pseudomallei. However, the number of internalized B. pseudomallei substantially decreased and the bacterial cells disappeared during the observation period, suggesting they had been digested. We found that B. pseudomallei promoted the growth of Acanthamoeba sp. and isolate A-ST39-E1 in co-cultures at MOI 100 at 30°C, 24 h. These findings indicated that P. ustiana, Acanthamoeba sp. and isolate A-ST39-E1 may prey upon B. pseudomallei rather than representing potential environmental reservoirs in which the bacteria can persist.

Late Holocene palaeohydrological changes in a Sphagnum peat bog from NW Romania based on testate amoebae

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Andrei-Cosmin Diaconu

2016-04-01

Full Text Available This paper investigates the possibility of reconstructing the palaeohydrological changes in an active Sphagnum peat bog from north-western Romania using testate amoebae fauna and organic matter content determined by loss on ignition (LOI. In total 28 taxa of testate amoebae were identified of which 11 were frequent enough to present a remarkable ecological significance. Based on the relative abundance of these taxa nine zones were identified, crossing from very wet to dry climate conditions. The wet periods identified are characterized by taxa like Centropyxis cassis, Amphitrema flavum and Hyalosphenia papilio, while in the dry periods Difflugia pulex and Nebela militaris thrive. We showed that combining qualitative information regarding hydrological preferences with the quantitative percentage data from the fossil record it is possible to obtain information regarding major surface moisture changes from the peat bog surface. Furthermore we identified a link between distribution of testate amoebae assemblages, organic matter variation and minerogenic material.

Caffeine sensitive repair and mutation induction in UV- or γ-ray-irradiated Dictyostelium discoideum

International Nuclear Information System (INIS)

Kanishi, Nobuji; Kinjo, Yasuhito; Watanabe, Makoto.

1990-01-01

It seems that certain kinds of chemical substances increase the distortion in molecules, change the high order microstructures of nuclei and chromosomes, and exert large variation to the function of repairing the damage of genes due to radiation and others, by coupling with DNA, protein or enzyme system. It has been well known that caffeine is one of such compounds, and by coupling with DNA, it increases the damage due to ultraviolet ray and gives the action of obstructing repair in addition to the action of inducing the abnormality of chromosomes and mutation. Dictyostelium discoideum has the simplest nuclear structure, and shows extremely high resistance to radiation by its high restoration ability. The authors have advanced the research by paying attention to its characteristics, and comparing the Dictyostelium discoideum as one model system with the lymphocyte system of higher animals. This time, the authors analyzed the characteristics of two kinds of sensitivity repair process of caffeine, and investigated into their relation with the occurrence of mutation. The experimental method and the results are reported. (K.I.)

Caffeine sensitive repair and mutation induction in UV- or. gamma. -ray-irradiated Dictyostelium discoideum

Energy Technology Data Exchange (ETDEWEB)

Kanishi, Nobuji (Tokyo Metropolitan Research Lab. of Public Health (Japan)); Kinjo, Yasuhito; Watanabe, Makoto

1990-01-01

It seems that certain kinds of chemical substances increase the distortion in molecules, change the high order microstructures of nuclei and chromosomes, and exert large variation to the function of repairing the damage of genes due to radiation and others, by coupling with DNA, protein or enzyme system. It has been well known that caffeine is one of such compounds, and by coupling with DNA, it increases the damage due to ultraviolet ray and gives the action of obstructing repair in addition to the action of inducing the abnormality of chromosomes and mutation. Dictyostelium discoideum has the simplest nuclear structure, and shows extremely high resistance to radiation by its high restoration ability. The authors have advanced the research by paying attention to its characteristics, and comparing the Dictyostelium discoideum as one model system with the lymphocyte system of higher animals. This time, the authors analyzed the characteristics of two kinds of sensitivity repair process of caffeine, and investigated into their relation with the occurrence of mutation. The experimental method and the results are reported. (K.I.).

Seasonal abundances of naked amoebae in biofilms on shells of zebra mussels (Dreissena polymorpha) with comparative data from rock scrapings.

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Bischoff, Paul J; Wetmore, Scott

2009-01-01

In North America, zebra mussels (Dreissena polymorpha) are notoriously known as invasive species. The abundance of naked amoebae sampled from the shells of zebra mussels was compared with abundances from rock scrapings at approximately monthly intervals for 1 year. The sites were 2 km apart along the same shoreline. No significant difference in abundance of naked amoebae (F = 1.44; P amoebae in winter, followed by peaks in early spring. The percent encysted increased from a low of 1% in the summer to 80% in early winter.

Testate amoebae communities sensitive to surface moisture conditions in Patagonian peatlands

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Loisel, J.; Booth, R.; Charman, D.; van Bellen, S.; Yu, Z.

2017-12-01

Here we examine moss surface samples that were collected during three field campaigns (2005, 2010, 2014) across southern Patagonian peatlands to assess the potential use of testate amoebae and 13C isotope data as proxy indicators of soil moisture. These proxies have been widely tested across North America, but their use as paleoecological tools remains sparse in the southern hemisphere. Samples were collected along a hydrological gradient spanning a range of water table depth from 0cm in wet hollows to over 85cm in dry hummocks. Moss moisture content was measured in the field. Over 25 taxa were identified, with many of them not found in North America. Ordinations indicate statistically significant and dominant effects of soil moisture and water table depth on testate assemblages, though interestingly 13C is even more strongly correlated with testates amoebae than direct soil conditions. It is possible that moss 13C signature constitutes a compound indicator that represents seasonal soil moisture better than opportunistic sampling during field campaigns. There is no significant effect of year or site across the dataset. In addition to providing a training set that translates testate amoebae moisture tolerance range into water tabel depth for Patagonian peatlands, we also compare our results with those from the North American training set to show that, despite 'novel' Patagonian taxa, the robustness of international training sets is probably sufficient to quantify most changes in soil moisture from any site around the world. We also identify key indicator species that are shown to be of universal value in peat-based hydrological reconstructions.

Evidence of test detachment in Astrorhiza limicola and two consequential synonyms: Amoeba gigantea and Megamoebomyxa argillobia (Foraminiferida)

DEFF Research Database (Denmark)

Cedhagen, Tomas; Tendal, Ole S.

1989-01-01

Laboratory observations and experiments demonstrate that the naked rhizopods Amoeba gigantea SANDAHL, 1857 and Megamoebomyxa argillo~ia NYHOLM, 1950, and the foraminifers Astrorhiza arenifera STSCHEDRlNA, 1946, A. sabulifera STSCHEDRINA, 1946 and A. arctlca STSCHEDRINA, 1958 are synonyms of Astro......Laboratory observations and experiments demonstrate that the naked rhizopods Amoeba gigantea SANDAHL, 1857 and Megamoebomyxa argillo~ia NYHOLM, 1950, and the foraminifers Astrorhiza arenifera STSCHEDRlNA, 1946, A. sabulifera STSCHEDRINA, 1946 and A. arctlca STSCHEDRINA, 1958 are synonyms...

Control of Branchionus sp. and Amoeba sp. in cultures of Arthrospira sp. Control de Branchionus sp. y Amoeba sp. en cultivos de Arthrospira sp.

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Carlos Méndez

2012-09-01

Full Text Available Cultivation of cyanobacterium Arthrospira sp. has been developed in many countries for the production of proteins, pigments and other compounds. Outdoor mass cultures are often affected by biological contamination, drastically reducing productivity as far as bringing death. This study evaluates the control of Branchionus sp. and Amoeba sp. with two chemical compounds: urea (U and ammonium bicarbonate (AB, in laboratory conditions and outdoor mass culture of Arthrospira sp. The lethal concentration 100 (LC100 at 24 h for Branchionus sp. and Amoeba sp. determined was of 60-80 mg L-1 (U and 100-150 mg L-1 (AB. The average effective inhibition concentration for 50% of the population (IC50 in Arthrospira sp., after 72 h, was 80 mg L-1 (U and 150 mg L-1 (AB. The application of doses of 60 mg L-1 (U or 100 mg L-1 (AB in the outdoor mass culture of this contaminated microalga, completely inhibited grazing and did not affect the growth of Arthrospira sp. but rather promoted rapid recovery of algal density at levels prior to infestation. These compounds provided an economical and effective control of predators in cultures of Arthrospira sp.El cultivo de la cianobacteria Arthrospira sp. ha sido desarrollado en muchos países para la obtención de proteínas, pigmentos y otros compuestos. Cultivo que a nivel industrial se ve afectado frecuentemente por contaminación biológica, reduciendo drásticamente la productividad hasta causar la muerte. Este estudio evalúa el control de Branchionus sp. y de Amoeba sp. con dos compuestos químicos, la urea (U y bicarbonato de amonio (AB en cultivos de Arthrospira sp. La concentración letal 100 (LC100 determinada a las 24 h para Branchionus sp. y Amoeba sp. fue de 60-80 mg L-1 (U y 100-150 mg L-1 (AB. La concentración media de inhibición efectiva, después de 72 h, para el 50% de la población (IC50 en Arthrospira fue de 80 mg L-1 (U y 150 mg L-1 (AB. La aplicación de dosis de 60 mg L-1 (U ó 100 mg L-1 (AB en

Pathogenic waterborne free-living amoebae: An update from selected Southeast Asian countries

Science.gov (United States)

Abdul Majid, Mohamad Azlan; Mahboob, Tooba; Mong, Brandon G. J.; Jaturas, Narong; Richard, Reena Leeba; Tian-Chye, Tan; Phimphila, Anusorn; Mahaphonh, Panomphanh; Aye, Kyaw Nyein; Aung, Wai Lynn; Chuah, Joon; Ziegler, Alan D.; Yasiri, Atipat; Sawangjaroen, Nongyao; Lim, Yvonne A. L.; Nissapatorn, Veeranoot

2017-01-01

Data on the distribution of free-living amoebae is still lacking especially in Southeast Asian region. The aquatic environment revealed a high occurrence of free-living amoebae (FLA) due to its suitable condition and availability of food source, which subsequently causes infection to humans. A total of 94 water samples consisted of both treated and untreated from Laos (31), Myanmar (42), and Singapore (21) were investigated for the presence of pathogenic FLA. Each water sample was filtered and cultured onto non-nutrient agar seeded with live suspension of Escherichia coli and incubated at room temperature. Morphological identification was conducted for both trophozoites and cysts via microscopic stains (Giemsa and immunofluorescence). The presence of Naegleria-like structures was the most frequently encountered in both treated and untreated water samples, followed by Acanthamoeba-like and Vermamoeba-like features. To identify the pathogenic isolates, species-specific primer sets were applied for molecular identification of Acanthamoeba, Naegleria, and Vermamoeba. The pathogenic species of Acanthamoeba lenticulata and A. triangularis were detected from untreated water samples, while Vermamoeba vermiformis was found in both treated and untreated water samples. Our results suggested that poor water quality as well as inadequate maintenance and treatment might be the cause of this alarming problem since chlorine disinfection is ineffective in eradicating these amoebas in treated water samples. Regular monitoring and examination of water qualities are necessary in order to control the growth, hence, further preventing the widespread of FLA infections among the public. PMID:28212409

Contrasting diversity of testate amoebae communities in Sphagnum and brown-moss dominated patches in relation to shell counts.

Science.gov (United States)

Lizoňová, Zuzana; Horsák, Michal

2017-04-01

Ecological studies of peatland testate amoebae are generally based on totals of 150 individuals per sample. However, the suitability of this standard has never been assessed for alkaline habitats such as spring fens. We explored the differences in testate amoeba diversity between Sphagnum and brown-moss microhabitats at a mire site with a highly diversified moss layer which reflects the small-scale heterogeneity in groundwater chemistry. Relationships between sampling efficiency and sample completeness were explored using individual-based species accumulation curves and the effort required to gain an extra species was assessed. Testate amoeba diversity differed substantially between microhabitats, with brown mosses hosting on average twice as many species and requiring greater shell totals to reach comparable sample analysis efficiency as for Sphagnum. Thus, for samples from alkaline conditions an increase in shell totals would be required and even an overall doubling up to 300 individuals might be considered for reliable community description. Our small-scale data are likely not robust enough to provide an ultimate solution for the optimization of shell totals. However, the results proved that testate amoebae communities from acidic and alkaline environments differ sharply in both species richness and composition and they might call for different methodological approaches. Copyright © 2017 Elsevier GmbH. All rights reserved.

Effect of drugs on lipid methylation, receptor-adenylate cyclase coupling and cyclic AMP secretion in Dictyostelium discoideum

NARCIS (Netherlands)

Van Waarde, Aren; Van Haastert, P.J.M.

1986-01-01

Intercellular communication in Dictyostelium discoldeum takes place by means of cyclic AMP-induced cyclic AMP-synthesis and secretion. Since phospholipid methylation has been suggested to play a role in receptor-adenylate cyclase coupling, we examined the effects of transmethylation inhibitors on

External stimulation strength controls actin response dynamics in Dictyostelium cells

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Hsu, Hsin-Fang; Westendorf, Christian; Tarantola, Marco; Zykov, Vladimir; Bodenschatz, Eberhard; Beta, Carsten

2015-03-01

Self-sustained oscillation and the resonance frequency of the cytoskeletal actin polymerization/depolymerization have recently been observed in Dictyostelium, a model system for studying chemotaxis. Here we report that the resonance frequency is not constant but rather varies with the strength of external stimuli. To understand the underlying mechanism, we analyzed the polymerization and depolymerization time at different levels of external stimulation. We found that polymerization time is independent of external stimuli but the depolymerization time is prolonged as the stimulation increases. These observations can be successfully reproduced in the frame work of our time delayed differential equation model.

Collective Behavior of Amoebae in Thin Films

Science.gov (United States)

Bae, Albert

2005-03-01

We have discovered new aspects of social behavior in Dictyostelium discoideum by culturing high density colonies in liquid media depleted of nutrients in confined geometries by using three different preparations: I. thin (15-40um thick) and II. ultrathin (behavior of cells despite flattening that increased their areas by over an order of magnitude. We also observed that the earliest synchronized response of cells following the onset of starvation, a precursor to aggregation, was hastened by reducing the thickness of the aqueous culture layer. We were surprised to find that the threshold concentration for aggregation was raised by thin film confinement when compared to bulk behavior. Finally, both the ultra thin and microfluidic preparations reveal, with new clarity, vortex states of aggregation.

TRE5-A retrotransposition profiling reveals putative RNA polymerase III transcription complex binding sites on the Dictyostelium extrachromosomal rDNA element.

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Thomas Spaller

Full Text Available The amoeba Dictyostelium discoideum has a haploid genome in which two thirds of the DNA encodes proteins. Consequently, the space available for selfish mobile elements to expand without excess damage to the host genome is limited. The non-long terminal repeat retrotransposon TRE5-A maintains an active population in the D. discoideum genome and apparently adapted to this gene-dense environment by targeting positions ~47 bp upstream of tRNA genes that are devoid of protein-coding regions. Because only ~24% of tRNA genes are associated with a TRE5-A element in the reference genome, we evaluated whether TRE5-A retrotransposition is limited to this subset of tRNA genes. We determined that a tagged TRE5-A element (TRE5-Absr integrated at 384 of 405 tRNA genes, suggesting that expansion of the current natural TRE5-A population is not limited by the availability of targets. We further observed that TRE5-Absr targets the ribosomal 5S gene on the multicopy extrachromosomal DNA element that carries the ribosomal RNA genes, indicating that TRE5-A integration may extend to the entire RNA polymerase III (Pol III transcriptome. We determined that both natural TRE5-A and cloned TRE5-Absr retrotranspose to locations on the extrachromosomal rDNA element that contain tRNA gene-typical A/B box promoter motifs without displaying any other tRNA gene context. Based on previous data suggesting that TRE5-A targets tRNA genes by locating Pol III transcription complexes, we propose that A/B box loci reflect Pol III transcription complex assembly sites that possess a function in the biology of the extrachromosomal rDNA element.

What is the optimum sample size for the study of peatland testate amoeba assemblages?

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Mazei, Yuri A; Tsyganov, Andrey N; Esaulov, Anton S; Tychkov, Alexander Yu; Payne, Richard J

2017-10-01

Testate amoebae are widely used in ecological and palaeoecological studies of peatlands, particularly as indicators of surface wetness. To ensure data are robust and comparable it is important to consider methodological factors which may affect results. One significant question which has not been directly addressed in previous studies is how sample size (expressed here as number of Sphagnum stems) affects data quality. In three contrasting locations in a Russian peatland we extracted samples of differing size, analysed testate amoebae and calculated a number of widely-used indices: species richness, Simpson diversity, compositional dissimilarity from the largest sample and transfer function predictions of water table depth. We found that there was a trend for larger samples to contain more species across the range of commonly-used sample sizes in ecological studies. Smaller samples sometimes failed to produce counts of testate amoebae often considered minimally adequate. It seems likely that analyses based on samples of different sizes may not produce consistent data. Decisions about sample size need to reflect trade-offs between logistics, data quality, spatial resolution and the disturbance involved in sample extraction. For most common ecological applications we suggest that samples of more than eight Sphagnum stems are likely to be desirable. Copyright © 2017 Elsevier GmbH. All rights reserved.

Pathogenic free-living amoebae in a closed-loop power plant; risk assessment and risk management

International Nuclear Information System (INIS)

Cabanes, P.; Pernin, P.

1998-01-01

Since 1980, the water used for cooling in French power plants has been tested for pathogenic amoebae, especially Naegleria fowleri, the causative agent of Primary Amoebic Meningoencephalitis (PAM), a rapid fatal disease of the central nervous system. The replacement of brass condensers by stainless steel condensers resulted in increased Naegleria fowleri development, to a density of as much as 3000 l -1 in the Dampierre power plant cooling water. Downstream from Dampierre, the maximum detected density of this amoeba during the summer of 1995 was 80 l -1 , at low river flow. The replacement of a second condenser in 1996 at the same power plant was expected to double the amoebae concentration in the river. The hypothetical PAM risk for swimmers was then predicted to be 10 -4 per swim. To reduce the risk continuous chlorination of the closed-loop cooling system was implemented at a free residual chlorine level in the range of 0.3-0.5 mg.l -1 . Naegleria fowleri concentrations decreased immediately and thereafter remained under 4 l -1 . Total residual chlorine and chlorinated organic compounds were also monitored in the evaluation of the environmental impact of this preventive action. (authors)

Chemotaxis to cyclic AMP and folic acid is mediated by different G proteins in Dictyostelium discoideum

NARCIS (Netherlands)

Kesbeke, Fanja; Haastert, Peter J.M. van; Wit, René J.W. de; Snaar-Jagalska, B. Ewa

1990-01-01

Mutant Frigid A (fgdA) of Dictyostelium discoideum is defective in a functional Gα2 subunit of a G protein and is characterized by a complete blockade of the cyclic AMP-mediated sensory transduction steps, including cyclic AMP relay, chemotaxis and the cyclic GMP response. Folic acid-mediated

Dictyostelium cells bind a secreted autocrine factor that represses cell proliferation

OpenAIRE

Choe, Jonathan M; Bakthavatsalam, Deenadayalan; Phillips, Jonathan E; Gomer, Richard H

2009-01-01

Abstract Background Dictyostelium cells secrete the proteins AprA and CfaD. Cells lacking either AprA or CfaD proliferate faster than wild type, while AprA or CfaD overexpressor cells proliferate slowly, indicating that AprA and CfaD are autocrine factors that repress proliferation. CfaD interacts with AprA and requires the presence of AprA to slow proliferation. To determine if CfaD is necessary for the ability of AprA to slow proliferation, whether AprA binds to cells, and if so whether the...

An electronic implementation of amoeba anticipation

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Ziegler, Martin; Ochs, Karlheinz; Hansen, Mirko; Kohlstedt, Hermann

2014-02-01

In nature, the capability of memorizing environmental changes and recalling past events can be observed in unicellular organisms like amoebas. Pershin and Di Ventra have shown that such learning behavior can be mimicked in a simple memristive circuit model consisting of an LC (inductance capacitance) contour and a memristive device. Here, we implement this model experimentally by using an Ag/TiO2- x /Al memristive device. A theoretical analysis of the circuit is used to gain insight into the functionality of this model and to give advice for the circuit implementation. In this respect, the transfer function, resonant frequency, and damping behavior for a varying resistance of the memristive device are discussed in detail.

Heteromeric p97/p97R155C complexes induce dominant negative changes in wild-type and autophagy 9-deficient Dictyostelium strains.

Directory of Open Access Journals (Sweden)

Khalid Arhzaouy

Full Text Available Heterozygous mutations in the human VCP (p97 gene cause autosomal-dominant IBMPFD (inclusion body myopathy with early onset Paget's disease of bone and frontotemporal dementia, ALS14 (amyotrophic lateral sclerosis with or without frontotemporal dementia and HSP (hereditary spastic paraplegia. Most prevalent is the R155C point mutation. We studied the function of p97 in the social amoeba Dictyostelium discoideum and have generated strains that ectopically express wild-type (p97 or mutant p97 (p97(R155C fused to RFP in AX2 wild-type and autophagy 9 knock-out (ATG9(KO cells. Native gel electrophoresis showed that both p97 and p97(R155C assemble into hexamers. Co-immunoprecipitation studies revealed that endogenous p97 and p97(R155C-RFP form heteromers. The mutant strains displayed changes in cell growth, phototaxis, development, proteasomal activity, ubiquitinylated proteins, and ATG8(LC3 indicating mis-regulation of multiple essential cellular processes. Additionally, immunofluorescence analysis revealed an increase of protein aggregates in ATG9(KO/p97(R155C-RFP and ATG9(KO cells. They were positive for ubiquitin in both strains, however, solely immunoreactive for p97 in the ATG9(KO mutant. A major finding is that the expression of p97(R155C-RFP in the ATG9(KO strain partially or fully rescued the pleiotropic phenotype. We also observed dose-dependent effects of p97 on several cellular processes. Based on findings in the single versus the double mutants we propose a novel mode of p97 interaction with the core autophagy protein ATG9 which is based on mutual inhibition.

[CHROMATIN ORGANIZATION IN CELL CYCLE OF AMOEBA PROTEUS ACCORDING TO OPTICAL TOMOGRAPHY DATA].

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Demin, S Yu; Berdieva, M A; Podlipaeva, Yu I; Yudin, A L; Goodkov, A V

2015-01-01

For the first time the nuclear cycle of large freshwater amoeba Amoeba proteus was studied by the method of optical tomography. The nuclei were fixed in situ in the cells of synchronized culture, stained by DAPI and examined by confocal laser scanning microscope. 3D-images of intranuclear chromatin were studied in details at different stages of nuclear cycle. The obtained data, together with literary ones allow represent the dynamics of structural organization of the nucleus in Amoeba proteus cell cycle in a new fashion. It was concluded that in this species the two-stage interphase takes place, as well as mitosis of peculiar type which does not correspond to any known type of mitosis according to classification existing now. It is presumed that in the course of nuclear cycle the chromosomes and/or their fragments are amplified, this presumption being in a good correspondence with the data about nuclear DNA hyperreplication in the cell cycle of A. proteus. As a result of chromosomes amplification their number may vary at different stages of cell cycle, and it allows to explain the contradictory data concerning the exact number of chromosomes in this species. The elimination of extra-DNA occurs mainly at the stage between prophase and prometaphase. We presume the majority of chromosomes, or may be even all of them to be referred to cholocentric type according to their behaviour during the mitosis.

Nucleus-associated phosphorylation of Ins(1,4,5)P3 to InsP6 in Dictyostelium

NARCIS (Netherlands)

Kaay, Jeroen van der; Wesseling, Jelle; Haastert, Peter J.M. van

1995-01-01

Although many cells contain large amounts of InsP(6), its metabolism and function is still largely unknown. In Dictyostelium lysates, the formation of InsP(6) by sequential phosphorylation of inositol via Ins(3,4,6)P-3 has been described [Stevens and Irvine (1990) Nature (London) 346, 580-583]; the

Evaluating the use of testate amoebae for palaeohydrological reconstruction in permafrost peatlands

DEFF Research Database (Denmark)

Swindles, Graeme T.; Amesbury, Matthew J.; Turner, T. Edward

2015-01-01

The melting of high-latitude permafrost peatlands is a major concern due to a potential positive feedback on global climate change. We examine the ecology of testate amoebae in permafrost peatlands, based on sites in Sweden (similar to 200 km north of the Arctic Circle). Multivariate statistical ...

The cellulose-binding activity of the PsB multiprotein complex is required for proper assembly of the spore coat and spore viability in Dictyostelium discoideum.

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Srinivasan, S; Griffiths, K R; McGuire, V; Champion, A; Williams, K L; Alexander, S

2000-08-01

The terminal event of spore differentiation in the cellular slime mould Dictyostelium discoideum is the assembly of the spore coat, which surrounds the dormant amoeba and allows the organism to survive during extended periods of environmental stress. The spore coat is a polarized extracellular matrix composed of glycoproteins and cellulose. The process of spore coat formation begins by the regulated secretion of spore coat proteins from the prespore vesicles (PSVs). Four of the major spore coat proteins (SP96, PsB/SP85, SP70 and SP60) exist as a preassembled multiprotein complex within the PSVs. This complete complex has an endogenous cellulose-binding activity. Mutant strains lacking either the SP96 or SP70 proteins produce partial complexes that do not have cellulose-binding activity, while mutants lacking SP60 produce a partial complex that retains this activity. Using a combination of immunofluorescence microscopy and biochemical methods we now show that the lack of cellulose-binding activity in the SP96 and SP70 mutants results in abnormally assembled spore coats and spores with greatly reduced viability. In contrast, the SP60 mutant, in which the PsB complex retains its cellulose-binding activity, produces spores with apparently unaltered structure and viability. Thus, it is the loss of the cellulose-binding activity of the PsB complex, rather than the mere loss of individual spore coat proteins, that results in compromised spore coat structure. These results support the idea that the cellulose-binding activity associated with the complete PsB complex plays an active role in the assembly of the spore coat.

Curcumin inhibits development and cell adhesion in Dictyostelium discoideum: Implications for YakA signaling and GST enzyme function

Energy Technology Data Exchange (ETDEWEB)

Garige, Mamatha; Walters, Eric, E-mail: ewalters@howard.edu

2015-11-13

The molecular basis for nutraceutical properties of the polyphenol curcumin (Curcuma longa, Turmeric) is complex, affecting multiple factors that regulate cell signaling and homeostasis. Here, we report the effect of curcumin on cellular and developmental mechanisms in the eukaryotic model, Dictyostelium discoideum. Dictyostelium proliferation was inhibited in the presence of curcumin, which also suppressed the prestarvation marker, discoidin I, members of the yakA-mediated developmental signaling pathway, and expression of the extracellular matrix/cell adhesion proteins (DdCAD and csA). This resulted in delayed chemotaxis, adhesion, and development of the organism. In contrast to the inhibitory effects on developmental genes, curcumin induced gstA gene expression, overall GST activity, and generated production of reactive oxygen species. These studies expand our knowledge of developmental and biochemical signaling influenced by curcumin, and lends greater consideration of GST enzyme function in eukaryotic cell signaling, development, and differentiation.

Curcumin inhibits development and cell adhesion in Dictyostelium discoideum: Implications for YakA signaling and GST enzyme function

International Nuclear Information System (INIS)

Garige, Mamatha; Walters, Eric

2015-01-01

The molecular basis for nutraceutical properties of the polyphenol curcumin (Curcuma longa, Turmeric) is complex, affecting multiple factors that regulate cell signaling and homeostasis. Here, we report the effect of curcumin on cellular and developmental mechanisms in the eukaryotic model, Dictyostelium discoideum. Dictyostelium proliferation was inhibited in the presence of curcumin, which also suppressed the prestarvation marker, discoidin I, members of the yakA-mediated developmental signaling pathway, and expression of the extracellular matrix/cell adhesion proteins (DdCAD and csA). This resulted in delayed chemotaxis, adhesion, and development of the organism. In contrast to the inhibitory effects on developmental genes, curcumin induced gstA gene expression, overall GST activity, and generated production of reactive oxygen species. These studies expand our knowledge of developmental and biochemical signaling influenced by curcumin, and lends greater consideration of GST enzyme function in eukaryotic cell signaling, development, and differentiation.

The role of cGMP and the rear of the cell in Dictyostelium chemotaxis and cell streaming

NARCIS (Netherlands)

Veltman, Douwe M.; van Haastert, Peter J. M.

2008-01-01

During chemotaxis, pseudopod extensions lead the cell towards the source of attractant. The role of actin-filled pseudopodia at the front of the cell is well recognized, whereas the function of the rear of the cell in chemotaxis and cell-cell interactions is less well known. Dictyostelium cell

Determination of inositol 1,4,5-trisphosphate levels in Dictyostelium by isotope dilution assay

International Nuclear Information System (INIS)

Van Haastert, P.J.

1989-01-01

A commercial isotope dilution assay was used for the determination of Ins(1,4,5)P3 levels in the microorganism Dictyostelium discoideum. Cross-reactivity in the assay was detected with extracts from cells and the medium. The compound which induced this cross-reactivity was tentatively identified as Ins(1,4,5)P3 by (i) codegradation with authentic [ 32 P]Ins(1,4,5)P3 by three specific Ins(1,4,5)P3 phosphatases, and (ii) co-chromatography with authentic [ 32 P]Ins(1,4,5)P3 on HPLC columns. The cellular concentration was estimated as 165 +/- 42 pmol/10(8) cells, yielding a mean intracellular Ins(1,4,5)P3 concentration of 3.3 microM. Dictyostelium cells secrete large amounts of Ins(1,4,5)P3 at a rate of about 10% of the cellular content per minute, yielding about 0.13 microM extracellular Ins(1,4,5)P3 after 15 min in a suspension of 10(8) cells/ml. The chemoattractant cAMP induced a transient increase of the Ins(1,4,5)P3 concentration; the data suggest an intracacellular rise from 3.3 to 5.5 microM with a maximum at 6 s after stimulation

Effect of Wildfire on Sequoiadendron giganteum Growth and CO2 Flux

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Barwegen, S.

2016-12-01

Due to global warming, parts of the United States are becoming drier than ever before. In 2015, we surpassed 9 million acres burned by wildfires nationally (Rice 2015). Wildfires are most common in the Western United States due to drought, and the fact that the summer months are drier than other areas such as the East Coast, so there is a higher risk for wildland fires (Donegan 2016). These high-growth forests that are more frequently burned by wildfires each year are located near mountain ranges on the west side of the United States. They are important to tourism, contain many endangered species, and need to maintain the natural cycle of fire and regrowth for the continued success of the native plant life. This project investigated the effect of burnt soil on Sequoiadendron giganteum trees. Three were grown in burnt potting soil that had been roasted over a grill for 45 minutes (which is the average destructive fire time), and the other three were the control group in unburned potting soil. We assessed growth by measuring height, color, photosynthetically active radiation (PAR), and CO2 flux to evaluate the health of the trees in the two soil conditions. We noted that after two weeks the trunks of the trees growing in burnt soil began to brown in color, and they lost leaves. Over the course of the experiment, the trees growing in burnt soil had reduced levels of photosynthesis as compared to the unburned soil (as measured by the net change in CO2 concentration in a sealed chamber over the course of fifteen minutes intervals). On average, the trees growing in burnt soil had flux rates that were 19.59 ppm CO2 /min. more than those growing in unburned soil. In the dark reactions, the burnt soil flux was 54.5 ppm CO2/min., while the unburned soil averaged 40.5 ppm CO2/min. Our results help quantify the impact of fire on delicate ecosystems that are experiencing an increase in fire activity caused by global warming.

A Dictyostelium chalone uses G proteins to regulate proliferation.

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Bakthavatsalam, Deenadayalan; Choe, Jonathan M; Hanson, Nana E; Gomer, Richard H

2009-07-27

Several studies have shown that organ size, and the proliferation of tumor metastases, may be regulated by negative feedback loops in which autocrine secreted factors called chalones inhibit proliferation. However, very little is known about chalones, and how cells sense them. We previously identified two secreted proteins, AprA and CfaD, which act as chalones in Dictyostelium. Cells lacking AprA or CfaD proliferate faster than wild-type cells, and adding recombinant AprA or CfaD to cells slows their proliferation. We show here that cells lacking the G protein components Galpha8, Galpha9, and Gbeta proliferate faster than wild-type cells despite secreting normal or high levels of AprA and CfaD. Compared with wild-type cells, the proliferation of galpha8-, galpha9- and gbeta- cells are only weakly inhibited by recombinant AprA (rAprA). Like AprA and CfaD, Galpha8 and Gbeta inhibit cell proliferation but not cell growth (the rate of increase in mass and protein per nucleus), whereas Galpha9 inhibits both proliferation and growth. galpha8- cells show normal cell-surface binding of rAprA, whereas galpha9- and gbeta- cells have fewer cell-surface rAprA binding sites, suggesting that Galpha9 and Gbeta regulate the synthesis or processing of the AprA receptor. Like other ligands that activate G proteins, rAprA induces the binding of [3H]GTP to membranes, and GTPgammaS inhibits the binding of rAprA to membranes. Both AprA-induced [3H]GTP binding and the GTPgammaS inhibition of rAprA binding require Galpha8 and Gbeta but not Galpha9. Like aprA- cells, galpha8- cells have reduced spore viability. This study shows that Galpha8 and Gbeta are part of the signal transduction pathway used by AprA to inhibit proliferation but not growth in Dictyostelium, whereas Galpha9 is part of a differealnt pathway that regulates both proliferation and growth, and that a chalone signal transduction pathway uses G proteins.

Antimicrobial activity of denture adhesive associated with Equisetum giganteum- and Punica granatum-enriched fractions against Candida albicans biofilms on acrylic resin surfaces.

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Almeida, Nara Ligia Martins; Saldanha, Luiz Leonardo; da Silva, Rafaela Alves; Pinke, Karen Henriette; da Costa, Eliane Ferraz; Porto, Vinicius Carvalho; Dokkedal, Anne Lígia; Lara, Vanessa Soares

2018-01-01

Candida biofilms adhere to the internal surface of removable dentures, which is an etiological factor in the pathogenesis of denture stomatitis (DS). Adhesive materials are used at the base of maxillary complete dentures to improve their retention and chewing qualities. This article reports the antimicrobial activity of the enriched fractions of Equisetum giganteum and Punica granatum incorporated into a denture adhesive against C. albicans biofilm. The biofilms were induced on the surface of heat-cured acrylic resin specimens that were previously treated with a mixture of adhesive/herb extracts. The antimicrobial activity was evaluated by CFU counts, XTT reduction, and SEM and CLSM analysis. Both herb extracts amplified the anti-biofilm action of the adhesive on the acrylic resin by up to 12 h. Therefore, when these extracts were combined with COREGA®, they played a collaborative and innovative role in biofilm control and can be considered alternatives for temporary use in the treatment and/or prevention of DS.

A retinoblastoma orthologue is a major regulator of S-phase, mitotic, and developmental gene expression in Dictyostelium.

Directory of Open Access Journals (Sweden)

Kimchi Strasser

Full Text Available The retinoblastoma tumour suppressor, Rb, has two major functions. First, it represses genes whose products are required for S-phase entry and progression thus stabilizing cells in G1. Second, Rb interacts with factors that induce cell-cycle exit and terminal differentiation. Dictyostelium lacks a G1 phase in its cell cycle but it has a retinoblastoma orthologue, rblA.Using microarray analysis and mRNA-Seq transcriptional profiling, we show that RblA strongly represses genes whose products are involved in S phase and mitosis. Both S-phase and mitotic genes are upregulated at a single point in late G2 and again in mid-development, near the time when cell cycling is reactivated. RblA also activates a set of genes unique to slime moulds that function in terminal differentiation.Like its mammalian counterpart Dictyostelium, RblA plays a dual role, regulating cell-cycle progression and transcriptional events leading to terminal differentiation. In the absence of a G1 phase, however, RblA functions in late G2 controlling the expression of both S-phase and mitotic genes.

Identification of Pentatricopeptide Repeat Proteins in the Model Organism Dictyostelium discoideum

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Sam Manna

2013-01-01

Full Text Available Pentatricopeptide repeat (PPR proteins are RNA binding proteins with functions in organelle RNA metabolism. They are found in all eukaryotes but have been most extensively studied in plants. We report on the identification of 12 PPR-encoding genes in the genome of the protist Dictyostelium discoideum, with potential homologs in other members of the same lineage and some predicted novel functions for the encoded gene products in protists. For one of the gene products, we show that it localizes to the mitochondria, and we also demonstrate that antisense inhibition of its expression leads to slower growth, a phenotype associated with mitochondrial dysfunction.

A Dictyostelium secreted factor requires a PTEN-like phosphatase to slow proliferation and induce chemorepulsion.

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Herlihy, Sarah E; Tang, Yitai; Gomer, Richard H

2013-01-01

In Dictyostelium discoideum, AprA and CfaD are secreted proteins that inhibit cell proliferation. We found that the proliferation of cells lacking CnrN, a phosphatase and tensin homolog (PTEN)-like phosphatase, is not inhibited by exogenous AprA and is increased by exogenous CfaD. The expression of CnrN in cnrN cells partially rescues these altered sensitivities, suggesting that CnrN is necessary for the ability of AprA and CfaD to inhibit proliferation. Cells lacking CnrN accumulate normal levels of AprA and CfaD. Like cells lacking AprA and CfaD, cnrN cells proliferate faster and reach a higher maximum cell density than wild type cells, tend to be multinucleate, accumulate normal levels of mass and protein per nucleus, and form less viable spores. When cnrN cells expressing myc-tagged CnrN are stimulated with a mixture of rAprA and rCfaD, levels of membrane-associated myc-CnrN increase. AprA also causes chemorepulsion of Dictyostelium cells, and CnrN is required for this process. Combined, these results suggest that CnrN functions in a signal transduction pathway downstream of AprA and CfaD mediating some, but not all, of the effects of AprA and CfaD.

DupA: a key regulator of the amoebal MAP kinase response to Legionella pneumophila

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Li, Zhiru; Dugan, Aisling S.; Bloomfield, Gareth; Skelton, Jason; Ivens, Alasdair; Losick, Vicki; Isberg, Ralph R.

2009-01-01

SUMMARY The dupA gene, encoding a putative tyrosine kinase/dual specificity phosphatase (Dusp), was identified in a screen for Dictyostelium discoideum mutants altered in supporting Legionella pneumophila intracellular replication. The absence of dupA resulted in hyperphosphorylation of ERK1, consistent with the loss of a phosphatase activity, as well as degradation of ERK2. ERK1 hyperphosphorylation mimicked the response of this protein after bacterial challenge of wild type amoebae. Similar to Dusps in higher eukaryotic cells, the amoebal dupA gene was induced after bacterial contact, indicating a response of Dusps that is conserved from amoebae to mammals. A large set of genes was misregulated in the dupA− mutant that largely overlaps with genes responding to L. pneumophila infection. Some of the amoebal genes appear to be involved in a response similar to innate immunity in higher eukaryotes, indicating there was misregulation of a conserved response to bacteria. PMID:19748467

Remote measurement of canopy water content in giant sequoias (Sequoiadendron giganteum) during drought

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Martin, Roberta E.; Asner, Gregory P.; Francis, Emily; Ambrose, Anthony; Baxter, Wendy; Das, Adrian J.; Vaughn, Nicolas R.; Paz-Kagan, Tarin; Dawson, Todd E.; Nydick, Koren R.; Stephenson, Nathan L.

2018-01-01

California experienced severe drought from 2012 to 2016, and there were visible changes in the forest canopy throughout the State. In 2014, unprecedented foliage dieback was recorded in giant sequoia (Sequoiadendron giganteum) trees in Sequoia National Park, in the southern California Sierra Nevada mountains. Although visible changes in sequoia canopies can be recorded, biochemical and physiological responses to drought stress in giant sequoia canopies are not well understood. Ground-based measurements provide insight into the mechanisms of drought responses in trees, but are often limited to few individuals, especially in trees of tall stature such as giant sequoia. Recent studies demonstrate that remotely measured forest canopy water content (CWC) is a general indicator of canopy response to drought, but the underpinning leaf- to canopy-level causes of observed variation in CWC remain poorly understood. We combined field and airborne remote sensing measurements taken in 2015 and 2016 to assess the biophysical responses of giant sequoias to drought. In 49 study trees, CWC was related to leaf water potential, but not to the other foliar traits, suggesting that changes in CWC were made at whole-canopy rather than leaf scales. We found a non-random, spatially varying pattern in mapped CWC, with lower CWC values at lower elevation and along the outer edges of the groves. This pattern was also observed in empirical measurements of foliage dieback from the ground, and in mapped CWC across multiple sequoia groves in this region, supporting the hypothesis that drought stress is expressed in canopy-level changes in giant sequoias. The fact that we can clearly detect a relationship between CWC and foliage dieback, even without taking into account prior variability or new leaf growth, strongly suggests that remotely sensed CWC, and changes in CWC, are a useful measure of water stress in giant sequoia, and valuable for assessing and managing these iconic forests in drought.

Growth-supporting activity for Legionella pneumophila in tap water cultures and implication of hartmannellid amoebae as growth factors.

Science.gov (United States)

Wadowsky, R M; Butler, L J; Cook, M K; Verma, S M; Paul, M A; Fields, B S; Keleti, G; Sykora, J L; Yee, R B

1988-11-01

Photosynthetic cyanobacteria, heterotrophic bacteria, free-living amoebae, and ciliated protozoa may support growth of Legionella pneumophila. Studies were done with two tap water cultures (WS1 and WS2) containing L. pneumophila and associated microbiota to characterize growth-supporting activity and assess the relative importance of the microbiota in supporting multiplication of L. pneumophila. The water cultures were incubated in the dark at 35 degrees C. The growth-supporting factor(s) was separated from each culture by filtration through 1-micron-pore-size membrane filters. The retentate was then suspended in sterile tap water. Multiplication of L. pneumophila occurred when both the retentate suspension and the filtrate from either culture were inoculated into sterile tap water. L. pneumophila did not multiply in tap water inoculated with only the filtrate, even though filtration did not reduce the concentration of L. pneumophila or heterotrophic bacteria in either culture. Growth-supporting activity of the retentate suspension from WS1 was inactivated at 60 degrees C but unaffected at 0, 25, and 45 degrees C after 30-min incubations. Filtration experiments indicated that the growth-supporting factor(s) in WS1 was 2 to 5 micron in diameter. Ciliated protozoa were not detected in either culture. Hartmannellid amoebae were conclusively demonstrated in WS2 but not in WS1. L. pneumophila multiplied in tap water inoculated with the amoebae (10(3)/ml) and the 1-micron filtrate of WS2. No multiplication occurred in tap water inoculated with the filtrate only. Growth-supporting activity for L. pneumophila may be present in plumbing systems; hartmannellid amoebae appear to be important determinants of multiplication of L. pneumophila in some tap water cultures.

Ecological niche models reveal the importance of climate variability for the biogeography of protosteloid amoebae.

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Aguilar, María; Lado, Carlos

2012-08-01

Habitat availability and environmental preferences of species are among the most important factors in determining the success of dispersal processes and therefore in shaping the distribution of protists. We explored the differences in fundamental niches and potential distributions of an ecological guild of slime moulds-protosteloid amoebae-in the Iberian Peninsula. A large set of samples collected in a north-east to south-west transect of approximately 1000 km along the peninsula was used to test the hypothesis that, together with the existence of suitable microhabitats, climate conditions may determine the probability of survival of species. Although protosteloid amoebae share similar morphologies and life history strategies, canonical correspondence analyses showed that they have varied ecological optima, and that climate conditions have an important effect in niche differentiation. Maxent environmental niche models provided consistent predictions of the probability of presence of the species based on climate data, and they were used to generate maps of potential distribution in an 'everything is everywhere' scenario. The most important climatic factors were, in both analyses, variables that measure changes in conditions throughout the year, confirming that the alternation of fruiting bodies, cysts and amoeboid stages in the life cycles of protosteloid amoebae constitutes an advantage for surviving in a changing environment. Microhabitat affinity seems to be influenced by climatic conditions, which suggests that the micro-environment may vary at a local scale and change together with the external climate at a larger scale.

The Dictyostelium Bcr/Abr-related protein DRG regulates both Rac- and Rab-dependent pathways

OpenAIRE

Knetsch, Menno L.W.; Schäfers, Nicole; Horstmann, Heinz; Manstein, Dietmar J.

2001-01-01

Dictyostelium discoideum DdRacGap1 (DRG) contains both Rho-GEF and Rho-GAP domains, a feature it shares with mammalian Bcr and Abr. To elucidate the physiological role of this multifunctional protein, we characterized the enzymatic activity of recombinant DRG fragments in vitro, created DRG-null cells, and studied the function of the protein in vivo by analysing the phenotypic changes displayed by DRG-depleted cells and DRG-null cells complemented with DRG or DRG fragments. Our results show t...

Specificity of the Cyclic GMP-Binding Activity and of a Cyclic GMP-Dependent Cyclic GMP Phosphodiesterase in Dictyostelium discoideum

NARCIS (Netherlands)

Haastert, Peter J.M. van; Walsum, Hans van; Meer, Rob C. van der; Bulgakov, Roman; Konijn, Theo M.

1982-01-01

The nucleotide specificity of the cyclic GMP-binding activity in a homogenate of Dictyostelium discoideum was determined by competition of cyclic GMP derivatives with [8-3H] cyclic GMP for the binding sites. The results indicate that cyclic GMP is bound to the binding proteins by hydrogen bonds at

Holocene environmental changes in southern Kamchatka, Far Eastern Russia, inferred from a pollen and testate amoebae peat succession record

Science.gov (United States)

Klimaschewski, A.; Barnekow, L.; Bennett, K. D.; Andreev, A. A.; Andrén, E.; Bobrov, A. A.; Hammarlund, D.

2015-11-01

High resolution palaeoenvironmental records in Far-Eastern Russia are rare, and the Kamchatka Peninsula is among the least studied areas of the region. This paper describes a record spanning the last ca. 11,000 yr, obtained from a bog in the southern part of Kamchatka. The radiocarbon dated core was analysed for pollen, testate amoebae, charcoal and loss-on-ignition (LOI). The vegetation during the early Holocene was dominated by grasses (Poaceae), birch (Betula) and heath (Ericaceae p. p.). Around 10,300 cal yr BP there was a substantial change in the vegetation cover to shrub alder (Alnus viridis s.l.) stands with sedges and ferns (Polypodiophyta) as well as herbs such as meadow rue (Thalictrum) in the understory. In the surroundings of Utka peatlands started to form. The variations in the vegetation cover were most probably caused by climatic changes. At the beginning of sediment accumulation, before 10,300 cal yr BP, the composition of the vegetation points to cooler summers and/or decreased annual precipitation. Around 10,300 cal yr BP, changes in vegetation occurred due to rising temperatures and/or changed water regimes. Increased abundancies of dry indicating testate amoebae after 9100 cal yr BP point to intermediate to dry soil conditions. Between 8600 and 7700 cal yr BP tree alder (Alnus incana) was widely spread at the site which probably indicates optimal environmental conditions. The tephra layer at 381-384.5 cm (ca. 8500 cal yr BP) produces a strong impact on the testate amoebae assemblages. At 7700 cal yr BP there was a sudden drop of A. incana in the local vegetation. From this time on, A. incana and also A. viridis decrease continuously whereas Betula gradually increases. The upper part of the sequence (after 6300 cal yr BP) shows higher abundancies of meadowsweet (Filipendula) and sweet gale (Myrica) pollen. After 6300 cal yr BP, changes in testate amoebae demonstrate variable soil moisture conditions at the site. Between 3700 and 1800 cal yr BP

Exposure to synthetic greywater inhibits amoebae encystation and alters expression of Legionella pneumophila virulence genes

Science.gov (United States)

Water conservation efforts have focused on greywater (GW) usage, especially for applications that do not require potable water quality. However, there is a need to better understand environmental pathogens and their free-living amoebae (FLA) hosts within GW. Using synthetic gre...

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFC231 (Link to dictyBase) - - - Contig-U16593-1 VFC231P (Link... to Original site) VFC231F 428 VFC231Z 202 VFC231P 630 - - Show VFC231 Library VF (Link to library) Clone ID VFC231 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16593-1 Original site URL http://dict...amoeba histolytica genomic, DNA sequence. 48 0.13 1 AC116984 |AC116984.2 Dictyostelium discoideum chromosome...mbrane 4.0 %: vesicles of secretory system 4.0 %: extracellular, including cell wall >> predict

Natural products from the ascidian Botrylloides giganteum, from the sponges Verongula gigantea, Ircinia felix, Cliona delitrix and from the nudibranch Tambja eliora, from the Brazilian coastline; Produtos naturais da ascidia Botrylloides giganteum, das esponjas Verongula gigantea, Ircinia felix, Cliona delitrix e do nudibranquio Tambja eliora, da costa do Brasil

Energy Technology Data Exchange (ETDEWEB)

Granato, Ana Claudia; Oliveira, Jaine H.H.L. de; Seleghim, Mirna H.R.; Berlinck, Roberto G.S. [Sao Paulo Univ., Sao Carlos, SP (Brazil). Inst. de Quimica]. E-mail: rgsberlinck@iqsc.usp.br; Macedo, Mario L.; Ferreira, Antonio G. [Sao Carlos Univ., SP (Brazil). Dept. de Quimica; Rocha, Rosana M. da [Parana Univ., Curitiba, PR (Brazil). Setor de Ciencias Biologicas. Dept. de Zoologia; Hajdu, Eduardo [Universidade Federal, Rio de Janeiro, RJ (Brazil). Museu Nacional; Peixinho, Solange [Bahia Univ., Salvador, BA (Brazil). Dept. de Biologia; Pessoa, Claudia O.; Moraes, Manoel O.; Cavalcanti, Bruno C. [Ceara Univ., Fortaleza, CE (Brazil). Dept. de Fisiologia e Farmacologia

2005-04-01

Two new marine metabolites, 3Z, 6Z, 9Z-dodecatrien-1-ol (1) from the ascidian Botrylloides giganteum and 4H-pyran-2ol acetate from the sponge Ircinia felix (4) are herein reported. The known bromotyrosine compounds, 2-(3,5-dibromo-4-methoxyphenyl)-N,N,Ndimethylethanammonium (2) and 2,6-dibromo-4-(2-(trimethylammonium)ethyl)phenol (3), have been isolated from the sponge Verongula gigantea. Serotonin (5) is reported for the first time from the sponge Cliona delitrix, and tambjamines A (15) and D (16) isolated as their respective salts from the nudibranch Tambja eliora. Only tambjamine D presented cytotoxicity against CEM (IC{sub 5})0 12.2 {mu}g/mL) and HL60 (IC{sub 50} 13.2 {mu}g/mL) human leukemia cells, MCF-7 breast cancer cells (IC{sub 50} 13.2 {mu}g/mL), colon HCT-8 cancer cells (IC{sub 50} 10.1 {mu}g/mL) and murine melanoma B16 cancer cells (IC{sub 50} 6.7 {mu}g/mL). (author)

A Dictyostelium chalone uses G proteins to regulate proliferation

Directory of Open Access Journals (Sweden)

Hanson Nana E

2009-07-01

Full Text Available Abstract Background Several studies have shown that organ size, and the proliferation of tumor metastases, may be regulated by negative feedback loops in which autocrine secreted factors called chalones inhibit proliferation. However, very little is known about chalones, and how cells sense them. We previously identified two secreted proteins, AprA and CfaD, which act as chalones in Dictyostelium. Cells lacking AprA or CfaD proliferate faster than wild-type cells, and adding recombinant AprA or CfaD to cells slows their proliferation. Results We show here that cells lacking the G protein components Galpha8, Galpha9, and Gbeta proliferate faster than wild-type cells despite secreting normal or high levels of AprA and CfaD. Compared with wild-type cells, the proliferation of galpha8-, galpha9- and gbeta- cells are only weakly inhibited by recombinant AprA (rAprA. Like AprA and CfaD, Galpha8 and Gbeta inhibit cell proliferation but not cell growth (the rate of increase in mass and protein per nucleus, whereas Galpha9 inhibits both proliferation and growth. galpha8- cells show normal cell-surface binding of rAprA, whereas galpha9- and gbeta- cells have fewer cell-surface rAprA binding sites, suggesting that Galpha9 and Gbeta regulate the synthesis or processing of the AprA receptor. Like other ligands that activate G proteins, rAprA induces the binding of [3H]GTP to membranes, and GTPgammaS inhibits the binding of rAprA to membranes. Both AprA-induced [3H]GTP binding and the GTPgammaS inhibition of rAprA binding require Galpha8 and Gbeta but not Galpha9. Like aprA- cells, galpha8- cells have reduced spore viability. Conclusion This study shows that Galpha8 and Gbeta are part of the signal transduction pathway used by AprA to inhibit proliferation but not growth in Dictyostelium, whereas Galpha9 is part of a differealnt pathway that regulates both proliferation and growth, and that a chalone signal transduction pathway uses G proteins.

Produtos naturais da ascídia Botrylloides giganteum, das esponjas Verongula gigantea, Ircinia felix, Cliona delitrix e do nudibrânquio Tambja eliora, da costa do Brasil Natural products from the ascidian Botrylloides giganteum, from the sponges Verongula gigantea, Ircinia felix, Cliona delitrix and from the nudibranch Tambja eliora, from the Brazilian coastline

Directory of Open Access Journals (Sweden)

Ana Claudia Granato

2005-03-01

Full Text Available Two new marine metabolites, 3Z, 6Z, 9Z-dodecatrien-1-ol (1 from the ascidian Botrylloides giganteum and 4H-pyran-2ol acetate from the sponge Ircinia felix (4 are herein reported. The known bromotyrosine compounds, 2-(3,5-dibromo-4-methoxyphenyl-N,N,N-dimethylethanammonium (2 and 2,6-dibromo-4-(2-(trimethylammoniumethylphenol (3, have been isolated from the sponge Verongula gigantea. Serotonin (5 is reported for the first time from the sponge Cliona delitrix, and tambjamines A (15 and D (16 isolated as their respective salts from the nudibranch Tambja eliora. Only tambjamine D presented cytotoxicity against CEM (IC50 12.2 µg/mL and HL60 (IC50 13.2 µg/mL human leukemya cells, MCF-7 breast cancer cells (IC50 13.2 µg/mL, colon HCT-8 cancer cells (IC50 10.1 µg/mL and murine melanoma B16 cancer cells (IC50 6.7 µg/mL.

Characterization of a 1,4-. beta. -D-glucan synthase from Dictyostelium discoideum

Energy Technology Data Exchange (ETDEWEB)

Blanton, R.L.

1992-01-15

Various aspects of research concerning Dictyostelium discoideum are presented. The initial focus of this project was upon: the characterization of potential probes for the cellulose synthase (antibody and nucleic acid), the determination of the cultural induction conditions of cellulose synthesis, the solubilization of the enzyme activity, the development of a non-inhibitory disruption buffer, the generation and isolation of mutant strains deficient in cellulose synthesis, and the development of the capability to determine the degree of polymerization of the in vitro product. I have briefly summarized our most significant findings with only selected data sets being shown in this report in the interest of brevity.

A Dictyostelium secreted factor requires a PTEN-like phosphatase to slow proliferation and induce chemorepulsion.

Directory of Open Access Journals (Sweden)

Sarah E Herlihy

Full Text Available In Dictyostelium discoideum, AprA and CfaD are secreted proteins that inhibit cell proliferation. We found that the proliferation of cells lacking CnrN, a phosphatase and tensin homolog (PTEN-like phosphatase, is not inhibited by exogenous AprA and is increased by exogenous CfaD. The expression of CnrN in cnrN cells partially rescues these altered sensitivities, suggesting that CnrN is necessary for the ability of AprA and CfaD to inhibit proliferation. Cells lacking CnrN accumulate normal levels of AprA and CfaD. Like cells lacking AprA and CfaD, cnrN cells proliferate faster and reach a higher maximum cell density than wild type cells, tend to be multinucleate, accumulate normal levels of mass and protein per nucleus, and form less viable spores. When cnrN cells expressing myc-tagged CnrN are stimulated with a mixture of rAprA and rCfaD, levels of membrane-associated myc-CnrN increase. AprA also causes chemorepulsion of Dictyostelium cells, and CnrN is required for this process. Combined, these results suggest that CnrN functions in a signal transduction pathway downstream of AprA and CfaD mediating some, but not all, of the effects of AprA and CfaD.

Brain-Eating Amoebae: Predilection Sites in the Brain and Disease Outcome

OpenAIRE

Ong, Timothy Yu Yee; Khan, Naveed Ahmed; Siddiqui, Ruqaiyyah

2017-01-01

Acanthamoeba spp. and Balamuthia mandrillaris are causative agents of granulomatous amoebic encephalitis (GAE), while Naegleria fowleri causes primary amoebic meningoencephalitis (PAM). PAM is an acute infection that lasts a few days, while GAE is a chronic to subacute infection that can last up to several months. Here, we present a literature review of 86 case reports from 1968 to 2016, in order to explore the affinity of these amoebae for particular sites of the brain, diagnostic modalities...

Mitochondrial Stress Tests Using Seahorse Respirometry on Intact Dictyostelium discoideum Cells.

Science.gov (United States)

Lay, Sui; Sanislav, Oana; Annesley, Sarah J; Fisher, Paul R

2016-01-01

Mitochondria not only play a critical and central role in providing metabolic energy to the cell but are also integral to the other cellular processes such as modulation of various signaling pathways. These pathways affect many aspects of cell physiology, including cell movement, growth, division, differentiation, and death. Mitochondrial dysfunction which affects mitochondrial bioenergetics and causes oxidative phosphorylation defects can thus lead to altered cellular physiology and manifest in disease. The assessment of the mitochondrial bioenergetics can thus provide valuable insights into the physiological state, and the alterations to the state of the cells. Here, we describe a method to successfully use the Seahorse XF(e)24 Extracellular Flux Analyzer to assess the mitochondrial respirometry of the cellular slime mold Dictyostelium discoideum.

Interactions Between Testate Amoebae and Saprotrophic Microfungi in a Scots Pine Litter Microcosm

Czech Academy of Sciences Publication Activity Database

Vohník, Martin; Burdíková, Zuzana; Vyhnal, Aleš; Koukol, O.

2011-01-01

Roč. 61, č. 3 (2011), s. 660-668 ISSN 0095-3628 R&D Projects: GA ČR GP206/09/P340; GA ČR(CZ) GD204/09/H084 Institutional research plan: CEZ:AV0Z50110509; CEZ:AV0Z60050516 Keywords : testate amoebae * saprotrophic fungi * litter Subject RIV: EF - Botanics Impact factor: 2.912, year: 2011

Growth regulation of Legionella Pneumophila in biofilms and amoebae; Wachstumsregulation von Legionella Pneumophila in Biofilmen und Amoeben

Energy Technology Data Exchange (ETDEWEB)

Hilbi, H.

2006-07-01

This final report for the Swiss Federal Office of Energy (SFOE) presents the results of studies made on the regulation of the growth of Legionella Pneumophila bacteria in biofilms and amoebae. In a first project, the formation of biofilms by Legionella Pneumophila bacteria was analysed in static and dynamic systems using a complex growth medium. Under static and dynamic clinical and environmental conditions, the adherence of the biofilms on polystyrene tissue was studied. This was also examined under dynamic flow conditions. In a second part of the project, the regulation of growth of Legionella Pneumophila in amoebae was examined in that changes were made to the genome of the bacteria. The importance of the work for the de-activation of Legionella Pneumophila bacteria in biofilms is noted in the conclusions of the report.

A flavin-dependent halogenase catalyzes the chlorination step in the biosynthesis of Dictyostelium differentiation-inducing factor 1

OpenAIRE

Neumann, Christopher S.; Walsh, Christopher T.; Kay, Robert R.

2010-01-01

Differentiation-inducing factor 1 (DIF-1) is a polyketide-derived morphogen which drives stalk cell formation in the developmental cycle of Dictyostelium discoideum. Previous experiments demonstrated that the biosynthetic pathway proceeds via dichlorination of the precursor molecule THPH, but the enzyme responsible for this transformation has eluded characterization. Our recent studies on prokaryotic flavin-dependent halogenases and insights from the sequenced Dd genome led us to a candidate ...

Impact of two hot and dry summers on the community structure and functional diversity of testate amoebae in an artificial bog, illustrating their use as bioindicators of peatland health

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I. Koenig

2018-04-01

Full Text Available Ongoing climate warming threatens the survival of bogs at the warm/dry limit of their distribution (e.g. in central Europe, and jeopardises the restoration of damaged bogs even more. Because vegetation changes can be slow, early indicators of hydrological change such as testate amoebae are useful. We used testate amoeba community structure and community weighted mean of functional traits to monitor the impact of two very hot and dry summers on a small (around 100 m2 artificial peatland constructed in the botanic garden of Neuchâtel, Switzerland. We collected analogous samples in a naturally regenerating cutover peatland at 1000 m a.s.l. in the Jura Mountains as a reference. The comparison of living and dead assemblages in the botanic garden showed an increased representation of smaller testate amoeba taxa (Corythion dubium, small Euglypha sp. with a small pseudostome (indicative of dry conditions and a loss of mixotrophy in 2015, followed by a weaker further shift in 2016. Nevertheless, the testate amoeba community structure in 2016 still indicated a dry Sphagnum bog. Testate amoeba analysis allows rapid assessment of peatland health and/or restoration success. The comparison of living and dead assemblages makes it possible to observe changes within a season in a single sampling campaign.

Quadrulella texcalense sp nov from a Mexican desert: An unexpected new environment for hyalospheniid testate amoebae

Czech Academy of Sciences Publication Activity Database

Perez-Juarez, H.; Serrano-Vazquez, A.; Kosakyan, Anush; Mitchell, E.A.D.; Rivera Aguilar, V. M.; Lahr, D. J. G.; Hernandez Moreno, M. M.; Macías Cuellar, H.; Eguiarte, L. E.; Lara, E.

2017-01-01

Roč. 61, 17 July (2017), s. 253-264 ISSN 0932-4739 Institutional support: RVO:60077344 Keywords : Adaptation * Biological soil crust desert * Protist * Tehuacain-Cuicatlain Biosphere Reserve * Testate amoebae Subject RIV: EG - Zoology OBOR OECD: Zoology Impact factor: 2.581, year: 2016

Ecology of Testate Amoebae in the Komořany Ponds in the Vltava Basin

Czech Academy of Sciences Publication Activity Database

Burdíková, Zuzana; Čapek, Martin; Švindrych, Zdeněk; Gryndler, M.; Kubínová, Lucie; Holcová, K.

2012-01-01

Roč. 64, č. 1 (2012), s. 117-130 ISSN 0095-3628 R&D Projects: GA MŠk(CZ) LC06063; GA ČR(CZ) GAP108/11/0794 Institutional research plan: CEZ:AV0Z50110509 Keywords : ecology * freshwater ecosystem * testate amoebae * seasonal variability Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.277, year: 2012

Sphagnum-dwelling testate amoebae in subarctic bogs are more sensitive to soil warming in the growing season than in winter: the results of eight-year field climate manipulations.

Science.gov (United States)

Tsyganov, Andrey N; Aerts, Rien; Nijs, Ivan; Cornelissen, Johannes H C; Beyens, Louis

2012-05-01

Sphagnum-dwelling testate amoebae are widely used in paleoclimate reconstructions as a proxy for climate-induced changes in bogs. However, the sensitivity of proxies to seasonal climate components is an important issue when interpreting proxy records. Here, we studied the effects of summer warming, winter snow addition solely and winter snow addition together with spring warming on testate amoeba assemblages after eight years of experimental field climate manipulations. All manipulations were accomplished using open top chambers in a dry blanket bog located in the sub-Arctic (Abisko, Sweden). We estimated sensitivity of abundance, diversity and assemblage structure of living and empty shell assemblages of testate amoebae in the living and decaying layers of Sphagnum. Our results show that, in a sub-arctic climate, testate amoebae are more sensitive to climate changes in the growing season than in winter. Summer warming reduced species richness and shifted assemblage composition towards predominance of xerophilous species for the living and empty shell assemblages in both layers. The higher soil temperatures during the growing season also decreased abundance of empty shells in both layers hinting at a possible increase in their decomposition rates. Thus, although possible effects of climate changes on preservation of empty shells should always be taken into account, species diversity and structure of testate amoeba assemblages in dry subarctic bogs are sensitive proxies for climatic changes during the growing season. Copyright © 2011 Elsevier GmbH. All rights reserved.

Brain-Eating Amoebae: Predilection Sites in the Brain and Disease Outcome

Science.gov (United States)

Ong, Timothy Yu Yee; Siddiqui, Ruqaiyyah

2017-01-01

ABSTRACT Acanthamoeba spp. and Balamuthia mandrillaris are causative agents of granulomatous amoebic encephalitis (GAE), while Naegleria fowleri causes primary amoebic meningoencephalitis (PAM). PAM is an acute infection that lasts a few days, while GAE is a chronic to subacute infection that can last up to several months. Here, we present a literature review of 86 case reports from 1968 to 2016, in order to explore the affinity of these amoebae for particular sites of the brain, diagnostic modalities, treatment options, and disease outcomes in a comparative manner. PMID:28404683

SSU rRNA reveals a sequential increase in shell complexity among the euglyphid testate amoebae (Rhizaria: Euglyphida)

DEFF Research Database (Denmark)

Lara, Enrique; Heger, Thierry J; Mitchell, Edward A D

2007-01-01

The existing data on the molecular phylogeny of filose testate amoebae from order Euglyphida has revealed contradictions between traditional morphological classification and SSU rRNA phylogeny and, moreover, the position of several important genera remained unknown. We therefore carried out a stu...

Distribution of Legionella pneumophila bacteria and Naegleria and Hartmannella amoebae in thermal saline baths used in balneotherapy.

Science.gov (United States)

Zbikowska, Elżbieta; Walczak, Maciej; Krawiec, Arkadiusz

2013-01-01

The present study was aimed at investigating the coexistence and interactions between free living amoebae of Naegleria and Hartmannella genera and pathogenic Legionella pneumophila bacteria in thermal saline baths used in balneotherapy in central Poland. Water samples were collected from November 2010 to May 2011 at intervals longer than 1 month. The microorganisms were detected with the use of a very sensitive fluorescence in situ hybridisation method. In addition, the morphology of the amoebae was studied. Despite relatively high salinity level, ranging from 1.5 to 5.0 %, L. pneumophila were found in all investigated baths, although their number never exceeded 10(6) cells dm(-3). Hartmannella were not detected, while Naegleria fowleri were found in one bath. The observation that N. fowleri and L. pneumophila may coexist in thermal saline baths is the first observation emphasising potential threat from these microorganisms in balneotherapy.

The ROCO Kinase QkgA Is Necessary for Proliferation Inhibition by Autocrine Signals in Dictyostelium discoideum▿

OpenAIRE

Phillips, Jonathan E.; Gomer, Richard H.

2010-01-01

AprA and CfaD are secreted proteins that function as autocrine signals to inhibit cell proliferation in Dictyostelium discoideum. Cells lacking AprA or CfaD proliferate rapidly, and adding AprA or CfaD to cells slows proliferation. Cells lacking the ROCO kinase QkgA proliferate rapidly, with a doubling time 83% of that of the wild type, and overexpression of a QkgA-green fluorescent protein (GFP) fusion protein slows cell proliferation. We found that qkgA− cells accumulate normal levels of ex...

Tinker-OpenMM: Absolute and relative alchemical free energies using AMOEBA on GPUs.

Science.gov (United States)

Harger, Matthew; Li, Daniel; Wang, Zhi; Dalby, Kevin; Lagardère, Louis; Piquemal, Jean-Philip; Ponder, Jay; Ren, Pengyu

2017-09-05

The capabilities of the polarizable force fields for alchemical free energy calculations have been limited by the high computational cost and complexity of the underlying potential energy functions. In this work, we present a GPU-based general alchemical free energy simulation platform for polarizable potential AMOEBA. Tinker-OpenMM, the OpenMM implementation of the AMOEBA simulation engine has been modified to enable both absolute and relative alchemical simulations on GPUs, which leads to a ∼200-fold improvement in simulation speed over a single CPU core. We show that free energy values calculated using this platform agree with the results of Tinker simulations for the hydration of organic compounds and binding of host-guest systems within the statistical errors. In addition to absolute binding, we designed a relative alchemical approach for computing relative binding affinities of ligands to the same host, where a special path was applied to avoid numerical instability due to polarization between the different ligands that bind to the same site. This scheme is general and does not require ligands to have similar scaffolds. We show that relative hydration and binding free energy calculated using this approach match those computed from the absolute free energy approach. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Old lineages in a new ecosystem: diversification of arcellinid amoebae (Amoebozoa and peatland mosses.

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Omar Fiz-Palacios

Full Text Available Arcellinid testate amoebae (Amoebozoa form a group of free-living microbial eukaryotes with one of the oldest fossil records known, yet several aspects of their evolutionary history remain poorly understood. Arcellinids occur in a range of terrestrial, freshwater and even brackish habitats; however, many arcellinid morphospecies such as Hyalosphenia papilio are particularly abundant in Sphagnum-dominated peatlands, a relatively new ecosystem that appeared during the diversification of Sphagnum species in the Miocene (5-20 Myr ago. Here, we reconstruct divergence times in arcellinid testate amoebae after selecting several fossils for clock calibrations and then infer whether or not arcellinids followed a pattern of diversification that parallels the pattern described for Sphagnum. We found that the diversification of core arcellinids occurred during the Phanerozoic, which is congruent with most arcellinid fossils but not with the oldest known amoebozoan fossil (i.e. at ca. 662 or ca. 750 Myr. Overall, Sphagnum and the Hyalospheniidae exhibit different patterns of diversification. However, an extensive molecular phylogenetic analysis of distinct clades within H. papilio species complex demonstrated a correlation between the recent diversification of H. papilio, the recent diversification of Sphagnum mosses, and the establishment of peatlands.

The Phanerozoic diversification of silica-cycling testate amoebae and its possible links to changes in terrestrial ecosystems

Science.gov (United States)

Bosak, Tanja; Lara, Enrique; Mitchell, Edward A.D.

2015-01-01

The terrestrial cycling of Si is thought to have a large influence on the terrestrial and marine primary production, as well as the coupled biogeochemical cycles of Si and C. Biomineralization of silica is widespread among terrestrial eukaryotes such as plants, soil diatoms, freshwater sponges, silicifying flagellates and testate amoebae. Two major groups of testate (shelled) amoebae, arcellinids and euglyphids, produce their own silica particles to construct shells. The two are unrelated phylogenetically and acquired biomineralizing capabilities independently. Hyalosphenids, a group within arcellinids, are predators of euglyphids. We demonstrate that hyalosphenids can construct shells using silica scales mineralized by the euglyphids. Parsimony analyses of the current hyalosphenid phylogeny indicate that the ability to “steal” euglyphid scales is most likely ancestral in hyalosphenids, implying that euglyphids should be older than hyalosphenids. However, exactly when euglyphids arose is uncertain. Current fossil record contains unambiguous euglyphid fossils that are as old as 50 million years, but older fossils are scarce and difficult to interpret. Poor taxon sampling of euglyphids has also prevented the development of molecular clocks. Here, we present a novel molecular clock reconstruction for arcellinids and consider the uncertainties due to various previously used calibration points. The new molecular clock puts the origin of hyalosphenids in the early Carboniferous (∼370 mya). Notably, this estimate coincides with the widespread colonization of land by Si-accumulating plants, suggesting possible links between the evolution of Arcellinid testate amoebae and the expansion of terrestrial habitats rich in organic matter and bioavailable Si. PMID:26734499

dictyExpress: a Dictyostelium discoideum gene expression database with an explorative data analysis web-based interface

Science.gov (United States)

Rot, Gregor; Parikh, Anup; Curk, Tomaz; Kuspa, Adam; Shaulsky, Gad; Zupan, Blaz

2009-01-01

Background Bioinformatics often leverages on recent advancements in computer science to support biologists in their scientific discovery process. Such efforts include the development of easy-to-use web interfaces to biomedical databases. Recent advancements in interactive web technologies require us to rethink the standard submit-and-wait paradigm, and craft bioinformatics web applications that share analytical and interactive power with their desktop relatives, while retaining simplicity and availability. Results We have developed dictyExpress, a web application that features a graphical, highly interactive explorative interface to our database that consists of more than 1000 Dictyostelium discoideum gene expression experiments. In dictyExpress, the user can select experiments and genes, perform gene clustering, view gene expression profiles across time, view gene co-expression networks, perform analyses of Gene Ontology term enrichment, and simultaneously display expression profiles for a selected gene in various experiments. Most importantly, these tasks are achieved through web applications whose components are seamlessly interlinked and immediately respond to events triggered by the user, thus providing a powerful explorative data analysis environment. Conclusion dictyExpress is a precursor for a new generation of web-based bioinformatics applications with simple but powerful interactive interfaces that resemble that of the modern desktop. While dictyExpress serves mainly the Dictyostelium research community, it is relatively easy to adapt it to other datasets. We propose that the design ideas behind dictyExpress will influence the development of similar applications for other model organisms. PMID:19706156

Selfish DNA: a pharmaceutical perspective.

Science.gov (United States)

Winckler, T

2013-07-01

Almost 25 years ago, Theo Dingermann published the discovery of a new mobile genetic element in the unicellular microbe Dictyostelium discoideum in the journal Science. An interesting property of this new molecular parasite, the Dictyostelium Repetitive Element (DRE), was that all integrations were found approximately 50 base pairs (bp) upstream of transfer RNA (tRNA) genes in the D. discoideum genome, thus implying an active targeting mechanism to avoid the disruption of host cell genes by the retrotransposition process. Since then, the facultative multicellular "social amoeba" D. discoideum has become a popular model for analyzing complex cellular functions such as cell movement, chemotaxis, phagocytosis, and cell differentiation, important areas of biomedical research that are often hard to investigate in cells from "higher organisms" including humans. Therefore, progress in the development of methods to study Dictyostelium biology has also provoked research on transposable elements in this organism. Early work on the DRE element suggested that studying its molecular mechanism of site-specific integration might promote human gene therapy technology through the design of integrating gene transfer vectors with low intrinsic genotoxic potential. In this review article, I will briefly review the original research performed on the DRE transposable element in the Dingermann lab and report on how the emergence of genomics technologies and the development of tools to analyze de novo retrotransposition events in D. discoideum cells will expand our knowledge of DRE biology in the future.

First Record of Potentially Pathogenic Amoeba Vermamoeba vermiformis (Lobosea: Gymnamoebia Isolated from a Freshwater of Dokdo Island in the East Sea, Korea

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Jong Soo Park

2016-01-01

Full Text Available Vermamoeba vermiformis is a very important free-living amoeba for human health in association with Legionnaires’ disease and keratitis. This interesting amoeba was firstly isolated from a freshwater of Dokdo (island, which was historically used for drinking water. Trophozoites and cyst forms of V. vermiformis strain MG1 are very similar to previous reported species. Trophozoites of V. vermiformis strain MG1 showed cylindrical shape with prominent anterior hyaline region. The average ratio of length and width was about 6.5. Typically, cysts of the strain MG1 showed a spherical or slightly ovoidal shape with smooth wall, and lacked cyst pores. Some cysts had crenulatewalled ectocyst, which was separated from endocyst wall. Further, 18S rRNA gene sequence of V. vermiformis strain MG1 showed very high similarity to other V. vermiformis species (99.4%-99.9% identity. Molecular phylogenetic analysis based on 18S rRNA gene sequences clearly confirmed that the isolate was one strain of V. vermiformis with maximum bootstrap value (maximum likelihood: 100% and Bayesian posterior probability of 1. Thus, the freshwater of Dokdo in Korea could harbor potentially pathogenic amoeba that may cause diseases in humans.

Check-list of microscopic protosteloid amoebae from the Southwest of Europe

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Aguilar, María

2012-12-01

Full Text Available A biodiversity survey for protosteloid amoebae was carried out in Spain, Portugal and France between 2005 and 2010. Samples were collected from three different microhabitats – aerial litter, ground litter, and bark of living plants – in a total of 97 localities. As result 26 to 28 species out of the 33 species of microscopic protosteloid amoebae described to date were recorded. An annotated list that comprises all available data about these organisms from this part of the world, a key to the species, comments on the morphology of the sporocarps and the trophic stages is presented. Photomicrographs of the fruiting bodies of most species, and distribution maps are also included.

Se ha realizado un estudio de la biodiversidad de las amebas protos - teloides en España, Portugal y Francia entre 2005 y 2010. Las muestras se recolectaron en tres microhábitats diferentes –hojarasca aérea, hojarasca del suelo y corteza de plantas vivas– en un total de 97 localidades. Como resultado se encontraron entre 26 y 28 especies de las 33 especies de amebas protosteloides microscópicas descritas. Se presenta una lista comentada que contiene todos los datos disponibles sobre estos organismos en esta parte del mundo, una clave de las especies y comentarios sobre la morfología de los esporocarpos y de los estados tróficos. También se incluyen fotomicrografías de los cuerpos fructíferos de la mayoría de las especies y mapas de distribución.

A free-living amoeba with unusual pattern of mitochondrial structure isolated from Atlantic salmon, Salmo salar L

Czech Academy of Sciences Publication Activity Database

Dyková, Iva; Veverková, Marie; Fiala, Ivan; Macháčková, Blanka

2002-01-01

Roč. 41, - (2002), s. 415-419 ISSN 0065-1583 R&D Projects: GA AV ČR IAA6022202 Institutional research plan: CEZ:AV0Z6022909 Keywords : free-living amoeba * mitochondrial cristae * Salmo salar Subject RIV: EA - Cell Biology Impact factor: 0.446, year: 2002

Effect of sodium fluoride on the amount of polyribosomes, single ribosomes and ribosomal subunits in a cellular slime mold, Dictyostelium discoideum

Energy Technology Data Exchange (ETDEWEB)

Sameshima, M; Ito, K; Iwabuchi, M

1972-01-01

In the slime mold, Dictyostelium discoideum, when the rate of protein synthesis was decreased by NaF, free 80-S ribosomes accumulated at the expense of polyribosomes, while 60-S and 40-S ribosomal subunits remained almost constant. The same level of ribosomal subunits was also maintained in cells after incubation with cycloheximide or at the stationary phase of growth.

A polycystin-type transient receptor potential (Trp channel that is activated by ATP

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David Traynor

2017-02-01

Full Text Available ATP and ADP are ancient extra-cellular signalling molecules that in Dictyostelium amoebae cause rapid, transient increases in cytosolic calcium due to an influx through the plasma membrane. This response is independent of hetero-trimeric G-proteins, the putative IP3 receptor IplA and all P2X channels. We show, unexpectedly, that it is abolished in mutants of the polycystin-type transient receptor potential channel, TrpP. Responses to the chemoattractants cyclic-AMP and folic acid are unaffected in TrpP mutants. We report that the DIF morphogens, cyclic-di-GMP, GABA, glutamate and adenosine all induce strong cytoplasmic calcium responses, likewise independently of TrpP. Thus, TrpP is dedicated to purinergic signalling. ATP treatment causes cell blebbing within seconds but this does not require TrpP, implicating a separate purinergic receptor. We could detect no effect of ATP on chemotaxis and TrpP mutants grow, chemotax and develop almost normally in standard conditions. No gating ligand is known for the human homologue of TrpP, polycystin-2, which causes polycystic kidney disease. Our results now show that TrpP mediates purinergic signalling in Dictyostelium and is directly or indirectly gated by ATP.

Sampling gene diversity across the supergroup Amoebozoa: large EST data sets from Acanthamoeba castellanii, Hartmannella vermiformis, Physarum polycephalum, Hyperamoeba dachnaya and Hyperamoeba sp.

Science.gov (United States)

Watkins, Russell F; Gray, Michael W

2008-04-01

From comparative analysis of EST data for five taxa within the eukaryotic supergroup Amoebozoa, including two free-living amoebae (Acanthamoeba castellanii, Hartmannella vermiformis) and three slime molds (Physarum polycephalum, Hyperamoeba dachnaya and Hyperamoeba sp.), we obtained new broad-range perspectives on the evolution and biosynthetic capacity of this assemblage. Together with genome sequences for the amoebozoans Dictyostelium discoideum and Entamoeba histolytica, and including partial genome sequence available for A. castellanii, we used the EST data to identify genes that appear to be exclusive to the supergroup, and to specific clades therein. Many of these genes are likely involved in cell-cell communication or differentiation. In examining on a broad scale a number of characters that previously have been considered in simpler cross-species comparisons, typically between Dictyostelium and Entamoeba, we find that Amoebozoa as a whole exhibits striking variation in the number and distribution of biosynthetic pathways, for example, ones for certain critical stress-response molecules, including trehalose and mannitol. Finally, we report additional compelling cases of lateral gene transfer within Amoebozoa, further emphasizing that although this process has influenced genome evolution in all examined amoebozoan taxa, it has done so to a variable extent.

Autonomous and nonautonomous regulation of axis formation by antagonistic signaling via 7-span cAMP receptors and GSK3 in Dictyostelium.

Science.gov (United States)

Ginsburg, G T; Kimmel, A R

1997-08-15

Early during Dictyostelium development a fundamental cell-fate decision establishes the anteroposterior (prestalk/prespore) axis. Signaling via the 7-transmembrane cAMP receptor CAR4 is essential for creating and maintaining a normal pattern; car4-null alleles have decreased levels of prestalk-specific mRNAs but enhanced expression of prespore genes. car4- cells produce all of the signals required for prestalk differentiation but lack an extracellular factor necessary for prespore differentiation of wild-type cells. This secreted factor decreases the sensitivity of prespore cells to inhibition by the prestalk morphogen DIF-1. At the cell autonomous level, CAR4 is linked to intracellular circuits that activate prestalk but inhibit prespore differentiation. The autonomous action of CAR4 is antagonistic to the positive intracellular signals mediated by another cAMP receptor, CAR1 and/or CAR3. Additional data indicate that these CAR-mediated pathways converge at the serine/threonine protein kinase GSK3, suggesting that the anterior (prestalk)/posterior (prespore) axis of Dictyostelium is regulated by an ancient mechanism that is shared by the Wnt/Fz circuits for dorsoventral patterning during early Xenopus development and establishing Drosophila segment polarity.

An Autocrine Proliferation Repressor Regulates Dictyostelium discoideum Proliferation and Chemorepulsion Using the G Protein-Coupled Receptor GrlH

OpenAIRE

Yu Tang; Yuantai Wu; Sarah E. Herlihy; Francisco J. Brito-Aleman; Jose H. Ting; Chris Janetopoulos; Richard H. Gomer; Scott D. Emr

2018-01-01

In eukaryotic microbes, little is known about signals that inhibit the proliferation of the cells that secrete the signal, and little is known about signals (chemorepellents) that cause cells to move away from the source of the signal. Autocrine proliferation repressor protein A (AprA) is a protein secreted by the eukaryotic microbe Dictyostelium discoideum. AprA is a chemorepellent for and inhibits the proliferation of D. discoideum. We previously found that cells sense AprA using G proteins...

Natural products from the ascidian Botrylloides giganteum, from the sponges Verongula gigantea, Ircinia felix, Cliona delitrix and from the nudibranch Tambja eliora, from the Brazilian coastline

International Nuclear Information System (INIS)

Granato, Ana Claudia; Oliveira, Jaine H.H.L. de; Seleghim, Mirna H.R.; Berlinck, Roberto G.S.; Macedo, Mario L.; Ferreira, Antonio G.; Rocha, Rosana M. da; Hajdu, Eduardo; Peixinho, Solange; Pessoa, Claudia O.; Moraes, Manoel O.; Cavalcanti, Bruno C.

2005-01-01

Two new marine metabolites, 3Z, 6Z, 9Z-dodecatrien-1-ol (1) from the ascidian Botrylloides giganteum and 4H-pyran-2ol acetate from the sponge Ircinia felix (4) are herein reported. The known bromotyrosine compounds, 2-(3,5-dibromo-4-methoxyphenyl)-N,N,Ndimethylethanammonium (2) and 2,6-dibromo-4-(2-(trimethylammonium)ethyl)phenol (3), have been isolated from the sponge Verongula gigantea. Serotonin (5) is reported for the first time from the sponge Cliona delitrix, and tambjamines A (15) and D (16) isolated as their respective salts from the nudibranch Tambja eliora. Only tambjamine D presented cytotoxicity against CEM (IC 5 )0 12.2 μg/mL) and HL60 (IC 50 13.2 μg/mL) human leukemia cells, MCF-7 breast cancer cells (IC 50 13.2 μg/mL), colon HCT-8 cancer cells (IC 50 10.1 μg/mL) and murine melanoma B16 cancer cells (IC 50 6.7 μg/mL). (author)

Differential growth of Legionella pneumophila strains within a range of amoebae at various temperatures associated with in-premise plumbing

Science.gov (United States)

The potential effect of in-premise plumbing temperatures (24, 32, 37 and 41 °C) on the growth of five different L. pneumophila strains within free-living amoebae (Acanthamoeba polyphaga, Hartmannella vermiformis and Naegleria fowleri) was examined. Compared to controls only fed E...

Ecology of testate amoebae in an Amazonian peatland and development of a transfer function for palaeohydrological reconstruction.

Science.gov (United States)

Swindles, Graeme T; Reczuga, Monika; Lamentowicz, Mariusz; Raby, Cassandra L; Turner, T Edward; Charman, Dan J; Gallego-Sala, Angela; Valderrama, Elvis; Williams, Christopher; Draper, Frederick; Honorio Coronado, Euridice N; Roucoux, Katherine H; Baker, Tim; Mullan, Donal J

2014-08-01

Tropical peatlands represent globally important carbon sinks with a unique biodiversity and are currently threatened by climate change and human activities. It is now imperative that proxy methods are developed to understand the ecohydrological dynamics of these systems and for testing peatland development models. Testate amoebae have been used as environmental indicators in ecological and palaeoecological studies of peatlands, primarily in ombrotrophic Sphagnum-dominated peatlands in the mid- and high-latitudes. We present the first ecological analysis of testate amoebae in a tropical peatland, a nutrient-poor domed bog in western (Peruvian) Amazonia. Litter samples were collected from different hydrological microforms (hummock to pool) along a transect from the edge to the interior of the peatland. We recorded 47 taxa from 21 genera. The most common taxa are Cryptodifflugia oviformis, Euglypha rotunda type, Phryganella acropodia, Pseudodifflugia fulva type and Trinema lineare. One species found only in the southern hemisphere, Argynnia spicata, is present. Arcella spp., Centropyxis aculeata and Lesqueresia spiralis are indicators of pools containing standing water. Canonical correspondence analysis and non-metric multidimensional scaling illustrate that water table depth is a significant control on the distribution of testate amoebae, similar to the results from mid- and high-latitude peatlands. A transfer function model for water table based on weighted averaging partial least-squares (WAPLS) regression is presented and performs well under cross-validation (r(2)(apparent)= 0.76, RMSE = 4.29; r(2)(jack)= 0.68, RMSEP =5.18). The transfer function was applied to a 1-m peat core, and sample-specific reconstruction errors were generated using bootstrapping. The reconstruction generally suggests near-surface water tables over the last 3,000 years, with a shift to drier conditions at c. cal. 1218-1273 AD.

An analysis of hereditary increase in frequency of cell mortality induced by external factors (Experiments on nuclear transplantation in amoebae)

International Nuclear Information System (INIS)

Bychkovskaya, I.B.; Ochinskaya, G.K.; Yudin, A.L.; AN SSSR, Leningrad. Inst. Tsitologii)

1980-01-01

By using nuclear transplantations in Amoeba proteus a study was made of a peculiar heritable effect, a stable increase in the frequency of cell mortality incuced by comparatively low doses of x radiation (50 Gy) or slight heating (29 0 C during 6 to 7 h). This effect differs qualitatively from the known radiation effects (reproductive death, lethal sectoring) by its being non-specific for radiation. In addition, the effect is saltatory appearing in 100% of the treated cells and the extent of its expression is not dependent on the dose of an inducing factor (at supra-threshold doses) and the period of time after treatment. It was found that (1) the hereditary changes in amoebae, unlike those resulting in reproductive death, are transmitted during intercellular transplantations both by the nucleus and cytoplasm of an altered cell; (2) the transfer of the character under test is accomplished by means of a certiin factor capable of shuttling between the nucleus and cytoplasm, (3) the effect is not necessarily a consequence of primary injury of nuclear structures and it may be induced by treatment of the cytoplasm of an enucleated cell renucleated then by the nucleus of a normal amoeba. In this respect, the effect under test differs also from the known types of hereditary post-radiation lethal effects which are commonly suggested to involve primary injury of the nucleus. Possible mechanisms of genetic control over the character tested are discussed. (author)

Down-regulation of Cell Surface Cyclic AMP Receptors and Desensitization of Cyclic AMP-stimulated Adenylate Cyclase by Cyclic AMP in Dictyostelium discoideum. Kinetics and Concentration Dependence

NARCIS (Netherlands)

Haastert, Peter J.M. van

1987-01-01

cAMP binds to Dictyostelium discoideum surface receptors and induces a transient activation of adenylate cyclase, which is followed by desensitization. cAMP also induces a loss of detectable surface receptors (down-regulation). Cells were incubated with constant cAMP concentrations, washed free of

Evidence of parasexual activity in "asexual amoebae" Cochliopodium spp. (Amoebozoa): extensive cellular and nuclear fusion.

Science.gov (United States)

Tekle, Yonas I; Anderson, O Roger; Lecky, Ariel F

2014-09-01

The majority of microbial eukaryotes have long been considered asexual, though new evidence indicates sex, or sexual-like (parasexual) behaviors that deviate from the usual union of two gametes, among other variant aspects. Over a dozen amoebozoans are implicated to have sexual stages. However, the exact mechanism by which sex occurs in these lineages remains elusive. This is mainly due to the diverse quality and cryptic nature of their life cycle. In this study we present evidence of some previously unreported aspects of the life cycle of an amoeba, Cochliopodium, that undergoes unusual intraspecific interactions using light microscopy and immunocytochemistry. Similar to other amoebozoans, Cochliopodium, is considered asexual with no published reports of sex or parasexuality. We also investigated environmental conditions that govern the observed intraspecific interactions. Both light microscopic and immunocytochemistry evidence demonstrates Cochliopodium undergoes cellular fusion (plasmogamy) and nuclear fusion (karyogamy). Large plasmodia eventually undergo karyogamy and contain large fused, polyploid, nuclei. These are observed to fragment, subsequently, by karyotomy (nuclear fission) and cytoplasmic fission to yield uninucleated amoebae. This process could lead to a non-meiotic, parasexual exchange of chromosomes in Cochliopodium. These findings strongly suggest that Cochliopodium is involved in parasexual activity and should no longer be considered strictly asexual. Copyright © 2014 Elsevier GmbH. All rights reserved.

Isolamento de amebas de vida livre potencialmente patogênicas em poeira de hospitais Isolation of potencially pathogenic free-living amoebas in hospital dust

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Maria Aparecida da Silva

2003-04-01

Full Text Available OBJETIVO: Observar a ocorrência de amebas de vida livre dos gêneros Acanthamoeba e Naegleria em amostras de poeira coletadas em hospitais. MÉTODOS: Foram coletadas 132 amostras de poeira em dois hospitais do município de Presidente Prudente, São Paulo. Os locais da coleta foram: Unidade de Terapia Intensiva, Centro Cirúrgico, Isolamento de Moléstias Infecciosas, Berçário, Emergência e Cozinha. As amostras foram semeadas em três meios de cultura: meio de ágar não nutriente com Escherichia coli, meio de ágar infusão de soja e microcultivo em meio de Pavlova modificado por Giazzi. As amebas isoladas foram identificadas segundo critérios morfológicos. RESULTADOS: O índice geral de positividade para amebas de vida livre, potencialmente patogênicas, dos gêneros Acanthamoeba e Naegleria, foi de 45,5%, sendo positivas 41,6% das amostras de poeira coletadas no hospital universitário e 50% no hospital estadual. Obtiveram-se 45,5% de positividade do gênero Acanthamoeba e 3,8% para amebas do gênero Naegleria. CONCLUSÕES: As amebas de vida livre, potencialmente patogênicas, estavam presentes em todos os ambientes estudados dos dois hospitais, sendo que as espécies do gênero Acanthamoeba foram as isoladas com maior freqüência.OBJECTIVE: To evaluate the occurrence of free-living amoebas of the genera Acanthamoeba and Naegleria is dust samples colleted in two hospitals. METHODS: One-hundred and thirty-two dust samples were collected in two hospitals in Brazil. Hospital collection sites were the following: intensive care unit, operation rooms, nursery, kitchen, emergency and infectious diseases isolation room . The isolation of the amoebas was performed in three culture media: non-nutrient agar inoculated with Escherichia coli, soy agar, and microculture in Giazzi-modified Pavlova's medium. The amoebas were identified according to morphological criteria. RESULTS: Amoebas of the genera Acanthamoeba and Naegleria were found in 45.5% of

Changes in Structure and Functioning of Protist (Testate Amoebae Communities Due to Conversion of Lowland Rainforest into Rubber and Oil Palm Plantations.

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Valentyna Krashevska

Full Text Available Large areas of tropical rainforest are being converted to agricultural and plantation land uses, but little is known of biodiversity and ecological functioning under these replacement land uses. We investigated the effects of conversion of rainforest into jungle rubber, intensive rubber and oil palm plantations on testate amoebae, diverse and functionally important protists in litter and soil. Living testate amoebae species richness, density and biomass were all lower in replacement land uses than in rainforest, with the impact being more pronounced in litter than in soil. Similar abundances of species of high and low trophic level in rainforest suggest that trophic interactions are more balanced, with a high number of functionally redundant species, than in rubber and oil palm. In contrast, plantations had a low density of high trophic level species indicating losses of functions. This was particularly so in oil palm plantations. In addition, the relative density of species with siliceous shells was >50% lower in the litter layer of oil palm and rubber compared to rainforest and jungle rubber. This difference suggests that rainforest conversion changes biogenic silicon pools and increases silicon losses. Overall, the lower species richness, density and biomass in plantations than in rainforest, and the changes in the functional composition of the testate amoebae community, indicate detrimental effects of rainforest conversion on the structure and functioning of microbial food webs.

Changes in Structure and Functioning of Protist (Testate Amoebae) Communities Due to Conversion of Lowland Rainforest into Rubber and Oil Palm Plantations.

Science.gov (United States)

Krashevska, Valentyna; Klarner, Bernhard; Widyastuti, Rahayu; Maraun, Mark; Scheu, Stefan

2016-01-01

Large areas of tropical rainforest are being converted to agricultural and plantation land uses, but little is known of biodiversity and ecological functioning under these replacement land uses. We investigated the effects of conversion of rainforest into jungle rubber, intensive rubber and oil palm plantations on testate amoebae, diverse and functionally important protists in litter and soil. Living testate amoebae species richness, density and biomass were all lower in replacement land uses than in rainforest, with the impact being more pronounced in litter than in soil. Similar abundances of species of high and low trophic level in rainforest suggest that trophic interactions are more balanced, with a high number of functionally redundant species, than in rubber and oil palm. In contrast, plantations had a low density of high trophic level species indicating losses of functions. This was particularly so in oil palm plantations. In addition, the relative density of species with siliceous shells was >50% lower in the litter layer of oil palm and rubber compared to rainforest and jungle rubber. This difference suggests that rainforest conversion changes biogenic silicon pools and increases silicon losses. Overall, the lower species richness, density and biomass in plantations than in rainforest, and the changes in the functional composition of the testate amoebae community, indicate detrimental effects of rainforest conversion on the structure and functioning of microbial food webs.

Uncovering a Role for the Tail of the Dictyostelium discoideum SadA Protein in Cell-Substrate Adhesion ▿ †

OpenAIRE

Kowal, Anthony S.; Chisholm, Rex L.

2011-01-01

Previous work from our laboratory showed that the Dictyostelium discoideum SadA protein plays a central role in cell-substrate adhesion. SadA null cells exhibit a loss of adhesion, a disrupted actin cytoskeleton, and a cytokinesis defect. How SadA mediates these phenotypes is unknown. This work addresses the mechanism of SadA function, demonstrating an important role for the C-terminal cytoplasmic tail in SadA function. We found that a SadA tailless mutant was unable to rescue the sadA adhesi...

Vesicular Trafficking Defects, Developmental Abnormalities, and Alterations in the Cellular Death Process Occur in Cell Lines that Over-Express Dictyostelium GTPase, Rab2, and Rab2 Mutants

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Katherine Maringer

2014-08-01

Full Text Available Small molecular weight GTPase Rab2 has been shown to be a resident of pre-Golgi intermediates and required for protein transport from the ER to the Golgi complex, however, the function of Rab2 in Dictyostelium has yet to be fully characterized. Using cell lines that over-express DdRab2, as well as cell lines over-expressing constitutively active (CA, and dominant negative (DN forms of the GTPase, we report a functional role in vesicular transport specifically phagocytosis, and endocytosis. Furthermore, Rab2 like other GTPases cycles between an active GTP-bound and an inactive GDP-bound state. We found that this GTP/GDP cycle for DdRab2 is crucial for normal Dictyostelium development and cell–cell adhesion. Similar to Rab5 and Rab7 in C. elegans, we found that DdRab2 plays a role in programmed cell death, possibly in the phagocytic removal of apoptotic corpses.

Binding and assembly of actin filaments by plasma membranes from dictyostelium discoideum

International Nuclear Information System (INIS)

Schwartz, M.A.; Luna, E.J.

1986-01-01

The binding of native, 125 I-Bolton-Hunter-labeled actin to purified Dictyostelium discoideum plasma membranes was measured using a sedimentation assay. Binding was saturable only in the presence of the actin capping protein, gelsolin. The binding curves were sigmoidal, indicating positive cooperativity at low actin concentrations. This cooperativity appeared to be due to actin-actin associations during polymerization, since phalloidin converted the curve to a hyperbolic shape. This membrane-bound actin stained with rhodamine-phalloidin and was cross-linked by m-maleimidobenzoyl succinimide ester, a bifunctional cross-linker, into multimers with the same pattern observed for cross-linked F-actin. The authors conclude that D. discoideum plasma membranes bind actin specifically and saturably and that these membranes organize actin into filaments below the normal critical concentration for polymerization. This interaction probably occurs between multiple binding sites on the membrane and the side of the actin filament, and may be related to the clustering of membrane proteins

Cytochemical study of the nucleolus of the slime mold Dictyostelium discoideum

International Nuclear Information System (INIS)

Benichou, J.C.; Quiviger, B.; Ryter, A.

1983-01-01

The nucleus of the slime mold Dictyostelium discoideum is characterized by the presence of several large dense masses which are all in tight contact with the nuclear membrane. These dense masses, considered as nucleoli, present a rather homogeneous texture, in which dense chromatin, fibrillar, and granular material are not easily detected. The autoradiographic study of [ 3 H]uridine pulse-labeled cells showed that the majority of the silver grains were located inside these masses. The use of EDTA regressive-staining, acetylation and enzymatic digestion indicated that they are mostly composed of RNP and are totally devoid of dense chromatin as the rest of the nucleus is. After treatment with actinomycin D, fibrillar and granular material segregated but no chromatin could be found. All these observations confirmed that the dense masses correspond to nucleoli despite their peculiar ultrastructure. It can also be concluded that this type of nucleoli cannot be considered as a taxonomic character of the slime molds because it does not exist in all slime molds and was observed in some dinoflagellates, and ascomycetes

Influence of fast advective flows on pattern formation of Dictyostelium discoideum

Science.gov (United States)

Bae, Albert; Zykov, Vladimir; Bodenschatz, Eberhard

2018-01-01

We report experimental and numerical results on pattern formation of self-organizing Dictyostelium discoideum cells in a microfluidic setup under a constant buffer flow. The external flow advects the signaling molecule cyclic adenosine monophosphate (cAMP) downstream, while the chemotactic cells attached to the solid substrate are not transported with the flow. At high flow velocities, elongated cAMP waves are formed that cover the whole length of the channel and propagate both parallel and perpendicular to the flow direction. While the wave period and transverse propagation velocity are constant, parallel wave velocity and the wave width increase linearly with the imposed flow. We also observe that the acquired wave shape is highly dependent on the wave generation site and the strength of the imposed flow. We compared the wave shape and velocity with numerical simulations performed using a reaction-diffusion model and found excellent agreement. These results are expected to play an important role in understanding the process of pattern formation and aggregation of D. discoideum that may experience fluid flows in its natural habitat. PMID:29590179

Giants among larges: how gigantism impacts giant virus entry into amoebae.

Science.gov (United States)

Rodrigues, Rodrigo Araújo Lima; Abrahão, Jônatas Santos; Drumond, Betânia Paiva; Kroon, Erna Geessien

2016-06-01

The proposed order Megavirales comprises the nucleocytoplasmic large DNA viruses (NCLDV), infecting a wide range of hosts. Over time, they co-evolved with different host cells, developing various strategies to penetrate them. Mimiviruses and other giant viruses enter cells through phagocytosis, while Marseillevirus and other large viruses explore endocytosis and macropinocytosis. These differing strategies might reflect the evolution of those viruses. Various scenarios have been proposed for the origin and evolution of these viruses, presenting one of the most enigmatic issues to surround these microorganisms. In this context, we believe that giant viruses evolved independently by massive gene/size gain, exploring the phagocytic pathway of entry into amoebas. In response to gigantism, hosts developed mechanisms to evade these parasites. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ubiquiter circovirus sequences raise challenges in laboratory diagnosis: the case of honey bee and bee mite, reptiles, and free living amoebae.

Science.gov (United States)

Marton, Szilvia; Ihász, Katalin; Lengyel, György; Farkas, Szilvia L; Dán, Ádám; Paulus, Petra; Bányai, Krisztián; Fehér, Enikő

2015-03-01

Circoviruses of pigs and birds are established pathogens, however, the exact role of other, recently described circoviruses and circovirus-like viruses remains to be elucidated. The aim of this study was the detection of circoviruses in neglected host species, including honey bees, exotic reptiles and free-living amoebae by widely used broad-spectrum polymerase chain reaction (PCR) assays specific for the replication initiation protein coding gene of these viruses. The majority of sequences obtained from honey bees were highly similar to canine and porcine circoviruses, or, were distantly related to dragonfly cycloviruses. Other rep sequences detected in some honey bees, reptiles and amoebae showed similarities to various rep sequences deposited in the GenBank. Back-to-back PCR primers designed for the amplification of whole viral genomes failed to work that suggested the existence of integrated rep-like elements in many samples. Rolling circle amplification and exonuclease treatment confirmed the absence of small circular DNA genomes in the specimens analysed. In case of honey bees Varroa mite DNA contamination might be a source of the identified endogenous rep-like elements. The reptile and amoebae rep-like sequences were nearly identical with each other and with sequences detected in chimpanzee feces raising the possibility that detection of novel or unusual rep-like elements in some host species might originate from the microbial community of the host. Our results indicate that attention is needed when broad-spectrum rep gene specific polymerase chain reaction is chosen for laboratory diagnosis of circovirus infections.

Species richness of testate amoebae in different environments from the upper Paraná river floodplain (PR/MS - doi: 10.4025/actascibiolsci.v33i3.7261 Species richness of testate amoebae in different environments from the upper Paraná river floodplain (PR/MS - doi: 10.4025/actascibiolsci.v33i3.7261

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Fábio Amodêo Lansac-Tôha

2011-07-01

Full Text Available This study evaluated the species richness of testate amoebae in the plankton from different environments of the upper Paraná river floodplain. Samplings were performed at subsurface of pelagic region from twelve environments using motorized pump and plankton net (68 µm, during four hydrological periods. We identified 67 taxa, distributed in seven families and Arcellidae, Difflugiidae and Centropyxidae were the most representative families. Higher values of species richness were observed in the lakes (connected and isolated during the flood pulses. Centropyxis aculeata, Difflugia gramem and D. pseudogramem were frequent throughout the study period. Seasonal variability of species in the channels and isolated lakes was evidenced by beta diversity. Besides that, in the rivers, extreme changes in species composition were verified during the high-water period. Our results highlight the importance of the present study to improve the knowledge about the diversity and geographic distribution of these organisms in Brazil and emphasize the importance of current flow in the displacement of testate amoebae from their preferred habitats, marginal vegetation and sediment.This study evaluated the species richness of testate amoebae in the plankton from different environments of the upper Paraná river floodplain. Samplings were performed at subsurface of pelagic region from twelve environments using motorized pump and plankton net (68 µm, during four hydrological periods. We identified 67 taxa, distributed in seven families and Arcellidae, Difflugiidae and Centropyxidae were the most representative families. Higher values of species richness were observed in the lakes (connected and isolated during the flood pulses. Centropyxis aculeata, Difflugia gramem and D. pseudogramem were frequent throughout the study period. Seasonal variability of species in the channels and isolated lakes was evidenced by beta diversity. Besides that, in the rivers, extreme

[i]Legionella spp[/i]., amoebae and not-fermenting Gram negative bacteria in an Italian university hospital water system

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Pasqualina Laganà

2014-09-01

Full Text Available [b]Introduction. [/b]In hospital and other health care facilities, contamination of water systems by potentially infectious microorganisms, such as bacteria, viruses and protozoa, is a source of nosocomial infections, which may originate fromcolonization of water pipes, cooling towers, spa pools, taps, showers and water supplies. [b]Objective. [/b]The study focuses on the occurrence of [i]Legionella spp.[/i], free-living amoebae and non-fermenting Gram-negative microorganisms in a University hospital water system located in the town of Messina (Sicily, Italy, which had never been examined previously. Materials and Methods. From January 2008 – March 2009, hot tap water samples were collected from 10 wards.[i] Legionella spp[/i]. recovered on selective culture medium were identified by microagglutination latex test; free-living amoebae were cultured using [i]Escherichia coli [/i]as a food source. Non-fermenting Gram negative microorganisms were identified by API 20 NE strips. [b]Results.[/b] [i]Legionella spp.[/i] were found in 33.33% of the samples. [i]L. pneumophila[/i] serogroup 1 was recovered from the Laboratory Diagnostic and Anaesthesia-Neurology Wards, with a peak of 3.5 × 10[sup]4[/sup] cfu/L in May 2008. [i]L. pneumophila[/i] serogroups 2–14 were found in the Othorhinolaryngology, Pathologic Anatomy, Paediatrics and Surgery Wards, and peaked (4 × 10[sup]4[/sup] cfu/L in April 2008. Pseudomonadaceae and Hyphomycetes were also detected. Legionella spp. were recovered from samples positive for non-pathogenic amoebae [i]Hartmannella spp[/i]. [b]Conclusion.[/b] This first study of a Messina hospital water system suggested potential health risks related to the detection of [i]Hartmannella spp[/i]., as reservoirs for[i] Legionella spp.[/i], and Pseudomonas aeruginosa, a Gram negative non-fermenting bacterium frequently causing nosocomial pneumonia. The urgent need for monitoring programmes and prevention measures to ensure hospital water

A long-range foresight for the medical application of apoptosis specifically induced by Dd-MRP4, Dictyostelium mitochondrial ribosomal protein S4, to cancer therapy.

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Maeda, Yasuo

2015-02-10

Apoptosis (programmed cell death) is regarded as ultimate differentiation of the cell. We have recently demonstrated that a targeted delivery of Dd-MRP4 (Dictyostelium mitochondrial ribosomal protein S4) suppresses specifically the proliferation of the human cancer cells, by inducing their apoptotic cell death (Chida et al., 2014, doi:10.1186/1475-2867-14-56). This amazing fact was discovered, simply based on the finding that Dd-MRP4 expression is absolutely required for transition of Dictyostelium cells from growth to differentiation (Chida et al., 2008, doi:10.1186/1471-2156-9-25; Maeda et al., 2013, doi:10.3390/biom3040943). Dd-MRP4 protein has quite unique structural characters, in that it is highly basic (pI: about 11.5) and interestingly has several nuclear-localization signals within the molecule. In this review, we introduce briefly the efficacy of several apoptosis-inducing substances reported thus far for cancer therapy, and speculate the possible mechanisms, by which apoptosis is specifically induced by Dd-MRP4, on the basis of its structural uniqueness. We also discuss several issues to be solved for the medical application of ectopically expressed Dd-MRP4 in human cancer cells.

Preferential feeding in Naegleria fowleri; intracellular bacteria isolated from amoebae in operational drinking water distribution systems.

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Miller, Haylea C; Morgan, Matthew J; Walsh, Tom; Wylie, Jason T; Kaksonen, Anna H; Puzon, Geoffrey J

2018-05-06

The amoeba Naegleria fowleri is the causative agent of the highly fatal disease, primary amoebic meningoencephalitis, and estimated to cause 16 deaths per year in the United States alone. Colonisation of drinking water distribution systems (DWDSs) by the N. fowleri is a significant public health issue. Understanding the factors which enable this pathogen to colonise and thrive in DWDSs is critical for proper management. The microbial ecology within DWDSs may influence the ability of N. fowleri to colonise DWDSs by facilitating the availability of an appropriate food source. Using biofilm samples obtained from operational DWDSs, 16S rRNA amplicon metabarcoding was combined with genus-specific PCR and Sanger sequencing of intracellular associated bacteria from isolated amoeba and their parental biofilms to identify Meiothermus chliarophilus as a potential food source for N. fowleri. Meiothermus was confirmed as a food source for N. fowleri following successful serial culturing of axenic N. fowleri with M. chliarophilus or M. ruber as the sole food source. The ability to identify environmental and ecological conditions favourable to N. fowleri colonisation, including the detection of appropriate food sources such as Meiothermus, could provide water utilities with a predictive tool for managing N. fowleri colonisation within the DWDS. Copyright © 2018 Elsevier Ltd. All rights reserved.

Derivatives of Dictyostelium differentiation-inducing factors inhibit lysophosphatidic acid–stimulated migration of murine osteosarcoma LM8 cells

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Kubohara, Yuzuru, E-mail: ykuboha@juntendo.ac.jp [Department of Molecular and Cellular Biology, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, Maebashi 371-8512 (Japan); Department of Health Science, Juntendo University Graduate School of Health and Sports Science, Inzai 270-1695 (Japan); Komachi, Mayumi [Department of Molecular and Cellular Biology, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, Maebashi 371-8512 (Japan); Department of Radiation Oncology, Gunma University Graduate School of Medicine, Maebashi 371-8511 (Japan); Homma, Yoshimi [Department of Biomolecular Science, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima 960-1295 (Japan); Kikuchi, Haruhisa; Oshima, Yoshiteru [Laboratory of Natural Product Chemistry, Tohoku University Graduate School of Pharmaceutical Sciences, Aoba-yama, Aoba-ku, Sendai 980-8578 (Japan)

2015-08-07

Osteosarcoma is a common metastatic bone cancer that predominantly develops in children and adolescents. Metastatic osteosarcoma remains associated with a poor prognosis; therefore, more effective anti-metastatic drugs are needed. Differentiation-inducing factor-1 (DIF-1), −2, and −3 are novel lead anti-tumor agents that were originally isolated from the cellular slime mold Dictyostelium discoideum. Here we investigated the effects of a panel of DIF derivatives on lysophosphatidic acid (LPA)-induced migration of mouse osteosarcoma LM8 cells by using a Boyden chamber assay. Some DIF derivatives such as Br-DIF-1, DIF-3(+2), and Bu-DIF-3 (5–20 μM) dose-dependently suppressed LPA-induced cell migration with associated IC{sub 50} values of 5.5, 4.6, and 4.2 μM, respectively. On the other hand, the IC{sub 50} values of Br-DIF-1, DIF-3(+2), and Bu-DIF-3 versus cell proliferation were 18.5, 7.2, and 2.0 μM, respectively, in LM8 cells, and >20, 14.8, and 4.3 μM, respectively, in mouse 3T3-L1 fibroblasts (non-transformed). Together, our results demonstrate that Br-DIF-1 in particular may be a valuable tool for the analysis of cancer cell migration, and that DIF derivatives such as DIF-3(+2) and Bu-DIF-3 are promising lead anti-tumor agents for the development of therapies that suppress osteosarcoma cell proliferation, migration, and metastasis. - Highlights: • LPA induces cell migration (invasion) in murine osteosarcoma LM8 cells. • DIFs are novel lead anti-tumor agents found in Dictyostelium discoideum. • We examined the effects of DIF derivatives on LPA-induced LM8 cell migration in vitro. • Some of the DIF derivatives inhibited LPA-induced LM8 cell migration.

Crystallization and preliminary characterization of dihydropteridine reductase from Dictyostelium discoideum

International Nuclear Information System (INIS)

Chen, Cong; Seo, Kyung Hye; Kim, Hye Lim; Zhuang, Ningning; Park, Young Shik; Lee, Kon Ho

2008-01-01

The dihydropteridine reductase from D. discoideum has been crystallized. Diffraction data were collected from a rectangular-shaped crystal to 2.16 Å resolution. Dihydropteridine reductase from Dictyostelium discoideum (dicDHPR) can produce d-threo-BH 4 [6R-(1′R,2′R)-5,6,7,8-tetrahydrobiopterin], a stereoisomer of l-erythro-BH 4 , in the last step of tetrahydrobiopterin (BH 4 ) recycling. In this reaction, DHPR uses NADH as a cofactor to reduce quinonoid dihydrobiopterin back to BH 4 . To date, the enzyme has been purified to homogeneity from many sources. In this report, the dicDHPR–NAD complex has been crystallized using the hanging-drop vapour-diffusion method with PEG 3350 as a precipitant. Rectangular-shaped crystals were obtained. Crystals grew to maximum dimensions of 0.4 × 0.6 × 0.1 mm. The crystal belonged to space group P2 1 , with unit-cell parameters a = 49.81, b = 129.90, c = 78.76 Å, β = 100.00°, and contained four molecules in the asymmetric unit, forming two closely interacting dicDHPR–NAD dimers. Diffraction data were collected to 2.16 Å resolution using synchrotron radiation. The crystal structure has been determined using the molecular-replacement method

Characterization of a 1,4-{beta}-D-glucan synthase from Dictyostelium discoideum. Progress report, May 1990--January 1992

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Blanton, R.L.

1992-01-15

Various aspects of research concerning Dictyostelium discoideum are presented. The initial focus of this project was upon: the characterization of potential probes for the cellulose synthase (antibody and nucleic acid), the determination of the cultural induction conditions of cellulose synthesis, the solubilization of the enzyme activity, the development of a non-inhibitory disruption buffer, the generation and isolation of mutant strains deficient in cellulose synthesis, and the development of the capability to determine the degree of polymerization of the in vitro product. I have briefly summarized our most significant findings with only selected data sets being shown in this report in the interest of brevity.

Ontogenia de los estróbilos, desarrollo de los esporangios y esporogénesis de Equisetum giganteum (Equisetaceae en los Andes de Colombia

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Edgar Javier Rincón Barón

2011-12-01

Full Text Available Estudios sobre la ontogenia del estróbilo, los esporangios y la biología reproductiva de Equisetum son escasos, por lo tanto, para la especie E. giganteum, se estudiaron estos aspectos en especímenes recolectados a orillas del Río Frío, Santander, Colombia (2 200m. Los estróbilos en diferentes etapas de maduración fueron fijados, deshidratados, embebidos en parafina, seccionados en micrótomo rotatorio y teñidos con safranina O-fast green. Las observaciones se efectuaron mediante un microscopio óptico de alta resolución con contraste diferencial de interferencia (DIC y microscopio de fluorescencia. Los estróbilos se inician a partir del meristemo apical, tanto en el eje principal como en los laterales, sin diferencias en el proceso de ontogenia y esporogénesis entre estróbilos de diferentes ejes. Sucesivas mitosis y diferenciación celular conducen al crecimiento del estróbilo, y a la formación de los esporangióforos peltados, formados por el manubrio, o porción basal con aspecto de pedicelo, el escutelo, o porción apical aplanada y las iniciales del esporangio, los cuales se diferenciarán para formar la pared del esporangio, los esporocitos y el tapete. No se forma arquesporio y los esporocitos experimentan meiosis para formar tétradas de esporas. El tapete mantiene la integridad histológica hasta la formación de las tétradas y en esa etapa forma un plasmodio que invade la cavidad esporangial la cual rodea parcialmente las tétradas y luego las esporas, y aparecen las cámaras plasmodiales, un término propuesto aquí para las formaciones designadas en inglés "tapetal gaps". La pared del esporangio queda reducida a dos capas celulares: una externa con engrosamientos lignificados en todas las paredes celulares y una interna picnótica. Al finalizar la esporogénesis, el tapete degenera, y las esporas, con exosporio, perisporio delgado, casi membranáceo y eláteres quedan libres en la cavidad esporangial. El esporodermo

Quantifying the degree of persistence in random amoeboid motion based on the Hurst exponent of fractional Brownian motion.

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Makarava, Natallia; Menz, Stephan; Theves, Matthias; Huisinga, Wilhelm; Beta, Carsten; Holschneider, Matthias

2014-10-01

Amoebae explore their environment in a random way, unless external cues like, e.g., nutrients, bias their motion. Even in the absence of cues, however, experimental cell tracks show some degree of persistence. In this paper, we analyzed individual cell tracks in the framework of a linear mixed effects model, where each track is modeled by a fractional Brownian motion, i.e., a Gaussian process exhibiting a long-term correlation structure superposed on a linear trend. The degree of persistence was quantified by the Hurst exponent of fractional Brownian motion. Our analysis of experimental cell tracks of the amoeba Dictyostelium discoideum showed a persistent movement for the majority of tracks. Employing a sliding window approach, we estimated the variations of the Hurst exponent over time, which allowed us to identify points in time, where the correlation structure was distorted ("outliers"). Coarse graining of track data via down-sampling allowed us to identify the dependence of persistence on the spatial scale. While one would expect the (mode of the) Hurst exponent to be constant on different temporal scales due to the self-similarity property of fractional Brownian motion, we observed a trend towards stronger persistence for the down-sampled cell tracks indicating stronger persistence on larger time scales.

Phg1/TM9 proteins control intracellular killing of bacteria by determining cellular levels of the Kil1 sulfotransferase in Dictyostelium.

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Marion Le Coadic

Full Text Available Dictyostelium discoideum has largely been used to study phagocytosis and intracellular killing of bacteria. Previous studies have shown that Phg1A, Kil1 and Kil2 proteins are necessary for efficient intracellular killing of Klebsiella bacteria. Here we show that in phg1a KO cells, cellular levels of lysosomal glycosidases and lysozyme are decreased, and lysosomal pH is increased. Surprisingly, overexpression of Kil1 restores efficient killing in phg1a KO cells without correcting these lysosomal anomalies. Conversely, kil1 KO cells are defective for killing, but their enzymatic content and lysosomal pH are indistinguishable from WT cells. The killing defect of phg1a KO cells can be accounted for by the observation that in these cells the stability and the cellular amount of Kil1 are markedly reduced. Since Kil1 is the only sulfotransferase characterized in Dictyostelium, an (unidentified sulfated factor, defective in both phg1a and kil1 KO cells, may play a key role in intracellular killing of Klebsiella bacteria. In addition, Phg1B plays a redundant role with Phg1A in controlling cellular amounts of Kil1 and intracellular killing. Finally, cellular levels of Kil1 are unaffected in kil2 KO cells, and Kil1 overexpression does not correct the killing defect of kil2 KO cells, suggesting that Kil2 plays a distinct role in intracellular killing.

Reaching an entrepreneurial management system of amoebas. A qualitative insight into the European experiences

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Urban Wiesław

2016-03-01

Full Text Available The aim of the study is an assessment of the Amoeba Management System (AMS introduction advancements in some European companies. The study takes the practically focused research approach. The approaches, achievements and phases whilst introducing the AMS principles by companies are observed and critically assessed. First insight into the challenges of AMS introduction is taken basing on critical study of the literature output. The scientific studies and managerial publications are taken into consideration. The empirical part of the study is based on the qualitative approach. A multiple case study methodology is employed. The research objects are three companies, one of them operates in Sweden, the next two in Poland. Each of them have different experiences in AMS implementation, they also manifest different management styles and habits. The study demonstrates that AMS is a very prospective management methodology which can support companies in employees commitment during their journey towards operational excellence. The analysis results show different motivations for AMS introduction as well as different development paths, these are harmonized with different management styles in companies and culture occurring in countries. The study is particularly valuable because this is one of the first empirical investigations of AMS implementation in European companies. In the field of theory the study proposes the four level scale for amoebas system maturity. This scale allows to classify companies following AMS principles and, at the same time, this scale is also the kind of path of AMS implementation. The study points out basic tools for companies which support AMS implementation. These tools are already known in management literature, but experience of investigated companies shows that they are fundamental for successful AMS implementation.

Identification and characterization of peptide: N- glycanase from Dictyostelium discoideum

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Gosain Anuradha

2012-06-01

Full Text Available Abstract Background Peptide: N- glycanase (PNGase enzyme cleaves oligosaccharides from the misfolded glycoproteins and prepares them for degradation. This enzyme plays a role in the endoplasmic reticulum associated degradation (ERAD pathway in yeast and mice but its biological importance and role in multicellular development remain largely unknown. Results In this study, the PNGase from the cellular slime mold, Dictyostelium discoideum (DdPNGase was identified based on the presence of a common TG (transglutaminase core domain and its sequence homology with the known PNGases. The domain architecture and the sequence comparison validated the presence of probable functional domains in DdPNGase. The tertiary structure matched with the mouse PNGase. Here we show that DdPNGase is an essential protein, required for aggregation during multicellular development and a knockout strain of it results in small sized aggregates, all of which did not form fruiting bodies. The in situ hybridization and RT-PCR results show higher level of expression during the aggregate stage. The expression gets restricted to the prestalk region during later developmental stages. DdPNGase is a functional peptide:N-glycanase enzyme possessing deglycosylation activity, but does not possess any significant transamidation activity. Conclusions We have identified and characterized a novel PNGase from D. discoideum and confirmed its deglycosylation activity. The results emphasize the importance of PNGase in aggregation during multicellular development of this organism.

Amoeba-like self-oscillating polymeric fluids with autonomous sol-gel transition.

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Onoda, Michika; Ueki, Takeshi; Tamate, Ryota; Shibayama, Mitsuhiro; Yoshida, Ryo

2017-07-13

In the field of polymer science, many kinds of polymeric material systems that show a sol-gel transition have been created. However, most systems are unidirectional stimuli-responsive systems that require physical signals such as a change in temperature. Here, we report on the design of a block copolymer solution that undergoes autonomous and periodic sol-gel transition under constant conditions without any on-off switching through external stimuli. The amplitude of this self-oscillation of the viscosity is about 2,000 mPa s. We also demonstrate an intermittent forward motion of a droplet of the polymer solution synchronized with the autonomous sol-gel transition. This polymer solution bears the potential to become the base for a type of slime-like soft robot that can transform its shape kaleidoscopically and move autonomously, which is associated with the living amoeba that moves forward by a repeated sol-gel transition.

Nucleocytoplasmic protein translocation during mitosis in the social amoebozoan Dictyostelium discoideum.

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O'Day, Danton H; Budniak, Aldona

2015-02-01

Mitosis is a fundamental and essential life process. It underlies the duplication and survival of all cells and, as a result, all eukaryotic organisms. Since uncontrolled mitosis is a dreaded component of many cancers, a full understanding of the process is critical. Evolution has led to the existence of three types of mitosis: closed, open, and semi-open. The significance of these different mitotic species, how they can lead to a full understanding of the critical events that underlie the asexual duplication of all cells, and how they may generate new insights into controlling unregulated cell division remains to be determined. The eukaryotic microbe Dictyostelium discoideum has proved to be a valuable biomedical model organism. While it appears to utilize closed mitosis, a review of the literature suggests that it possesses a form of mitosis that lies in the middle between truly open and fully closed mitosis-it utilizes a form of semi-open mitosis. Here, the nucleocytoplasmic translocation patterns of the proteins that have been studied during mitosis in the social amoebozoan D. discoideum are detailed followed by a discussion of how some of them provide support for the hypothesis of semi-open mitosis. © 2014 The Authors. Biological Reviews published by John Wiley & Sons Ltd on behalf of Cambridge Philosophical Society.

Activation of G-proteins by receptor-stimulated nucleoside diphosphate kinase in Dictyostelium.

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Bominaar, A A; Molijn, A C; Pestel, M; Veron, M; Van Haastert, P J

1993-01-01

Recently, interest in the enzyme nucleoside diphosphate kinase (EC2.7.4.6) has increased as a result of its possible involvement in cell proliferation and development. Since NDP kinase is one of the major sources of GTP in cells, it has been suggested that the effects of an altered NDP kinase activity on cellular processes might be the result of altered transmembrane signal transduction via guanine nucleotide-binding proteins (G-proteins). In the cellular slime mould Dictyostelium discoideum, extracellular cAMP induces an increase of phospholipase C activity via a surface cAMP receptor and G-proteins. In this paper it is demonstrated that part of the cellular NDP kinase is associated with the membrane and stimulated by cell surface cAMP receptors. The GTP produced by the action of NDP kinase is capable of activating G-proteins as monitored by altered G-protein-receptor interaction and the activation of the effector enzyme phospholipase C. Furthermore, specific monoclonal antibodies inhibit the effect of NDP kinase on G-protein activation. These results suggest that receptor-stimulated NDP kinase contributes to the mediation of hormone action by producing GTP for the activation of GTP-binding proteins. Images PMID:8389692

Overexpression of TOR (target of rapamycin) inhibits cell proliferation in Dictyostelium discoideum.

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Swer, Pynskhem Bok; Mishra, Himanshu; Lohia, Rakhee; Saran, Shweta

2016-05-01

TOR (target of rapamycin) protein kinase acts as a central controller of cell growth and development of an organism. Present study was undertaken to find the expression pattern and role of TOR during growth and development of Dictyostelium discoideum. Failures to generate either knockout and/or knockdown mutants indicate that interference with its levels led to cellular defects. Thus, the effects of TOR (DDB_G0281569) overexpression specifically, cells expressing Dd(Δ211-TOR)-Eyfp mutant was analyzed. Elevated expression of (Δ211-TOR)-Eyfp reduced both cell size and cell proliferation. DdTOR was found to be closer to fungus. mRNA level of TOR was found maximally in the freshly starved/aggregate cells that gradually declined. This was also strengthened by the expression patterns observed by in situ and the analysis of β-galactosidase reporter driven by the putative TOR promoter. The TOR protein was found to be highest at the aggregate stage. The fusion protein, (Δ211-TOR)-Eyfp was localized to the cell membrane, cytosol, and the nucleus. We suggest, DdTOR to be an essential protein and high TOR expression inhibits cell proliferation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The reconstruction of late Holocene depth-to-water-table based on testate amoebae in an eastern Australian mire

Science.gov (United States)

Zheng, X.; Money, S.; Hope, G.

2017-12-01

There are relatively few quantitative palaeo-hydrological records available in eastern Australia, and those that are available, for example from dendroclimatology and the reconstruction of lake level, are often relatively short or have a relatively coarse temporal resolution (e.g. Wilkins et al. 2013; Palmer et al. 2015). Testate amoebae, a widely used hydrological proxy in the Northern Hemisphere, were used here to reconstruct depth to water table (DWT) at Snowy Flat, which is a Sphagnum-Richea-Empodismahigh altitude (1618 m asl) shrub bog in the Australian Capital Territory, Australia. Testate amoebae were quantified in a Snowy Flat core representing 4,200 cal Y BP and the community composition was used to reconstruct DWT based on our recently established transfer functions. Results from three different types of transfer functions (Fig. 1) consistently show there was a decreasing DWT (wetter) period centred on about 3350 cal Y BP, a trend towards increased dryness from about 3300 to 2200 cal Y BP and a distinctly drier period 850 to 700 cal Y BP which was immediately followed by a wetter period from 700 to 500 cal Y BP. We discuss these episodes and trends in relation to the drivers of climatic variability in this region and in particular, by comparing our results with other south-eastern Australia records, comment on the history of the southern annular mode.

1H, 15N and 13C assignments of domain 5 of Dictyostelium discoideum gelation factor (ABP-120) in its native and 8M urea-denatured states.

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Hsu, Shang-Te Danny; Cabrita, Lisa D; Christodoulou, John; Dobson, Christopher M

2009-06-01

The gelation factor from Dictyostelium discoideum (ABP-120) is an actin binding protein consisting of six immunoglobulin (Ig) domains in the C-terminal rod domain. We have recently used the pair of domains 5 and 6 of ABP-120 as a model system for studying multi-domain nascent chain folding on the ribosome. Here we present the NMR assignments of domain 5 in its native and 8M urea-denatured states.

Lateral gene exchanges shape the genomes of amoeba-resisting microorganisms

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Claire eBertelli

2012-08-01

Full Text Available Based on Darwin’s concept of the tree of life, vertical inheritance was thought to be dominant, and mutations, deletions and duplication were streaming the genomes of living organisms. In the current genomic era, increasing data indicated that both vertical and lateral gene inheritance interact in space and time to trigger genome evolution, particularly among microorganisms sharing a given ecological niche. As a paradigm to their diversity and their survival in a variety of cell types, intracellular microorganisms, and notably intracellular bacteria, were considered as less prone to lateral genetic exchanges. Such specialized microorganisms generally have a smaller gene repertoire because they do rely on their host’s factors for some basic regulatory and metabolic functions. Here we review events of lateral gene transfer (LGT that illustrate the genetic exchanges among intra-amoebal microorganisms or between the microorganism and its amoebal host. We tentatively investigate the functions of laterally transferred genes in the light of the interaction with their host as they should confer a selective advantage and success to the amoeba-resisting microorganisms.

A novel Ras-interacting protein required for chemotaxis and cyclic adenosine monophosphate signal relay in Dictyostelium.

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Lee, S; Parent, C A; Insall, R; Firtel, R A

1999-09-01

We have identified a novel Ras-interacting protein from Dictyostelium, RIP3, whose function is required for both chemotaxis and the synthesis and relay of the cyclic AMP (cAMP) chemoattractant signal. rip3 null cells are unable to aggregate and lack receptor activation of adenylyl cyclase but are able, in response to cAMP, to induce aggregation-stage, postaggregative, and cell-type-specific gene expression in suspension culture. In addition, rip3 null cells are unable to properly polarize in a cAMP gradient and chemotaxis is highly impaired. We demonstrate that cAMP stimulation of guanylyl cyclase, which is required for chemotaxis, is reduced approximately 60% in rip3 null cells. This reduced activation of guanylyl cyclase may account, in part, for the defect in chemotaxis. When cells are pulsed with cAMP for 5 h to mimic the endogenous cAMP oscillations that occur in wild-type strains, the cells will form aggregates, most of which, however, arrest at the mound stage. Unlike the response seen in wild-type strains, the rip3 null cell aggregates that form under these experimental conditions are very small, which is probably due to the rip3 null cell chemotaxis defect. Many of the phenotypes of the rip3 null cell, including the inability to activate adenylyl cyclase in response to cAMP and defects in chemotaxis, are very similar to those of strains carrying a disruption of the gene encoding the putative Ras exchange factor AleA. We demonstrate that aleA null cells also exhibit a defect in cAMP-mediated activation of guanylyl cyclase similar to that of rip3 null cells. A double-knockout mutant (rip3/aleA null cells) exhibits a further reduction in receptor activation of guanylyl cyclase, and these cells display almost no cell polarization or movement in cAMP gradients. As RIP3 preferentially interacts with an activated form of the Dictyostelium Ras protein RasG, which itself is important for cell movement, we propose that RIP3 and AleA are components of a Ras

Predicting the distribution of spiral waves from cell properties in a developmental-path model of Dictyostelium pattern formation.

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Daniel Geberth

2009-07-01

Full Text Available The slime mold Dictyostelium discoideum is one of the model systems of biological pattern formation. One of the most successful answers to the challenge of establishing a spiral wave pattern in a colony of homogeneously distributed D. discoideum cells has been the suggestion of a developmental path the cells follow (Lauzeral and coworkers. This is a well-defined change in properties each cell undergoes on a longer time scale than the typical dynamics of the cell. Here we show that this concept leads to an inhomogeneous and systematic spatial distribution of spiral waves, which can be predicted from the distribution of cells on the developmental path. We propose specific experiments for checking whether such systematics are also found in data and thus, indirectly, provide evidence of a developmental path.

Amoebae of the genera Vannella Bovee, 1965 and Platyamoeba Page, 1969 isolated from fish and their phylogeny inferred from SSU rRNA gene and ITS sequences

Czech Academy of Sciences Publication Activity Database

Dyková, Iva; Boháčová, Lenka; Fiala, Ivan; Macháčková, Blanka; Pecková, Hana; Dvořáková, Helena

2005-01-01

Roč. 41, č. 3 (2005), s. 219-230 ISSN 0932-4739 R&D Projects: GA AV ČR IAA6022202 Institutional research plan: CEZ:AV0Z60220518 Keywords : fish-isolated amoebae * Vannella * Platyamoeba Subject RIV: EA - Cell Biology Impact factor: 1.253, year: 2005

Immobilization of Deoxyadenosine Kinase from Dictyostelium discoideum (DddAK) and Its Application in the 5’-Phosphorylation of Arabinosyladenine and Arabinosyl-2-fluoroadenine

DEFF Research Database (Denmark)

Serra, Immacolata; Ubiali, Daniela; Piskur, Jure

2017-01-01

Deoxyadenosine kinase from Dictyostelium discoideum (DddAK) phosphorylates its natural substrate (2’‐deoxyadenosine, dAdo) as well as the arabinosyladenine analogues vidarabine (araA) and fludarabine (F‐araA) to their corresponding 5’‐monophosphates. DddAK has been here immobilized by ionic...... interaction on an aminated epoxy‐functionalized support (SepabeadsTM EC‐EP), and cross‐linked with oxidized dextran. The final activity recovery was 33–42 %, depending on the protein loading. Immobilization enhanced the stability of DddAK at pH 10 and, to a lesser extent, at 45 °C. Phosphorylation of d...

Testate amoebae analysis in the peat deposits of the swamp Dolgon’koye in the south of Western Siberia and peatland paleohydrology for last 3100 years

Science.gov (United States)

Kurina, Irina V.; Blyakharchuk, Tatiana A.

2018-03-01

Our research is devoted to paleohydrological reconstruction in the swamp located in the river valley on the piedmont of the Altai Mountains in the south of Western Siberia. The reconstruction was carried out based on rhizopod analysis for the last 3100 cal yr. A large amount of different testate amoebae was found in the peat. Total 64 testate amoebae taxa were recorded in the peat core with the most abundant being: Trinema lineare, Centropyxis aculeata, C. aerophila, Euglypha rotunda, Cryptodifflugia sp. Decrease of surface wetness in the swamp are observed 2280, 2140, 1900–600 cal yr BP and increase – in 2700, 2500–1900, 230–215 cal yr BP. The results of our reconstruction of the swamp paleohydrology agrees well with the paleoclimatic data obtained earlier for the central area of the south of Western Siberia Plain. It indicates a high sensitivity of the swamp to climatic changes in the Holocene. The rhizopod analysis proved to be very effective when used for paleohydrology reconstruction in minerotrophic peat.

PKC-Mediated ZYG1 Phosphorylation Induces Fusion of Myoblasts as well as of Dictyostelium Cells

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Aiko Amagai

2012-01-01

Full Text Available We have previously demonstrated that a novel protein ZYG1 induces sexual cell fusion (zygote formation of Dictyostelium cells. In the process of cell fusion, involvements of signal transduction pathways via Ca2+ and PKC (protein kinase C have been suggested because zygote formation is greatly enhanced by PKC activators. In fact, there are several deduced sites phosphorylated by PKC in ZYG1 protein. Thereupon, we designed the present work to examine whether or not ZYG1 is actually phosphorylated by PKC and localized at the regions of cell-cell contacts where cell fusion occurs. These were ascertained, suggesting that ZYG1 might be the target protein for PKC. A humanized version of zyg1 cDNA (mzyg1 was introduced into myoblasts to know if ZYG1 is also effective in cell fusion of myoblasts. Quite interestingly, enforced expression of ZYG1 in myoblasts was found to induce markedly their cell fusion, thus strongly suggesting the existence of a common signaling pathway for cell fusion beyond the difference of species.

Sphagnum-dwelling testate amoebae in subarctic bogs are more sensitive to soil warming in the growing season than in winter: the results of eight-year field climate manipulations.

NARCIS (Netherlands)

Tsyganov, A.N.; Aerts, R.; Nijs, I.; Cornelissen, J.H.C.; Beyens, L.

2012-01-01

Sphagnum-dwelling testate amoebae are widely used in paleoclimate reconstructions as a proxy for climate-induced changes in bogs. However, the sensitivity of proxies to seasonal climate components is an important issue when interpreting proxy records. Here, we studied the effects of summer warming,

Inhibitors of Mycobacterium marinum virulence identified in a Dictyostelium discoideum host model.

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Hajer Ouertatani-Sakouhi

Full Text Available Tuberculosis remains one of the major threats to public health worldwide. Given the prevalence of multi drug resistance (MDR in Mycobacterium tuberculosis strains, there is a strong need to develop new anti-mycobacterial drugs with modes of action distinct from classical antibiotics. Inhibitors of mycobacterial virulence might target new molecular processes and may represent a potential new therapeutic alternative. In this study, we used a Dictyostelium discoideum host model to assess virulence of Mycobacterium marinum and to identify compounds inhibiting mycobacterial virulence. Among 9995 chemical compounds, we selected 12 inhibitors of mycobacterial virulence that do not inhibit mycobacterial growth in synthetic medium. Further analyses revealed that 8 of them perturbed functions requiring an intact mycobacterial cell wall such as sliding motility, bacterial aggregation or cell wall permeability. Chemical analogs of two compounds were analyzed. Chemical modifications altered concomitantly their effect on sliding motility and on mycobacterial virulence, suggesting that the alteration of the mycobacterial cell wall caused the loss of virulence. We characterized further one of the selected compounds and found that it inhibited the ability of mycobacteria to replicate in infected cells. Together these results identify new antimycobacterial compounds that represent new tools to unravel the molecular mechanisms controlling mycobacterial pathogenicity. The isolation of compounds with anti-virulence activity is the first step towards developing new antibacterial treatments.

Bioaccumulation of pathogenic bacteria and amoeba by zebra mussels and their presence in watercourses.

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Mosteo, R; Goñi, P; Miguel, N; Abadías, J; Valero, P; Ormad, M P

2016-01-01

Dreissena polymorpha (the zebra mussel) has been invading freshwater bodies in Europe since the beginning of the nineteenth century. Filter-feeding organisms can accumulate and concentrate both chemical and biological contaminants in their tissues. Therefore, zebra mussels are recognized as indicators of freshwater quality. In this work, the capacity of the zebra mussel to accumulate human pathogenic bacteria and protozoa has been evaluated and the sanitary risk associated with their presence in surface water has also been assessed. The results show a good correlation between the pathogenic bacteria concentration in zebra mussels and in watercourses. Zebra mussels could therefore be used as an indicator of biological contamination. The bacteria (Escherichia coli, Enterococcus spp., Pseudomonas spp., and Salmonella spp.) and parasites (Cryptosporidium oocysts and free-living amoebae) detected in these mussels reflect a potential sanitary risk in water.

Ras proteins have multiple functions in vegetative cells of Dictyostelium.

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Bolourani, Parvin; Spiegelman, George; Weeks, Gerald

2010-11-01

During the aggregation of Dictyostelium cells, signaling through RasG is more important in regulating cyclic AMP (cAMP) chemotaxis, whereas signaling through RasC is more important in regulating the cAMP relay. However, RasC is capable of substituting for RasG for chemotaxis, since rasG⁻ cells are only partially deficient in chemotaxis, whereas rasC⁻/rasG⁻ cells are totally incapable of chemotaxis. In this study we have examined the possible functional overlap between RasG and RasC in vegetative cells by comparing the vegetative cell properties of rasG⁻, rasC⁻, and rasC⁻/rasG⁻ cells. In addition, since RasD, a protein not normally found in vegetative cells, is expressed in vegetative rasG⁻ and rasC⁻/rasG⁻ cells and appears to partially compensate for the absence of RasG, we have also examined the possible functional overlap between RasG and RasD by comparing the properties of rasG⁻ and rasC⁻/rasG⁻ cells with those of the mutant cells expressing higher levels of RasD. The results of these two lines of investigation show that RasD is capable of totally substituting for RasG for cytokinesis and growth in suspension, whereas RasC is without effect. In contrast, for chemotaxis to folate, RasC is capable of partially substituting for RasG, but RasD is totally without effect. Finally, neither RasC nor RasD is able to substitute for the role that RasG plays in regulating actin distribution and random motility. These specificity studies therefore delineate three distinct and none-overlapping functions for RasG in vegetative cells.

The actin cytoskeleton of chemotactic amoebae operates close to the onset of oscillations

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Westendorf, Christian; Negrete, Jose, Jr.; Bae, Albert; Sandmann, Rabea; Bodenschatz, Eberhard; Beta, Carsten

2013-03-01

We report evidence that the actin machinery of chemotactic Dictyostelium cells operates close to an oscillatory instability. The averaged F-actin response of many cells to a short-time pulse of cAMP is reminiscent of a damped oscillation. At the single-cell level, however, the response dynamics ranged from short, strongly damped responses to slowly decaying, weakly damped oscillations. Furthermore, in a small subpopulation, we observed self-sustained oscillations in the cortical F-actin concentration. We systematically exposed a large number of cells to periodic pulse trains. The results indicate a resonance peak at periodic inputs of around 20 s. We propose a delayed feedback model that explains our experimental findings based on a time-delay in the actin regulatory network. To quantitatively test the model, we performed stimulation experiments with cells that express GFP-tagged fusion proteins of Coronin and Aip1. These served as markers of the F-actin disassembly process and thus allow us to estimate the delay time. Based on this independent estimate, our model predicts an intrinsic period of 20 s, which agrees with the resonance observed experimentally. Financial support by the Max-Planck Society and the DFG (SFB 937).

Analyzing the spatial positioning of nuclei in polynuclear giant cells

International Nuclear Information System (INIS)

Stange, Maike; Hintsche, Marius; Sachse, Kirsten; Gerhardt, Matthias; Beta, Carsten; Valleriani, Angelo

2017-01-01

How cells establish and maintain a well-defined size is a fundamental question of cell biology. Here we investigated to what extent the microtubule cytoskeleton can set a predefined cell size, independent of an enclosing cell membrane. We used electropulse-induced cell fusion to form giant multinuclear cells of the social amoeba Dictyostelium discoideum . Based on dual-color confocal imaging of cells that expressed fluorescent markers for the cell nucleus and the microtubules, we determined the subcellular distributions of nuclei and centrosomes in the giant cells. Our two- and three-dimensional imaging results showed that the positions of nuclei in giant cells do not fall onto a regular lattice. However, a comparison with model predictions for random positioning showed that the subcellular arrangement of nuclei maintains a low but still detectable degree of ordering. This can be explained by the steric requirements of the microtubule cytoskeleton, as confirmed by the effect of a microtubule degrading drug. (paper)

Analyzing the spatial positioning of nuclei in polynuclear giant cells

Science.gov (United States)

Stange, Maike; Hintsche, Marius; Sachse, Kirsten; Gerhardt, Matthias; Valleriani, Angelo; Beta, Carsten

2017-11-01

How cells establish and maintain a well-defined size is a fundamental question of cell biology. Here we investigated to what extent the microtubule cytoskeleton can set a predefined cell size, independent of an enclosing cell membrane. We used electropulse-induced cell fusion to form giant multinuclear cells of the social amoeba Dictyostelium discoideum. Based on dual-color confocal imaging of cells that expressed fluorescent markers for the cell nucleus and the microtubules, we determined the subcellular distributions of nuclei and centrosomes in the giant cells. Our two- and three-dimensional imaging results showed that the positions of nuclei in giant cells do not fall onto a regular lattice. However, a comparison with model predictions for random positioning showed that the subcellular arrangement of nuclei maintains a low but still detectable degree of ordering. This can be explained by the steric requirements of the microtubule cytoskeleton, as confirmed by the effect of a microtubule degrading drug.

Amoeboid swimming: a generic self-propulsion of cells in fluids by means of membrane deformations.

Science.gov (United States)

Farutin, Alexander; Rafaï, Salima; Dysthe, Dag Kristian; Duperray, Alain; Peyla, Philippe; Misbah, Chaouqi

2013-11-27

Microorganisms, such as bacteria, algae, or spermatozoa, are able to propel themselves forward thanks to flagella or cilia activity. By contrast, other organisms employ pronounced changes of the membrane shape to achieve propulsion, a prototypical example being the Eutreptiella gymnastica. Cells of the immune system as well as dictyostelium amoebas, traditionally believed to crawl on a substratum, can also swim in a similar way. We develop a model for these organisms: the swimmer is mimicked by a closed incompressible membrane with force density distribution (with zero total force and torque). It is shown that fast propulsion can be achieved with adequate shape adaptations. This swimming is found to consist of an entangled pusher-puller state. The autopropulsion distance over one cycle is a universal linear function of a simple geometrical dimensionless quantity A/V(2/3) (V and A are the cell volume and its membrane area). This study captures the peculiar motion of Eutreptiella gymnastica with simple force distribution.

BTG interacts with retinoblastoma to control cell fate in Dictyostelium.

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Daniele Conte

Full Text Available BACKGROUND: In the genesis of many tissues, a phase of cell proliferation is followed by cell cycle exit and terminal differentiation. The latter two processes overlap: genes involved in the cessation of growth may also be important in triggering differentiation. Though conceptually distinct, they are often causally related and functional interactions between the cell cycle machinery and cell fate control networks are fundamental to coordinate growth and differentiation. A switch from proliferation to differentiation may also be important in the life cycle of single-celled organisms, and genes which arose as regulators of microbial differentiation may be conserved in higher organisms. Studies in microorganisms may thus contribute to understanding the molecular links between cell cycle machinery and the determination of cell fate choice networks. METHODOLOGY/PRINCIPAL FINDINGS: Here we show that in the amoebozoan D. discoideum, an ortholog of the metazoan antiproliferative gene btg controls cell fate, and that this function is dependent on the presence of a second tumor suppressor ortholog, the retinoblastoma-like gene product. Specifically, we find that btg-overexpressing cells preferentially adopt a stalk cell (and, more particularly, an Anterior-Like Cell fate. No btg-dependent preference for ALC fate is observed in cells in which the retinoblastoma-like gene has been genetically inactivated. Dictyostelium btg is the only example of non-metazoan member of the BTG family characterized so far, suggesting that a genetic interaction between btg and Rb predated the divergence between dictyostelids and metazoa. CONCLUSIONS/SIGNIFICANCE: While the requirement for retinoblastoma function for BTG antiproliferative activity in metazoans is known, an interaction of these genes in the control of cell fate has not been previously documented. Involvement of a single pathway in the control of mutually exclusive processes may have relevant implication in the

Fluorographic detection of tritiated glycopeptides and oligosaccharides separated on polyacrylamide gels: analysis of glycans from Dictyostelium discoideum glycoproteins

International Nuclear Information System (INIS)

Prem Das, O.; Henderson, E.J.

1986-01-01

Previous workers have shown that oligosaccharides and glycopeptides can be separated by electrophoresis in buffers containing borate ions. However, normal fluorography of tritium-labeled structures cannot be performed because the glycans are soluble and can diffuse during equilibration with scintillants. This problem has been circumvented by equilibration of the gel with 2,5-diphenyloxazole (PPO) prior to electrophoresis. The presence of PPO in the gel during electrophoresis does not alter mobility of the glycopeptides and oligosaccharides. After electrophoresis, the gel is simply dried and fluorography performed. This allows sensitive and precise comparisons of labeled samples in parallel lanes of a slab gel and, since mobilities are highly reproducible, between different gels. The procedure is preparative in that after fluorography the gel bands can be quantitatively eluted for further study, without any apparent modification by the procedure. In this report, the procedure is illustrated by fractionation of both neutral and anionic glycopeptides produced by the cellular slime mold Dictyostelium discoideum

Review: Occurrence of the pathogenic amoeba Naegleria fowleri in groundwater

Science.gov (United States)

Bright, Kelly R.; Gerba, Charles P.

2017-06-01

Naegleria fowleri is a thermophilic free-living amoeba found worldwide in soils and warm freshwater. It is the causative agent of primary amebic meningoencephalitis, a nearly always fatal disease afflicting mainly children and young adults. Humans are exposed to the organism via swimming, bathing, or other recreational activity during which water is forcefully inhaled into the upper nasal passages. Although many studies have looked at the occurrence of N. fowleri in surface waters, limited information is available regarding its occurrence in groundwater and geothermally heated natural waters such as hot springs. This paper reviews the current literature related to the occurrence of N. fowleri in these waters and the methods employed for its detection. Case reports of potential groundwater exposures are also included. Despite increased interest in N. fowleri in recent years due to well-publicized cases linked to drinking water, many questions still remain unanswered. For instance, why the organism persists in some water sources and not in others is not well understood. The role of biofilms in groundwater wells and plumbing in individual buildings, and the potential for warming due to climate change to expand the occurrence of the organism into new regions, are still unclear. Additional research is needed to address these questions in order to better understand the ecology of N. fowleri and the conditions that result in greater risks to bathers.

Correlated waves of actin filaments and PIP3 in Dictyostelium cells.

Science.gov (United States)

Asano, Yukako; Nagasaki, Akira; Uyeda, Taro Q P

2008-12-01

Chemotaxis-deficient amiB-null mutant Dictyostelium cells show two distinct movements: (1) they extend protrusions randomly without net displacements; (2) they migrate persistently and unidirectionally in a keratocyte-like manner. Here, we monitored the intracellular distribution of phosphatidylinositol (3,4,5)-trisphosphate (PIP(3)) to gain insight into roles PIP(3) plays in those spontaneous motilities. In keratocyte-like cells, PIP(3) showed convex distribution over the basal membrane, with no anterior enrichment. In stalled cells, as well as in wild type cells, PIP(3) repeated wave-like changes, including emergence, expansion and disappearance, on the basal membrane. The waves induced lamellipodia when they approached the cell edge, and the advancing speed of the waves was comparable to the migration speed of the keratocyte-like cells. LY294002, an inhibitor of PI3 kinase, abolished PIP(3) waves in stalled cells and stopped keratocyte-like cells. These results together suggested that keratocyte-like cells are "surfing" on the PIP(3) waves by coupling steady lamellipodial protrusions to the PIP(3) waves. Simultaneous live observation of actin filaments and PIP(3) in wild type or stalled amiB(-) cells indicated that the PIP(3) waves were correlated with wave-like distributions of actin filaments. Most notably, PIP(3) waves often followed actin waves, suggesting that PIP(3) induces local depolymerization of actin filaments. Consistent with this idea, cortical accumulation of PIP(3) was often correlated with local retraction of the periphery. We propose that the waves of PIP(3) and actin filaments are loosely coupled with each other and play important roles in generating spontaneous cell polarity. Copyright 2008 Wiley-Liss, Inc.

Aframomum stipulatum (Gagnep) K. Schum and Aframomum giganteum (Oliv. & Hanb) K. Schum as Aroma Tincto Oleo Crops resources: essential oil, fatty acids, sterols, tocopherols, and tocotrienols composition of different fruit parts of Congo varieties.

Science.gov (United States)

Ngakegni-Limbili, Adolphe Christian; Zebib, Bachar; Cerny, Muriel; Tsiba, Gouolally; Elouma Ndinga, Arnold Murphy; Mouloungui, Zéphirin; Fourastier, Isabelle; Ouamba, Jean-Maurille

2013-01-15

Today, few known plant species provide both an essential oil (EO) and a vegetable oil (VO). Seed and husk of two Aframomum species were investigated and compared in terms of EO, fatty acids, tocopherols, and tocotrienols. EO yield reaches 15.3 g kg(-1) in the seeds and 3.2 g kg(-1) in the husks, while VO yield is 180.0 g kg(-1) in the seeds and 25.0 g kg(-1) in the husks. β-Pinene, 1,8-cineol, α-selinene, terpine-4-ol, linalool, myrtenal and β-caryophyllene are the major compounds of seed and husk EO. Fatty acid analysis of two Aframomum species shows that oleic, linoleic, and palmitic acids were the major compounds of VO. Total sterol contents reached 4.3 g kg(-1) in seed VO and 8.5 g kg(-1) in husk VO. An appreciable amount of tocopherols (0.52 g kg(-1) ) was found in seed VO. The seed and husk oil of A. stipulatum and A. giganteum fruits are rich sources of many bioactive constituents such as fatty acids, sterols, tocopherols and tocotrienols. These tropical wild fruits can be considered as new Aroma Tincto Oleo Crops (ATOC) resources that contain both EOs and VOs. Copyright © 2012 Society of Chemical Industry.

Dictyostelium discoideum: mutants in the biosynthesis of the lipid-linked precursor of N-linked oligosaccharides

International Nuclear Information System (INIS)

Freeze, H.; Willies, L.; Hamilton, S.

1986-01-01

The lysosomal enzymes of Dictyostelium discoideum share highly immunogenic oligosaccharides which contain multiple Man-6-SO 4 residues. Two mutant strains which lack the shared antigenic determinant were analyzed in an attempt to identify the primary defect in each. [ 3 H]Man labelled N-linked oligosaccharides of secreted glycoproteins were released by Endo/PNGaseF digestion and analyzed. Both of the mutant strains produced smaller, less sulfated oligosaccharides compared to the wild-type, yet both still contained considerable amounts of Man-6-SO 4 . The size of the precursor lipid-linked oligosaccharide from the wild-type is consistent with a Glc 3 Man 9 GlcNAc 2 structure, while those from both of the mutants have an oligosaccharide the size of Man 5 GlcNAc 2 . The authors conclude that both of the mutants are defective in the biosynthesis of the precursor oligosaccharide. Both oligosaccharides from the mutants contain a tri-mannosyl core and are not glucosylated. Two of the five Man residues are released by a 1,2 specific α mannosidase. Based on the size and mannosidase digestions the authors conclude that 4/5 of the Man residues on the α1,6 branch of the β-linked Man residues are missing. Thus, these residues must be required to define the shared antigenic determinant

Cooperation induces other cooperation: Fruiting bodies promote the evolution of macrocysts in Dictyostelium discoideum.

Science.gov (United States)

Shibasaki, Shota; Shirokawa, Yuka; Shimada, Masakazu

2017-05-21

Biological studies of the evolution of cooperation are challenging because this process is vulnerable to cheating. Many mechanisms, including kin discrimination, spatial structure, or by-products of self-interested behaviors, can explain this evolution. Here we propose that the evolution of cooperation can be induced by other cooperation. To test this idea, we used a model organism Dictyostelium discoideum because it exhibits two cooperative dormant phases, the fruiting body and the macrocyst. In both phases, the same chemoattractant, cyclic AMP (cAMP), is used to collect cells. This common feature led us to hypothesize that the evolution of macrocyst formation would be induced by coexistence with fruiting bodies. Before forming a mathematical model, we confirmed that macrocysts coexisted with fruiting bodies, at least under laboratory conditions. Next, we analyzed our evolutionary game theory-based model to investigate whether coexistence with fruiting bodies would stabilize macrocyst formation. The model suggests that macrocyst formation represents an evolutionarily stable strategy and a global invader strategy under this coexistence, but is unstable if the model ignores the fruiting body formation. This result indicates that the evolution of macrocyst formation and maintenance is attributable to coexistence with fruiting bodies. Therefore, macrocyst evolution can be considered as an example of evolution of cooperation induced by other cooperation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Acetate and succinate production in amoebae, helminths, diplomonads, trichomonads and trypanosomatids: common and diverse metabolic strategies used by parasitic lower eukaryotes.

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Bringaud, F; Ebikeme, C; Boshart, M

2010-08-01

Parasites that often grow anaerobically in their hosts have adopted a fermentative strategy relying on the production of partially oxidized end products, including lactate, glycerol, ethanol, succinate and acetate. This review focuses on recent progress in understanding acetate production in protist parasites, such as amoebae, diplomonads, trichomonads, trypanosomatids and in the metazoan parasites helminths, as well as the succinate production pathway(s) present in some of them. We also describe the unconventional organisation of the tricarboxylic acid cycle associated with the fermentative strategy adopted by the procyclic trypanosomes, which may resemble the probable structure of the primordial TCA cycle in prokaryotes.

PsB multiprotein complex of Dictyostelium discoideum. Demonstration of cellulose binding activity and order of protein subunit assembly.

Science.gov (United States)

McGuire, V; Alexander, S

1996-06-14

The differentiated spores of Dictyostelium are surrounded by an extracellular matrix, the spore coat, which protects them from environmental factors allowing them to remain viable for extended periods of time. This presumably is a major evolutionary advantage. This unique extracellular matrix is composed of cellulose and glycoproteins. Previous work has shown that some of these spore coat glycoproteins exist as a preassembled multiprotein complex (the PsB multiprotein complex) which is stored in the prespore vesicles (Watson, N., McGuire, V., and Alexander, S (1994) J. Cell Sci. 107, 2567-2579). Later in development, the complex is synchronously secreted from the prespore vesicles and incorporated into the spore coat. We now have shown that the PsB complex has a specific in vitro cellulose binding activity. The analysis of mutants lacking individual subunits of the PsB complex revealed the relative order of assembly of the subunit proteins and demonstrated that the protein subunits must be assembled for cellulose binding activity. These results provide a biochemical explanation for the localization of this multiprotein complex in the spore coat.

The p21-activated kinase (PAK family member PakD is required for chemorepulsion and proliferation inhibition by autocrine signals in Dictyostelium discoideum.

Directory of Open Access Journals (Sweden)

Jonathan E Phillips

Full Text Available In Dictyostelium discoideum, the secreted proteins AprA and CfaD function as reporters of cell density and regulate cell number by inhibiting proliferation at high cell densities. AprA also functions to disperse groups of cells at high density by acting as a chemorepellent. However, the signal transduction pathways associated with AprA and CfaD are not clear, and little is known about how AprA affects the cytoskeleton to regulate cell movement. We found that the p21-activated kinase (PAK family member PakD is required for both the proliferation-inhibiting activity of AprA and CfaD and the chemorepellent activity of AprA. Similar to cells lacking AprA or CfaD, cells lacking PakD proliferate to a higher cell density than wild-type cells. Recombinant AprA and CfaD inhibit the proliferation of wild-type cells but not cells lacking PakD. Like AprA and CfaD, PakD affects proliferation but does not significantly affect growth (the accumulation of mass on a per-nucleus basis. In contrast to wild-type cells, cells lacking PakD are not repelled from a source of AprA, and colonies of cells lacking PakD expand at a slower rate than wild-type cells, indicating that PakD is required for AprA-mediated chemorepulsion. A PakD-GFP fusion protein localizes to an intracellular punctum that is not the nucleus or centrosome, and PakD-GFP is also occasionally observed at the rear cortex of moving cells. Vegetative cells lacking PakD show excessive actin-based filopodia-like structures, suggesting that PakD affects actin dynamics, consistent with previously characterized roles of PAK proteins in actin regulation. Together, our results implicate PakD in AprA/CfaD signaling and show that a PAK protein is required for proper chemorepulsive cell movement in Dictyostelium.

The p21-activated kinase (PAK) family member PakD is required for chemorepulsion and proliferation inhibition by autocrine signals in Dictyostelium discoideum.

Science.gov (United States)

Phillips, Jonathan E; Gomer, Richard H

2014-01-01

In Dictyostelium discoideum, the secreted proteins AprA and CfaD function as reporters of cell density and regulate cell number by inhibiting proliferation at high cell densities. AprA also functions to disperse groups of cells at high density by acting as a chemorepellent. However, the signal transduction pathways associated with AprA and CfaD are not clear, and little is known about how AprA affects the cytoskeleton to regulate cell movement. We found that the p21-activated kinase (PAK) family member PakD is required for both the proliferation-inhibiting activity of AprA and CfaD and the chemorepellent activity of AprA. Similar to cells lacking AprA or CfaD, cells lacking PakD proliferate to a higher cell density than wild-type cells. Recombinant AprA and CfaD inhibit the proliferation of wild-type cells but not cells lacking PakD. Like AprA and CfaD, PakD affects proliferation but does not significantly affect growth (the accumulation of mass) on a per-nucleus basis. In contrast to wild-type cells, cells lacking PakD are not repelled from a source of AprA, and colonies of cells lacking PakD expand at a slower rate than wild-type cells, indicating that PakD is required for AprA-mediated chemorepulsion. A PakD-GFP fusion protein localizes to an intracellular punctum that is not the nucleus or centrosome, and PakD-GFP is also occasionally observed at the rear cortex of moving cells. Vegetative cells lacking PakD show excessive actin-based filopodia-like structures, suggesting that PakD affects actin dynamics, consistent with previously characterized roles of PAK proteins in actin regulation. Together, our results implicate PakD in AprA/CfaD signaling and show that a PAK protein is required for proper chemorepulsive cell movement in Dictyostelium.

Functional characterisation of parvulin-type peptidyl prolyl cis-trans isomerase, PinA in Dictyostelium discoideum

International Nuclear Information System (INIS)

Haokip, Nemneineng; Naorem, Aruna

2017-01-01

Pin1-type parvulins are unique among PPIases that can catalyse an otherwise slow cis-trans isomerisation of phosphorylated peptide bond preceding proline in target proteins. This prolyl isomerisation process can regulate activity, stability and localisation of target proteins and thus control cellular processes like eukaryotic cell proliferation, cell cycle progression and gene regulation. Towards understanding the function of Pin1-type prolyl isomerisation in Dictyostelium discoideum, a slime mould with distinct growth and developmental phases, we identified PinA as a novel Pin1-type parvulin by its ability to complement the temperature sensitivity phenotype associated with a mutation in ESS1 in S. cerevisiae. In D. discoideum, pinA is temporally and spatially regulated during growth and development. PinA is both nuclear as well as cytoplasmic in the growing cells. We further show that loss of pinA (pinA − ) leads to decreased growth rate, reduced spore formation and abnormal prespore-prestalk patterning. We conclude that PinA is required for normal growth as well as development in D. discoideum. - Highlights: • PinA is a bona fide homologue of S. cerevisiae Ess1. • PinA is required for normal cell proliferation of D. discoideum. • PinA is spatially localised in developmental structures. • PinA is important for cell differentiation and patterning.

Evidence for a functional link between Dd-STATa and Dd-PIAS, a Dictyostelium PIAS homologue.

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Kawata, Takefumi; Hirano, Tatsunori; Ogasawara, Shun; Aoshima, Ryota; Yachi, Ayako

2011-09-01

Several mammalian protein families inhibit the activity of signal transducer and activator of transcription (STAT) proteins. The protein inhibitor of activated STAT (PIAS) was initially identified through its ability to interact with human STAT proteins. We isolated a gene (pisA) encoding a Dictyostelium orthologue of PIAS, Dd-PIAS, which possesses almost all the representative motifs and domains of mammalian PIAS proteins. A Dd-PIAS null mutant strain displays a normal terminal morphology but with accelerated development once cells are aggregated. In contrast, Dd-PIAS overexpressor strains demonstrate delayed aggregation, almost no slug phototaxis, impaired slug motility, and a prolonged slug migration period. This strain is a near phenocopy of the Dd-STATa null mutant, although it eventually forms a fruiting body, albeit inefficiently. The expression of several Dd-STATa-activated genes is upregulated in the Dd-PIAS null mutant and there is ectopic expression of pstAB makers. The concentration of a PIAS-green fluorescent protein (GFP) fusion protein, expressed under the PIAS promoter, is greatest in the pstO cells and gradually decreases with proximity to the tip of the slug and culminant: a pattern diametrically opposite to that of Dd-STATa. Our results suggest a functional interrelationship between Dd-PIAS and Dd-STATa that influences gene expression and development. © 2011 The Authors. Development, Growth & Differentiation © 2011 Japanese Society of Developmental Biologists.

Desynchronization of cells on the developmental path triggers the formation of spiral waves of cAMP during Dictyostelium aggregation.

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Lauzeral, J; Halloy, J; Goldbeter, A

1997-08-19

Whereas it is relatively easy to account for the formation of concentric (target) waves of cAMP in the course of Dictyostelium discoideum aggregation after starvation, the origin of spiral waves remains obscure. We investigate a physiologically plausible mechanism for the spontaneous formation of spiral waves of cAMP in D. discoideum. The scenario relies on the developmental path associated with the continuous changes in the activity of enzymes such as adenylate cyclase and phosphodiesterase observed during the hours that follow starvation. These changes bring the cells successively from a nonexcitable state to an excitable state in which they relay suprathreshold cAMP pulses, and then to autonomous oscillations of cAMP, before the system returns to an excitable state. By analyzing a model for cAMP signaling based on receptor desensitization, we show that the desynchronization of cells on this developmental path triggers the formation of fully developed spirals of cAMP. Developmental paths that do not correspond to the sequence of dynamic transitions no relay-relay-oscillations-relay are less able or fail to give rise to the formation of spirals.

Actin cytoskeleton of chemotactic amoebae operates close to the onset of oscillations

Science.gov (United States)

Westendorf, Christian; Negrete, Jose; Bae, Albert J.; Sandmann, Rabea; Bodenschatz, Eberhard; Beta, Carsten

2013-01-01

The rapid reorganization of the actin cytoskeleton in response to external stimuli is an essential property of many motile eukaryotic cells. Here, we report evidence that the actin machinery of chemotactic Dictyostelium cells operates close to an oscillatory instability. When averaging the actin response of many cells to a short pulse of the chemoattractant cAMP, we observed a transient accumulation of cortical actin reminiscent of a damped oscillation. At the single-cell level, however, the response dynamics ranged from short, strongly damped responses to slowly decaying, weakly damped oscillations. Furthermore, in a small subpopulation, we observed self-sustained oscillations in the cortical F-actin concentration. To substantiate that an oscillatory mechanism governs the actin dynamics in these cells, we systematically exposed a large number of cells to periodic pulse trains of different frequencies. Our results indicate a resonance peak at a stimulation period of around 20 s. We propose a delayed feedback model that explains our experimental findings based on a time-delay in the regulatory network of the actin system. To test the model, we performed stimulation experiments with cells that express GFP-tagged fusion proteins of Coronin and actin-interacting protein 1, as well as knockout mutants that lack Coronin and actin-interacting protein 1. These actin-binding proteins enhance the disassembly of actin filaments and thus allow us to estimate the delay time in the regulatory feedback loop. Based on this independent estimate, our model predicts an intrinsic period of 20 s, which agrees with the resonance observed in our periodic stimulation experiments. PMID:23431176

Epilepsy research methods update: Understanding the causes of epileptic seizures and identifying new treatments using non-mammalian model organisms.

Science.gov (United States)

Cunliffe, Vincent T; Baines, Richard A; Giachello, Carlo N G; Lin, Wei-Hsiang; Morgan, Alan; Reuber, Markus; Russell, Claire; Walker, Matthew C; Williams, Robin S B

2015-01-01

This narrative review is intended to introduce clinicians treating epilepsy and researchers familiar with mammalian models of epilepsy to experimentally tractable, non-mammalian research models used in epilepsy research, ranging from unicellular eukaryotes to more complex multicellular organisms. The review focuses on four model organisms: the social amoeba Dictyostelium discoideum, the roundworm Caenorhabditis elegans, the fruit fly Drosophila melanogaster and the zebrafish Danio rerio. We consider recent discoveries made with each model organism and discuss the importance of these advances for the understanding and treatment of epilepsy in humans. The relative ease with which mutations in genes of interest can be produced and studied quickly and cheaply in these organisms, together with their anatomical and physiological simplicity in comparison to mammalian species, are major advantages when researchers are trying to unravel complex disease mechanisms. The short generation times of most of these model organisms also mean that they lend themselves particularly conveniently to the investigation of drug effects or epileptogenic processes across the lifecourse. Copyright © 2014 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.

An Autocrine Proliferation Repressor Regulates Dictyostelium discoideum Proliferation and Chemorepulsion Using the G Protein-Coupled Receptor GrlH

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Yu Tang

2018-02-01

Full Text Available In eukaryotic microbes, little is known about signals that inhibit the proliferation of the cells that secrete the signal, and little is known about signals (chemorepellents that cause cells to move away from the source of the signal. Autocrine proliferation repressor protein A (AprA is a protein secreted by the eukaryotic microbe Dictyostelium discoideum. AprA is a chemorepellent for and inhibits the proliferation of D. discoideum. We previously found that cells sense AprA using G proteins, suggesting the existence of a G protein-coupled AprA receptor. To identify the AprA receptor, we screened mutants lacking putative G protein-coupled receptors. We found that, compared to the wild-type strain, cells lacking putative receptor GrlH (grlH{macron} cells show rapid proliferation, do not have large numbers of cells moving away from the edges of colonies, are insensitive to AprA-induced proliferation inhibition and chemorepulsion, and have decreased AprA binding. Expression of GrlH in grlH{macron} cells (grlH{macron}/grlHOE rescues the phenotypes described above. These data indicate that AprA signaling may be mediated by GrlH in D. discoideum.

Uncovering a role for the tail of the Dictyostelium discoideum SadA protein in cell-substrate adhesion.

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Kowal, Anthony S; Chisholm, Rex L

2011-05-01

Previous work from our laboratory showed that the Dictyostelium discoideum SadA protein plays a central role in cell-substrate adhesion. SadA null cells exhibit a loss of adhesion, a disrupted actin cytoskeleton, and a cytokinesis defect. How SadA mediates these phenotypes is unknown. This work addresses the mechanism of SadA function, demonstrating an important role for the C-terminal cytoplasmic tail in SadA function. We found that a SadA tailless mutant was unable to rescue the sadA adhesion deficiency, and overexpression of the SadA tail domain reduced adhesion in wild-type cells. We also show that SadA is closely associated with the actin cytoskeleton. Mutagenesis studies suggested that four serine residues in the tail, S924/S925 and S940/S941, may regulate association of SadA with the actin cytoskeleton. Glutathione S-transferase pull-down assays identified at least one likely interaction partner of the SadA tail, cortexillin I, a known actin bundling protein. Thus, our data demonstrate an important role for the carboxy-terminal cytoplasmic tail in SadA function and strongly suggest that a phosphorylation event in this tail regulates an interaction with cortexillin I. Based on our data, we propose a model for the function of SadA.

The human homologue of Dictyostelium discoideum phg1A is expressed by human metastatic melanoma cells.

Science.gov (United States)

Lozupone, Francesco; Perdicchio, Maurizio; Brambilla, Daria; Borghi, Martina; Meschini, Stefania; Barca, Stefano; Marino, Maria Lucia; Logozzi, Mariantonia; Federici, Cristina; Iessi, Elisabetta; de Milito, Angelo; Fais, Stefano

2009-12-01

Tumour cannibalism is a characteristic of malignancy and metastatic behaviour. This atypical phagocytic activity is a crucial survival option for tumours in conditions of low nutrient supply, and has some similarities to the phagocytic activity of unicellular microorganisms. In fact, Dictyostelium discoideum has been used widely as a model to study phagocytosis. Recently, phg1A has been described as a protein that is primarily involved in the phagocytic process of this microorganism. The closest human homologue to phg1A is transmembrane 9 superfamily protein member 4 (TM9SF4). Here, we report that TM9SF4 is highly expressed in human malignant melanoma cells deriving from metastatic lesions, whereas it is undetectable in healthy human tissues and cells. TM9SF4 is predominantly expressed in acidic vesicles of melanoma cells, in which it co-localizes with the early endosome antigens Rab5 and early endosome antigen 1. TM9SF4 silencing induced marked inhibition of cannibal activity, which is consistent with a derangement of intracellular pH gradients, with alkalinization of acidic vesicles and acidification of the cell cytosol. We propose TM9SF4 as a new marker of malignancy, representing a potential new target for anti-tumour strategies with a specific role in tumour cannibalism and in the establishment of a metastatic phenotype.

A Simple Retroelement Based Knock-Down System in Dictyostelium: Further Insights into RNA Interference Mechanisms.

Science.gov (United States)

Friedrich, Michael; Meier, Doreen; Schuster, Isabelle; Nellen, Wolfgang

2015-01-01

We have previously shown that the most abundant Dictyostelium discoideum retroelement DIRS-1 is suppressed by RNAi mechanisms. Here we provide evidence that both inverted terminal repeats have strong promoter activity and that bidirectional expression apparently generates a substrate for Dicer. A cassette containing the inverted terminal repeats and a fragment of a gene of interest was sufficient to activate the RNAi response, resulting in the generation of ~21 nt siRNAs, a reduction of mRNA and protein expression of the respective endogene. Surprisingly, no transitivity was observed on the endogene. This was in contrast to previous observations, where endogenous siRNAs caused spreading on an artificial transgene. Knock-down was successful on seven target genes that we examined. In three cases a phenotypic analysis proved the efficiency of the approach. One of the target genes was apparently essential because no knock-out could be obtained; the RNAi mediated knock-down, however, resulted in a very slow growing culture indicating a still viable reduction of gene expression. ADVANTAGES OF THE DIRS-1–RNAI SYSTEM: The knock-down system required a short DNA fragment (~400 bp) of the target gene as an initial trigger. Further siRNAs were generated by RdRPs since we have shown some siRNAs with a 5'-triphosphate group. Extrachromosomal vectors facilitate the procedure and allowed for molecular and phenotypic analysis within one week. The system provides an efficient and rapid method to reduce protein levels including those of essential genes.

Assets of the non-pathogenic microorganism Dictyostelium discoideum as a model for the study of eukaryotic extracellular vesicles [v1; ref status: indexed, http://f1000r.es/pa

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Irène Tatischeff

2013-03-01

Full Text Available Dictyostelium discoideum microvesicles have recently been presented as a valuable model for eukaryotic extracellular vesicles. Here, the advantages of D. discoideum for unraveling important biological functions of extracellular vesicles in general are detailed. D. discoideum, a non-pathogenic eukaryotic microorganism, belongs to a billion-year-old Amoeboza lineage, which diverged from the animal-fungal lineage after the plant animal-split. During growth and early starvation-induced development, it presents analogies with lymphocytes and macrophages with regard to motility and phagocytosis capability, respectively. Its 6-chromosome genome codes for about 12,500 genes, some showing analogies with human genes. The presence of extracellular vesicles during cell growth has been evidenced as a detoxification mechanism of various structurally unrelated drugs. Controls led to the discovery of constitutive extracellular vesicle secretion in this microorganism, which was an important point. It means that the secretion of extracellular vesicles occurs, in the absence of any drug, during both cell growth and early development. This constitutive secretion of D. discoideum cells is very likely to play a role in intercellular communication. The detoxifying secreted vesicles, which can transport drugs outside the cells, can also act as "Trojan horses", capable of transferring these drugs not only into naïve D. discoideum cells, but into human cells as well. Therefore, these extracellular vesicles were proposed as a new biological drug delivery tool. Moreover, Dictyostelium, chosen by the NIH (USA as a new model organism for biomedical research, has already been used for studying some human diseases. These cells, which are much easier to manipulate than human cells, can be easily designed in simple conditioned medium experiments. Owing to the increasing consensus that extracellular vesicles are probably important mediators of intercellular communication, D

Sociogenomics of self vs. non-self cooperation during development of Dictyostelium discoideum.

Science.gov (United States)

Li, Si I; Buttery, Neil J; Thompson, Christopher R L; Purugganan, Michael D

2014-07-21

Dictyostelium discoideum, a microbial model for social evolution, is known to distinguish self from non-self and show genotype-dependent behavior during chimeric development. Aside from a small number of cell-cell recognition genes, however, little is known about the genetic basis of self/non-self recognition in this species. Based on the key hypothesis that there should be differential expression of genes if D. discoideum cells were interacting with non-clone mates, we performed transcriptomic profiling study in this species during clonal vs. chimeric development. The transcriptomic profiles of D. discoideum cells in clones vs. different chimeras were compared at five different developmental stages using a customized microarray. Effects of chimerism on global transcriptional patterns associated with social interactions were observed. We find 1,759 genes significantly different between chimera and clone, 1,144 genes associated significant strain differences, and 6,586 genes developmentally regulated over time. Principal component analysis showed a small amount of the transcriptional variance to chimerism-related factors (Chimerism: 0.18%, Chimerism × Timepoint: 0.03%). There are 162 genes specifically regulated under chimeric development, with continuous small differences between chimera vs. clone over development. Almost 60% of chimera-associated differential genes were differentially expressed at the 4 h aggregate stage, which corresponds to the initial transition of D. discoideum from solitary life to a multicellular phase. A relatively small proportion of over-all variation in gene expression is explained by differences between chimeric and clonal development. The relatively small modifications in gene expression associated with chimerism is compatible with the high level of cooperation observed among different strains of D. discoideum; cells of distinct genetic backgrounds will co-aggregate indiscriminately and co-develop into fruiting bodies. Chimeric

On different types of hereditable changes in the viability of Amoeba protens cells x-irradiated with varying doses

International Nuclear Information System (INIS)

Bychkovskaya, I.B.; Ochinskaya, G.K.; Erokhina, G.M.

1976-01-01

Qualitatively different types of cells lethality have been observed in the posterity of amoebae irradiated with doses ranging from 0.5 to 40 kR and from 60 to 120 kR. At doses of 0.5 to 40 kR, a certain part of cells in a population dies, and the effect is characterized by stability and independency of a radiation dose, hereditable radiation damage of all the cells in the population, and by the fact that it might be caused not only by a derect action of radiation but also by a preirradiated culture medium. Higher doses (60 to 120 kR) cause a more drastic but sell stable effect. Depending on a dose value, a varying percentage of cells has shown the effect not being caused by the action of the preirradiated medium. The data obtained indicate that there are different mechanisms of hereditable radiation damages to cells caused by varying radiation doses

Ontogenia de los estróbilos, desarrollo de los esporangios y esporogénesis de Equisetum giganteum (Equisetaceae en los Andes de Colombia

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Edgar Javier Rincón Barón

2011-12-01

Full Text Available Estudios sobre la ontogenia del estróbilo, los esporangios y la biología reproductiva de Equisetum son escasos, por lo tanto, para la especie E. giganteum, se estudiaron estos aspectos en especímenes recolectados a orillas del Río Frío, Santander, Colombia (2 200m. Los estróbilos en diferentes etapas de maduración fueron fijados, deshidratados, embebidos en parafina, seccionados en micrótomo rotatorio y teñidos con safranina O-fast green. Las observaciones se efectuaron mediante un microscopio óptico de alta resolución con contraste diferencial de interferencia (DIC y microscopio de fluorescencia. Los estróbilos se inician a partir del meristemo apical, tanto en el eje principal como en los laterales, sin diferencias en el proceso de ontogenia y esporogénesis entre estróbilos de diferentes ejes. Sucesivas mitosis y diferenciación celular conducen al crecimiento del estróbilo, y a la formación de los esporangióforos peltados, formados por el manubrio, o porción basal con aspecto de pedicelo, el escutelo, o porción apical aplanada y las iniciales del esporangio, los cuales se diferenciarán para formar la pared del esporangio, los esporocitos y el tapete. No se forma arquesporio y los esporocitos experimentan meiosis para formar tétradas de esporas. El tapete mantiene la integridad histológica hasta la formación de las tétradas y en esa etapa forma un plasmodio que invade la cavidad esporangial la cual rodea parcialmente las tétradas y luego las esporas, y aparecen las cámaras plasmodiales, un término propuesto aquí para las formaciones designadas en inglés "tapetal gaps". La pared del esporangio queda reducida a dos capas celulares: una externa con engrosamientos lignificados en todas las paredes celulares y una interna picnótica. Al finalizar la esporogénesis, el tapete degenera, y las esporas, con exosporio, perisporio delgado, casi membranáceo y eláteres quedan libres en la cavidad esporangial. El esporodermo

Dicty_cDB: Contig-U13443-1 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available lignments: (bits) Value N ( AF305060 ) Dictyostelium discoideum Wiscott-Aldrich syndrome... 529 0.0 10 ( BJ3... AF305060 ) Dictyostelium discoideum Wiscott-Aldrich syndrome protein (wasA) gene...icant alignments: (bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott...0_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott-Aldrich syndrome protein (wasA) gene, complete cds

Arcellacea (testate amoebae) as bio-indicators of road salt contamination in lakes.

Science.gov (United States)

Roe, Helen M; Patterson, R Timothy

2014-08-01

Winter deicing operations occur extensively in mid- to high-latitude metropolitan regions around the world and result in a significant reduction in road accidents. Deicing salts can, however, pose a major threat to water quality and aquatic organisms. In this paper, we examine the utility of Arcellacea (testate amoebae) for monitoring lakes that have become contaminated by winter deicing salts, particularly sodium chloride. We analysed 50 sediment samples and salt-related water property variables (chloride concentrations; conductivity) from 15 lakes in the Greater Toronto Area and adjacent areas of southern Ontario, Canada. The sampled lakes included lakes in proximity to major highways and suburban roads and control lakes in forested settings away from road influences. Samples from the most contaminated lakes, with chloride concentrations in excess of 400 mg/l and conductivities of >800 μS/cm, were dominated by species typically found in brackish and/or inhospitable lake environments and by lower faunal diversities (lowest Shannon diversity index values) than samples with lower readings. Q-R-mode cluster analysis and detrended correspondence analysis (DCA) resulted in the recognition of four assemblage groupings. These reflect varying levels of salt contamination in the study lakes, along with other local influences, including nutrient loading. The response to nutrients can, however, be isolated if the planktic eutrophic indicator species Cucurbitella tricuspis is removed from the counts. The findings show that the group has considerable potential for biomonitoring in salt-contaminated lakes, and their presence in lake sediment cores may provide significant insights into long-term benthic community health, which is integral for remedial efforts.

Lamarckian evolution of the giant Mimivirus in allopatric laboratory culture on amoebae.

Science.gov (United States)

Colson, Philippe; Raoult, Didier

2012-01-01

Acanthamoeba polyphaga Mimivirus has been subcultured 150 times on germ-free amoebae. This allopatric niche is very different from that found in the natural environment, where the virus is in competition with many other organisms. In this experiment, substantial gene variability and loss occurred concurrently with the emergence of phenotypically different viruses. We sought to quantify the respective roles of Lamarckian and Darwinian evolution during this experiment. We postulated that the Mimivirus genes that were down-regulated at the beginning of the allopatric laboratory culture and inactivated after 150 passages experienced Lamarckian evolution because phenotypic modifications preceded genotypic modifications, whereas we considered that genes that were highly transcribed in the new niche but were later inactivated obeyed Darwinian rules. We used the total transcript abundances and sequences described for the genes of Mimivirus at the beginning of its laboratory life and after 150 passages in allopatric culture on Acanthamoeba spp. We found a statistically significant positive correlation between the level of gene expression at the beginning of the culture and gene inactivation during the 150 passages. In particular, the mean transcript abundance at baseline was significantly lower for inactivated genes than for unchanged genes (165 ± 589 vs. 470 ± 1,625; p allopatric laboratory culture if they were encoded by variable genes than if they were encoded by conserved genes (9 vs. 15%; p = 0.062). Finally, Lamarckian evolution represented the evolutionary process encountered by 63% of the inactivated genes. Such observations may be explained by the lower level of DNA repair of useless genes.

Quadrulella texcalense sp. nov. from a Mexican desert: An unexpected new environment for hyalospheniid testate amoebae.

Science.gov (United States)

Pérez-Juárez, Horacio; Serrano-Vázquez, Angélica; Kosakyan, Anush; Mitchell, Edward A D; Rivera Aguilar, Víctor M; Lahr, Daniel J G; Hernández Moreno, Mayra M; Cuellar, Humberto Macías; Eguiarte, Luis E; Lara, Enrique

2017-10-01

Quadrulella (Amoebozoa, Arcellinida, Hyalospheniidae) is a genus of testate amoebae with unmistakable morphology, which secretes characteristic square plates to reinforce the test. They are mainly known from fens and freshwater habitats and have never been documented in deserts. We describe a new species, Quadrulella texcalense, from biological soil crusts in the intertropical desert of Tehuacán (state of Puebla, Mexico). Quadrulella texcalense occurred only at altitudes between 2140 and 2221m.a.s.l., together with the bryophyte genera Pseudocrossidium, Weissia, Bryum, Didymodon, Neohyophyla and Aloina. The soil was extremely dry (moisture of 1.97-2.6%), which contrasts sharply with previous reports for the Quadrulella genus. Single cell mitochondrial cytochrome oxidase I (COI) barcoding of thirteen isolated cells showed an important morphological variability despite having all the same COI barcode sequence. Quadrulella texcalense was placed in a tree containing other Hyalsopheniidae, including a newly barcoded South African species, Q. elegans. Q. texcalense unambiguously branched within genus Quadrulella in a compact clade but with a long branch, suggesting accelerated evolution due to a transition towards a new environment and/or under-sampling. Copyright © 2017 Elsevier GmbH. All rights reserved.

Regulation of Spatiotemporal Patterns by Biological Variability: General Principles and Applications to Dictyostelium discoideum.

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Miriam Grace

2015-11-01

Full Text Available Spatiotemporal patterns often emerge from local interactions in a self-organizing fashion. In biology, the resulting patterns are also subject to the influence of the systematic differences between the system's constituents (biological variability. This regulation of spatiotemporal patterns by biological variability is the topic of our review. We discuss several examples of correlations between cell properties and the self-organized spatiotemporal patterns, together with their relevance for biology. Our guiding, illustrative example will be spiral waves of cAMP in a colony of Dictyostelium discoideum cells. Analogous processes take place in diverse situations (such as cardiac tissue, where spiral waves occur in potentially fatal ventricular fibrillation so a deeper understanding of this additional layer of self-organized pattern formation would be beneficial to a wide range of applications. One of the most striking differences between pattern-forming systems in physics or chemistry and those in biology is the potential importance of variability. In the former, system components are essentially identical with random fluctuations determining the details of the self-organization process and the resulting patterns. In biology, due to variability, the properties of potentially very few cells can have a driving influence on the resulting asymptotic collective state of the colony. Variability is one means of implementing a few-element control on the collective mode. Regulatory architectures, parameters of signaling cascades, and properties of structure formation processes can be "reverse-engineered" from observed spatiotemporal patterns, as different types of regulation and forms of interactions between the constituents can lead to markedly different correlations. The power of this biology-inspired view of pattern formation lies in building a bridge between two scales: the patterns as a collective state of a very large number of cells on the one hand

Dicty_cDB: AFM869 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available Dictyostelium discoideum slug cDNA, clone SLH341. 404 e-128 3 ( AF305060 ) Dictyostelium discoideum Wiscott-...ucing significant alignments: (bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott-

Hydroecology of Amazonian lacustrine Arcellinida (testate amoebae): A case study from Lake Quistococha, Peru.

Science.gov (United States)

Patterson, R Timothy; Huckerby, Gail; Kelly, Thomas J; Swindles, Graeme T; Nasser, Nawaf A

2015-10-01

Organic rich sediments were obtained from seven core tops taken in Lake Quistococha, near the city of Iquitos in the Peruvian Amazon. Subsamples from 0 to 4cm depth in each core were analyzed under dissecting light microscopy to carry out the first investigation of Arcellinida (testate lobose amoebae) from a lacustrine environment in this ecologically important region. The fauna was characterized by a low diversity, low abundance community dominated by centropyxids. This fauna is similar to 'stressed' assemblages reported from temperate latitudes, except that test concentrations were two orders of magnitude lower than typical in temperate lakes. Principle arcellinidan stressors in Lake Quistococha likely include the low pH 4 conditions in the lake, and a general lack of suitable minerogenic material to construct tests in the organic rich lake substrate. The low pH conditions are the result of runoff and seepage of water high in dissolved organic carbon from the adjacent similarly low pH 4 terrestrial peatland. The dearth of minerogenic material is the result of the lake being isolated from riverine input for the past ∼2000 years, even during flooding events. Other limiting factors contributing to depressed arcellinidan populations may include nutrient supply, predation pressure, competition, and post-mortem taphonomic factors. Copyright © 2015 Elsevier GmbH. All rights reserved.

The ROCO kinase QkgA is necessary for proliferation inhibition by autocrine signals in Dictyostelium discoideum.

Science.gov (United States)

Phillips, Jonathan E; Gomer, Richard H

2010-10-01

AprA and CfaD are secreted proteins that function as autocrine signals to inhibit cell proliferation in Dictyostelium discoideum. Cells lacking AprA or CfaD proliferate rapidly, and adding AprA or CfaD to cells slows proliferation. Cells lacking the ROCO kinase QkgA proliferate rapidly, with a doubling time 83% of that of the wild type, and overexpression of a QkgA-green fluorescent protein (GFP) fusion protein slows cell proliferation. We found that qkgA(-) cells accumulate normal levels of extracellular AprA and CfaD. Exogenous AprA or CfaD does not slow the proliferation of cells lacking qkgA, and expression of QkgA-GFP in qkgA(-) cells rescues this insensitivity. Like cells lacking AprA or CfaD, cells lacking QkgA tend to be multinucleate, accumulate nuclei rapidly, and show a mass and protein accumulation per nucleus like those of the wild type, suggesting that QkgA negatively regulates proliferation but not growth. Despite their rapid proliferation, cells lacking AprA, CfaD, or QkgA expand as a colony on bacteria less rapidly than the wild type. Unlike AprA and CfaD, QkgA does not affect spore viability following multicellular development. Together, these results indicate that QkgA is necessary for proliferation inhibition by AprA and CfaD, that QkgA mediates some but not all of the effects of AprA and CfaD, and that QkgA may function downstream of these proteins in a signal transduction pathway regulating proliferation.

Dicty_cDB: SFF823 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available gy vs DNA Score E Sequences producing significant alignments: (bits) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott...id:none) Dictyostelium discoideum Wiscott-A... 83 3e-15 AC117076_18( AC117076 |pid:none) Dictyostelium disco

NCBI nr-aa BLAST: CBRC-DDIS-01-0111 [SEVENS

Lifescience Database Archive (English)

Full Text Available CBRC-DDIS-01-0111 ref|XP_636760.1| alkaline dihydroceramidase [Dictyostelium discoi...deum AX4] gb|AAQ98884.1| alkaline dihydroceramidase [Dictyostelium discoideum] gb|EAL63276.1| alkaline dihydroceramidase [Dictyostelium discoideum AX4] XP_636760.1 7e-59 45% ...

NCBI nr-aa BLAST: CBRC-DDIS-01-0132 [SEVENS

Lifescience Database Archive (English)

Full Text Available CBRC-DDIS-01-0132 ref|XP_646256.1| cellulose synthase [Dictyostelium discoideum AX4...] gb|AAF00200.1|AF163835_1 cellulose synthase [Dictyostelium discoideum] gb|EAL71912.1| cellulose synthase [Dictyostelium discoideum AX4] XP_646256.1 0.0 99% ...

Uncovering a Role for the Tail of the Dictyostelium discoideum SadA Protein in Cell-Substrate Adhesion ▿ †

Science.gov (United States)

Kowal, Anthony S.; Chisholm, Rex L.

2011-01-01

Previous work from our laboratory showed that the Dictyostelium discoideum SadA protein plays a central role in cell-substrate adhesion. SadA null cells exhibit a loss of adhesion, a disrupted actin cytoskeleton, and a cytokinesis defect. How SadA mediates these phenotypes is unknown. This work addresses the mechanism of SadA function, demonstrating an important role for the C-terminal cytoplasmic tail in SadA function. We found that a SadA tailless mutant was unable to rescue the sadA adhesion deficiency, and overexpression of the SadA tail domain reduced adhesion in wild-type cells. We also show that SadA is closely associated with the actin cytoskeleton. Mutagenesis studies suggested that four serine residues in the tail, S924/S925 and S940/S941, may regulate association of SadA with the actin cytoskeleton. Glutathione S-transferase pull-down assays identified at least one likely interaction partner of the SadA tail, cortexillin I, a known actin bundling protein. Thus, our data demonstrate an important role for the carboxy-terminal cytoplasmic tail in SadA function and strongly suggest that a phosphorylation event in this tail regulates an interaction with cortexillin I. Based on our data, we propose a model for the function of SadA. PMID:21441344

Dicty_cDB: VHJ195 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available -B/AFN547Q.Seq.d/ 1342 0.0 SLE172 (SLE172Q) /CSM/SL/SLE1-C/SLE172Q.Seq.d/ 1102 0.0 SLD492 (SLD492Q) /CSM/SL/SLD4-D/SLD492...8502 ) Dictyostelium discoideum cDNA clone:dda28m11, 5' ... 839 0.0 2 ( AU052538 ) Dictyostelium discoideum slug cDNA, clone SLD492...2597 ) Dictyostelium discoideum slug cDNA, clone SLD569. 113 2e-20 1 ( AU061182 ) Dictyostelium discoideum slug cDNA, clone SLD492

Dictyostelium cells bind a secreted autocrine factor that represses cell proliferation.

Science.gov (United States)

Choe, Jonathan M; Bakthavatsalam, Deenadayalan; Phillips, Jonathan E; Gomer, Richard H

2009-02-02

Dictyostelium cells secrete the proteins AprA and CfaD. Cells lacking either AprA or CfaD proliferate faster than wild type, while AprA or CfaD overexpressor cells proliferate slowly, indicating that AprA and CfaD are autocrine factors that repress proliferation. CfaD interacts with AprA and requires the presence of AprA to slow proliferation. To determine if CfaD is necessary for the ability of AprA to slow proliferation, whether AprA binds to cells, and if so whether the binding requires the presence of CfaD, we examined the binding and effect on proliferation of recombinant AprA. We find that the extracellular accumulation of AprA increases with cell density and reaches a concentration of 0.3 microg/ml near a stationary cell density. When added to wild-type or aprA- cells, recombinant AprA (rAprA) significantly slows proliferation at 0.1 microg/ml and higher concentrations. From 4 to 64 microg/ml, the effect of rAprA is at a plateau, slowing but not stopping proliferation. The proliferation-inhibiting activity of rAprA is roughly the same as that of native AprA in conditioned growth medium. Proliferating aprA- cells show saturable binding of rAprA to 92,000 +/- 11,000 cell-surface receptors with a KD of 0.03 +/- 0.02 microg/ml. There appears to be one class of binding site, and no apparent cooperativity. Native AprA inhibits the binding of rAprA to aprA- cells with a Ki of 0.03 mug/ml, suggesting that the binding kinetics of rAprA are similar to those of native AprA. The proliferation of cells lacking CrlA, a cAMP receptor-like protein, or cells lacking CfaD are not affected by rAprA. Surprisingly, both cell types still bind rAprA. Together, the data suggest that AprA functions as an autocrine proliferation-inhibiting factor by binding to cell surface receptors. Although AprA requires CfaD for activity, it does not require CfaD to bind to cells, suggesting the possibility that cells have an AprA receptor and a CfaD receptor, and activation of both receptors is

Response of forest soil euglyphid testate amoebae (Rhizaria: Cercozoa) to pig cadavers assessed by high-throughput sequencing.

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Seppey, Christophe V W; Fournier, Bertrand; Szelecz, Ildikò; Singer, David; Mitchell, Edward A D; Lara, Enrique

2016-03-01

Decomposing cadavers modify the soil environment, but the effect on soil organisms and especially on soil protists is still poorly documented. We conducted a 35-month experiment in a deciduous forest where soil samples were taken under pig cadavers, control plots and fake pigs (bags of similar volume as the pigs). We extracted total soil DNA, amplified the SSU ribosomal RNA (rRNA) gene V9 region and sequenced it by Illumina technology and analysed the data for euglyphid testate amoebae (Rhizaria: Euglyphida), a common group of protozoa known to respond to micro-environmental changes. We found 51 euglyphid operational taxonomic units (OTUs), 45 of which did not match any known sequence. Most OTUs decreased in abundance underneath cadavers between days 0 and 309, but some responded positively after a time lag. We sequenced the full-length SSU rRNA gene of two common OTUs that responded positively to cadavers; a phylogenetic analysis showed that they did not belong to any known euglyphid family. This study confirmed the existence of an unknown diversity of euglyphids and that they react to cadavers. Results suggest that metabarcoding of soil euglyphids could be used as a forensic tool to estimate the post-mortem interval (PMI) particularly for long-term (>2 months) PMI, for which no reliable tool exists.

Mitochondria are the target organelle of differentiation-inducing factor-3, an anti-tumor agent isolated from Dictyostelium discoideum [corrected].

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Yuzuru Kubohara

Full Text Available Differentiation-inducing factor-3 (DIF-3, found in the cellular slime mold Dictyostelium discoideum, and its derivatives such as butoxy-DIF-3 (Bu-DIF-3 are potent anti-tumor agents. However, the precise mechanisms underlying the actions of DIF-3 remain to be elucidated. In this study, we synthesized a green fluorescent derivative of DIF-3, BODIPY-DIF-3, and a control fluorescent compound, Bu-BODIPY (butyl-BODIPY, and investigated how DIF-like molecules behave in human cervical cancer HeLa cells by using both fluorescence and electron microscopy. BODIPY-DIF-3 at 5-20 µ M suppressed cell growth in a dose-dependent manner, whereas Bu-BODIPY had minimal effect on cell growth. When cells were incubated with BODIPY-DIF-3 at 20 µM, it penetrated cell membranes within 0.5 h and localized mainly in mitochondria, while Bu-BODIPY did not stain the cells. Exposure of cells for 1-3 days to DIF-3, Bu-DIF-3, BODIPY-DIF-3, or CCCP (a mitochondrial uncoupler induced substantial mitochondrial swelling, suppressing cell growth. When added to isolated mitochondria, DIF-3, Bu-DIF-3, and BOIDPY-DIF-3, like CCCP, dose-dependently promoted the rate of oxygen consumption, but Bu-BODIPY did not. Our results suggest that these bioactive DIF-like molecules suppress cell growth, at least in part, by disturbing mitochondrial activity. This is the first report showing the cellular localization and behavior of DIF-like molecules in mammalian tumor cells.

Colchicine affects cell motility, pattern formation and stalk cell differentiation in Dictyostelium by altering calcium signaling.

Science.gov (United States)

Poloz, Yekaterina; O'Day, Danton H

2012-04-01

Previous work, verified here, showed that colchicine affects Dictyostelium pattern formation, disrupts morphogenesis, inhibits spore differentiation and induces terminal stalk cell differentiation. Here we show that colchicine specifically induces ecmB expression and enhances accumulation of ecmB-expressing cells at the posterior end of multicellular structures. Colchicine did not induce a nuclear translocation of DimB, a DIF-1 responsive transcription factor in vitro. It also induced terminal stalk cell differentiation in a mutant strain that does not produce DIF-1 (dmtA-) and after the treatment of cells with DIF-1 synthesis inhibitor cerulenin (100 μM). This suggests that colchicine induces the differentiation of ecmB-expressing cells independent of DIF-1 production and likely through a signaling pathway that is distinct from the one that is utilized by DIF-1. Depending on concentration, colchicine enhanced random cell motility, but not chemotaxis, by 3-5 fold (10-50 mM colchicine, respectively) through a Ca(2+)-mediated signaling pathway involving phospholipase C, calmodulin and heterotrimeric G proteins. Colchicine's effects were not due to microtubule depolymerization as other microtubule-depolymerizing agents did not have these effects. Finally normal morphogenesis and stalk and spore cell differentiation of cells treated with 10 mM colchicine were rescued through chelation of Ca2+ by BAPTA-AM and EDTA and calmodulin antagonism by W-7 but not PLC inhibition by U-73122. Morphogenesis or spore cell differentiation of cells treated with 50 mM colchicine could not be rescued by the above treatments but terminal stalk cell differentiation was inhibited by BAPTA-AM, EDTA and W-7, but not U-73122. Thus colchicine disrupts morphogenesis and induces stalk cell differentiation through a Ca(2+)-mediated signaling pathway involving specific changes in gene expression and cell motility. Copyright © 2011 International Society of Differentiation. Published by Elsevier B

Influence of climate and geography on the occurrence of Legionella and amoebae in composting facilities.

Science.gov (United States)

Conza, Lisa; Casati Pagani, Simona; Gaia, Valeria

2014-11-24

The incidence of Legionnaires' disease (LD) in southern Switzerland is three times higher than in northern Switzerland. Climatic and geographic factors may be potential causes for this difference.We studied the prevalence of Legionella and free-living amoebae (FLA) in compost and bioaerosol in two Swiss regions to understand the role of climate and geography in the transmission of LD. We also tried to investigate whether or not compost storage duration would influence the composition of Legionella and FLA communities. A larger proportion of compost heaps in facilities from southern Switzerland harbor more diverse Legionella compared to the north (P=0.0146). FLA were isolated from composts in northern facilities at slightly higher rates (88.2% vs. 69.2%) and at lower rates from bioaerosols (6.3% vs. 13%) than in southern Switzerland. The diversity of FLA was higher in northern than in southern Switzerland (80% vs. 65%). A general decrease in the presence and variety of species was observed with decreasing compost storage time length. A discriminant model showed that values of vapour pressure, relative humidity and temperature distinguish the two regions, which were also characterised by different contamination rates by FLA and Legionella. The duration of outdoor storage may favour contamination of the compost by Legionella, and may increase the number and isolation of Legionella naturally occurring in compost. The climate in the south seems to favour higher Legionella contamination of compost heaps: this could explain the higher incidence of LD in southern Switzerland.

Unveiling exceptional Baltic bog ecohydrology, autogenic succession and climate change during the last 2000 years in CE Europe using replicate cores, multi-proxy data and functional traits of testate amoebae

Science.gov (United States)

Gałka, Mariusz; Tobolski, Kazimierz; Lamentowicz, Łukasz; Ersek, Vasile; Jassey, Vincent E. J.; van der Knaap, Willem O.; Lamentowicz, Mariusz

2017-01-01

We present the results of high-resolution, multi-proxy palaeoecological investigations of two parallel peat cores from the Baltic raised bog Mechacz Wielki in NE Poland. We aim to evaluate the role of regional climate and autogenic processes of the raised bog itself in driving the vegetation and hydrology dynamics. Based on partly synchronous changes in Sphagnum communities in the two study cores we suggest that extrinsic factors (climate) played an important role as a driver in mire development during the bog stage (500-2012 CE). Using a testate amoebae transfer function, we found exceptionally stable hydrological conditions during the last 2000 years with a relatively high water table and lack of local fire events that allowed for rapid peat accumulation (2.75 mm/year) in the bog. Further, the strong correlation between pH and community-weighted mean of testate amoeba traits suggests that other variables than water-table depth play a role in driving microbial properties under stable hydrological conditions. There is a difference in hydrological dynamics in bogs between NW and NE Poland until ca 1500 CE, after which the water table reconstructions show more similarities. Our results illustrate how various functional traits relate to different environmental variables in a range of trophic and hydrological scenarios on long time scales. Moreover, our data suggest a common regional climatic forcing in Mechacz Wielki, Gązwa and Kontolanrahka. Though it may still be too early to attempt a regional summary of wetness change in the southern Baltic region, this study is a next step to better understand the long-term peatland palaeohydrology in NE Europe.

Cell shape dynamics: from waves to migration.

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Meghan K Driscoll

Full Text Available We observe and quantify wave-like characteristics of amoeboid migration. Using the amoeba Dictyostelium discoideum, a model system for the study of chemotaxis, we demonstrate that cell shape changes in a wave-like manner. Cells have regions of high boundary curvature that propagate from the leading edge toward the back, usually along alternating sides of the cell. Curvature waves are easily seen in cells that do not adhere to a surface, such as cells that are electrostatically repelled from surfaces or cells that extend over the edge of micro-fabricated cliffs. Without surface contact, curvature waves travel from the leading edge to the back of a cell at -35 µm/min. Non-adherent myosin II null cells do not exhibit these curvature waves. At the leading edge of adherent cells, curvature waves are associated with protrusive activity. Like regions of high curvature, protrusive activity travels along the boundary in a wave-like manner. Upon contact with a surface, the protrusions stop moving relative to the surface, and the boundary shape thus reflects the history of protrusive motion. The wave-like character of protrusions provides a plausible mechanism for the zig-zagging of pseudopods and for the ability of cells both to swim in viscous fluids and to navigate complex three dimensional topography.

Dictyostelium cells bind a secreted autocrine factor that represses cell proliferation

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Phillips Jonathan E

2009-02-01

Full Text Available Abstract Background Dictyostelium cells secrete the proteins AprA and CfaD. Cells lacking either AprA or CfaD proliferate faster than wild type, while AprA or CfaD overexpressor cells proliferate slowly, indicating that AprA and CfaD are autocrine factors that repress proliferation. CfaD interacts with AprA and requires the presence of AprA to slow proliferation. To determine if CfaD is necessary for the ability of AprA to slow proliferation, whether AprA binds to cells, and if so whether the binding requires the presence of CfaD, we examined the binding and effect on proliferation of recombinant AprA. Results We find that the extracellular accumulation of AprA increases with cell density and reaches a concentration of 0.3 μg/ml near a stationary cell density. When added to wild-type or aprA- cells, recombinant AprA (rAprA significantly slows proliferation at 0.1 μg/ml and higher concentrations. From 4 to 64 μg/ml, the effect of rAprA is at a plateau, slowing but not stopping proliferation. The proliferation-inhibiting activity of rAprA is roughly the same as that of native AprA in conditioned growth medium. Proliferating aprA- cells show saturable binding of rAprA to 92,000 ± 11,000 cell-surface receptors with a KD of 0.03 ± 0.02 μg/ml. There appears to be one class of binding site, and no apparent cooperativity. Native AprA inhibits the binding of rAprA to aprA- cells with a Ki of 0.03 μg/ml, suggesting that the binding kinetics of rAprA are similar to those of native AprA. The proliferation of cells lacking CrlA, a cAMP receptor-like protein, or cells lacking CfaD are not affected by rAprA. Surprisingly, both cell types still bind rAprA. Conclusion Together, the data suggest that AprA functions as an autocrine proliferation-inhibiting factor by binding to cell surface receptors. Although AprA requires CfaD for activity, it does not require CfaD to bind to cells, suggesting the possibility that cells have an AprA receptor and a Cfa

Presence of Legionella and Free-Living Amoebae in Composts and Bioaerosols from Composting Facilities

Science.gov (United States)

Conza, Lisa; Pagani, Simona Casati; Gaia, Valeria

2013-01-01

Several species of Legionella cause Legionnaires’ disease (LD). Infection may occur through inhalation of Legionella or amoebal vesicles. The reservoirs of Legionella are water, soil, potting soil and compost. Some species of free-living amoebae (FLA) that are naturally present in water and soil were described as hosts for Legionella. This study aimed to understand whether or not the composting facilities could be sources of community-acquired Legionella infections after development of bioaerosols containing Legionella or FLA. We looked for the presence of Legionella (by co-culture) and FLA (by culture) in composts and bioaerosols collected at four composting facilities located in southern Switzerland. We investigated the association between the presence of Legionella and compost and air parameters and presence of FLA. Legionella spp. (including L. pneumophila) were detected in 69.3% (61/88) of the composts and FLA (mainly Acanthamoeba, Vermamoeba, Naegleria and Stenamoeba) in 92.0% (81/88). L. pneumophila and L. bozemanii were most frequently isolated. FLA as potential host for Legionella spp. were isolated from 40.9% (36/88) of the composts in all facilities. In Legionella-positive samples the temperature of compost was significantly lower (P = 0.012) than in Legionella-negative samples. Of 47 bioaerosol samples, 19.1% (9/47) were positive for FLA and 10.6% (5/47) for L. pneumophila. Composts (62.8%) were positive for Legionella and FLA contemporaneously, but both microorganisms were never detected simultaneously in bioaerosols. Compost can release bioaerosol containing FLA or Legionella and could represent a source of infection of community-acquired Legionella infections for workers and nearby residents. PMID:23844174

Presence of Legionella and free-living Amoebae in composts and bioaerosols from composting facilities.

Directory of Open Access Journals (Sweden)

Lisa Conza

Full Text Available Several species of Legionella cause Legionnaires' disease (LD. Infection may occur through inhalation of Legionella or amoebal vesicles. The reservoirs of Legionella are water, soil, potting soil and compost. Some species of free-living amoebae (FLA that are naturally present in water and soil were described as hosts for Legionella. This study aimed to understand whether or not the composting facilities could be sources of community-acquired Legionella infections after development of bioaerosols containing Legionella or FLA. We looked for the presence of Legionella (by co-culture and FLA (by culture in composts and bioaerosols collected at four composting facilities located in southern Switzerland. We investigated the association between the presence of Legionella and compost and air parameters and presence of FLA. Legionella spp. (including L. pneumophila were detected in 69.3% (61/88 of the composts and FLA (mainly Acanthamoeba, Vermamoeba, Naegleria and Stenamoeba in 92.0% (81/88. L. pneumophila and L. bozemanii were most frequently isolated. FLA as potential host for Legionella spp. were isolated from 40.9% (36/88 of the composts in all facilities. In Legionella-positive samples the temperature of compost was significantly lower (P = 0.012 than in Legionella-negative samples. Of 47 bioaerosol samples, 19.1% (9/47 were positive for FLA and 10.6% (5/47 for L. pneumophila. Composts (62.8% were positive for Legionella and FLA contemporaneously, but both microorganisms were never detected simultaneously in bioaerosols. Compost can release bioaerosol containing FLA or Legionella and could represent a source of infection of community-acquired Legionella infections for workers and nearby residents.

Environmental factors shaping cultured free-living amoebae and their associated bacterial community within drinking water network.

Science.gov (United States)

Delafont, Vincent; Bouchon, Didier; Héchard, Yann; Moulin, Laurent

2016-09-01

Free-living amoebae (FLA) constitute an important part of eukaryotic populations colonising drinking water networks. However, little is known about the factors influencing their ecology in such environments. Because of their status as reservoir of potentially pathogenic bacteria, understanding environmental factors impacting FLA populations and their associated bacterial community is crucial. Through sampling of a large drinking water network, the diversity of cultivable FLA and their bacterial community were investigated by an amplicon sequencing approach, and their correlation with physicochemical parameters was studied. While FLA ubiquitously colonised the water network all year long, significant changes in population composition were observed. These changes were partially explained by several environmental parameters, namely water origin, temperature, pH and chlorine concentration. The characterisation of FLA associated bacterial community reflected a diverse but rather stable consortium composed of nearly 1400 OTUs. The definition of a core community highlighted the predominance of only few genera, majorly dominated by Pseudomonas and Stenotrophomonas. Co-occurrence analysis also showed significant patterns of FLA-bacteria association, and allowed uncovering potentially new FLA - bacteria interactions. From our knowledge, this study is the first that combines a large sampling scheme with high-throughput identification of FLA together with associated bacteria, along with their influencing environmental parameters. Our results demonstrate the importance of physicochemical parameters in the ecology of FLA and their bacterial community in water networks. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dicty_cDB: VFD730 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available omology vs DNA Score E Sequences producing significant alignments: (bits) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wisco...otein Score E Sequences producing significant alignments: (bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wisco...tt-Aldrich syndrome protein (wasA) gene, complete cds. 4...tt-A... 83 3e-15 AC117076_18( AC117076 |pid:none) Dictyostelium discoideum chromoso

Amoeba-inspired Tug-of-War algorithms for exploration-exploitation dilemma in extended Bandit Problem.

Science.gov (United States)

Aono, Masashi; Kim, Song-Ju; Hara, Masahiko; Munakata, Toshinori

2014-03-01

The true slime mold Physarum polycephalum, a single-celled amoeboid organism, is capable of efficiently allocating a constant amount of intracellular resource to its pseudopod-like branches that best fit the environment where dynamic light stimuli are applied. Inspired by the resource allocation process, the authors formulated a concurrent search algorithm, called the Tug-of-War (TOW) model, for maximizing the profit in the multi-armed Bandit Problem (BP). A player (gambler) of the BP should decide as quickly and accurately as possible which slot machine to invest in out of the N machines and faces an "exploration-exploitation dilemma." The dilemma is a trade-off between the speed and accuracy of the decision making that are conflicted objectives. The TOW model maintains a constant intracellular resource volume while collecting environmental information by concurrently expanding and shrinking its branches. The conservation law entails a nonlocal correlation among the branches, i.e., volume increment in one branch is immediately compensated by volume decrement(s) in the other branch(es). Owing to this nonlocal correlation, the TOW model can efficiently manage the dilemma. In this study, we extend the TOW model to apply it to a stretched variant of BP, the Extended Bandit Problem (EBP), which is a problem of selecting the best M-tuple of the N machines. We demonstrate that the extended TOW model exhibits better performances for 2-tuple-3-machine and 2-tuple-4-machine instances of EBP compared with the extended versions of well-known algorithms for BP, the ϵ-Greedy and SoftMax algorithms, particularly in terms of its short-term decision-making capability that is essential for the survival of the amoeba in a hostile environment. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Air pollution effects on giant sequoia ecosystems.

Science.gov (United States)

P.R. Miller; Nancy Grulke; K.W. Stolte

1994-01-01

Giant sequoia [Sequoiadendron giganteum (Lindl.) Buchholz] groves are found entirely within the Sierra Nevada mixed-conifer type. Several of its companion tree species, mainly ponderosa pine (Pinus ponderosa Dougl. ex Laws.) and Jeffrey pine (P. jeffreyi Grev. & Balf.), show foliar injury after...

Dicty_cDB: CFC194 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available equences producing significant alignments: (bits) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott...nts: (bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott

Properties of a non-bioactive fluorescent derivative of differentiation-inducing factor-3, an anti-tumor agent found in Dictyostelium discoideum

Directory of Open Access Journals (Sweden)

Yuzuru Kubohara

2014-03-01

Full Text Available Differentiation-inducing factor-3 (DIF-3, found in the cellular slime mold Dictyostelium discoideum, and its derivatives, such as butoxy-DIF-3 (Bu-DIF-3, are potent anti-tumor agents. To investigate the activity of DIF-like molecules in tumor cells, we recently synthesized a green fluorescent DIF-3 derivative, BODIPY-DIF-3G, and analyzed its bioactivity and cellular localization. In this study, we synthesized a red (orange fluorescent DIF-3 derivative, BODIPY-DIF-3R, and compared the cellular localization and bioactivities of the two BODIPY-DIF-3s in HeLa human cervical cancer cells. Both fluorescent compounds penetrated the extracellular membrane within 0.5 h and localized mainly to the mitochondria. In formalin-fixed cells, the two BODIPY-DIF-3s also localized to the mitochondria, indicating that the BODIPY-DIF-3s were incorporated into mitochondria independently of the mitochondrial membrane potential. After treatment for 3 days, BODIPY-DIF-3G, but not BODIPY-DIF-3R, induced mitochondrial swelling and suppressed cell proliferation. Interestingly, the swollen mitochondria were stainable with BODIPY-DIF-3G but not with BODIPY-DIF-3R. When added to isolated mitochondria in vitro, BODIPY-DIF-3G increased dose-dependently the rate of O2 consumption, but BODIPY-DIF-3R did not. These results suggest that the bioactive BODIPY-DIF-3G suppresses cell proliferation, at least in part, by altering mitochondrial activity, whereas the non-bioactive BODIPY-DIF-3R localizes to the mitochondria but does not affect mitochondrial activity or cell proliferation.

Formation of the outer layer of the Dictyostelium spore coat depends on the inner-layer protein SP85/PsB.

Science.gov (United States)

Metcalf, Talibah; Kelley, Karen; Erdos, Gregory W; Kaplan, Lee; West, Christopher M

2003-02-01

The Dictyostelium spore is surrounded by a 220 microm thick trilaminar coat that consists of inner and outer electron-dense layers surrounding a central region of cellulose microfibrils. In previous studies, a mutant strain (TL56) lacking three proteins associated with the outer layer exhibited increased permeability to macromolecular tracers, suggesting that this layer contributes to the coat permeability barrier. Electron microscopy now shows that the outer layer is incomplete in the coats of this mutant and consists of a residual regular array of punctate electron densities. The outer layer is also incomplete in a mutant lacking a cellulose-binding protein associated with the inner layer, and these coats are deficient in an outer-layer protein and another coat protein. To examine the mechanism by which this inner-layer protein, SP85, contributes to outer-layer formation, various domain fragments were overexpressed in forming spores. Most of these exert dominant negative effects similar to the deletion of outer-layer proteins, but one construct, consisting of a fusion of the N-terminal and Cys-rich C1 domain, induces a dense mat of novel filaments at the surface of the outer layer. Biochemical studies show that the C1 domain binds cellulose, and a combination of site-directed mutations that inhibits its cellulose-binding activity suppresses outer-layer filament induction. The results suggest that, in addition to a previously described early role in regulating cellulose synthesis, SP85 subsequently contributes a cross-bridging function between cellulose and other coat proteins to organize previously unrecognized structural elements in the outer layer of the coat.

Detection of viable Helicobacter pylori inside free-living amoebae in wastewater and drinking water samples from Eastern Spain.

Science.gov (United States)

Moreno-Mesonero, Laura; Moreno, Yolanda; Alonso, José Luis; Ferrús, M Antonia

2017-10-01

Helicobacter pylori is one of the most concerning emerging waterborne pathogens. It has been suggested that it could survive in water inside free-living amoebae (FLA), but nobody has studied this relationship in the environment yet. Thus, we aimed to detect viable H. pylori cells from inside FLA in water samples. Sixty-nine wastewater and 31 drinking water samples were collected. FLA were purified and identified by PCR and sequencing. For exclusively detecting H. pylori inside FLA, samples were exposed to sodium hypochlorite and assayed by specific PMA-qPCR, DVC-FISH and culture. FLA were detected in 38.7% of drinking water and 79.7% of wastewater samples, even after disinfection. In wastewater, Acanthamoeba spp. and members of the family Vahlkampfiidae were identified. In drinking water, Acanthamoeba spp. and Echinamoeba and/or Vermamoeba were present. In 39 (58.2%) FLA-positive samples, H. pylori was detected by PMA-qPCR. After DVC-FISH, 21 (31.3%) samples harboured viable H. pylori internalized cells. H. pylori was cultured from 10 wastewater samples. To our knowledge, this is the first report that demonstrates that H. pylori can survive inside FLA in drinking water and wastewater, strongly supporting the hypothesis that FLA could play an important role in the transmission of H. pylori to humans. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

An Autocrine Proliferation Repressor Regulates Dictyostelium discoideum Proliferation and Chemorepulsion Using the G Protein-Coupled Receptor GrlH.

Science.gov (United States)

Tang, Yu; Wu, Yuantai; Herlihy, Sarah E; Brito-Aleman, Francisco J; Ting, Jose H; Janetopoulos, Chris; Gomer, Richard H

2018-02-13

In eukaryotic microbes, little is known about signals that inhibit the proliferation of the cells that secrete the signal, and little is known about signals (chemorepellents) that cause cells to move away from the source of the signal. Autocrine proliferation repressor protein A (AprA) is a protein secreted by the eukaryotic microbe Dictyostelium discoideum AprA is a chemorepellent for and inhibits the proliferation of D. discoideum We previously found that cells sense AprA using G proteins, suggesting the existence of a G protein-coupled AprA receptor. To identify the AprA receptor, we screened mutants lacking putative G protein-coupled receptors. We found that, compared to the wild-type strain, cells lacking putative receptor GrlH ( grlH¯ cells) show rapid proliferation, do not have large numbers of cells moving away from the edges of colonies, are insensitive to AprA-induced proliferation inhibition and chemorepulsion, and have decreased AprA binding. Expression of GrlH in grlH¯ cells ( grlH¯/grlH OE ) rescues the phenotypes described above. These data indicate that AprA signaling may be mediated by GrlH in D. discoideum IMPORTANCE Little is known about how eukaryotic cells can count themselves and thus regulate the size of a tissue or density of cells. In addition, little is known about how eukaryotic cells can sense a repellant signal and move away from the source of the repellant, for instance, to organize the movement of cells in a developing embryo or to move immune cells out of a tissue. In this study, we found that a eukaryotic microbe uses G protein-coupled receptors to mediate both cell density sensing and chemorepulsion. Copyright © 2018 Tang et al.

Dicty_cDB: AFE360 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available t alignments: (bits) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott-Aldrich syndrome protein ...(bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott-A..

The putative bZIP transcription factor BzpN slows proliferation and functions in the regulation of cell density by autocrine signals in Dictyostelium.

Directory of Open Access Journals (Sweden)

Jonathan E Phillips

Full Text Available The secreted proteins AprA and CfaD function as autocrine signals that inhibit cell proliferation in Dictyostelium discoideum, thereby regulating cell numbers by a negative feedback mechanism. We report here that the putative basic leucine zipper transcription factor BzpN plays a role in the inhibition of proliferation by AprA and CfaD. Cells lacking BzpN proliferate more rapidly than wild-type cells but do not reach a higher stationary density. Recombinant AprA inhibits wild-type cell proliferation but does not inhibit the proliferation of cells lacking BzpN. Recombinant CfaD also inhibits wild-type cell proliferation, but promotes the proliferation of cells lacking BzpN. Overexpression of BzpN results in a reduced cell density at stationary phase, and this phenotype requires AprA, CfaD, and the kinase QkgA. Conditioned media from high-density cells stops the proliferation of wild-type but not bzpN(- cells and induces a nuclear localization of a BzpN-GFP fusion protein, though this localization does not require AprA or CfaD. Together, the data suggest that BzpN is necessary for some but not all of the effects of AprA and CfaD, and that BzpN may function downstream of AprA and CfaD in a signal transduction pathway that inhibits proliferation.

The Putative bZIP Transcripton Factor BzpN Slows Proliferation and Functions in the Regulation of Cell Density by Autocrine Signals in Dictyostelium

Science.gov (United States)

Phillips, Jonathan E.; Huang, Eryong; Shaulsky, Gad; Gomer, Richard H.

2011-01-01

The secreted proteins AprA and CfaD function as autocrine signals that inhibit cell proliferation in Dictyostelium discoideum, thereby regulating cell numbers by a negative feedback mechanism. We report here that the putative basic leucine zipper transcription factor BzpN plays a role in the inhibition of proliferation by AprA and CfaD. Cells lacking BzpN proliferate more rapidly than wild-type cells but do not reach a higher stationary density. Recombinant AprA inhibits wild-type cell proliferation but does not inhibit the proliferation of cells lacking BzpN. Recombinant CfaD also inhibits wild-type cell proliferation, but promotes the proliferation of cells lacking BzpN. Overexpression of BzpN results in a reduced cell density at stationary phase, and this phenotype requires AprA, CfaD, and the kinase QkgA. Conditioned media from high-density cells stops the proliferation of wild-type but not bzpN− cells and induces a nuclear localization of a BzpN-GFP fusion protein, though this localization does not require AprA or CfaD. Together, the data suggest that BzpN is necessary for some but not all of the effects of AprA and CfaD, and that BzpN may function downstream of AprA and CfaD in a signal transduction pathway that inhibits proliferation. PMID:21760904

The putative bZIP transcription factor BzpN slows proliferation and functions in the regulation of cell density by autocrine signals in Dictyostelium.

Science.gov (United States)

Phillips, Jonathan E; Huang, Eryong; Shaulsky, Gad; Gomer, Richard H

2011-01-01

The secreted proteins AprA and CfaD function as autocrine signals that inhibit cell proliferation in Dictyostelium discoideum, thereby regulating cell numbers by a negative feedback mechanism. We report here that the putative basic leucine zipper transcription factor BzpN plays a role in the inhibition of proliferation by AprA and CfaD. Cells lacking BzpN proliferate more rapidly than wild-type cells but do not reach a higher stationary density. Recombinant AprA inhibits wild-type cell proliferation but does not inhibit the proliferation of cells lacking BzpN. Recombinant CfaD also inhibits wild-type cell proliferation, but promotes the proliferation of cells lacking BzpN. Overexpression of BzpN results in a reduced cell density at stationary phase, and this phenotype requires AprA, CfaD, and the kinase QkgA. Conditioned media from high-density cells stops the proliferation of wild-type but not bzpN(-) cells and induces a nuclear localization of a BzpN-GFP fusion protein, though this localization does not require AprA or CfaD. Together, the data suggest that BzpN is necessary for some but not all of the effects of AprA and CfaD, and that BzpN may function downstream of AprA and CfaD in a signal transduction pathway that inhibits proliferation.

Dicty_cDB: AFF743 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available Sequences producing significant alignments: (bits) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott...oducing significant alignments: (bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott

Dicty_cDB: SFC807 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available icant alignments: (bits) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott-Aldrich syndrome prot...ng significant alignments: (bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott

Antimicrobial activities of two Nigerian edible macro-fungi ...

African Journals Online (AJOL)

P< 0.05). The best inhibitory zone (24.0mm) was recorded in ethanol extract of L. giganteum with inhibitory zone of 21.0mm. The least inhibitory zone, (4.0mm) was recorded with the aqueous extract of L. pusilum against Proteus vulgaris.

Dicty_cDB: VFN644 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available A clone:ddv28g12, 3' ... 404 0.0 5 ( AF305060 ) Dictyostelium discoideum Wiscott-...ng significant alignments: (bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott-A..

Dicty_cDB: AFG687 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available ant alignments: (bits) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott...n Score E Sequences producing significant alignments: (bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott

NCBI nr-aa BLAST: CBRC-DDIS-01-0111 [SEVENS

Lifescience Database Archive (English)

Full Text Available CBRC-DDIS-01-0111 ref|XP_646081.1| alkaline dihydroceramidase [Dictyostelium discoi...deum AX4] gb|EAL72137.1| alkaline dihydroceramidase [Dictyostelium discoideum AX4] XP_646081.1 1e-164 100% ...

Dicty_cDB: VFA863 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available ore E Sequences producing significant alignments: (bits) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott...gnificant alignments: (bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott-A... 83

Dicty_cDB: CFG253 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott-Aldrich syndrome protein (wasA) gene, complete...ences producing significant alignments: (bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott

Dicty_cDB: SSG705 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available NA Score E Sequences producing significant alignments: (bits) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott...quences producing significant alignments: (bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott

Dicty_cDB: SFC789 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available ments: (bits) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott-Aldri...ne) Dictyostelium discoideum Wiscott-A... 34 0.031 protein update 2009. 1. 7 PSORT psg: 0.84 gvh: 0.42 alm:

Structure, dynamics and folding of an immunoglobulin domain of the gelation factor (ABP-120) from Dictyostelium discoideum.

Science.gov (United States)

Hsu, Shang-Te Danny; Cabrita, Lisa D; Fucini, Paola; Dobson, Christopher M; Christodoulou, John

2009-05-15

We have carried out a detailed structural and dynamical characterisation of the isolated fifth repeat of the gelation factor (ABP-120) from Dictyostelium discoideum (ddFLN5) by NMR spectroscopy to provide a basis for studies of co-translational folding on the ribosome of this immunoglobulin-like domain. The isolated ddFLN5 can fold autonomously in solution into a structure that resembles very closely the crystal structure of the domain in a construct in which the adjacent sixth repeat (ddFLN6) is covalently linked to its C-terminus in tandem but deviates locally from a second crystal structure in which ddFLN5 is flanked by ddFLN4 and ddFLN6 at both N- and C-termini. Conformational fluctuations were observed via (15)N relaxation methods and are primarily localised in the interstrand loops that encompass the C-terminal hemisphere. These fluctuations are distinct in location from the region where line broadening is observed in ddFLN5 when attached to the ribosome as part of a nascent chain. This observation supports the conclusion that the broadening is associated with interactions with the ribosome surface [Hsu, S. T. D., Fucini, P., Cabrita, L. D., Launay, H., Dobson, C. M. & Christodoulou, J. (2007). Structure and dynamics of a ribosome-bound nascent chain by NMR spectroscopy. Proc. Natl. Acad. Sci. USA, 104, 16516-16521]. The unfolding of ddFLN5 induced by high concentrations of urea shows a low population of a folding intermediate, as inferred from an intensity-based analysis, a finding that differs from that of ddFLN5 as a ribosome-bound nascent chain. These results suggest that interesting differences in detail may exist between the structure of the domain in isolation and when linked to the ribosome and between protein folding in vitro and the folding of a nascent chain as it emerges from the ribosome.

Dicty_cDB: SLH341 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available 5 ( AF305060 ) Dictyostelium discoideum Wiscott-Aldrich syndrome... 404 0.0 5 ( B...ts) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott-A... 83 8e-15 AC117076_18( AC1170

Dicty_cDB: SFJ736 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available 060.1 Dictyostelium discoideum Wiscott-Aldrich syndrome protein (wasA) gene, complete cds. 470 e-129 2 BQ923...1( AF305060 |pid:none) Dictyostelium discoideum Wiscott-A... 81 1e-14 AC117076_18

Binding and Endocytosis of Bovine Hololactoferrin by the Parasite Entamoeba histolytica

Directory of Open Access Journals (Sweden)

Guillermo Ortíz-Estrada

2015-01-01

Full Text Available Entamoeba histolytica is a human parasite that requires iron (Fe for its metabolic function and virulence. Bovine lactoferrin (B-Lf and its peptides can be found in the digestive tract after dairy products are ingested. The aim of this study was to compare virulent trophozoites recently isolated from hamster liver abscesses with nonvirulent trophozoites maintained for more than 30 years in cultures in vitro regarding their interaction with iron-charged B-Lf (B-holo-Lf. We performed growth kinetics analyses of trophozoites in B-holo-Lf and throughout several consecutive transfers. The virulent parasites showed higher growth and tolerance to iron than nonvirulent parasites. Both amoeba variants specifically bound B-holo-Lf with a similar Kd. However, averages of 9.45 × 105 and 6.65 × 106 binding sites/cell were found for B-holo-Lf in nonvirulent and virulent amoebae, respectively. Virulent amoebae bound more efficiently to human and bovine holo-Lf, human holo-transferrin, and human and bovine hemoglobin than nonvirulent amoebae. Virulent amoebae showed two types of B-holo-Lf binding proteins. Although both amoebae endocytosed this glycoprotein through clathrin-coated vesicles, the virulent amoebae also endocytosed B-holo-Lf through a cholesterol-dependent mechanism. Both amoeba variants secreted cysteine proteases cleaving B-holo-Lf. These data demonstrate that the B-Lf endocytosis is more efficient in virulent amoebae.

Binding and Endocytosis of Bovine Hololactoferrin by the Parasite Entamoeba histolytica.

Science.gov (United States)

Ortíz-Estrada, Guillermo; Calderón-Salinas, Víctor; Shibayama-Salas, Mineko; León-Sicairos, Nidia; de la Garza, Mireya

2015-01-01

Entamoeba histolytica is a human parasite that requires iron (Fe) for its metabolic function and virulence. Bovine lactoferrin (B-Lf) and its peptides can be found in the digestive tract after dairy products are ingested. The aim of this study was to compare virulent trophozoites recently isolated from hamster liver abscesses with nonvirulent trophozoites maintained for more than 30 years in cultures in vitro regarding their interaction with iron-charged B-Lf (B-holo-Lf). We performed growth kinetics analyses of trophozoites in B-holo-Lf and throughout several consecutive transfers. The virulent parasites showed higher growth and tolerance to iron than nonvirulent parasites. Both amoeba variants specifically bound B-holo-Lf with a similar K d . However, averages of 9.45 × 10(5) and 6.65 × 10(6) binding sites/cell were found for B-holo-Lf in nonvirulent and virulent amoebae, respectively. Virulent amoebae bound more efficiently to human and bovine holo-Lf, human holo-transferrin, and human and bovine hemoglobin than nonvirulent amoebae. Virulent amoebae showed two types of B-holo-Lf binding proteins. Although both amoebae endocytosed this glycoprotein through clathrin-coated vesicles, the virulent amoebae also endocytosed B-holo-Lf through a cholesterol-dependent mechanism. Both amoeba variants secreted cysteine proteases cleaving B-holo-Lf. These data demonstrate that the B-Lf endocytosis is more efficient in virulent amoebae.

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB593 (Link to dictyBase) - - - Contig-U02438-1 VFB593E (Link...) Clone ID VFB593 (Link to dictyBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U02438-1 Ori...0.009 6 AC116986 |AC116986.2 Dictyostelium discoideum chromosome 2 map 2234041-25...sequence. 46 0.031 2 AC115577 |AC115577.2 Dictyostelium discoideum chromosome 2 m...ap 4657875-4914984 strain AX4, complete sequence. 34 0.051 14 AC116960 |AC116960.2 Dictyostelium discoideum

Dicty_cDB: SHE721 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available E Sequences producing significant alignments: (bits) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott...305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott-A... 83 8e-15 AC117076_18( AC117076 |pid:none

Dicty_cDB: Contig-U12991-1 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available ( AF272150 ) Dictyostelium discoideum deliriumA (dlrA) gene, c... 2022 0.0 3 ( BJ...39594 ) TT1EP48TV Tetrahymena thermophila SB210 cDNA libr... 38 10.0 2 >( AF272150 ) Dictyostelium discoideum delirium

Bacterivory: a novel dual role for thraustochytrids in the sea

Digital Repository Service at National Institute of Oceanography (India)

Raghukumar, S.

in the presence of bacteria, both species produced amoebae, which moved using pseudopodia and phagocytosed bacterial cells. Several amoebae were produced in 'sporangia', or isolated vegetative cells transformed directly into amoebae. These findings were confirmed...

Management of Giant Sequoia on Mountain Home Demonstration State Forest

Science.gov (United States)

Norman J. Benson

1986-01-01

Established in 1946, the Mountain Home Demonstration State Forest, Tulare County, California, is managed by the California Department of Forestry. It is a multiple-use forest with recreation as its primary focus, although timber management has always played an important role. Giant sequoia (Sequoiadendron giganteum [Lindl. ] Buchholz) occurs in...

Dicty_cDB: SFK712 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available deum cDNA clone:dda5o08, 3' e... 404 e-125 2 ( AF305060 ) Dictyostelium discoideum Wiscott-Aldrich syndrome....ore E Sequences producing significant alignments: (bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott

Dicty_cDB: VSJ735 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available |AF305060.1 Dictyostelium discoideum Wiscott-Aldrich syndrome protein (wasA) gene, complete cds. 436 0.0 5 A... AF305060 |pid:none) Dictyostelium discoideum Wiscott-A... 214 2e-54 BC087802_1( BC087802 |pid:none) Xenopus

Dicty_cDB: VSC304 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available 05060 |AF305060.1 Dictyostelium discoideum Wiscott-Aldrich syndrome protein (wasA) gene, complete cds. 622 0...bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott-A... 167 1e-44 AC117076_18( AC1

Dicty_cDB: CFG349 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available its) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott-Aldrich syndrome protein (wasA) gene, com...060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott-A... 247 4e-64 DQ985464_1( DQ985464 |pid:none) S

Dicty_cDB: SFG565 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available 5060.1 Dictyostelium discoideum Wiscott-Aldrich syndrome protein (wasA) gene, complete cds. 626 0.0 8 AC1170...bits) Value AF305060_1( AF305060 |pid:none) Dictyostelium discoideum Wiscott-A... 254 4e-77 AC117076_18( AC1

NCBI nr-aa BLAST: CBRC-DDIS-03-0190 [SEVENS

Lifescience Database Archive (English)

Full Text Available CBRC-DDIS-03-0190 ref|XP_646956.1| ARID/BRIGHT DNA binding domain-containing protei...n [Dictyostelium discoideum AX4] gb|EAL72978.1| ARID/BRIGHT DNA binding domain-containing protein [Dictyostelium discoideum AX4] XP_646956.1 1e-06 23% ...

Dicty_cDB: CHD534 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available CH (Link to library) CHD534 (Link to dictyBase) - - - Contig-U15540-1 CHD534E (Link...) Clone ID CHD534 (Link to dictyBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U15540-1 Ori...nts: (bits) Value N AC114263 |AC114263.2 Dictyostelium discoideum chromosome 2 ma...p 215673-367476 strain AX4, complete sequence. 40 1e-05 6 AC117081 |AC117081.2 Dictyostelium discoideum chro...mosome 2 map 5862124-6045772 strain AX4, complete sequence. 40 2e-05 5 AJ277590 |AJ277590.1 Dictyostelium di

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB752 (Link to dictyBase) - - - Contig-U14717-1 VFB752E (Link...) Clone ID VFB752 (Link to dictyBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U14717-1 Ori...s: (bits) Value N AC116984 |AC116984.2 Dictyostelium discoideum chromosome 2 map 2567470-3108875 strain AX4,... complete sequence. 1215 0.0 11 AC115594 |AC115594.2 Dictyostelium discoideum chr...omosome 2 map 4071862-4101005 strain AX4, complete sequence. 113 3e-47 8 AC116920 |AC116920.2 Dictyostelium

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB606 (Link to dictyBase) - - - Contig-U16382-1 VFB606E (Link...) Clone ID VFB606 (Link to dictyBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16382-1 Ori...ucing significant alignments: (bits) Value N X03281 |X03281.1 Dictyostelium discoideum gene for actin A8. 22...28 0.0 1 AC116957 |AC116957.2 Dictyostelium discoideum chromosome 2 map 1685067-2...2028 0.0 1 AC115579 |AC115579.2 Dictyostelium discoideum chromosome 2 map 4915084-5005461 strain AX4, comple

The PsB glycoprotein complex is secreted as a preassembled precursor of the spore coat in Dictyostelium discoideum.

Science.gov (United States)

Watson, N; McGuire, V; Alexander, S

1994-09-01

The PsB glycoprotein in Dictyostelium discoideum is one of a diverse group of developmentally regulated, prespore-cell-specific proteins, that contain a common O-linked oligosaccharide. This post-translational modification is dependent on the wild-type modB allele. The PsB protein exists as part of a multiprotein complex of six different proteins, which have different post-translational modifications and are held together by both covalent and non-covalent interactions (Watson et al. (1993). J. Biol. Chem. 268, 22634-22641). In this study we have used microscopic and biochemical analyses to examine the cellular localization and function of the PsB complex during development. We found that the PsB complex first accumulates in prespore vesicles in slug cells and is secreted later during culmination and becomes localized to both the extracellular matrix of the apical spore mass of mature fruiting bodies and to the inner layer of the spore coat. The PsB associated with the spore coat is covalently bound by disulfide bridges. The PsB protein always exists in a multiprotein complex, but the composition of the PsB complex changes during secretion and spore maturation. Some of the PsB complex proteins have been identified as spore coat proteins. These data demonstrate that some of the proteins that form the spore coat exist as a preassembled precursor complex. The PsB complex is secreted in a developmentally regulated manner during the process of spore differentiation, at which time proteins of the complex, as well as additional spore coat proteins, become covalently associated in at least two forms of extracellular matrix: the interspore matrix and the spore coat. These and other studies show that proteins with modB dependent O-linked oligosaccharides are involved in a wide variety of processes underlying morphogenesis in this organism. These developmental processes are the direct result of cellular mechanisms regulating protein targeting, assembly and secretion, and the

Mutant p97 exhibits species-specific changes of its ATPase activity and compromises the UBXD9-mediated monomerisation of p97 hexamers.

Science.gov (United States)

Rijal, Ramesh; Arhzaouy, Khalid; Strucksberg, Karl-Heinz; Cross, Megan; Hofmann, Andreas; Schröder, Rolf; Clemen, Christoph S; Eichinger, Ludwig

2016-01-01

p97 (VCP) is a homo-hexameric triple-A ATPase that exerts a plethora of cellular processes. Heterozygous missense mutations of p97 cause at least five human neurodegenerative disorders. However, the specific molecular consequences of p97 mutations are hitherto widely unknown. Our in silico structural models of human and Dictyostelium p97 showed that the disease-causing human R93C, R155H, and R155C as well as Dictyostelium R154C, E219K, R154C/E219K p97 mutations constitute variations in surface-exposed locations. In-gel ATPase activity measurements of p97 monomers and hexamers revealed significant mutation- and species-specific differences. While all human p97 mutations led to an increase in ATPase activity, no changes could be detected for the Dictyostelium R154C mutant, which is orthologous to human R155C. The E219K mutation led to an almost complete loss of activity, which was partially recuperated in the R154C/E219K double-mutant indicating p97 inter-domain communication. By means of co-immunoprecipitation experiments we identified an UBX-domain containing Dictyostelium protein as a novel p97 interaction partner. We categorized all UBX-domain containing Dictyostelium proteins and named the interaction partner UBXD9. Pull-down assays and surface plasmon resonance analyses of Dictyostelium UBXD9 or the human orthologue TUG/ASPL/UBXD9 demonstrated direct interactions with p97 as well as species-, mutation- and ATP-dependent differences in the binding affinities. Sucrose density gradient assays revealed that both human and Dictyostelium UBXD9 proteins very efficiently disassembled wild-type, but to a lesser extent mutant p97 hexamers into monomers. Our results are consistent with a scenario in which p97 point mutations lead to differences in enzymatic activities and molecular interactions, which in the long-term result in a late-onset and progressive multisystem disease. Copyright © 2016 The Authors. Published by Elsevier GmbH.. All rights reserved.

Susceptibility of pathogenic and nonpathogenic Naegleria ssp

International Nuclear Information System (INIS)

Whiteman, L.Y.

1988-01-01

The susceptibility of four species of Naegleria amoebae to complement-mediated lysis was determined. The amoebicidal activity of normal human serum (NHS) and normal guinea pig serum (NGPS) for Naegleria amoebae was measured by an in vitro cytotoxicity assay. Release of radioactivity from amoebae labeled with 3 H-uridine and visual observation with a compound microscope were used as indices of lysis. Susceptibility or resistance to complement-mediated lysis in vitro correlated with the in vivo pathogenic potential. Nonpathogenic Naegleria amoebae were lysed at a faster rate and at higher cell concentrations than were pathogenic amoebae. Electrophoretic analysis of NHS incubated with pathogenic or nonpathogenic Naegleria spp. demonstrated that amoebae activate the complement cascade resulting in the production of C3 and C5 complement cleavage products. Treatment with papain or trypsin for 1 h, but not with sialidase, increase the susceptibility of highly pathogenic, mouse-passaged N. fowleri to lysis. Treatment with actinomycin D, cycloheximide or various protease inhibitors for 4 h did not increase susceptibility to lysis. Neither a repair process involving de novo protein synthesis nor a complement-inactivating protease appear to account for the increase resistance of N. fowleri amoebae to complement-mediated lysis. A binding study with 125 I radiolabeled C9 indicated that the terminal complement component does not remain stably bound to the membrane of pathogenic amoebae

cGMP signalling : different ways to create a pathway

NARCIS (Netherlands)

Roelofs, Jeroen; Smith, Janet L.; Haastert, Peter J.M. van

Recently, a novel cGMP signalling cascade was uncovered in Dictyostelium, a eukaryote that diverged from the lineage leading to metazoa after plants and before yeast. In both Dictyostelium and metazoa, the ancient cAMP-binding (cNB) motif of bacterial CAP has been modified and assembled with other

G-protein-mediated interconversions of cell-surface cAMP receptors and their involvement in excitation and desensitization of guanylate cyclase in Dictyostelium discoideum

International Nuclear Information System (INIS)

van Haastert, P.J.; de Wit, R.J.; Janssens, P.M.; Kesbeke, F.; DeGoede, J.

1986-01-01

In Dictyostelium discoideum cells, extracellular cAMP induces the rapid (within 2 s) activation of guanylate cyclase, which is followed by complete desensitization after about 10 s. cAMP binding to these cells is heterogeneous, showing a subclass of fast dissociating sites coupled to adenylate cyclase (A-sites) and a subclass of slowly dissociating sites coupled to guanylate cyclase (B-sites). The kinetics of the B-sites were further investigated on a seconds time scale. Statistical analysis of the association of [ 3 H]cAMP to the B-sites and dissociation of the complex revealed that the receptor can exist in three states which interconvert according to the following scheme. cAMP binds to the BF-state (off-rate 2.5 s) which rapidly (t1/2 = 3 s) converts to the BS-state (off-rate 15 s) and subsequently (without a detectable delay) into the BSS-state (off-rate 150 s). In membranes, both the BS- and BSS-states are converted to the BF-state by GTP and GDP, suggesting the involvement of a G-protein. Densensitized cells show a 80% reduction of the formation of the BSS-state, but no reduction of the BF- or BS-state. These data are combined into a model in which the transitions of the B-sites are mediated by a G-protein; activation of the G-protein and guanylate cyclase is associated with the transition of the BS- to the BSS-state of the receptor, whereas desensitization is associated with the inhibition of this transition

TgrC1 mediates cell-cell adhesion by interacting with TgrB1 via mutual IPT/TIG domains during development of Dictyostelium discoideum.

Science.gov (United States)

Chen, Gong; Wang, Jun; Xu, Xiaoqun; Wu, Xiangfu; Piao, Ruihan; Siu, Chi-Hung

2013-06-01

Cell-cell adhesion plays crucial roles in cell differentiation and morphogenesis during development of Dictyostelium discoideum. The heterophilic adhesion protein TgrC1 (Tgr is transmembrane, IPT, IG, E-set, repeat protein) is expressed during cell aggregation, and disruption of the tgrC1 gene results in the arrest of development at the loose aggregate stage. We have used far-Western blotting coupled with MS to identify TgrB1 as the heterophilic binding partner of TgrC1. Co-immunoprecipitation and pull-down studies showed that TgrB1 and TgrC1 are capable of binding with each other in solution. TgrB1 and TgrC1 are encoded by a pair of adjacent genes which share a common promoter. Both TgrB1 and TgrC1 are type I transmembrane proteins, which contain three extracellular IPT/TIG (immunoglobulin, plexin, transcription factor-like/transcription factor immunoglobulin) domains. Antibodies raised against TgrB1 inhibit cell reassociation at the post-aggregation stage of development and block fruiting body formation. Ectopic expression of TgrB1 and TgrC1 driven by the actin15 promoter leads to heterotypic cell aggregation of vegetative cells. Using recombinant proteins that cover different portions of TgrB1 and TgrC1 in binding assays, we have mapped the cell-binding regions in these two proteins to Lys(537)-Ala(783) in TgrB1 and Ile(336)-Val(360) in TgrC1, corresponding to their respective TIG3 and TIG2 domain.

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB770 (Link to dictyBase) - - - Contig-U16382-1 VFB770E (Link...) Clone ID VFB770 (Link to dictyBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16382-1 Ori...logy vs DNA Score E Sequences producing significant alignments: (bits) Value N X03281 |X03281.1 Dictyosteliu...m discoideum gene for actin A8. 2230 0.0 1 AC116957 |AC116957.2 Dictyostelium discoideum chromosome 2 map 16...deum actin 15 gene, complete cds. 2030 0.0 1 AC115579 |AC115579.2 Dictyostelium discoideum chromosome 2 map

Species richness and geographic distribution of testate amoebae (Rhizopoda in Brazilian freshwater environments = Riqueza de espécies e distribuição geográfica de amebas testáceas (Rhizopoda em ambientes aquáticos continentais brasileiros

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Fábio Amodêo Lansac-Tôha

2007-04-01

Full Text Available The present study aimed to analyze the species richness of testate amoebae, as well as to describe their geographic distribution and different habitat types in Brazilian freshwater environments. Until now, 346 infrageneric taxa have been recorded, belonging to 13 families and 40 genera. In the Center-West region, 267 taxa were recorded; 188 taxa in the Southeast; 129 taxa in the South, 53 taxa in the North; and 18 taxa in Northeast region. A total of 282 taxa were recorded in plankton; 80 taxa in aquatic macrophytes; 81 taxa insediment; and 73 taxa in moss/sphagnum. The results regarding testate amoebae species richness are not yet conclusive, given that most research on these organisms was carried out in central, southeastern and southern Brazil. The higher number of taxa observed in plankton may be due to the fact that most studies on testate amoebae in Brazil had been carried out in the planktonic compartment, including reservoirs, floodplain lagoons, channels, tributaries and rivers. In addition, the majority of studies with sediment samples were conducted in estuaries or coastal lagoons, where salinity is a restricting factor for the occurrence of these organisms.Este trabalho visa realizar um levantamento da riqueza de espécies de amebas testáceas, bem como descrever a distribuição geográfica e a distribuição em diferentes tipos de habitats desses organismos em ambientes aquáticos continentais brasileiros. Até o momento, são registrados 346 táxons infragenéricos, pertencentes a 13 famílias e 40 gêneros. São registrados 267 táxons na região centro-oeste, 188táxons na região sudeste, 129 táxons na região sul, 53 táxons na região norte e 18 táxons na região nordeste. São registrados 282 táxons no plâncton; 131 táxons em macrófitas aquáticas, 81 táxonsno sedimento e 73 táxons em musgos/esfágnos. Os resultados sobre a riqueza de tecamebas não é ainda conclusiva, visto que a maioria das pesquisas foi conduzida

Dicty_cDB: SLE172 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available d/ 1126 0.0 VHJ195 (VHJ195Q) /CSM/VH/VHJ1-D/VHJ195Q.Seq.d/ 1102 0.0 SLD492 (SLD492Q) /CSM/SL/SLD4-D/SLD492... 0.0 1 ( AU052538 ) Dictyostelium discoideum slug cDNA, clone SLD492. 817 0.0 1 ( C83939 ) Dictyostelium dis

Modulation of Zinc Homeostasis in Acanthamoeba castellanii as a Possible Antifungal Strategy against Cryptococcus gattii

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Nicole S. Ribeiro

2017-08-01

Full Text Available Cryptococcus gattii is a basidiomycetous yeast that can be found in the environment and is one of the agents of cryptococcosis, a life-threatening disease. During its life cycle, cryptococcal cells take hold inside environmental predators such as amoebae. Despite their evolutionary distance, macrophages and amoebae share conserved similar steps of phagocytosis and microbial killing. To evaluate whether amoebae also share other antifungal strategies developed by macrophages, we investigated nutritional immunity against cryptococcal cells. We focused on zinc homeostasis modulation in Acanthamoeba castellanii infected with C. gattii. The intracellular proliferation rate (IPR in amoebae was determined using C. gattii R265 and mutants for the ZIP1 gene, which displays defects of growth in zinc-limiting conditions. We detected a reduced IPR in cells lacking the ZIP1 gene compared to wild-type strains, suggesting that amoebae produce a low zinc environment to engulfed cells. Furthermore, flow cytometry analysis employing the zinc probe Zinpyr-1 confirmed the reduced concentration of zinc in cryptococcal-infected amoebae. qRT-PCR analysis of zinc transporter-coding genes suggests that zinc export by members of the ZnT family would be involved in the reduced intracellular zinc concentration. These results indicate that amoebae may use nutritional immunity to reduce fungal cell proliferation by reducing zinc availability for the pathogen.

Basic features of slime mould motility

Science.gov (United States)

Shirakawa, Tomohiro

2015-03-01

The plasmodium of Physarum polycephalum is a unicellular and multi-nuclear giant amoeba that is formed by fusions of myriads of uninucleate microscopic amoebae at a point in the life cycle of the organism. The very large unicellular form of the plasmodium is very uncommon in nature; on the contrary, almost all of the other higher organisms have multi-cellular bodies. Therefore, the plasmodium has an exceptional property: although the plasmodium is a unicellular organism, the size of the amoeba is variable. The smallest plasmodium consists of the fusion of two amoebae, so the smallest size is twice that of a usual amoeba. There is no upper limit to the largest size of the plasmodium, in principle. There is a record of very large plasmodium of more than a few metres. A more interesting point is that despite the variety in the size, the plasmodium can move, feed and form complex structures and adapt itself to the environment in an intelligent manner...

Identification of a general O-linked protein glycosylation system in Acinetobacter baumannii and its role in virulence and biofilm formation.

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Jeremy A Iwashkiw

Full Text Available Acinetobacter baumannii is an emerging cause of nosocomial infections. The isolation of strains resistant to multiple antibiotics is increasing at alarming rates. Although A. baumannii is considered as one of the more threatening "superbugs" for our healthcare system, little is known about the factors contributing to its pathogenesis. In this work we show that A. baumannii ATCC 17978 possesses an O-glycosylation system responsible for the glycosylation of multiple proteins. 2D-DIGE and mass spectrometry methods identified seven A. baumannii glycoproteins, of yet unknown function. The glycan structure was determined using a combination of MS and NMR techniques and consists of a branched pentasaccharide containing N-acetylgalactosamine, glucose, galactose, N-acetylglucosamine, and a derivative of glucuronic acid. A glycosylation deficient strain was generated by homologous recombination. This strain did not show any growth defects, but exhibited a severely diminished capacity to generate biofilms. Disruption of the glycosylation machinery also resulted in reduced virulence in two infection models, the amoebae Dictyostelium discoideum and the larvae of the insect Galleria mellonella, and reduced in vivo fitness in a mouse model of peritoneal sepsis. Despite A. baumannii genome plasticity, the O-glycosylation machinery appears to be present in all clinical isolates tested as well as in all of the genomes sequenced. This suggests the existence of a strong evolutionary pressure to retain this system. These results together indicate that O-glycosylation in A. baumannii is required for full virulence and therefore represents a novel target for the development of new antibiotics.

Identification of a General O-linked Protein Glycosylation System in Acinetobacter baumannii and Its Role in Virulence and Biofilm Formation

Science.gov (United States)

Iwashkiw, Jeremy A.; Seper, Andrea; Weber, Brent S.; Scott, Nichollas E.; Vinogradov, Evgeny; Stratilo, Chad; Reiz, Bela; Cordwell, Stuart J.; Whittal, Randy; Schild, Stefan; Feldman, Mario F.

2012-01-01

Acinetobacter baumannii is an emerging cause of nosocomial infections. The isolation of strains resistant to multiple antibiotics is increasing at alarming rates. Although A. baumannii is considered as one of the more threatening “superbugs” for our healthcare system, little is known about the factors contributing to its pathogenesis. In this work we show that A. baumannii ATCC 17978 possesses an O-glycosylation system responsible for the glycosylation of multiple proteins. 2D-DIGE and mass spectrometry methods identified seven A. baumannii glycoproteins, of yet unknown function. The glycan structure was determined using a combination of MS and NMR techniques and consists of a branched pentasaccharide containing N-acetylgalactosamine, glucose, galactose, N-acetylglucosamine, and a derivative of glucuronic acid. A glycosylation deficient strain was generated by homologous recombination. This strain did not show any growth defects, but exhibited a severely diminished capacity to generate biofilms. Disruption of the glycosylation machinery also resulted in reduced virulence in two infection models, the amoebae Dictyostelium discoideum and the larvae of the insect Galleria mellonella, and reduced in vivo fitness in a mouse model of peritoneal sepsis. Despite A. baumannii genome plasticity, the O-glycosylation machinery appears to be present in all clinical isolates tested as well as in all of the genomes sequenced. This suggests the existence of a strong evolutionary pressure to retain this system. These results together indicate that O-glycosylation in A. baumannii is required for full virulence and therefore represents a novel target for the development of new antibiotics. PMID:22685409

Sensing of substratum rigidity and directional migration by fast-crawling cells

Science.gov (United States)

Okimura, Chika; Sakumura, Yuichi; Shimabukuro, Katsuya; Iwadate, Yoshiaki

2018-05-01

Living cells sense the mechanical properties of their surrounding environment and respond accordingly. Crawling cells detect the rigidity of their substratum and migrate in certain directions. They can be classified into two categories: slow-moving and fast-moving cell types. Slow-moving cell types, such as fibroblasts, smooth muscle cells, mesenchymal stem cells, etc., move toward rigid areas on the substratum in response to a rigidity gradient. However, there is not much information on rigidity sensing in fast-moving cell types whose size is ˜10 μ m and migration velocity is ˜10 μ m /min . In this study, we used both isotropic substrata with different rigidities and an anisotropic substratum that is rigid on the x axis but soft on the y axis to demonstrate rigidity sensing by fast-moving Dictyostelium cells and neutrophil-like differentiated HL-60 cells. Dictyostelium cells exerted larger traction forces on a more rigid isotropic substratum. Dictyostelium cells and HL-60 cells migrated in the "soft" direction on the anisotropic substratum, although myosin II-null Dictyostelium cells migrated in random directions, indicating that rigidity sensing of fast-moving cell types differs from that of slow types and is induced by a myosin II-related process.

An N-terminal nuclear localization sequence but not the calmodulin-binding domain mediates nuclear localization of nucleomorphin, a protein that regulates nuclear number in Dictyostelium

International Nuclear Information System (INIS)

Myre, Michael A.; O'Day, Danton H.

2005-01-01

Nucleomorphin is a novel nuclear calmodulin (CaM)-binding protein (CaMBP) containing an extensive DEED (glu/asp repeat) domain that regulates nuclear number. GFP-constructs of the 38 kDa NumA1 isoform localize as intranuclear patches adjacent to the inner nuclear membrane. The translocation of CaMBPs into nuclei has previously been shown by others to be mediated by both classic nuclear localization sequences (NLSs) and CaM-binding domains (CaMBDs). Here we show that NumA1 possesses a CaMBD ( 171 EDVSRFIKGKLLQKQQKIYKDLERF 195 ) containing both calcium-dependent-binding motifs and an IQ-like motif for calcium-independent binding. GFP-constructs containing only NumA1 residues 1-129, lacking the DEED and CaMBDs, still localized as patches at the internal periphery of nuclei thus ruling out a direct role for the CaMBD in nuclear import. These constructs contained the amino acid residues 48 KKSYQDPEIIAHSRPRK 64 that include both a putative bipartite and classical NLS. GFP-bipartite NLS constructs localized uniformly within nuclei but not as patches. As with previous work, removal of the DEED domain resulted in highly multinucleate cells. However as shown here, multinuclearity only occurred when the NLS was present allowing the protein to enter nuclei. Site-directed mutation analysis in which the NLS was changed to 48 EF 49 abolished the stability of the GFP fusion at the protein but not RNA level preventing subcellular analyses. Cells transfected with the 48 EF 49 construct exhibited slowed growth when compared to parental AX3 cells and other GFP-NumA1 deletion mutants. In addition to identifying an NLS that is sufficient for nuclear translocation of nucleomorphin and ruling out CaM-binding in this event, this work shows that the nuclear localization of NumA1 is crucial to its ability to regulate nuclear number in Dictyostelium

Scyphophyllidium uruguayense n. sp. (Eucestoda: Tetraphyllidea) in Mustelus mento (Cope, 1877) (Chondrichthyes: Carcharhiniformes: Triakidae) from La Paloma, Uruguay.

Science.gov (United States)

Brooks, D R; Marques, F; Perroni, C; Sidagis, C

1999-06-01

A new species of Scyphophyllidium inhabits Mustelus mento near La Paloma, Uruguay. It resembles Scyphophyllidium giganteum from the Atlantic Ocean and specimens identified as S. giganteum from California by having anapolytic strobilae 155-258 mm long, 250-300 craspedote proglottids, scoleces 1.2-1.4 mm wide, necks 34-41 mm long, immature and mature proglottids wider than long, gravid proglottids wider than long to longer than wide, genital pores averaging 28% of proglottid length from the anterior end, relatively flat ovaries with digitiform lobes reaching the lateralmost extent of the testicular field, vitellaria in 2 fields converging toward the proglottid midline, straight and short cirrus sacs, and postvaginal vas deferens. The bothridia of the new species have accessory bothridial suckers that are smaller than those of California specimens; European specimens reportedly lack accessory bothridial suckers. The new species possesses a uterine duct that joins the uterus at the level of the genital atrium and ventral osmoregulatory ducts medial rather than lateral to the dorsal ducts, an arrangement described for Californian but not European specimens. It differs from both European and Californian specimens by having longer cirri, more testes per proglottid, prominent scales covering the neck, and vaginae and uterine ducts coiled immediately preovarially. Pithophorus, Marsupiobothrium, and Scyphophyllidium may form a clade.

Response of sphagnum peatland testate amoebae to a 1-year transplantation experiment along an artificial hydrological gradient.

Science.gov (United States)

Marcisz, Katarzyna; Fournier, Bertrand; Gilbert, Daniel; Lamentowicz, Mariusz; Mitchell, Edward A D

2014-05-01

Peatland testate amoebae (TA) are well-established bioindicators for depth to water table (DWT), but effects of hydrological changes on TA communities have never been tested experimentally. We tested this in a field experiment by placing Sphagnum carpets (15 cm diameter) collected in hummock, lawn and pool microsites (origin) at three local conditions (dry, moist and wet) using trenches dug in a peatland. One series of samples was seeded with microorganism extract from all microsites. TA community were analysed at T0: 8-2008, T1: 5-2009 and T2: 8-2009. We analysed the data using conditional inference trees, principal response curves (PRC) and DWT inferred from TA communities using a transfer function used for paleoecological reconstruction. Density declined from T0 to T1 and then increased sharply by T2. Species richness, Simpson diversity and Simpson evenness were lower at T2 than at T0 and T1. Seeded communities had higher species richness in pool samples at T0. Pool samples tended to have higher density, lower species richness, Simpson diversity and Simpson Evenness than hummock and/or lawn samples until T1. In the PRC, the effect of origin was significant at T0 and T1, but the effect faded away by T2. Seeding effect was strongest at T1 and lowest vanished by T2. Local condition effect was strong but not in line with the wetness gradient at T1 but started to reflect it by T2. Likewise, TA-inferred DWT started to match the experimental conditions by T2, but more so in hummock and lawn samples than in pool samples. This study confirmed that TA responds to hydrological changes over a 1-year period. However, sensitivity of TA to hydrological fluctuations, and thus the accuracy of inferred DWT changes, was habitat specific, pool TA communities being least responsive to environmental changes. Lawns and hummocks may be thus better suited than pools for paleoecological reconstructions. This, however, contrasts with the higher prediction error and species' tolerance for

Efecto de la estructuración por macrófitas y por recursos alimentarios en la distribución horizontal de tecamebas y rotíferos en un lago andino patagónico Effect of macrophytes and food resources on the horizontal distribution of testate amoebae and rotifers in an Andean-Patagonian lake

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MARCELA BASTIDAS-NAVARRO

2007-09-01

con el aumento de la abundancia de la cianofita Coelosphaerium kuetzingianum. Las diferencias señaladas indican que los recursos alimentarios serían un factor determinante en la distribución de especies de tecamebas y rotíferos en el lago Escondido. Para estos zoopláncteres de pequeño tamaño las macrófitas litorales brindarían alimento al favorecer el incremento del fitoplancton de redThe presence of macrophytes in the littoral zone of lakes produces particular conditions including higher resource availability for consumers. For this reason, the littoral zone is generally the area with the highest diversity of lakes and rivers. In this work we studied the horizontal distribution of testate amoebae and rotifers in Lago Escondido (Argentina in relation to food resources availability. The study was carried out along a north-south transect that includes the littoral and the pelagic zone of the lake. Phytoplankton and zooplankton were sampled during summer and spring (2001-2003 in five sampling stations: one pelagic and four littoral. Rotifers and testate amoebae, as well as phytoplanktonic algae abundance and biomass were estimated. Food resources were classified as nanoplankton ( 20 μm and the biovolume of these fractions varied significantly within the pelagic and littoral zones of the lake. Nanoplankon dominated the pelagic zone and was mainly composed by nanoflagellates while net phytoplankton prevailed in the littoral zone and was composed by diatoms, cyanophytes and chlorophytes. The highest number of species and diversity of testate amoebae and rotifers were observed in the littoral stations; nevertheless, no significant differences between the zones colonized by different macrophytes were observed. The CCA analysis showed four different groups. Keratella cochlearis, Synchaeta spp., Polyarthra vulgaris and Collotheca mutabilis characterized the pelagic samples and were related with a high abundance of nanoplankton. On the other hand, rotifers like

Species richness of testate amoebae in different environments from the upper Paraná river floodplain (PR/MS = Riqueza de amebas testáceas em diferentes ambientes da planície de inundação do alto rio Paraná (PR/MS

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Deise de Morais Costa

2011-07-01

Full Text Available This study evaluated the species richness of testate amoebae in the plankton from different environments of the upper Parana river floodplain. Samplings were performed at subsurface of pelagic region from twelve environments using motorized pump and plankton net (68 ƒÝm, during four hydrological periods. We identified 67 taxa, distributed in seven families and Arcellidae, Difflugiidae and Centropyxidae were the most representative families. Higher values of species richness were observed in the lakes (connected and isolated during the flood pulses. Centropyxis aculeata, Difflugia gramem and D.pseudogramem were frequent throughout the study period. Seasonal variability of species in the channels and isolated lakes was evidenced by beta diversity. Besides that, in the rivers, extreme changes in species composition were verified during the high-water period. Our results highlight the importance of the present study to improve the knowledge about the diversity and geographic distribution of these organisms in Brazil and emphasize the importance of current flow in the displacement of testate amoebae from their preferredhabitats, marginal vegetation and sediment.Este estudo objetivou avaliar a riqueza de taxons de amebas testaceas no plancton de diferentes ambientes da planicie de inundacao do alto rio Parana. Foram amostrados 12 pontos da regiao pelagica em diferentes ambientes (rios, canais e lagoas e em quatro periodos hidrologicos. Foram identificados 67 taxons, distribuidos em sete familias. Arcellidae, Difflugiidae e Centropyxidae foram as familiasmais especiosas. Nas lagoas (abertas e fechadas, durante os pulsos de inundacao, foram observados os maiores valores para a riqueza de especies. Centropyxis aculeata, Difflugia gramem e D. pseudogramem foram frequentes durante todo o periodo estudado. Os dados obtidos pela diversidade beta evidenciaram a variabilidade sazonal das especies nos canais e lagoas fechadas. Nos rios, as alteracoes

Heterogeneity in the genus Allovahlkampfia and the description of the new genus Parafumarolamoeba (Vahlkampfiidae; Heterolobosea)

NARCIS (Netherlands)

Geisen, Stefan; Bonkowski, Michael; Zhang, Junling; De Jonckheere, Johan F.

Abstract Heterolobosean amoebae are common and diverse members of soil protist communities. In this study, we isolated seven strains of amoebae from soil samples taken in Tibet (at high altitude), Sardinia and the Netherlands, all resembling to belong to a similar heterolobosean morphospecies.

Long-term survival of Naegleria polaris from Antarctica after 10 years of storage at 4 °C.

Science.gov (United States)

Matsuo, Junji; Nakamura, Shinji; Okubo, Torahiko; Fukui, Manabu; Yamaguchi, Hiroyuki

2018-03-01

A free-living amoeba, Naegleria is ubiquitously distributed in various natural environments. Since some Naegleria spp. are exclusively distributed in the Arctic and sub-Antarctic regions, we hypothesized that the amoeba may be useful to determine long-term survival of Naegleria in laboratory conditions at 4 °C. The main objective of the study is to determine that a species of an environmental amoebal isolated can live at low temperatures after a long time. Here, we therefore show long-term survival of an amoeba, Naegleria polaris isolated from a sediment sample, which was collected from Antarctica 10 years ago, and since stored at 4 °C. The sample was put on non-nutrient agar plates with heat-killed Escherichia coli, and then the plate was incubated at 4, 15, or 30 °C. Motile amoebae were seen only when the plate was incubated at 15 °C. The sequencing of ribosomal DNA including internal transcribed spacers (ITS) 1, 5.8S rDNA, and ITS2 region revealed the amoebae to be N. polaris, which is exclusively distributed in the Arctic and sub-Antarctic regions. Scanning electron microscopic observation showed that no typical sucker-like structure was seen on the surface of N. polaris, but the cysts were similar to those of Naegleria fowleri. Thus, our result shows, for the first time, that N. polaris can survive after 10 years of storage at 4 °C. This finding may help us understand the still undescribed effects of environmental samples on viability of amoebae.

Journal of Biosciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

However, our studies have shown that amoebae and giardia contain splicoeosomal introns, ras-family signal-transduction proteins, ATP-binding casettes (ABC)-family drug transporters, Golgi, and a mitochondrion-derived organelle (amoebae only). These results suggest that most of the organelles of higher eukaryotes ...

[Detection and differentiation of Entamoeba histolytica and Entamoeba dispar by polymerase chain reaction in a community in Zulia State, Venezuela].

Science.gov (United States)

Rivero, Zulbey; Bracho, Angela; Calchi, Marinella; Díaz, Iris; Acurero, Ellen; Maldonado, Adriana; Chourio, Glenis; Arráiz, Nailet; Corzo, Gilbert

2009-01-01

Differential identification of Entamoeba histolytica and Entamoeba dispar is essential for both appropriate patient treatment and epidemiological purposes. To determine the prevalence of these amoeba infections in Santa Rosa de Agua (Maracaibo, Zulia State, Venezuela), a PCR assay using specific primers for each species was standardized and applied. 204 stool samples were analyzed through direct microscopic examination with SSF (0.85%) and lugol, formol-ether concentration, and PCR. Under direct microscopy, 42 individuals (20.58%) presented the E. histolytica/E. dispar complex. Meanwhile PCR showed 47 positive cases for these amoebas: 22 E. histolytica (10.78%), 16 E. dispar (7.84%), and 9 (4.41%) mixed infections. There was no significant difference in the presence of E. histolytica and/or E. dispar according to either gender or age. There were no cases of these amoebas in children under 2 years of age. Observed frequency of E. histolytica (31/204) shows the endemic nature of amoeba infection in this community.

Fitness Trade-offs Result in the Illusion of Social Success.

Science.gov (United States)

Wolf, Jason B; Howie, Jennifer A; Parkinson, Katie; Gruenheit, Nicole; Melo, Diogo; Rozen, Daniel; Thompson, Christopher R L

2015-04-20

Cooperation is ubiquitous across the tree of life, from simple microbes to the complex social systems of animals. Individuals cooperate by engaging in costly behaviors that can be exploited by other individuals who benefit by avoiding these associated costs. Thus, if successful exploitation of social partners during cooperative interactions increases relative fitness, then we expect selection to lead to the emergence of a single optimal winning strategy in which individuals maximize their gain from cooperation while minimizing their associated costs. Such social "cheating" appears to be widespread in nature, including in several microbial systems, but despite the fitness advantages favoring social cheating, populations tend to harbor significant variation in social success rather than a single optimal winning strategy. Using the social amoeba Dictyostelium discoideum, we provide a possible explanation for the coexistence of such variation. We find that genotypes typically designated as "cheaters" because they produce a disproportionate number of spores in chimeric fruiting bodies do not actually gain higher fitness as a result of this apparent advantage because they produce smaller, less viable spores than putative "losers." As a consequence of this trade-off between spore number and viability, genotypes with different spore production strategies, which give the appearance of differential social success, ultimately have similar realized fitness. These findings highlight the limitations of using single fitness proxies in evolutionary studies and suggest that interpreting social trait variation in terms of strategies like cheating or cooperating may be misleading unless these behaviors are considered in the context of the true multidimensional nature of fitness. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Dissipative structures and biological rhythms

Science.gov (United States)

Goldbeter, Albert

2017-10-01

Sustained oscillations abound in biological systems. They occur at all levels of biological organization over a wide range of periods, from a fraction of a second to years, and with a variety of underlying mechanisms. They control major physiological functions, and their dysfunction is associated with a variety of physiological disorders. The goal of this review is (i) to give an overview of the main rhythms observed at the cellular and supracellular levels, (ii) to briefly describe how the study of biological rhythms unfolded in the course of time, in parallel with studies on chemical oscillations, (iii) to present the major roles of biological rhythms in the control of physiological functions, and (iv) the pathologies associated with the alteration, disappearance, or spurious occurrence of biological rhythms. Two tables present the main examples of cellular and supracellular rhythms ordered according to their period, and their role in physiology and pathophysiology. Among the rhythms discussed are neural and cardiac rhythms, metabolic oscillations such as those occurring in glycolysis in yeast, intracellular Ca++ oscillations, cyclic AMP oscillations in Dictyostelium amoebae, the segmentation clock that controls somitogenesis, pulsatile hormone secretion, circadian rhythms which occur in all eukaryotes and some bacteria with a period close to 24 h, the oscillatory dynamics of the enzymatic network driving the cell cycle, and oscillations in transcription factors such as NF-ΚB and tumor suppressors such as p53. Ilya Prigogine's concept of dissipative structures applies to temporal oscillations and allows us to unify within a common framework the various rhythms observed at different levels of biological organization, regardless of their period and underlying mechanism.

Molybdate transporter ModABC is important for Pseudomonas aeruginosa chronic lung infection.

Science.gov (United States)

Périnet, Simone; Jeukens, Julie; Kukavica-Ibrulj, Irena; Ouellet, Myriam M; Charette, Steve J; Levesque, Roger C

2016-01-12

Mechanisms underlying the success of Pseudomonas aeruginosa in chronic lung infection among cystic fibrosis (CF) patients are poorly defined. The modA gene was previously linked to in vivo competitiveness of P. aeruginosa by a genetic screening in the rat lung. This gene encodes a subunit of transporter ModABC, which is responsible for extracellular uptake of molybdate. This compound is essential for molybdoenzymes, including nitrate reductases. Since anaerobic growth conditions are known to occur during CF chronic lung infection, inactivation of a molybdate transporter could inhibit proliferation through the inactivation of denitrification enzymes. Hence, we performed phenotypic characterization of a modA mutant strain obtained by signature-tagged mutagenesis (STM_modA) and assessed its virulence in vivo with two host models. The STM_modA mutant was in fact defective for anaerobic growth and unable to use nitrates in the growth medium for anaerobic respiration. Bacterial growth and nitrate usage were restored when the medium was supplemented with molybdate. Most significantly, the mutant strain showed reduced virulence compared to wild-type strain PAO1 according to a competitive index in the rat model of chronic lung infection and a predation assay with Dictyostelium discoideum amoebae. As the latter took place in aerobic conditions, the in vivo impact of the mutation in modA appears to extend beyond its effect on anaerobic growth. These results support the modABC-encoded transporter as important for the pathogenesis of P. aeruginosa, and suggest that enzymatic machinery implicated in anaerobic growth during chronic lung infection in CF merits further investigation as a potential target for therapeutic intervention.

Dicty_cDB: SLH678 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available SL (Link to library) SLH678 (Link to dictyBase) - - - Contig-U04159-1 SLH678E (Link... to Original site) - - - - - - SLH678E 373 Show SLH678 Library SL (Link to library) Clone ID SLH678 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U04159-1 Original site URL http://dict... producing significant alignments: (bits) Value N ( AU039970 ) Dictyostelium discoideum slug cDNA, clone SLG...865. 323 e-129 2 ( AU039381 ) Dictyostelium discoideum slug cDNA, clone SLH678. 3

Dicty_cDB: SSC836 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available SS (Link to library) SSC836 (Link to dictyBase) - - - - SSC836E (Link to Original s...ite) - - - - - - SSC836E 502 Show SSC836 Library SS (Link to library) Clone ID SSC836 (Link to dictyBase) Atlas ID - NBRP ID - dict...yBase ID - Link to Contig - Original site URL http://dictycdb.biol.tsukuba.ac.jp/CSM/...t alignments: (bits) Value N M77492 |M77492.1 Dictyostelium discoideum glycoprotein phosphorylase 2 (glpD) g...ene, complete cds. 779 0.0 1 AC116984 |AC116984.2 Dictyostelium discoideum chromo

Dicty_cDB: SLD420 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available SL (Link to library) SLD420 (Link to dictyBase) - - - Contig-U16325-1 SLD420E (Link... to Original site) - - - - - - SLD420E 434 Show SLD420 Library SL (Link to library) Clone ID SLD420 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16325-1 Original site URL http://dict... 7 Homology vs DNA Score E Sequences producing significant alignments: (bits) Value N ( AF066071 ) Dict...yostelium discoideum SP85 (pspB) gene, comple... 860 0.0 1 ( AC117075 ) Dictyostelium

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB585 (Link to dictyBase) - - - Contig-U09875-1 VFB585Z (Link... to Original site) - - VFB585Z 664 - - - - Show VFB585 Library VF (Link to library) Clone ID VFB585 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U09875-1 Original site URL http://dict...Score E Sequences producing significant alignments: (bits) Value N AC116551 |AC116551.2 Dictyostelium discoi...ces producing significant alignments: (bits) Value AC116551_43( AC116551 |pid:none) Dictyostelium discoideum

Dicty_cDB: Contig-U15060-1 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available 000227 |pid:none) Bacillus cereus Q1, complete ge... 114 3e-23 B83991( B83991 ) glycolate oxidase subunit BH2730 [imported...ana interm... 56 2e-15 5 ( AF211126 ) Carsonella ruddii natural-host Bactericera cocker....psnkfvpqrlfqq*fvf tiqrkln*vllgnqvkvl*vnsqvqwlksifitfvplisrmfvslslvskvqrrl*isie lqfsissprmlplv*vlllvklgpkkdmi... la... 1074 0.0 1 ( AB000109 ) Dictyostelium discoideum mitochondrial DNA, compl... 1074 0.0 1 ( BJ412759 ) Dictyosteli...7, 3' ... 731 0.0 1 ( DQ336395 ) Dictyostelium citrinum mitochondrion, complete ge... 456 0.0 3 ( BJ387435 ) Dictyosteli

An Assessment of Sub-Meter Scale Spatial Variability of Arcellinida (Testate Lobose Amoebae) Assemblages in a Temperate Lake: Implications for Limnological Studies.

Science.gov (United States)

Steele, Riley E; Nasser, Nawaf A; Patterson, R Timothy; Gregory, Braden R B; Roe, Helen M; Reinhardt, Eduard G

2018-03-04

Arcellinida (testate lobose amoebae), a group of benthic protists, were examined from 46 sediment-water interface samples collected from oligotrophic Oromocto Lake, New Brunswick, Canada. To assess (1) assemblage homogeneity at a sub-meter spatial scale and (2) the necessity for collecting samples from multiple stations during intra-lake surveys; multiple samples were collected from three stations (quadrats 1, 2, and 3) across the north basin of Oromocto Lake, with quadrat 1 (n = 16) being the furthest to the west, quadrat 2 (n = 15) situated closer to the center of the basin, and quadrat 3 (n = 15) positioned 300 m south of the mouth of Dead Brook, an inlet stream. Results from cluster analysis and non-metric multidimensional scaling (NMDS) analysis identified two major Arcellinida assemblages, A1 and A2, the latter containing two sub-assemblages (A2a and A2b). Redundancy analysis and variance partitioning results indicated that seven statistically significant environmental variables (K, S, Sb, Ti, Zn, Fe, and Mn) explained 41.5% of the total variation in the Arcellinida distribution. Iron, Ti and K, indicators of detrital runoff, had the greatest influence on assemblage variance. The results of this study reveal that closely spaced samples (~ 10 cm) in an open-water setting are comprised of homogenous arcellinidan assemblages, indicating that replicate sampling is not required. The results, however, must be tempered with respect to the various water properties and physical characteristics that comprise individual lakes as collection of several samples may likely be necessary when sampling multiple sites of a lake basin characterized by varying water depths (e.g., littoral zone vs. open water), or lakes impacted by geogenic or anthropogenic stressors (e.g., eutrophication, or industrial contamination).

Molecular Detection of Legionella spp. and their associations with Mycobacterium spp., Pseudomonas aeruginosa and amoeba hosts in a drinking water distribution system.

Science.gov (United States)

Lu, J; Struewing, I; Vereen, E; Kirby, A E; Levy, K; Moe, C; Ashbolt, N

2016-02-01

This study investigated waterborne opportunistic pathogens (OPs) including potential hosts, and evaluated the use of Legionella spp. for indicating microbial water quality for OPs within a full-scale operating drinking water distribution system (DWDS). To investigate the occurrence of specific microbial pathogens within a major city DWDS we examined large volume (90 l drinking water) ultrafiltration (UF) concentrates collected from six sites between February, 2012 and June, 2013. The detection frequency and concentration estimates by qPCR were: Legionella spp. (57%/85 cell equivalent, CE l(-1) ), Mycobacterium spp. (88%/324 CE l(-1) ), Pseudomonas aeruginosa (24%/2 CE l(-1) ), Vermamoeba vermiformis (24%/2 CE l(-1) ) and Acanthamoeba spp. (42%/5 cyst equivalent, CE l(-1) ). There was no detection of the following microorganisms: human faecal indicator Bacteroides (HF183), Salmonella enterica, Campylobacter spp., Escherichia coli O157:H7, Giardia intestinalis, Cryptosporidium spp. or Naegleria fowleri. There were significant correlations between the qPCR signals of Legionella spp. and Mycobacterium spp., and their potential hosts V. vermiformis and Acanthamoeba spp. Sequencing of Legionella spp. demonstrated limited diversity, with most sequences coming from two dominant groups, of which the larger dominant group was an unidentified species. Other known species including Legionella pneumophila were detected, but at low frequency. The densities of Legionella spp. and Mycobacterium spp. were generally higher (17 and 324 folds, respectively) for distal sites relative to the entry point to the DWDS. Legionella spp. occurred, had significant growth and were strongly associated with free-living amoebae (FLA) and Mycobacterium spp., suggesting that Legionella spp. could provide a useful DWDS monitoring role to indicate potential conditions for non-faecal OPs. The results provide insight into microbial pathogen detection that may aid in the monitoring of microbial water

Prevalence of pathogenic free-living amoeba and other protozoa in natural and communal piped tap water from Queen Elizabeth protected area, Uganda.

Science.gov (United States)

Sente, Celsus; Erume, Joseph; Naigaga, Irene; Mulindwa, Julius; Ochwo, Sylvester; Magambo, Phillip Kimuda; Namara, Benigna Gabriela; Kato, Charles Drago; Sebyatika, George; Muwonge, Kevin; Ocaido, Michael

2016-08-03

Pathogenic water dwelling protozoa such as Acanthamoeba spp., Hartmannella spp., Naegleria spp., Cryptosporidium spp. and Giardia spp. are often responsible for devastating illnesses especially in children and immunocompromised individuals, yet their presence and prevalence in certain environment in sub-Saharan Africa is still unknown to most researchers, public health officials and medical practitioners. The objective of this study was to establish the presence and prevalence of pathogenic free-living amoeba (FLA), Cryptosporidium and Giardia in Queen Elizabeth Protected Area (QEPA). Samples were collected from communal taps and natural water sites in QEPA. Physical water parameters were measured in situ. The samples were processed to detect the presence of FLA trophozoites by xenic cultivation, Cryptosporidium oocysts by Ziehl-Neelsen stain and Giardia cysts by Zinc Sulphate floatation technique. Parasites were observed microscopically, identified, counted and recorded. For FLA, genomic DNA was extracted for amplification and sequencing. Both natural and tap water sources were contaminated with FLA, Cryptosporidium spp. and Giardia spp. All protozoan parasites were more abundant in the colder rainy season except for Harmannella spp. and Naegleria spp. which occurred more in the warmer months. The prevalence of all parasites was higher in tap water than in natural water samples. There was a strong negative correlation between the presence of Acanthamoeba spp., Hartmannella spp., Cryptosporidium spp. and Giardia spp. with Dissolved Oxygen (DO) (P protozoa that could possibly be the cause of a number of silent morbidities and mortalities among rural households in QEPA. This implies that water used by communities in QEPA is of poor quality and predisposes them to a variety of protozoan infections including the FLA whose public health importance was never reported, thus necessitating adoption of proper water safety measures.

How could sympatric megaherbivores coexist? Example of niche partitioning within a proboscidean community from the Miocene of Europe

Science.gov (United States)

Calandra, Ivan; Göhlich, Ursula B.; Merceron, Gildas

2008-09-01

Although low in diversity, megaherbivores (mammals weighting over 103 kg) and especially proboscideans have a powerful impact on the structure and dynamics of present-day ecosystems. During the Neogene (23 to 2.6 Ma) of Europe, the diversity and geographic distribution of these megaherbivores was much greater. Nonetheless, their role in past ecosystems is unclear. Nutrition is one of the main bonds between organisms and their environment. Therefore, the ecology of organisms can be inferred from their dietary habits. The present study is aimed at characterizing the feeding habits of diverse megaherbivores through dental microwear analyses. This method was applied on cheek teeth of three sympatric species of proboscideans from the middle/late Miocene of the Molasse Basin in Southern Germany: Gomphotherium subtapiroideum, Gomphotherium steinheimense, and Deinotherium giganteum. The microwear signatures are significantly different between these taxa, suggesting differences in feeding habits and ecological niches within a woodland environment. D. giganteum probably browsed on dicotyledonous foliages whereas the two species of gomphotheres were neither strict grazers nor strict browsers and instead probably fed on a large spectrum of vegetal resources. The differences of occlusal molar morphology between the two gomphotheres are supported by the dental microwear pattern. Indeed, G. subtapiroideum probably ingested more abrasive material than G. steinheimense. Thus, our results suggest that these proboscideans did not compete for food resources.

La cola de caballo (Equisetum, Equisetaceae comercializada y exportada del Perú

Directory of Open Access Journals (Sweden)

Blanca León

2013-06-01

Full Text Available Varios productos derivados de plantas se exportan del Perú como suplementos nutricionales, condimentos y otros usos, entre estos últimos tipos se encuentra el helecho “cola de caballo”. Tres nombres se emplean en el comercio: Equisetum arvense, E. bogotensey “E. hiemale”, los cuales no corresponden a las plantas exportadas, las que en cambio son E. giganteum, una especie reconocible por detalles morfológicos en sus ejes, ornamentación y distribución de sus estomas.

Polarization and charge transfer in the hydration of chloride ions

International Nuclear Information System (INIS)

Zhao Zhen; Rogers, David M.; Beck, Thomas L.

2010-01-01

A theoretical study of the structural and electronic properties of the chloride ion and water molecules in the first hydration shell is presented. The calculations are performed on an ensemble of configurations obtained from molecular dynamics simulations of a single chloride ion in bulk water. The simulations utilize the polarizable AMOEBA force field for trajectory generation and MP2-level calculations are performed to examine the electronic structure properties of the ions and surrounding waters in the external field of more distant waters. The ChelpG method is employed to explore the effective charges and dipoles on the chloride ions and first-shell waters. The quantum theory of atoms in molecules (QTAIM) is further utilized to examine charge transfer from the anion to surrounding water molecules. The clusters extracted from the AMOEBA simulations exhibit high probabilities of anisotropic solvation for chloride ions in bulk water. From the QTAIM analysis, 0.2 elementary charges are transferred from the ion to the first-shell water molecules. The default AMOEBA model overestimates the average dipole moment magnitude of the ion compared to the quantum mechanical value. The average magnitude of the dipole moment of the water molecules in the first shell treated at the MP2-level, with the more distant waters handled with an AMOEBA effective charge model, is 2.67 D. This value is close to the AMOEBA result for first-shell waters (2.72 D) and is slightly reduced from the bulk AMOEBA value (2.78 D). The magnitude of the dipole moment of the water molecules in the first solvation shell is most strongly affected by the local water-water interactions and hydrogen bonds with the second solvation shell, rather than by interactions with the ion.

Dicty_cDB: SSB373 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available SS (Link to library) SSB373 (Link to dictyBase) - G00609 DDB0216216 Contig-U04543-1...nk to library) Clone ID SSB373 (Link to dictyBase) Atlas ID - NBRP ID G00609 dictyBase ID DDB0216216 Link to... Contig Contig-U04543-1 Original site URL http://dictycdb.biol.tsukuba.ac.jp/CSM/...Value N AB016728 |AB016728.1 Dictyostelium discoideum sapA mRNA for saposin A, co... 44 7e-04 12 AC116330 |AC116330.2 Dictyostelium discoideum chromosome 2 map 3191214-3323468 strain AX4, comp

Dicty_cDB: CFE853 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available CF (Link to library) CFE853 (Link to dictyBase) - - - Contig-U16381-1 CFE853F (Link... to Original site) CFE853F 109 - - - - - - Show CFE853 Library CF (Link to library) Clone ID CFE853 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16381-1 Original site URL http://dict...uences producing significant alignments: (bits) Value N X51892 |X51892.1 Dictyost...elium discoideum SP60 gene for spore coat protein. 80 6e-21 2 X52105 |X52105.1 Dictyostelium discoideum SP60

Dicty_cDB: CFH668 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available CF (Link to library) CFH668 (Link to dictyBase) - - - Contig-U13860-1 - (Link to Or...iginal site) - - CFH668Z 651 - - - - Show CFH668 Library CF (Link to library) Clone ID CFH668 (Link to dicty...Base) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U13860-1 Original site URL http://dictycdb.b...s) Value N AC116987 |AC116987.2 Dictyostelium discoideum chromosome 2 map 3527441-3568052 strain AX4, comple...te sequence. 58 1e-11 6 AC116305 |AC116305.2 Dictyostelium discoideum chromosome

Dicty_cDB: AFL826 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available AF (Link to library) AFL826 (Link to dictyBase) - - - - AFL826P (Link to Original s...ite) AFL826F 588 AFL826Z 766 AFL826P 1334 - - Show AFL826 Library AF (Link to library) Clone ID AFL826 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig - Original site URL http://dictycdb.biol.t... Score E Sequences producing significant alignments: (bits) Value N ( BJ346543 ) Dictyostelium discoideum cD...NA clone:dda24d08, 3' ... 1100 0.0 1 ( BJ341682 ) Dictyostelium discoideum cDNA c

Dicty_cDB: AFL289 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available AF (Link to library) AFL289 (Link to dictyBase) - - - - AFL289F (Link to Original s...ite) AFL289F 123 - - - - - - Show AFL289 Library AF (Link to library) Clone ID AFL289 (Link to dictyBase) Atlas ID - NBRP ID - dict...yBase ID - Link to Contig - Original site URL http://dictycdb.biol.tsukuba.ac.jp/CSM/... E Sequences producing significant alignments: (bits) Value N X51892 |X51892.1 Dict...yostelium discoideum SP60 gene for spore coat protein. 82 5e-29 2 X52105 |X52105.1 Dictyostelium discoideu

Dicty_cDB: AFK740 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available AF (Link to library) AFK740 (Link to dictyBase) - - - Contig-U16381-1 AFK740F (Link... to Original site) AFK740F 107 - - - - - - Show AFK740 Library AF (Link to library) Clone ID AFK740 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16381-1 Original site URL http://dict...es producing significant alignments: (bits) Value N X51892 |X51892.1 Dictyosteliu...m discoideum SP60 gene for spore coat protein. 80 6e-21 2 X52105 |X52105.1 Dictyostelium discoideum SP60 gen

Dicty_cDB: SLF689 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available SL (Link to library) SLF689 (Link to dictyBase) - - - Contig-U16284-1 SLF689Z (Link... to Original site) - - SLF689Z 320 - - - - Show SLF689 Library SL (Link to library) Clone ID SLF689 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16284-1 Original site URL http://dict...DNA Score E Sequences producing significant alignments: (bits) Value N ( AC116305 ) Dictyostelium discoideum... chromosome 2 map 1005175... 478 e-131 1 ( AU053477 ) Dictyostelium discoideum slug cDNA, clone SLI726. 478 e-131 1 ( AU053102 ) Dict

Dicty_cDB: CFH744 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available CF (Link to library) CFH744 (Link to dictyBase) - - - Contig-U16381-1 - (Link to Or...iginal site) CFH744F 118 - - - - - - Show CFH744 Library CF (Link to library) Clone ID CFH744 (Link to dicty...Base) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16381-1 Original site URL http://dictycdb.b...ng significant alignments: (bits) Value N X51892 |X51892.1 Dictyostelium discoide...um SP60 gene for spore coat protein. 80 1e-23 3 AC115685 |AC115685.1 Dictyostelium discoideum chromosome 2 m

Dicty_cDB: VHI285 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VH (Link to library) VHI285 (Link to dictyBase) - - - Contig-U16073-1 - (Link to Or...iginal site) VHI285F 136 - - - - - - Show VHI285 Library VH (Link to library) Clone ID VHI285 (Link to dicty...Base) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16073-1 Original site URL http://dictycdb.b... DNA Score E Sequences producing significant alignments: (bits) Value N ( BJ423035 ) Dict...yostelium discoideum cDNA clone:ddv47i22, 5' ... 72 2e-27 3 ( BJ419916 ) Dictyostelium discoideum cD

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFC154 (Link to dictyBase) - - - Contig-U16363-1 VFC154Z (Link... to Original site) - - VFC154Z 551 - - - - Show VFC154 Library VF (Link to library) Clone ID VFC154 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16363-1 Original site URL http://dict...s: (bits) Value N U82513 |U82513.1 Dictyostelium discoideum random slug cDNA25 protein (rsc25) mRNA, partial...producing significant alignments: (bits) Value U82513_1( U82513 |pid:none) Dictyostelium discoideum random s

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB614 (Link to dictyBase) - - - Contig-U16382-1 VFB614Z (Link... to Original site) - - VFB614Z 219 - - - - Show VFB614 Library VF (Link to library) Clone ID VFB614 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16382-1 Original site URL http://dict...ments: (bits) Value N AC116957 |AC116957.2 Dictyostelium discoideum chromosome 2 ...tin mRNA ITL-1, 3' end. 339 9e-90 1 AC116986 |AC116986.2 Dictyostelium discoideum chromosome 2 map 2234041-2

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFC129 (Link to dictyBase) - - - Contig-U16543-1 VFC129F (Link... to Original site) VFC129F 276 - - - - - - Show VFC129 Library VF (Link to library) Clone ID VFC129 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16543-1 Original site URL http://dict... vs DNA Score E Sequences producing significant alignments: (bits) Value N M91382 |M91382.1 Dictyostelium di...scoideum thioredoxin (TRX2) mRNA, 5' end. 281 2e-96 3 M91384 |M91384.1 Dictyostelium discoideum thioredoxin

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFC191 (Link to dictyBase) - - - Contig-U16281-1 VFC191F (Link... to Original site) VFC191F 350 - - - - - - Show VFC191 Library VF (Link to library) Clone ID VFC191 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16281-1 Original site URL http://dict...ts) Value N AC116305 |AC116305.2 Dictyostelium discoideum chromosome 2 map 1005175-1418323 strain AX4, compl... 186 3e-46 AC116305_8( AC116305 |pid:none) Dictyostelium discoideum chromosom...

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB662 (Link to dictyBase) - - - Contig-U15118-1 VFB662E (Link...) Clone ID VFB662 (Link to dictyBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U15118-1 Ori... significant alignments: (bits) Value N AF039211 |AF039211.1 Dictyostelium discoideum ADP/ATP translocase mR...NA, complete cds. 1011 0.0 2 AF100676 |AF100676.1 Dictyostelium discoideum ADP/ATP translocase gene, complet...drial 4.0 %: extracellular, including cell wall 4.0 %: vacuolar 4.0 %: vesicles of secretory system >> predict

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB843 (Link to dictyBase) - - - Contig-U15729-1 VFB843F (Link... to Original site) VFB843F 566 - - - - - - Show VFB843 Library VF (Link to library) Clone ID VFB843 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U15729-1 Original site URL http://dict...roducing significant alignments: (bits) Value N U64830 |U64830.1 Dictyostelium discoideum AX2 protein tyrosi...ne kinase gene, complete cds. 1114 0.0 1 U01064 |U01064.1 Dictyostelium discoideum AX2 protein tyrosine kina

Holocene palaeohydrological history of the Tǎul Muced peat bog (Northern Carpathians, Romania) based on testate amoebae (Protozoa) and plant macrofossils

Science.gov (United States)

Cosmin Diaconu, Andrei; Feurdean, Angelica; Lamentowicz, Mariusz; Gałka, Mariusz; Tanţǎu, Ioan

2016-04-01

Knowledge of past local vs. regional hydro-climate variability is a priority in climate research. This is because ecosystems and human depend on local climatic conditions and the magnitude of these climate changes is more variable at local and regional rather than at global scales. Ombrotrophic bogs are highly suitable for hydro-climate reconstructions as they are entirely dependent on the water from precipitation. We used stratigraphy, radiocarbon dating, testate amoebae (TA) and plant macrofossils on a peat profile from an ombrotrophic bog (Tǎul Muced) located in the Biosphere Reserve of the Rodna National Park Romania. We performed quantitative reconstruction of the depth to water table (DWT) and pH over the last 8000 years in a continental area of CE Europe. We identified six main stages in the development of the bog based on changes in TA assemblages in time. Wet conditions and pH between 2 and 4.5 were recorded between 4600-2750 and 1300-400 cal. yr BP, by the occurrence of Archerella flavum, Amphitrema wrightianum and Hyalosphenia papilio. This was associated to a local vegetation primarily composed of Sphagnum magellanicum and S. angustifolium. Dry stages and pH of 2.5 to 5 were inferred between 7550-4600, 2750-1300 and -50 cal. yr BP, by the dominance of Nebela militaris, Difflugia pulex and Phryganella acropodia. These overall dry conditions were also connected with increased abundance of Eriophorum vaginatum. The period between 400 and -50 cal. yr BP was characterized by a rapid shift from dry to wet conditions on the surface of the bog. Vegetation shifted from Sphagnum magellanicum to Sphagnum russowii dominated community. Our reconstruction remains in relatively good agreement with other palaeohydrological records from Central Eastern Europe. However, it shows contrasting conditions to others particularly with records from NW Europe. The valuable information regarding bog hydrology offered by our record puts an accent on the need of more regional TA

Vernalophrys algivore gen. nov., sp. nov. (Rhizaria: Cercozoa: Vampyrellida), a New Algal Predator Isolated from Outdoor Mass Culture of Scenedesmus dimorphus.

Science.gov (United States)

Gong, Yingchun; Patterson, David J; Li, Yunguang; Hu, Zixuan; Sommerfeld, Milton; Chen, Yongsheng; Hu, Qiang

2015-06-15

Microbial contamination is the main cause of loss of biomass yield in microalgal cultures, especially under outdoor environmental conditions. Little is known about the identities of microbial contaminants in outdoor mass algal cultures. In this study, a new genus and species of vampyrellid amoeba, Vernalophrys algivore, is described from cultures of Scenedesmus dimorphus in open raceway ponds and outdoor flat-panel photobioreactors. This vampyrellid amoeba was a significant grazer of Scenedesmus and was frequently associated with a very rapid decline in algal numbers. We report on the morphology, subcellular structure, feeding behavior, molecular phylogeny, and life cycle. The new amoeba resembles Leptophrys in the shape of trophozoites and pseudopodia and in the mechanism of feeding (mainly by engulfment). It possesses two distinctive regions in helix E10_1 (nucleotides 117 to 119, CAA) and E23_1 (nucleotides 522 and 523, AG) of the 18S rRNA gene. It did not form a monophyletic group with Leptophrys in molecular phylogenetic trees. We establish a new genus, Vernalophrys, with the type species Vernalophrys algivore. The occurrence, impact of the amoeba on mass culture of S. dimorphus, and means to reduce vampyrellid amoeba contamination in Scenedesmus cultures are addressed. The information obtained from this study will be useful for developing an early warning system and control measures for preventing or treating this contaminant in microalgal mass cultures. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

The cAMP-induced G protein subunits dissociation monitored in live Dictyostelium cells by BRET reveals two activation rates, a positive effect of caffeine and potential role of microtubules.

Science.gov (United States)

Tariqul Islam, A F M; Yue, Haicen; Scavello, Margarethakay; Haldeman, Pearce; Rappel, Wouter-Jan; Charest, Pascale G

2018-08-01

To study the dynamics and mechanisms controlling activation of the heterotrimeric G protein Gα2βγ in Dictyostelium in response to stimulation by the chemoattractant cyclic AMP (cAMP), we monitored the G protein subunit interaction in live cells using bioluminescence resonance energy transfer (BRET). We found that cAMP induces the cAR1-mediated dissociation of the G protein subunits to a similar extent in both undifferentiated and differentiated cells, suggesting that only a small number of cAR1 (as expressed in undifferentiated cells) is necessary to induce the full activation of Gα2βγ. In addition, we found that treating cells with caffeine increases the potency of cAMP-induced Gα2βγ activation; and that disrupting the microtubule network but not F-actin inhibits the cAMP-induced dissociation of Gα2βγ. Thus, microtubules are necessary for efficient cAR1-mediated activation of the heterotrimeric G protein. Finally, kinetics analyses of Gα2βγ subunit dissociation induced by different cAMP concentrations indicate that there are two distinct rates at which the heterotrimeric G protein subunits dissociate when cells are stimulated with cAMP concentrations above 500 nM versus only one rate at lower cAMP concentrations. Quantitative modeling suggests that the kinetics profile of Gα2βγ subunit dissociation results from the presence of both uncoupled and G protein pre-coupled cAR1 that have differential affinities for cAMP and, consequently, induce G protein subunit dissociation through different rates. We suggest that these different signaling kinetic profiles may play an important role in initial chemoattractant gradient sensing. Copyright © 2018 Elsevier Inc. All rights reserved.

Constitutive type VI secretion system expression gives Vibrio cholerae intra- and interspecific competitive advantages.

Directory of Open Access Journals (Sweden)

Daniel Unterweger

Full Text Available The type VI secretion system (T6SS mediates protein translocation across the cell membrane of Gram-negative bacteria, including Vibrio cholerae - the causative agent of cholera. All V. cholerae strains examined to date harbor gene clusters encoding a T6SS. Structural similarity and sequence homology between components of the T6SS and the T4 bacteriophage cell-puncturing device suggest that the T6SS functions as a contractile molecular syringe to inject effector molecules into prokaryotic and eukaryotic target cells. Regulation of the T6SS is critical. A subset of V. cholerae strains, including the clinical O37 serogroup strain V52, express T6SS constitutively. In contrast, pandemic strains impose tight control that can be genetically disrupted: mutations in the quorum sensing gene luxO and the newly described regulator gene tsrA lead to constitutive T6SS expression in the El Tor strain C6706. In this report, we examined environmental V. cholerae isolates from the Rio Grande with regard to T6SS regulation. Rough V. cholerae lacking O-antigen carried a nonsense mutation in the gene encoding the global T6SS regulator VasH and did not display virulent behavior towards Escherichia coli and other environmental bacteria. In contrast, smooth V. cholerae strains engaged constitutively in type VI-mediated secretion and displayed virulence towards prokaryotes (E. coli and other environmental bacteria and a eukaryote (the social amoeba Dictyostelium discoideum. Furthermore, smooth V. cholerae strains were able to outcompete each other in a T6SS-dependent manner. The work presented here suggests that constitutive T6SS expression provides V. cholerae with an advantage in intraspecific and interspecific competition.

Stealth proteins: in silico identification of a novel protein family rendering bacterial pathogens invisible to host immune defense.

Directory of Open Access Journals (Sweden)

Peter Sperisen

2005-11-01

Full Text Available There are a variety of bacterial defense strategies to survive in a hostile environment. Generation of extracellular polysaccharides has proved to be a simple but effective strategy against the host's innate immune system. A comparative genomics approach led us to identify a new protein family termed Stealth, most likely involved in the synthesis of extracellular polysaccharides. This protein family is characterized by a series of domains conserved across phylogeny from bacteria to eukaryotes. In bacteria, Stealth (previously characterized as SacB, XcbA, or WefC is encoded by subsets of strains mainly colonizing multicellular organisms, with evidence for a protective effect against the host innate immune defense. More specifically, integrating all the available information about Stealth proteins in bacteria, we propose that Stealth is a D-hexose-1-phosphoryl transferase involved in the synthesis of polysaccharides. In the animal kingdom, Stealth is strongly conserved across evolution from social amoebas to simple and complex multicellular organisms, such as Dictyostelium discoideum, hydra, and human. Based on the occurrence of Stealth in most Eukaryotes and a subset of Prokaryotes together with its potential role in extracellular polysaccharide synthesis, we propose that metazoan Stealth functions to regulate the innate immune system. Moreover, there is good reason to speculate that the acquisition and spread of Stealth could be responsible for future epidemic outbreaks of infectious diseases caused by a large variety of eubacterial pathogens. Our in silico identification of a homologous protein in the human host will help to elucidate the causes of Stealth-dependent virulence. At a more basic level, the characterization of the molecular and cellular function of Stealth proteins may shed light on fundamental mechanisms of innate immune defense against microbial invasion.

Stealth Proteins: In Silico Identification of a Novel Protein Family Rendering Bacterial Pathogens Invisible to Host Immune Defense.

Directory of Open Access Journals (Sweden)

2005-11-01

Full Text Available There are a variety of bacterial defense strategies to survive in a hostile environment. Generation of extracellular polysaccharides has proved to be a simple but effective strategy against the host's innate immune system. A comparative genomics approach led us to identify a new protein family termed Stealth, most likely involved in the synthesis of extracellular polysaccharides. This protein family is characterized by a series of domains conserved across phylogeny from bacteria to eukaryotes. In bacteria, Stealth (previously characterized as SacB, XcbA, or WefC is encoded by subsets of strains mainly colonizing multicellular organisms, with evidence for a protective effect against the host innate immune defense. More specifically, integrating all the available information about Stealth proteins in bacteria, we propose that Stealth is a D-hexose-1-phosphoryl transferase involved in the synthesis of polysaccharides. In the animal kingdom, Stealth is strongly conserved across evolution from social amoebas to simple and complex multicellular organisms, such as Dictyostelium discoideum, hydra, and human. Based on the occurrence of Stealth in most Eukaryotes and a subset of Prokaryotes together with its potential role in extracellular polysaccharide synthesis, we propose that metazoan Stealth functions to regulate the innate immune system. Moreover, there is good reason to speculate that the acquisition and spread of Stealth could be responsible for future epidemic outbreaks of infectious diseases caused by a large variety of eubacterial pathogens. Our in silico identification of a homologous protein in the human host will help to elucidate the causes of Stealth-dependent virulence. At a more basic level, the characterization of the molecular and cellular function of Stealth proteins may shed light on fundamental mechanisms of innate immune defense against microbial invasion.

Dicty_cDB: FC-IC0102 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available FC-IC (Link to library) FC-IC0102 (Link to dictyBase) - - - Contig-U16527-1 FC-IC01...02F (Link to Original site) FC-IC0102F 434 - - - - - - Show FC-IC0102 Library FC-IC (Link to library) Clone ...ID FC-IC0102 (Link to dictyBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16527-1 Original site URL http://dict... (bits) Value N AB088483 |AB088483.1 Dictyostelium discoideum gene for gamete and mating-type specific prote...oducing significant alignments: (bits) Value AB088483_1( AB088483 |pid:none) Dictyostelium discoideum gmsA g

Dicty_cDB: SSC474 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available SS (Link to library) SSC474 (Link to dictyBase) - - - Contig-U07719-1 SSC474P (Link... to Original site) SSC474F 368 SSC474Z 238 SSC474P 606 - - Show SSC474 Library SS (Link to library) Clone ID SSC474 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U07719-1 Original site URL http://dict...logy vs DNA Score E Sequences producing significant alignments: (bits) Value N ( AU071762 ) Dictyostelium di...scoideum slug cDNA, clone SSC474. 448 e-121 1 ( AU060185 ) Dictyostelium discoideum slug cDNA, clone SLA535.

Dicty_cDB: VSH207 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VS (Link to library) VSH207 (Link to dictyBase) - - - Contig-U12548-1 VSH207P (Link... to Original site) VSH207F 228 VSH207Z 107 VSH207P 335 - - Show VSH207 Library VS (Link to library) Clone ID VSH207 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U12548-1 Original site URL http://dict...ents: (bits) Value N ( AU267072 ) Dictyostelium discoideum vegetative cDNA clone:VS... 206 2e-58 2 ( AC116982 ) Dict...yostelium discoideum chromosome 2 map 3622643... 206 4e-49 1 ( AU267073 ) Dict

Dicty_cDB: VHK278 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VH (Link to library) VHK278 (Link to dictyBase) - - - Contig-U16260-1 - (Link to Original site) VHK2...78F 533 - - - - - - Show VHK278 Library VH (Link to library) Clone ID VHK278 (Link to dicty...iol.tsukuba.ac.jp/CSM/VH/VHK2-D/VHK278Q.Seq.d/ Representative seq. ID - (Link to ...Original site) Representative DNA sequence >VHK278 (VHK278Q) /CSM/VH/VHK2-D/VHK278Q.Seq.d/ AACTCTCGAGTGCAAAA...BJ427875 ) Dictyostelium discoideum cDNA clone:ddv63k24, 5' ... 997 0.0 1 ( BJ427874 ) Dictyostelium discoideum cDNA clone:ddv63k2

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB489 (Link to dictyBase) - - - Contig-U16382-1 VFB489P (Link... to Original site) VFB489F 178 VFB489Z 501 VFB489P 679 - - Show VFB489 Library VF (Link to library) Clone ID VFB489 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16382-1 Original site URL http://dict...: (bits) Value N AC116986 |AC116986.2 Dictyostelium discoideum chromosome 2 map 2...e cds. 783 0.0 3 AC115579 |AC115579.2 Dictyostelium discoideum chromosome 2 map 4915084-5005461 strain AX4,

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB788 (Link to dictyBase) - - - Contig-U14924-1 VFB788P (Link... to Original site) VFB788F 158 VFB788Z 768 VFB788P 926 - - Show VFB788 Library VF (Link to library) Clone ID VFB788 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U14924-1 Original site URL http://dict... (bits) Value N AC115592 |AC115592.2 Dictyostelium discoideum chromosome 2 map 1-...2_6( AC115592 |pid:none) Dictyostelium discoideum chromosom... 520 e-146 CU459003_2449( CU459003 |pid:none)

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB895 (Link to dictyBase) - - - Contig-U10164-1 VFB895P (Link... to Original site) VFB895F 578 VFB895Z 699 VFB895P 1277 - - Show VFB895 Library VF (Link to library) Clone ID VFB895 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U10164-1 Original site URL http://dict...ore E Sequences producing significant alignments: (bits) Value N AC115604 |AC115604.2 Dictyostelium discoide...um chromosome 2 map 4354771-4414991 strain AX4, complete sequence. 42 5e-06 9 M18106 |M18106.1 Dictyostelium

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFC101 (Link to dictyBase) - - - Contig-U16544-1 VFC101Z (Link... to Original site) - - VFC101Z 556 - - - - Show VFC101 Library VF (Link to library) Clone ID VFC101 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16544-1 Original site URL http://dict...t alignments: (bits) Value N AY164994 |AY164994.1 Dictyostelium discoideum RTNLC (RTNLC) mRNA, complete cds.... 969 0.0 2 AY164656 |AY164656.1 Dictyostelium discoideum RTNLC (RTNLC) gene, complete cds. 565 0.0 3 AL71386

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFC254 (Link to dictyBase) - - - Contig-U15456-1 VFC254P (Link... to Original site) VFC254F 509 VFC254Z 569 VFC254P 1078 - - Show VFC254 Library VF (Link to library) Clone ID VFC254 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U15456-1 Original site URL http://dict...mology vs DNA Score E Sequences producing significant alignments: (bits) Value N Y16962 |Y16962.1 Dictyostel...ium discoideum mRNA for cathepsin D. 910 0.0 3 AJ243946 |AJ243946.1 Dictyostelium

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB645 (Link to dictyBase) - - - Contig-U16382-1 VFB645P (Link... to Original site) VFB645F 619 VFB645Z 413 VFB645P 1032 - - Show VFB645 Library VF (Link to library) Clone ID VFB645 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16382-1 Original site URL http://dict...mology vs DNA Score E Sequences producing significant alignments: (bits) Value N X03281 |X03281.1 Dictyostel...ium discoideum gene for actin A8. 1174 0.0 2 AC116957 |AC116957.2 Dictyostelium discoideum chromosome 2 map

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFC187 (Link to dictyBase) - - - Contig-U12289-1 VFC187P (Link... to Original site) VFC187F 411 VFC187Z 678 VFC187P 1089 - - Show VFC187 Library VF (Link to library) Clone ID VFC187 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U12289-1 Original site URL http://dict... N AC117176 |AC117176.2 Dictyostelium discoideum chromosome 2 map 5018074-5200947... strain AX4, complete sequence. 36 0.008 12 AC114263 |AC114263.2 Dictyostelium discoideum chromosome 2 map 2

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB837 (Link to dictyBase) - - - Contig-U14985-1 VFB837P (Link... to Original site) VFB837F 606 VFB837Z 689 VFB837P 1295 - - Show VFB837 Library VF (Link to library) Clone ID VFB837 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U14985-1 Original site URL http://dict... 13 AC116986 |AC116986.2 Dictyostelium discoideum chromosome 2 map 2234041-256737...0 strain AX4, complete sequence. 38 2e-05 15 AC116984 |AC116984.2 Dictyostelium discoideum chromosome 2 map

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB733 (Link to dictyBase) - - - Contig-U16279-1 VFB733P (Link... to Original site) VFB733F 608 VFB733Z 663 VFB733P 1271 - - Show VFB733 Library VF (Link to library) Clone ID VFB733 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16279-1 Original site URL http://dict...es producing significant alignments: (bits) Value N U23957 |U23957.1 Dictyostelium discoideum P52D mRNA, com...15 e-114 U23957_1( U23957 |pid:none) Dictyostelium discoideum P52D mRNA, co... 41

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB862 (Link to dictyBase) - - - Contig-U16311-1 VFB862P (Link... to Original site) VFB862F 624 VFB862Z 720 VFB862P 1344 - - Show VFB862 Library VF (Link to library) Clone ID VFB862 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16311-1 Original site URL http://dict...s) Value N U72746 |U72746.1 Dictyostelium discoideum cysteine proteinase (cprG) m...RNA, complete cds. 1209 0.0 5 U72745 |U72745.1 Dictyostelium discoideum cysteine proteinase (cprF) mRNA, com

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB769 (Link to dictyBase) - - - Contig-U15456-1 VFB769P (Link... to Original site) VFB769F 625 VFB769Z 690 VFB769P 1315 - - Show VFB769 Library VF (Link to library) Clone ID VFB769 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U15456-1 Original site URL http://dict...roducing significant alignments: (bits) Value N Y16962 |Y16962.1 Dictyostelium discoideum mRNA for cathepsin... D. 1257 0.0 3 AJ243946 |AJ243946.1 Dictyostelium discoideum ctsD gene for cathep

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB702 (Link to dictyBase) - - - Contig-U12284-1 VFB702P (Link... to Original site) VFB702F 478 VFB702Z 615 VFB702P 1093 - - Show VFB702 Library VF (Link to library) Clone ID VFB702 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U12284-1 Original site URL http://dict... N G65021 |G65021.1 DH0281 Dictyostelium discoideum ( P.Dear ) Dictyostelium disc...8.0 %: mitochondrial 4.0 %: vacuolar 4.0 %: Golgi >> prediction for VFB702 is nuc 5' end seq. ID VFB702F 5'

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB741 (Link to dictyBase) - - - Contig-U16382-1 VFB741P (Link... to Original site) VFB741F 545 VFB741Z 675 VFB741P 1220 - - Show VFB741 Library VF (Link to library) Clone ID VFB741 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16382-1 Original site URL http://dict...bits) Value N X03281 |X03281.1 Dictyostelium discoideum gene for actin A8. 1166 0....0 2 AC116957 |AC116957.2 Dictyostelium discoideum chromosome 2 map 1685067-2090751 strain AX4, complete seq

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB829 (Link to dictyBase) - - - - VFB829Z (Link to Original s...ite) - - VFB829Z 600 - - - - Show VFB829 Library VF (Link to library) Clone ID VFB829 (Link to dictyBase) Atlas ID - NBRP ID - dict...yBase ID - Link to Contig - Original site URL http://dictycdb.biol.tsukuba.ac.jp/CSM/... long chain poly-unsaturated fatty acids. 1189 0.0 1 AB029311 |AB029311.1 Dictyostelium discoideum Dd des5 g...ene for fatty acid desaturase, complete cds. 823 0.0 2 AB022097 |AB022097.1 Dictyostelium discoideum mRNA fo

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB710 (Link to dictyBase) - - - Contig-U16382-1 VFB710P (Link... to Original site) VFB710F 123 VFB710Z 689 VFB710P 812 - - Show VFB710 Library VF (Link to library) Clone ID VFB710 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16382-1 Original site URL http://dict... significant alignments: (bits) Value N X03281 |X03281.1 Dictyostelium discoideum... gene for actin A8. 1308 0.0 2 AC116957 |AC116957.2 Dictyostelium discoideum chromosome 2 map 1685067-209075

Dicty_cDB: SLC466 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available SL (Link to library) SLC466 (Link to dictyBase) - - - Contig-U16381-1 SLC466Z (Link... to Original site) - - SLC466Z 427 - - - - Show SLC466 Library SL (Link to library) Clone ID SLC466 (Link to...ycdb.biol.tsukuba.ac.jp/CSM/SL/SLC4-C/SLC466Q.Seq.d/ Representative seq. ID SLC46...6Z (Link to Original site) Representative DNA sequence >SLC466 (SLC466Q) /CSM/SL/SLC4-C/SLC466Q.Seq.d/ XXXXX... AU034556 ) Dictyostelium discoideum slug cDNA, clone SLC466. 176 2e-77 2 ( AU033496 ) Dictyostelium discoid

Dicty_cDB: SLC455 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available SL (Link to library) SLC455 (Link to dictyBase) - - - Contig-U16584-1 SLC455Z (Link... to Original site) - - SLC455Z 379 - - - - Show SLC455 Library SL (Link to library) Clone ID SLC455 (Link to...ycdb.biol.tsukuba.ac.jp/CSM/SL/SLC4-C/SLC455Q.Seq.d/ Representative seq. ID SLC45...5Z (Link to Original site) Representative DNA sequence >SLC455 (SLC455Q) /CSM/SL/SLC4-C/SLC455Q.Seq.d/ XXXXX...57 ) Dictyostelium discoideum slug cDNA, clone SLC469. 468 e-177 3 ( AU034549 ) Dictyostelium discoideum slug cDNA, clone SLC4

Francisella tularensis type A Strains Cause the Rapid Encystment of Acanthamoeba castellanii and Survive in Amoebal Cysts for Three Weeks post Infection

Energy Technology Data Exchange (ETDEWEB)

El-Etr, S H; Margolis, J; Monack, D; Robison, R; Cohen, M; Moore, E; Rasley, A

2009-07-28

Francisella tularensis, the causative agent of the zoonotic disease tularemia, has recently gained increased attention due to the emergence of tularemia in geographical areas where the disease has been previously unknown, and the organism's potential as a bioterrorism agent. Although F. tularensis has an extremely broad host range, the bacterial reservoir in nature has not been conclusively identified. In this study, the ability of virulent F. tularensis strains to survive and replicate in the amoeba Acanthamoeba castellanii was explored. We observe that A. castellanii trophozoites rapidly encyst in response to F. tularensis infection and that this rapid encystment phenotype (REP) is caused by factor(s) secreted by amoebae and/or F. tularensis into the co-culture media. Further, our results indicate that in contrast to LVS, virulent strains of F. tularensis can survive in A. castellanii cysts for at least 3 weeks post infection and that induction of rapid amoeba encystment is essential for survival. In addition, our data indicate that pathogenic F. tularensis strains block lysosomal fusion in A. castellanii. Taken together, these data suggest that the interactions between F. tularensis strains and amoeba may play a role in the environmental persistence of F. tularensis.

Protozoa Drive the Dynamics of Culturable Biocontrol Bacterial Communities.

Science.gov (United States)

Müller, Maren Stella; Scheu, Stefan; Jousset, Alexandre

2013-01-01

Some soil bacteria protect plants against soil-borne diseases by producing toxic secondary metabolites. Such beneficial biocontrol bacteria can be used in agricultural systems as alternative to agrochemicals. The broad spectrum toxins responsible for plant protection also inhibit predation by protozoa and nematodes, the main consumers of bacteria in soil. Therefore, predation pressure may favour biocontrol bacteria and contribute to plant health. We analyzed the effect of Acanthamoeba castellanii on semi-natural soil bacterial communities in a microcosm experiment. We determined the frequency of culturable bacteria carrying genes responsible for the production of the antifungal compounds 2,4-diacetylphloroglucinol (DAPG), pyrrolnitrin (PRN) and hydrogen cyanide (HCN) in presence and absence of A. castellanii. We then measured if amoebae affected soil suppressiveness in a bioassay with sugar beet seedlings confronted to the fungal pathogen Rhizoctonia solani. Amoebae increased the frequency of both DAPG and HCN positive bacteria in later plant growth phases (2 and 3 weeks), as well as the average number of biocontrol genes per bacterium. The abundance of DAPG positive bacteria correlated with disease suppression, suggesting that their promotion by amoebae may enhance soil health. However, the net effect of amoebae on soil suppressiveness was neutral to slightly negative, possibly because amoebae slow down the establishment of biocontrol bacteria on the recently emerged seedlings used in the assay. The results indicate that microfaunal predators foster biocontrol bacterial communities. Understanding interactions between biocontrol bacteria and their predators may thus help developing environmentally friendly management practices of agricultural systems.

Protozoa Drive the Dynamics of Culturable Biocontrol Bacterial Communities.

Directory of Open Access Journals (Sweden)

Maren Stella Müller

Full Text Available Some soil bacteria protect plants against soil-borne diseases by producing toxic secondary metabolites. Such beneficial biocontrol bacteria can be used in agricultural systems as alternative to agrochemicals. The broad spectrum toxins responsible for plant protection also inhibit predation by protozoa and nematodes, the main consumers of bacteria in soil. Therefore, predation pressure may favour biocontrol bacteria and contribute to plant health. We analyzed the effect of Acanthamoeba castellanii on semi-natural soil bacterial communities in a microcosm experiment. We determined the frequency of culturable bacteria carrying genes responsible for the production of the antifungal compounds 2,4-diacetylphloroglucinol (DAPG, pyrrolnitrin (PRN and hydrogen cyanide (HCN in presence and absence of A. castellanii. We then measured if amoebae affected soil suppressiveness in a bioassay with sugar beet seedlings confronted to the fungal pathogen Rhizoctonia solani. Amoebae increased the frequency of both DAPG and HCN positive bacteria in later plant growth phases (2 and 3 weeks, as well as the average number of biocontrol genes per bacterium. The abundance of DAPG positive bacteria correlated with disease suppression, suggesting that their promotion by amoebae may enhance soil health. However, the net effect of amoebae on soil suppressiveness was neutral to slightly negative, possibly because amoebae slow down the establishment of biocontrol bacteria on the recently emerged seedlings used in the assay. The results indicate that microfaunal predators foster biocontrol bacterial communities. Understanding interactions between biocontrol bacteria and their predators may thus help developing environmentally friendly management practices of agricultural systems.

Peristaltic transport and mixing of cytosol through the whole body of Physarum plasmodium.

Science.gov (United States)

Iima, Makoto; Nakagaki, Toshiyuki

2012-09-01

We study how the net transport and mixing of chemicals occur in a relatively large amoeba, the true slime mold Physarum polycephalum. The shuttle streaming of the amoeba is characterized by a rhythmic flow of the order of 1 μm/s in which the protoplasm streams back and forth. To explain the experimentally observed transport of chemicals, we formulate a simplified model to consider the mechanism by which net transport can be induced by shuttle (or periodic) motion inside the amoeba. This model is independent from the details of fluid property as it is based on the mass conservation law only. Even in such a simplified model, we demonstrate that sectional oscillations play an important role in net transport and discuss the effects of the sectional boundary motion on net transport in the microorganism.

Adaptation of Francisella tularensis to the Mammalian Environment Is Governed by Cues Which Can Be Mimicked In Vitro▿ †

OpenAIRE

Hazlett, Karsten R. O.; Caldon, Seth D.; McArthur, Debbie G.; Cirillo, Kerry A.; Kirimanjeswara, Girish S.; Magguilli, Micheal L.; Malik, Meenakshi; Shah, Aaloki; Broderick, Scott; Golovliov, Igor; Metzger, Dennis W.; Rajan, Krishna; Sellati, Timothy J.; Loegering, Daniel J.

2008-01-01

The intracellular bacterium Francisella tularensis survives in mammals, arthropods, and freshwater amoeba. It was previously established that the conventional media used for in vitro propagation of this microbe do not yield bacteria that mimic those harvested from infected mammals; whether these in vitro-cultivated bacteria resemble arthropod- or amoeba-adapted Francisella is unknown. As a foundation for our goal of identifying F. tularensis outer membrane proteins which are expressed during ...

Dicty_cDB: CFH244 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available CF (Link to library) CFH244 (Link to dictyBase) - - - Contig-U16381-1 CFH244F (Link... to Original site) CFH244F 124 - - - - - - Show CFH244 Library CF (Link to library) Clone ID CFH244 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16381-1 Original site URL http://dict...ts) Value N AC115685 |AC115685.1 Dictyostelium discoideum chromosome 2 map 4718821-4752388 strain AX4, compl...ete sequence. 82 2e-29 3 X51892 |X51892.1 Dictyostelium discoideum SP60 gene for spore coat protein. 82 4e-29 2 X52105 |X52105.1 Dict

Dicty_cDB: SLB690 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available r Dp87... 45 9e-04 AC117267_7( AC117267 |pid:none) Dictyostelium discoideum chromosom... 40 0.037 AY574051_1( AY574051 |pid:none) Ict...SL (Link to library) SLB690 (Link to dictyBase) - - - Contig-U16325-1 SLB690Z (Link... to Original site) - - SLB690Z 481 - - - - Show SLB690 Library SL (Link to library) Clone ID SLB690 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16325-1 Original site URL http://dict...t alignments: (bits) Value N ( AF066071 ) Dictyostelium discoideum SP85 (pspB) gene, comple... 831 0.0 1 ( AC117075 ) Dict

Dicty_cDB: CHD405 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available CH (Link to library) CHD405 (Link to dictyBase) - - - Contig-U15984-1 CHD405E (Link... Clone ID CHD405 (Link to dictyBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U15984-1 Original site URL http://dict...ts) Value N AC115599 |AC115599.2 Dictyostelium discoideum chromosome 2 map 422909...8-4354721 strain AX4, complete sequence. 42 3e-11 9 AC115598 |AC115598.2 Dictyostelium discoideum chromosome... 2 map 581427-735498 strain AX4, complete sequence. 50 4e-11 11 CK417372 |CK417372.1 AUF_IpInt_56_d19 Intestine cDNA library Ict

Dicty_cDB: CFH809 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available CF (Link to library) CFH809 (Link to dictyBase) - - - Contig-U16381-1 - (Link to Or...iginal site) CFH809F 135 - - - - - - Show CFH809 Library CF (Link to library) Clone ID CFH809 (Link to dicty...Base) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16381-1 Original site URL http://dictycdb.b...ce. 82 2e-29 3 X51892 |X51892.1 Dictyostelium discoideum SP60 gene for spore coat protein. 82 5e-29 2 X52105 |X52105.1 Dict...yostelium discoideum SP60 gene for spore coat protein. 80 9e-27 2 AC116977 |AC116977.2 Dict

Dicty_cDB: VHK202 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VH (Link to library) VHK202 (Link to dictyBase) - - - Contig-U16260-1 VHK202P (Link to Original site) VHK2...02F 618 VHK202Z 741 VHK202P 1339 - - Show VHK202 Library VH (Link to library) Clone ID VHK2...e URL http://dictycdb.biol.tsukuba.ac.jp/CSM/VH/VHK2-A/VHK202Q.Seq.d/ Representative seq. ID VHK2...02P (Link to Original site) Representative DNA sequence >VHK202 (VHK202Q) /CSM/VH/VHK2-A/VHK2...446805 ) Dictyostelium discoideum cDNA clone:ddv63k21, 3' ... 1449 0.0 1 ( BJ446732 ) Dictyostelium discoide

Dicty_cDB: VHK254 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VH (Link to library) VHK254 (Link to dictyBase) - - - Contig-U16260-1 VHK254P (Link to Original site) VHK2...54F 616 VHK254Z 744 VHK254P 1340 - - Show VHK254 Library VH (Link to library) Clone ID VHK2...e URL http://dictycdb.biol.tsukuba.ac.jp/CSM/VH/VHK2-C/VHK254Q.Seq.d/ Representative seq. ID VHK2...54P (Link to Original site) Representative DNA sequence >VHK254 (VHK254Q) /CSM/VH/VHK2-C/VHK2...BJ446805 ) Dictyostelium discoideum cDNA clone:ddv63k21, 3' ... 1455 0.0 1 ( BJ446732 ) Dictyostelium discoi

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFB886 (Link to dictyBase) - - - Contig-U16382-1 VFB886E (Link...) Clone ID VFB886 (Link to dictyBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16382-1 Ori...t alignments: (bits) Value N X03281 |X03281.1 Dictyostelium discoideum gene for actin A8. 2234 0.0 1 AC116957 |AC116957.2 Dict...4, complete sequence. 2107 0.0 3 M14146 |M14146.1 D.discoideum actin 15 gene, complete cds. 2034 0.0 1 AC115579 |AC115579.2 Dict...4 0.0 2 AC116986 |AC116986.2 Dictyostelium discoideum chromosome 2 map 2234041-25

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFC115 (Link to dictyBase) - - - Contig-U16382-1 VFC115E (Link...) Clone ID VFC115 (Link to dictyBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U16382-1 Ori...ant alignments: (bits) Value N X03281 |X03281.1 Dictyostelium discoideum gene for actin A8. 954 0.0 7 AC116957 |AC116957.2 Dict...X4, complete sequence. 906 0.0 9 M14146 |M14146.1 D.discoideum actin 15 gene, complete cds. 890 0.0 7 AC115579 |AC115579.2 Dict...0.0 7 U25660 |U25660.1 Dictyostelium discoideum actin gene, partial cds. 866 0.0

Dicty_cDB: [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available VF (Link to library) VFC138 (Link to dictyBase) - - - Contig-U15456-1 VFC138P (Link... to Original site) VFC138F 411 VFC138Z 440 VFC138P 851 - - Show VFC138 Library VF (Link to library) Clone ID VFC138 (Link to dict...yBase) Atlas ID - NBRP ID - dictyBase ID - Link to Contig Contig-U15456-1 Original site URL http://dict...ducing significant alignments: (bits) Value N Y16962 |Y16962.1 Dictyostelium discoideum mRNA for cathepsin D.... 815 0.0 4 AJ243946 |AJ243946.1 Dictyostelium discoideum ctsD gene for cathepsin D, exons 1 to 2. 815 0.0 5

To what extent do food preferences explain the trophic position of heterotrophic and mixotrophic microbial consumers in a Sphagnum peatland?

Science.gov (United States)

Jassey, Vincent E J; Meyer, Caroline; Dupuy, Christine; Bernard, Nadine; Mitchell, Edward A D; Toussaint, Marie-Laure; Metian, Marc; Chatelain, Auriel P; Gilbert, Daniel

2013-10-01

Although microorganisms are the primary drivers of biogeochemical cycles, the structure and functioning of microbial food webs are poorly studied. This is the case in Sphagnum peatlands, where microbial communities play a key role in the global carbon cycle. Here, we explored the structure of the microbial food web from a Sphagnum peatland by analyzing (1) the density and biomass of different microbial functional groups, (2) the natural stable isotope (δ(13)C and δ(15)N) signatures of key microbial consumers (testate amoebae), and (3) the digestive vacuole contents of Hyalosphenia papilio, the dominant testate amoeba species in our system. Our results showed that the feeding type of testate amoeba species (bacterivory, algivory, or both) translates into their trophic position as assessed by isotopic signatures. Our study further demonstrates, for H. papilio, the energetic benefits of mixotrophy when the density of its preferential prey is low. Overall, our results show that testate amoebae occupy different trophic levels within the microbial food web, depending on their feeding behavior, the density of their food resources, and their metabolism (i.e., mixotrophy vs. heterotrophy). Combined analyses of predation, community structure, and stable isotopes now allow the structure of microbial food webs to be more completely described, which should lead to improved models of microbial community function.

Defective ribosome assembly in Shwachman-Diamond syndrome.

Science.gov (United States)

Wong, Chi C; Traynor, David; Basse, Nicolas; Kay, Robert R; Warren, Alan J

2011-10-20

Shwachman-Diamond syndrome (SDS), a recessive leukemia predisposition disorder characterized by bone marrow failure, exocrine pancreatic insufficiency, skeletal abnormalities and poor growth, is caused by mutations in the highly conserved SBDS gene. Here, we test the hypothesis that defective ribosome biogenesis underlies the pathogenesis of SDS. We create conditional mutants in the essential SBDS ortholog of the ancient eukaryote Dictyostelium discoideum using temperature-sensitive, self-splicing inteins, showing that mutant cells fail to grow at the restrictive temperature because ribosomal subunit joining is markedly impaired. Remarkably, wild type human SBDS complements the growth and ribosome assembly defects in mutant Dictyostelium cells, but disease-associated human SBDS variants are defective. SBDS directly interacts with the GTPase elongation factor-like 1 (EFL1) on nascent 60S subunits in vivo and together they catalyze eviction of the ribosome antiassociation factor eukaryotic initiation factor 6 (eIF6), a prerequisite for the translational activation of ribosomes. Importantly, lymphoblasts from SDS patients harbor a striking defect in ribosomal subunit joining whose magnitude is inversely proportional to the level of SBDS protein. These findings in Dictyostelium and SDS patient cells provide compelling support for the hypothesis that SDS is a ribosomopathy caused by corruption of an essential cytoplasmic step in 60S subunit maturation.

Possible environmental sources of Acanthamoeba spp in contact lens wearers.

OpenAIRE

Seal, D; Stapleton, F; Dart, J

1992-01-01

The water supply and dust samples from the home environment (bathrooms and kitchens) of 50 wearers of contact lenses (CLs) were cultured for the presence of free-living amoebae. CL cases, solutions, and water taps were cultured for bacteria, which amoebae require for growth. Acanthamoeba spp were isolated from water drawn from six bathroom cold water taps (tank supplied), five in the presence of limescale, and from one kitchen cold water tap (mains supplied). There was an association between ...

Analysing the spatial patterns of livestock anthrax in Kazakhstan in relation to environmental factors: a comparison of local (Gi* and morphology cluster statistics

Directory of Open Access Journals (Sweden)

Ian T. Kracalik

2012-11-01

Full Text Available We compared a local clustering and a cluster morphology statistic using anthrax outbreaks in large (cattle and small (sheep and goats domestic ruminants across Kazakhstan. The Getis-Ord (Gi* statistic and a multidirectional optimal ecotope algorithm (AMOEBA were compared using 1st, 2nd and 3rd order Rook contiguity matrices. Multivariate statistical tests were used to evaluate the environmental signatures between clusters and non-clusters from the AMOEBA and Gi* tests. A logistic regression was used to define a risk surface for anthrax outbreaks and to compare agreement between clustering methodologies. Tests revealed differences in the spatial distribution of clusters as well as the total number of clusters in large ruminants for AMOEBA (n = 149 and for small ruminants (n = 9. In contrast, Gi* revealed fewer large ruminant clusters (n = 122 and more small ruminant clusters (n = 61. Significant environmental differences were found between groups using the Kruskall-Wallis and Mann- Whitney U tests. Logistic regression was used to model the presence/absence of anthrax outbreaks and define a risk surface for large ruminants to compare with cluster analyses. The model predicted 32.2% of the landscape as high risk. Approximately 75% of AMOEBA clusters corresponded to predicted high risk, compared with ~64% of Gi* clusters. In general, AMOEBA predicted more irregularly shaped clusters of outbreaks in both livestock groups, while Gi* tended to predict larger, circular clusters. Here we provide an evaluation of both tests and a discussion of the use of each to detect environmental conditions associated with anthrax outbreak clusters in domestic livestock. These findings illustrate important differences in spatial statistical methods for defining local clusters and highlight the importance of selecting appropriate levels of data aggregation.

Dictyostelids living in the soils of the Atlantic forest, Iguazú region, Misiones, Argentina: description of new species.

Science.gov (United States)

Vadell, Eduardo M; Cavender, James C

2007-01-01

Thirteen new species and varieties of dictyostelid cellular slime molds (csm) were isolated from soils of the Atlantic Subtropical Rain Forest at the Iguazú Falls, Northeastern Misiones Province, Argentina. Seven new species are described herein, one of them is a Polysphondylium, while the rest of the species belong to the genus Dictyostelium. Also, six taxa are new varieties of Dictyostelium and Acytostelium, which will be reported later. Fourteen Northern Hemisphere (Tikal) species have also been isolated from Iguazú soils, some of them new records for Southern South America. This csm community, when compared with others from forests of the Northern Hemisphere, particularly Tikal, Guatemala, give some insight into a possibly different evolutionary history and/or natural selection in the two areas.

Litter quality as driving factor for plant nutrition via grazing of protozoa on soil microorganisms.

Science.gov (United States)

Koller, Robert; Robin, Christophe; Bonkowski, Michael; Ruess, Liliane; Scheu, Stefan

2013-08-01

Plant residues provide a major source of nitrogen (N) for plant growth. Litter N mineralization varies with litter carbon-to-nitrogen (C-to-N) ratio and presence of bacterial-feeding fauna. We assessed the effect of amoebae, major bacterial feeders in soil, on mineralization of litter of low (high quality) and high C-to-N ratio (low quality) and evaluated consequences for plant growth. We used stable isotopes to determine plant N uptake from litter and plant C partitioning. Stable isotope probing of phospholipid fatty acids was used to follow incorporation of plant C into microorganisms. Amoebae increased plant N uptake independent of litter quality and thereby the biomass of shoots and roots by 33% and 66%, respectively. Plant allocation of total (13)C to roots in low (42%) exceeded that of high-quality litter treatments (26%). Amoebae increased plant allocation of (13)C to roots by 37%. Microbial community structure and incorporation of (13)C into PLFAs varied significantly with litter quality and in the low-quality litter treatment also with the presence of amoebae. Overall, the results suggest that in particular at low nutrient conditions, root-derived C fosters the mobilization of bacterial N by protozoa, thereby increasing plant growth when microorganisms and plants compete for nutrients. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Genome Dynamics in Legionella: The Basis of Versatility and Adaptation to Intracellular Replication

Science.gov (United States)

Gomez-Valero, Laura; Buchrieser, Carmen

2013-01-01

Legionella pneumophila is a bacterial pathogen present in aquatic environments that can cause a severe pneumonia called Legionnaires’ disease. Soon after its recognition, it was shown that Legionella replicates inside amoeba, suggesting that bacteria replicating in environmental protozoa are able to exploit conserved signaling pathways in human phagocytic cells. Comparative, evolutionary, and functional genomics suggests that the Legionella–amoeba interaction has shaped this pathogen more than previously thought. A complex evolutionary scenario involving mobile genetic elements, type IV secretion systems, and horizontal gene transfer among Legionella, amoeba, and other organisms seems to take place. This long-lasting coevolution led to the development of very sophisticated virulence strategies and a high level of temporal and spatial fine-tuning of bacteria host–cell interactions. We will discuss current knowledge of the evolution of virulence of Legionella from a genomics perspective and propose our vision of the emergence of this human pathogen from the environment. PMID:23732852

Journal of Biosciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

A model for cell type localization in the migrating slug of Dictyostelium discoideum based on differential ... a progressive maturation of chemotactic properties during the transdifferentiation of slug cell types. ... Journal of Biosciences | News ...

Novel Path Towards Colistin Resistance In Pseudomonas Aeruginosa During Chronic Infection Involves Polymorphisms In Uncharacterized Glycosyltransferase Gene

DEFF Research Database (Denmark)

Hermansen, Grith Miriam Maigaard; Jelsbak, Lars

2015-01-01

Introduction: Antibiotic resistance development in the gram-negative bacterium Pseudomonas aeruginosa is an increasing problem. The effect of colistin, one of the few last resort drugs commonly given to cystic fibrosis (CF) patients, is dependent on the lipopolysaccharide (LPS) structure. We have...... inhibitory concentration by microbroth dilution, virulence in an amoebae model and LPS structure by visualization in a silver-stained gel. Results: Reversion of the SNP to reference genotype resulted in increased colistin susceptibility, reduced virulence in an amoebae model and altered LPS structure...

Dicty_cDB: Contig-U16423-1 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available 65776 ) Dictyostelium discoideum cDNA clone:ddc36f16, 5' ... 74 3e-22 2 ( FG288312 ) 1108793266221 New World... 4e-19 3 ( FI057728 ) CHO_OF6610xh18r1.ab1 CHO_OF6 Nicotiana tabacum ge... 64 6e-19 3 ( FG286148 ) 1108770713996 New World...9c24,... 90 7e-18 3 ( CJ411606 ) Molgula tectiformis cDNA, larva clone:mtlv010d03,... 90 7e-18 3 ( FG288831 ) 1108793284713 New World...e-13 2 ( FG299437 ) 1108793335742 New World Screwworm Larvae 9387 EST... 80 2e-13 2 ( DV613229 ) EST1216225 ...BJ379331 ) Dictyostelium discoideum cDNA clone:ddc34c13, 3' ... 90 5e-13 1 ( FG300027 ) 1108793358668 New World

Expression of matrix metalloproteinases in Naegleria fowleri and their role in invasion of the central nervous system.

Science.gov (United States)

Lam, Charlton; Jamerson, Melissa; Cabral, Guy; Carlesso, Ana Maris; Marciano-Cabral, Francine

2017-10-01

Naegleria fowleri is a free-living amoeba found in freshwater lakes and ponds and is the causative agent of primary amoebic meningoencephalitis (PAM), a rapidly fatal disease of the central nervous system (CNS). PAM occurs when amoebae attach to the nasal epithelium and invade the CNS, a process that involves binding to, and degradation of, extracellular matrix (ECM) components. This degradation is mediated by matrix metalloproteinases (MMPs), enzymes that have been described in other pathogenic protozoa, and that have been linked to their increased motility and invasive capability. These enzymes also are upregulated in tumorigenic cells and have been implicated in metastasis of certain tumours. In the present study, in vitro experiments linked MMPs functionally to the degradation of the ECM. Gelatin zymography demonstrated enzyme activity in N. fowleri whole cell lysates, conditioned media and media collected from invasion assays. Western immunoblotting indicated the presence of the metalloproteinases MMP-2 (gelatinase A), MMP-9 (gelatinase B) and MMP-14 [membrane type-1 matrix metalloproteinase (MT1-MMP)]. Highly virulent mouse-passaged amoebae expressed higher levels of MMPs than weakly virulent axenically grown amoebae. The functional relevance of MMPs in media was indicated through the use of the MMP inhibitor, 1,10-phenanthroline. The collective in vitro results suggest that MMPs play a critical role in vivo in invasion of the CNS and that these enzymes may be amenable targets for limiting PAM.

Dicty_cDB: VFE551 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott-Aldrich syndrome protein (wasA) gene, complet...ictyostelium discoideum Wiscott-A... 112 4e-24 AC117076_18( AC117076 |pid:none) D

An Amoebal Grazer of Cyanobacteria Requires Cobalamin Produced by Heterotrophic Bacteria.

Science.gov (United States)

Ma, Amy T; Beld, Joris; Brahamsha, Bianca

2017-05-15

Amoebae are unicellular eukaryotes that consume microbial prey through phagocytosis, playing a role in shaping microbial food webs. Many amoebal species can be cultivated axenically in rich media or monoxenically with a single bacterial prey species. Here, we characterize heterolobosean amoeba LPG3, a recent natural isolate, which is unable to grow on unicellular cyanobacteria, its primary food source, in the absence of a heterotrophic bacterium, a Pseudomonas species coisolate. To investigate the molecular basis of this requirement for heterotrophic bacteria, we performed a screen using the defined nonredundant transposon library of Vibrio cholerae , which implicated genes in corrinoid uptake and biosynthesis. Furthermore, cobalamin synthase deletion mutations in V. cholerae and the Pseudomonas species coisolate do not support the growth of amoeba LPG3 on cyanobacteria. While cyanobacteria are robust producers of a corrinoid variant called pseudocobalamin, this variant does not support the growth of amoeba LPG3. Instead, we show that it requires cobalamin that is produced by the Pseudomonas species coisolate. The diversity of eukaryotes utilizing corrinoids is poorly understood, and this amoebal corrinoid auxotroph serves as a model for examining predator-prey interactions and micronutrient transfer in bacterivores underpinning microbial food webs. IMPORTANCE Cyanobacteria are important primary producers in aquatic environments, where they are grazed upon by a variety of phagotrophic protists and, hence, have an impact on nutrient flux at the base of microbial food webs. Here, we characterize amoebal isolate LPG3, which consumes cyanobacteria as its primary food source but also requires heterotrophic bacteria as a source of corrinoid vitamins. Amoeba LPG3 specifically requires the corrinoid variant produced by heterotrophic bacteria and cannot grow on cyanobacteria alone, as they produce a different corrinoid variant. This same corrinoid specificity is also

NCBI nr-aa BLAST: CBRC-DDIS-02-0043 [SEVENS

Lifescience Database Archive (English)

Full Text Available CBRC-DDIS-02-0043 gb|AAL92369.2| similar to Homo sapiens (Human). Testis intercellular mediator... Peas (Sortilin 1) (Hypothetical protein) (Testis intracellular mediator protein) [Dictyostelium discoideum] AAL92369.2 1e-178 98% ...

Acceleration of the sliding movement of actin filaments with the use of a non-motile mutant myosin in in vitro motility assays driven by skeletal muscle heavy meromyosin.

Directory of Open Access Journals (Sweden)

Kohei Iwase

Full Text Available We examined the movement of an actin filament sliding on a mixture of normal and genetically modified myosin molecules that were attached to a glass surface. For this purpose, we used a Dictyostelium G680V mutant myosin II whose release rates of Pi and ADP were highly suppressed relative to normal myosin, leading to a significantly extended life-time of the strongly bound state with actin and virtually no motility. When the mixing ratio of G680V mutant myosin II to skeletal muscle HMM (heavy myosin was 0.01%, the actin filaments moved intermittently. When they moved, their sliding velocities were about two-fold faster than the velocity of skeletal HMM alone. Furthermore, sliding movements were also faster when the actin filaments were allowed to slide on skeletal muscle HMM-coated glass surfaces in the motility buffer solution containing G680V HMM. In this case no intermittent movement was observed. When the actin filaments used were copolymerized with a fusion protein consisting of Dictyostelium actin and Dictyostelium G680V myosin II motor domain, similar faster sliding movements were observed on skeletal muscle HMM-coated surfaces. The filament sliding velocities were about two-fold greater than the velocities of normal actin filaments. We found that the velocity of actin filaments sliding on skeletal muscle myosin molecules increased in the presence of a non-motile G680V mutant myosin motor.

A model for cell type localization in the migrating slug of ...

Indian Academy of Sciences (India)

PRAKASH

. Localization of the three major cell types within the migrating slug stage is a dynamic process (Sternfeld 1992;. A model for cell type localization in the migrating slug of Dictyostelium discoideum based on differential chemotactic sensitivity to ...

Toward the Structure of Dynamic Membrane-Anchored Actin Networks

Science.gov (United States)

Weber, Igor

2007-01-01

In the cortex of a motile cell, membrane-anchored actin filaments assemble into structures of varying shape and function. Filopodia are distinguished by a core of bundled actin filaments within finger-like extensions of the membrane. In a recent paper by Medalia et al1 cryo-electron tomography has been used to reconstruct, from filopodia of Dictyostelium cells, the 3-dimensional organization of actin filaments in connection with the plasma membrane. A special arrangement of short filaments converging toward the filopod's tip has been called a “terminal cone”. In this region force is applied for protrusion of the membrane. Here we discuss actin organization in the filopodia of Dictyostelium in the light of current views on forces that are generated by polymerizing actin filaments, and on the resistance of membranes against deformation that counteracts these forces. PMID:19262130

Cellulose degradation: a therapeutic strategy in the improved treatment of Acanthamoeba infections.

Science.gov (United States)

Lakhundi, Sahreena; Siddiqui, Ruqaiyyah; Khan, Naveed Ahmed

2015-01-14

Acanthamoeba is an opportunistic free-living amoeba that can cause blinding keratitis and fatal brain infection. Early diagnosis, followed by aggressive treatment is a pre-requisite in the successful treatment but even then the prognosis remains poor. A major drawback during the course of treatment is the ability of the amoeba to enclose itself within a shell (a process known as encystment), making it resistant to chemotherapeutic agents. As the cyst wall is partly made of cellulose, thus cellulose degradation offers a potential therapeutic strategy in the effective targeting of trophozoite encased within the cyst walls. Here, we present a comprehensive report on the structure of cellulose and cellulases, as well as known cellulose degradation mechanisms with an eye to target the Acanthamoeba cyst wall. The disruption of the cyst wall will make amoeba (concealed within) susceptible to chemotherapeutic agents, and at the very least inhibition of the excystment process will impede infection recurrence, as we bring these promising drug targets into focus so that they can be explored to their fullest.

ORF Alignment: EHA1 [GENIUS II[Archive

Lifescience Database Archive (English)

Full Text Available coideum (Slime mold). Wiscott-aldrich ... syndrome protein gb|EAL71043.1| hypothetical protein ... ... EHA1 4.m00692 >1ceeB 8 59 36 87 3e-13 ... gb|AAS38848.1| similar to Dictyostelium dis

Evidence that the intra-amoebal Legionella drancourtii acquired a sterol reductase gene from eukaryotes

Directory of Open Access Journals (Sweden)

Fournier Pierre-Edouard

2009-03-01

Full Text Available Abstract Background Free-living amoebae serve as a natural reservoir for some bacteria that have evolved into «amoeba-resistant» bacteria. Among these, some are strictly intra-amoebal, such as Candidatus "Protochlamydia amoebophila" (Candidatus "P. amoebophila", whose genomic sequence is available. We sequenced the genome of Legionella drancourtii (L. drancourtii, another recently described intra-amoebal bacterium. By comparing these two genomes with those of their closely related species, we were able to study the genetic characteristics specific to their amoebal lifestyle. Findings We identified a sterol delta-7 reductase-encoding gene common to these two bacteria and absent in their relatives. This gene encodes an enzyme which catalyses the last step of cholesterol biosynthesis in eukaryotes, and is probably functional within L. drancourtii since it is transcribed. The phylogenetic analysis of this protein suggests that it was acquired horizontally by a few bacteria from viridiplantae. This gene was also found in the Acanthamoeba polyphaga Mimivirus genome, a virus that grows in amoebae and possesses the largest viral genome known to date. Conclusion L. drancourtii acquired a sterol delta-7 reductase-encoding gene of viridiplantae origin. The most parsimonious hypothesis is that this gene was initially acquired by a Chlamydiales ancestor parasite of plants. Subsequently, its descendents transmitted this gene in amoebae to other intra-amoebal microorganisms, including L. drancourtii and Coxiella burnetii. The role of the sterol delta-7 reductase in prokaryotes is as yet unknown but we speculate that it is involved in host cholesterol parasitism.

Dicty_cDB: SSL103 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available (bits) Value N AF305060 |AF305060.1 Dictyostelium discoideum Wiscott-Aldrich syndrome protein (wasA) gene, c...ctyostelium discoideum Wiscott-A... 306 4e-82 FN392319_1421( FN392319 |pid:none) Pichia pastoris GS115 chrom

Dicty_cDB: VHA340 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available _1( AY698035 |pid:none) Desmognathus marmoratus isolate 69... 33 5.9 AC116957_68( AC116957 |pid:none) Dictyo...stelium discoideum chromoso... 33 7.6 AY612344_1( AY612344 |pid:none) Desmognathus marmoratus voucher KH...

Dicty_cDB: Contig-U04690-1 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available scauevk mixed_tissue Sebastes... 34 9.9 2 >( AU071707 ) Dictyostelium discoideum slug cDNA, clone SSC319. L... ( AP006852 ) Candida albicans genomic DNA, chromosome 7, compl... 32 9.3 2 ( GE799624 ) EST_scau_evk_888927

Dicty_cDB: VHI760 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available 7( AC116551 |pid:none) Dictyostelium discoideum chromoso... 79 3e-13 AJ575138_1( AJ575138 |pid:none) Sorda...ria macrospora app gene for a... 50 1e-04 BX571864_113( BX571864 |pid:none) Photorh

Chemotaxis in the cellular slime molds : I. The effect of temperature

NARCIS (Netherlands)

Konijn, Theo M.

1965-01-01

The effect of temperature on chemotaxis in the cellular slime mold Dictyostelium discoideum has been studied by incubating small populations of washed myxamoebae at different temperatures. Droplets containing a cell suspension of known density were deposited on a hydrophobic agar surface. The

Dicty_cDB: VHK596 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available 34 4.7 AY698035_1( AY698035 |pid:none) Desmognathus marmoratus isolate 69... 33 6.1 AC116957_68( AC116957 |p...id:none) Dictyostelium discoideum chromoso... 33 8.0 AY612344_1( AY612344 |pid:none) Desmognathus marmoratus

Dicty_cDB: Contig-U04404-1 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available lone:VS... 498 e-176 2 ( AU266939 ) Dictyostelium discoideum vegetative cDNA clone:VS... 68 5e-07 1 ( FG2946...24 ) 1108770716152 New World Screwworm Larvae 9387 EST... 42 0.027 2 ( CU469174 ) Pig DNA sequence *** SEQUE

Fulltext PDF

Indian Academy of Sciences (India)

Madhu

2006-05-06

May 6, 2006 ... Dictyostelium Conference, held outside Grenoble, France last summer, was attended ... the surface of a Petri dish for several hours, depending on the ..... and it is the basic wild-type strain that has been used by hun- dreds of ...

Ammonia differentially suppresses the cAMP chemotaxis of anterior ...

Indian Academy of Sciences (India)

Unknown

ring sealed with high vacuum stopcock grease to the bottom of a 15 × 35 ..... membrane proton pump inhibition and stalk cell differentia- tion in Dictyostelium ... Genet. 1 13–20. Siegert F and Weijer C J 1992 Three-dimensional scroll waves.

Dicty_cDB: SSI186 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available daria macrospora app gene for a... 58 3e-07 BX571864_113... 25 k... 359 e-102 AC116551_17( AC116551 |pid:none) Dictyostelium discoideum chromoso... 98 2e-19 AJ575138_1( AJ575138 |pid:none) Sor

Dicty_cDB: Contig-U11964-1 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available .. 42 0.87 4 ( EK022497 ) 1092955341513 Global-Ocean-Sampling_GS-31-01-01-1... 48 1.1 1 ( EL474594 ) CHUL2538.b1_C12.ab1 CHU(LMS) puz...zle sunflower Hel... 48 1.1 1 ( BJ370153 ) Dictyostelium

Fulltext PDF

Indian Academy of Sciences (India)

SEARCHU

Molecular mechanisms underlying thermal adaptation of xeric animals. 489. Specific and unspecific responses of plants to cold and drought stress. 501. Adaptive ... Arachidonic Acid is a chemoattractant for Dictyostelium discoideum cells. 1281 .... Contribution of root to soil respiration and carbon balance in disturbed and ...

Journal of Biosciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

What history tells us XXXVII. ... Classification and expression analyses of homeobox genes from Dictyostelium discoideum .... TORC2 and eisosomes are spatially interdependent, requiring optimal level of phosphatidylinositol .... A sample of 14 schizophrenia patients and 14 healthy control subjects matched for age, sex and ...

Dicty_cDB: SSH868 [Dicty_cDB

Lifescience Database Archive (English)

Full Text Available 5 k... 329 5e-89 AC116551_17( AC116551 |pid:none) Dictyostelium discoideum chromoso... 95 2e-18 AJ575138_1( AJ575138 |pid:none) Sorda...ria macrospora app gene for a... 58 3e-07 BX571864_113(

Variation in the SSUrDNA of the Genus Protostelium Leads to a New Phylogenetic Understanding of the Genus and of the Species Concept for Protostelium mycophaga (Protosteliida, Amoebozoa).

Science.gov (United States)

Shadwick, John D L; Silberman, Jeffery D; Spiegel, Frederick W

2018-05-01

Members of the genus Protostelium (including P. mycophaga, P. nocturnum, and P. okumukumu) are protosteloid amoebae commonly found in terrestrial habitats on dead plant matter. They, along with the closely allied nominal genus Planoprotostelium, containing the single species Pl. aurantium, all have an amoeboid trophic stage with acutely pointed subpseudopodia and orange lipid droplets in the granuloplasm. These amoebae form stalked fruiting bodies topped with a single, usually deciduous spore. The species are identified based on their fruiting body morphologies except for Pl. aurantium which looks similar to P. mycophaga in fruiting morphology, but has amoebae that can make flagella in liquid medium. We built phylogenetic trees using nuclear small subunit ribosomal DNA sequences of 35 isolates from the genera Protostelium and Planoprotostelium and found that (1) the nonflagellated P. nocturnum and P. okumukumu branch basally in the genus Protostelium, (2) the flagellate, Pl. aurantium falls within the genus Protostelium in a monophyletic clade with the nominal variety, P. mycophaga var. crassipes, (3) the cultures initially identified as Protostelium mycophaga can be divided into at least three morphologically recognizable taxa, P. aurantium n. comb., P. apiculatum n. sp., and P. m. rodmani n. subsp., as well as a paraphyletic assemblage that includes the remainder of the P. mycophaga morphotype. These findings have implications for understanding the ecology, evolution, and diversity of these amoeboid organisms and for using these amoebae as models for other amoeboid groups. © 2017 The Author(s) Journal of Eukaryotic Microbiology © 2017 International Society of Protistologists.