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Sample records for homonuclear diatomic compounds

  1. Calculation of Ground State Rotational Populations for Kinetic Gas Homonuclear Diatomic Molecules including Electron-Impact Excitation and Wall Collisions

    Energy Technology Data Exchange (ETDEWEB)

    David R. Farley

    2010-08-19

    A model has been developed to calculate the ground-state rotational populations of homonuclear diatomic molecules in kinetic gases, including the effects of electron-impact excitation, wall collisions, and gas feed rate. The equations are exact within the accuracy of the cross sections used and of the assumed equilibrating effect of wall collisions. It is found that the inflow of feed gas and equilibrating wall collisions can significantly affect the rotational distribution in competition with non-equilibrating electron-impact effects. The resulting steady-state rotational distributions are generally Boltzmann for N≥3, with a rotational temperature between the wall and feed gas temperatures. The N=0,1,2 rotational level populations depend sensitively on the relative rates of electron-impact excitation versus wall collision and gas feed rates.

  2. Mass effects in the photodissociation of homonuclear diatomic molecules in helium nanodroplets: inelastic collision and viscous flow energy exchange regimes.

    Science.gov (United States)

    Vilà, Arnau; González, Miguel

    2016-10-05

    The influence of the mass in the photodissociation dynamics of a homonuclear diatomic molecule (X2), embedded in a superfluid helium nanodroplet (T = 0.37 K) of 300 atoms, has been investigated using a hybrid quantum dynamics method recently proposed by us. Several hypothetical isotopic variants of Cl2 have been examined in order to make possible the analysis of a wide diversity of masses (mX: 0.25mCl-1.50mCl). This is probably the first time that this problem has been considered theoretically. The photodissociation mechanism of X2(B) is very similar to that of Cl2(B) and the efficiency of the X2-helium energy exchange mechanism can be so great that it leads to the full and partial (≈86%) geminate recombination for the lower masses explored (mX = 0.25mCl and 0.50mCl, respectively). From the energy exchange perspective two dynamic regimes have been identified. The first regime occurs at the initial times of the photodissociation and corresponds to a perfectly inelastic collision (IC) between the atomic fragments (X) and some helium atoms of the solvation shell. The second regime occurs when the atomic fragments are moving through the nanodroplet, which behaves as a viscous fluid (VF). The ICVF mechanism has probably general character in the photodissociation of molecules embedded in superfluid helium nanodroplets.

  3. Study of the vibrational characteristics of the homonuclear diatomic nuclear schrödinger equation with a numerov method using a number of empirical potential functions

    Science.gov (United States)

    Heidari, Alireza; Anwar Bég, O.; Ghorbani, Mohammadali

    2013-02-01

    Many empirical potential energy functions have been modeled to represent the potential energy function of a diatomic molecule along whole range of internuclear distance coordinate, whereby one can determine certain molecular constants. Here we employ various potential functions such as Morse, Rydberg, Varshni(II), Varshni(III), Varshni(VI), Pöschl-Teller, Hulburt-Hirschfelder, Lippincott, Frost-Musulin, Linnet, and Rosen-Morse, and the Numerov method to solve the nuclear Schrödinger equation for F2, as an example of a homonuclear diatomic molecule. Herewith, the vibrational and vibration-rotation energy levels are obtained and excellent accuracy is achieved. The potential of employing the Numerov method in engineering physics computations is emphasized.

  4. Do independent-particle-model broken-symmetry solutions contain more physics than the symmetry-adapted ones? The case of homonuclear diatomics.

    Science.gov (United States)

    Li, Xiangzhu; Paldus, Josef

    2009-02-28

    We explore spin-preserving, singlet stability of restricted Hartree-Fock (RHF) solutions for a number of closed-shell, homonuclear diatomics in the entire relevant range of internuclear separations. In the presence of such instabilities we explore the implied broken-symmetry (bs) solutions and check their stability. We also address the occurrence of vanishing roots rendered by the stability problem in the case of bs solutions. The RHF bs solutions arise primarily due to the symmetry breaking of the relevant, mostly frontier, molecular orbitals, which approach atomic-type orbitals in the dissociation limit. The resulting bs RHF solutions yield more realistic potential energy curves (PECs) than do the symmetry adapted (sa) solutions. These PECs are shown to be very similar to those rendered by the density functional theory (DFT). Moreover, the sa DFT solutions are found to be stable in a much wider range of internuclear separations than are the RHF solutions, and their bs analogs differ very little from the sa ones. Finally, we examine a possible usefulness of bs RHF solutions in post-HF correlated approaches to the many-electron problem, specifically in the limited configuration interaction and coupled-cluster methods.

  5. Generation of circularly polarized XUV and soft-x-ray high-order harmonics by homonuclear and heteronuclear diatomic molecules subject to bichromatic counter-rotating circularly polarized intense laser fields

    Science.gov (United States)

    Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

    2017-12-01

    Recently, studies of bright circularly polarized high-harmonic beams from atoms in the soft-x-ray region as a source for x-ray magnetic circular dichroism measurement in a tabletop-scale setup have received considerable attention. In this paper, we address the problem with molecular targets and perform a detailed quantum study of H2 +, CO, and N2 molecules in bichromatic counter-rotating circularly polarized laser fields where we adopt wavelengths (1300 and 790 nm) and intensities (2 ×1014W /cm2 ) reported in a recent experiment [Proc. Natl. Acad. Sci. USA 112, 14206 (2015), 10.1073/pnas.1519666112]. Our treatment of multiphoton processes in homonuclear and heteronuclear diatomic molecules is nonperturbative and based on the time-dependent density-functional theory for multielectron systems. The calculated radiation spectrum contains doublets of left and right circularly polarized harmonics with high-energy photons in the XUV and soft-x-ray ranges. Our results reveal intriguing and substantially different nonlinear optical responses for homonuclear and heteronuclear diatomic molecules subject to circularly polarized intense laser fields. We study in detail the below- and above-threshold harmonic regions and analyze the ellipticity and phase of the generated harmonic peaks.

  6. Marine Benthic Diatoms Contain Compounds Able to Induce Leukemia Cell Death and Modulate Blood Platelet Activity

    Directory of Open Access Journals (Sweden)

    Lars Herfindal

    2009-11-01

    Full Text Available In spite of the high abundance and species diversity of diatoms, only a few bioactive compounds from them have been described. The present study reveals a high number of mammalian cell death inducing substances in biofilm-associated diatoms sampled from the intertidal zone. Extracts from the genera Melosira, Amphora, Phaeodactylum and Nitzschia were all found to induce leukemia cell death, with either classical apoptotic or autophagic features. Several extracts also contained inhibitors of thrombin-induced blood platelet activation. Some of this activity was caused by a high content of adenosine in the diatoms, ranging from 0.07 to 0.31 μg/mg dry weight. However, most of the bioactivity was adenosine deaminase-resistant. An adenosine deaminase-resistant active fraction from one of the extracts was partially purified and shown to induce apoptosis with a distinct phenotype. The results show that benthic diatoms typically found in the intertidal zone may represent a richer source of interesting bioactive compounds than hitherto recognized.

  7. Fluorine detected 2D NMR experiments for the practical determination of size and sign of homonuclear F-F and heteronuclear C-F multiple bond J-coupling constants in multiple fluorinated compounds

    Science.gov (United States)

    Aspers, Ruud L. E. G.; Ampt, Kirsten A. M.; Dvortsak, Peter; Jaeger, Martin; Wijmenga, Sybren S.

    2013-06-01

    The use of fluorine in molecules obtained from chemical synthesis has become increasingly important within the pharmaceutical and agricultural industry. NMR characterization of these compounds is of great value with respect to their structure elucidation, their screening in metabolomics investigations and binding studies. The favorable NMR properties of the fluorine nucleus make NMR with fluorine detection of great value in this respect. A suite of NMR 2D F-F- and F-C-correlation experiments with fluorine detection was applied to the assignment of resonances, nJCF- and nJFF-couplings as well as the determination of their size and sign. The utilization of this experiment suite was exemplarily demonstrated for a highly fluorinated vinyl alkyl ether. Especially F-C HSQC and J-scaled F-C HMBC experiments allowed determining the size of the J-couplings of this compound. The relative sign of its homo- and heteronuclear couplings was achieved by different combinations of 2D NMR experiments, including non-selective and F2-selective F-C XLOC, F2-selective F-C HMQC, and F-F COSY. The F2-one/two-site selective F-C XLOC versions were found highly useful, as they led to simplifications of the common E.COSY patterns and resulted in a higher confidence level of the assignment by using selective excitation. The combination of F2-one/two-site selective F-C XLOC experiments with a F2-one-site selective F-C HMQC experiment provided the signs of all nJCF- and nJFF-couplings in the vinyl moiety of the test compound. Other combinations of experiments were found useful as well for special purposes when focusing for example on homonuclear couplings a combination of F-F COSY-10 with a F2-one-site selective F-C HMQC could be used. The E.COSY patterns in the spectra demonstrated were analyzed by use of the spin-selective displacement vectors, and in case of the XLOC also by use of the DQ- and ZQ-displacement vectors. The variety of experiments presented shall contribute to facilitate the

  8. Growth and release of extracellular organic compounds by benthic diatoms depend on interactions with bacteria.

    Science.gov (United States)

    Bruckner, Christian G; Rehm, Charlotte; Grossart, Hans-Peter; Kroth, Peter G

    2011-04-01

    Phototrophic epilithic biofilms harbour a distinct assemblage of heterotrophic bacteria, cyanobacteria and photoautotrophic algae. Secretion of extracellular polymeric substances (EPS) by these organisms and the physicochemical properties of the EPS are important factors for the development of the biofilms. We have isolated representative diatom and bacteria strains from epilithic biofilms of Lake Constance. By pairwise co-cultivating these strains we found that diatom growth and EPS secretion by diatoms may depend on the presence of individual bacteria. Similar results were obtained after addition of spent bacterial medium to diatom cultures, suggesting that soluble substances from bacteria have an impact on diatom physiology. While searching for putative bacterial signal substances, we found that concentrations of various dissolved free amino acids (DFAA) within the diatom cultures changed drastically during co-cultivation with bacteria. Further, the secretion of extracellular carbohydrates and proteins can be influenced by bacteria or their extracellular substances. We have performed mass spectrometric peptide mapping to identify proteins which are secreted when co-cultivating the diatom Phaeodactylum tricornutum Bohlin and Escherichia coli. The identified proteins are possibly involved in signalling, extracellular carbohydrate modification and uptake, protein and amino acid modification, and cell/cell aggregation of diatom and bacteria strains. Our data indicate that diatom-bacteria biofilms might be regulated by a complex network of chemical factors involving EPS, amino acid monomers and other substances. Thus interactions with bacteria can be considered as one of the main factors driving biofilm formation by benthic diatoms. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

  9. Relativistic coupled cluster study of diatomic compounds of Hg, Cn, and Fl

    Energy Technology Data Exchange (ETDEWEB)

    Borschevsky, A. [Helmholtz Institute Mainz, Mainz D-55128 (Germany); Pershina, V. [GSI Helmholtzzentrum für Schwerionenforschung, Planckstr. 1, Darmstadt D-64291 (Germany); Eliav, E.; Kaldor, U. [School of Chemistry, Tel Aviv University, 69978 Tel Aviv (Israel)

    2014-08-28

    The structure and energetics of eight diatomic heavy-atom molecules are presented. These include the species MAu, M{sub 2}, and MHg, with M standing for the Hg, Cn (element 112), and Fl (element 114) atoms. The infinite-order relativistic 2-component Hamiltonian, known to closely reproduce 4-component results at lower computational cost, is used as framework. High-accuracy treatment of correlation is achieved by using the coupled cluster scheme with single, double, and perturbative triple excitations in large converged basis sets. The calculated interatomic separation and bond energy of Hg{sub 2}, the only compound with known experimental data, are in good agreement with measurements. The binding of Fl to Au is stronger than that of Cn, predicting stronger adsorption on gold surfaces. The bond in the M{sub 2} species is strongest for Fl{sub 2}, being of chemical nature; weaker bonds appear in Cn{sub 2} and Hg{sub 2}, which are bound by van der Waals interactions, with the former bound more strongly due to the smaller van der Waals radius. The same set of calculations was also performed using the relativistic density functional theory approach, in order to test the performance of the latter for these weakly bound systems with respect to the more accurate coupled cluster calculations. It was found that for the MAu species the B3LYP functional provides better agreement with the coupled cluster results than the B88/P86 functional. However, for the M{sub 2} and the MHg molecules, B3LYP tends to underestimate the binding energies.

  10. Molecular Dynamics and Spectra. II. Diatomic Raman.

    Science.gov (United States)

    1981-02-01

    a degeneracy factor g is introduced which depends on the symmetry of the molecule For our IT- homonuclear diatomic, z is gj, the nuclear spin...classi~a mechanical viewpoint. with some caveats for features In which anharmonicity is important, such as the de- tailed shape of Q branches. it is...to compute the Spectra of coa- plex molecular systems, for example of large molecules , clusters, liquids, solutions, and solids. Second, this

  11. The Diatoms

    Indian Academy of Sciences (India)

    IAS Admin

    Agharkar Research. Institute. She is studying the biogeography of freshwater diatoms in. Western Ghats for her thesis. (right) Balasubramanian. Karthick is Scientist with. Biodiversity and. Paleobiology group of. Agharkar Research. Institute. His interests include diatom taxonomy and ecology, microbial biogeography, and ...

  12. Exploring the Bermuda triangle of homonuclear diatomic spectroscopy: The electronic spectrum and structure of Ge2

    Science.gov (United States)

    Hostutler, David A.; Li, Haiyang; Clouthier, Dennis J.; Wannous, Ghassan

    2002-03-01

    The optical spectrum of jet-cooled Ge2 has been observed for the first time. Laser-induced fluorescence (LIF) and wavelength resolved emission spectra were recorded using the pulsed discharge technique with a tetramethylgermane precursor. Analysis of the spectra yielded the vibrational constants ωe″=287.9(47), ωexe″=0.81(55), ωeye″=0.0037(18), ωe'=189.0(15), ωexe'=6.41(30), and Te'=20 610.8(16) cm-1. High-resolution rotationally resolved spectra of several bands of 74Ge2 show two strong P and R branches and two very weak Q branches. We have assigned the band system as a Hund's case (c) Ω'=1-Ω″=1 transition from the ground 3Σg- state to a 3Σu- excited state. The bond lengths derived from the rotational constants are r0″=2.3680(1) Å and re'=2.5244(18) Å, an ˜0.16 Å increase on electronic excitation. Arguments are presented for assigning the transition to a σg2πu2→σg2πuπg electron promotion, although the observed increase in the bond length is much less than predicted by previous ab initio calculations. The absence of the 0u+-0g+ component in the spectra has been attributed to an excited state predissociation.

  13. Spectroscopic Constants for Selected Homonuclear Diatomic Molecules. Volume 2. K through Z

    Science.gov (United States)

    1976-02-16

    Characteristic Bands, X R R 6883.9(2,0) 4800, 6(3, 1) 4778. 8(2,0) 3358. 6(0,2) 3315.6(0, 1) Remarks Several bands of the isotopic ape cies...64. 47) (64. 47a) (64, 48) (64. 49) (65. 50) (65. 51) (65. 52) (65. 53) (65. 54) Isotope Displacements and Vibrational Structure, D... Radium 20, 915-7 (60. 33) Raman Spectrum, A. Weber and E. A. MacGinnis, J. Molec. Spectrosc. 4, 195-200 0-19 i 71 o. (61. 34

  14. The influence of extracellular compounds produced by selected Baltic cyanobacteria, diatoms and dinoflagellates on growth of green algae Chlorella vulgaris

    Science.gov (United States)

    Żak, Adam; Kosakowska, Alicja

    2015-12-01

    Secondary metabolites produced by bacteria, fungi, algae and plants could affect the growth and development of biological and agricultural systems. This natural process that occurs worldwide is known as allelopathy. The main goal of this work was to investigate the influence of metabolites obtained from phytoplankton monocultures on the growth of green algae Chlorella vulgaris. We selected 6 species occurring in the Baltic Sea from 3 different taxonomic groups: cyanobacteria (Aphanizomenon flos-aquae; Planktothrix agardhii), diatoms (Thalassiosira pseudonana; Chaetoceros wighamii) and dinoflagellates (Alexandrium ostenfeldii; Prorocentrum minimum). In this study we have demonstrated that some of selected organisms caused allelopathic effects against microalgae. Both the negative and positive effects of collected cell-free filtrates on C. vulgaris growth, chlorophyll a concentration and fluorescence parameters (OJIP, QY, NPQ) have been observed. No evidence has been found for the impact on morphology and viability of C. vulgaris cells.

  15. The Diatoms

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 10. The Diatoms: Big Significance of Tiny Glass Houses. Aditi Kale Balasubramanian Karthick. General Article Volume 20 Issue 10 October 2015 pp 919-930. Fulltext. Click here to view fulltext PDF. Permanent link:

  16. Spectroscopy of Vibrational States in Diatomic Iodine Molecules

    Science.gov (United States)

    Mulholland, Mary; Harrill, Charles H.; Smith, R. Seth

    2015-04-01

    This project is focused on understanding the vibrational structure of iodine, which is a homonuclear diatomic molecule. A 20 mW, 532 nm cw diode laser was used to selectively excite neutral iodine molecules to a higher energy electronic state. By performing spectroscopy on the transitions from this state to a lower energy electronic state, the data only showed those vibrational bands which connect the two electronic states. Since a number of vibrational levels are populated in the higher energy electronic state, the transitions to all of the allowed vibrational levels in the lower energy electronic state provided sufficient data to determine the vibrational structures of both states. Emission spectra were collected with an Ocean Optics USB4000 Compact CCD Spectrometer. The spectrometer had a range of 500 - 770 nm with a resolution of approximately 0.5 nm and was sensitive enough to resolve the vibrational states in diatomic iodine molecules. The results were compared to a simple harmonic oscillator model.

  17. Even harmonic generation in isotropic media of dissociating homonuclear molecules

    CERN Document Server

    Silva, R E F; Morales, F; Smirnova, O; Ivanov, M; Martín, F

    2016-01-01

    Isotropic gases irradiated by long pulses of intense IR light can generate very high harmonics of the incident field. It is generally accepted that, due to the symmetry of the generating medium, be it an atomic or an isotropic molecular gas, only odd harmonics of the driving field can be produced. Here we show how the interplay of electronic and nuclear dynamics can lead to a marked breakdown of this standard picture: a substantial part of the harmonic spectrum can consist of even rather than odd harmonics. We demonstrate the effect using ab-initio solutions of the time-dependent Schr\\"odinger equation for $H$$_2$$^+$ and its isotopes in full dimensionality. By means of a simple analytical model, we identify its physical origin, which is the appearance of a permanent dipole moment in dissociating homonuclear molecules, caused by light-induced localization of the electric charge during dissociation. The effect arises for sufficiently long laser pulses and the region of the spectrum where even harmonics are pro...

  18. Distance Measurements between Homonuclear Spins in Rotating Solids

    Science.gov (United States)

    Weintraub, O.; Vega, S.; Hoelger, C.; Limbach, H. H.

    The effective Hamiltonian of the "simple excitation for the dephasing of the rotational-echo amplitudes" (SEDRA) experiment has been derived. This experiment enables the determination of the strength of the dipolar interaction of a homonuclear spin pair in a solid, rotating at the magic angle, and thus provides a way to measure internuclear distances. The dipolar decay of the rotational-echo amplitudes of powder samples, generated by a set of π pulses, is measured together with the echo decay that is not influenced by the dipolar interaction. The latter is measured by the transverse-echo SEDRA experiment that refocuses the SEDRA decay. The Floquet theory approach is utilized to evaluate the effective Hamiltonians that describe the behavior of the spin systems. The influence of the chemical-shift anisotropy parameters of the interacting spins on the effective SEDRA Hamiltonian is also discussed. Results of Δ S/ S0 SEDRA experiments on the 15N spin pair in solid 3(5)-methyl-5(3) -phenylpyrazole- 15N 2 are shown and compared with exact calculations. The data suggest a nuclear distance between the nitrogen atoms of 1.385 ± 0.025 Å.

  19. Diatom-Specific Oligosaccharide and Polysaccharide Structures Help to Unravel Biosynthetic Capabilities in Diatoms

    Directory of Open Access Journals (Sweden)

    Bruno Gügi

    2015-09-01

    Full Text Available Diatoms are marine organisms that represent one of the most important sources of biomass in the ocean, accounting for about 40% of marine primary production, and in the biosphere, contributing up to 20% of global CO2 fixation. There has been a recent surge in developing the use of diatoms as a source of bioactive compounds in the food and cosmetic industries. In addition, the potential of diatoms such as Phaeodactylum tricornutum as cell factories for the production of biopharmaceuticals is currently under evaluation. These biotechnological applications require a comprehensive understanding of the sugar biosynthesis pathways that operate in diatoms. Here, we review diatom glycan and polysaccharide structures, thus revealing their sugar biosynthesis capabilities.

  20. Amino Acid Biosynthesis Pathways in Diatoms

    Directory of Open Access Journals (Sweden)

    Mariusz A. Bromke

    2013-04-01

    Full Text Available Amino acids are not only building blocks for proteins but serve as precursors for the synthesis of many metabolites with multiple functions in growth and other biological processes of a living organism. The biosynthesis of amino acids is tightly connected with central carbon, nitrogen and sulfur metabolism. Recent publication of genome sequences for two diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum created an opportunity for extensive studies on the structure of these metabolic pathways. Based on sequence homology found in the analyzed diatomal genes, the biosynthesis of amino acids in diatoms seems to be similar to higher plants. However, one of the most striking differences between the pathways in plants and in diatomas is that the latter possess and utilize the urea cycle. It serves as an important anaplerotic pathway for carbon fixation into amino acids and other N-containing compounds, which are essential for diatom growth and contribute to their high productivity.

  1. A discrete Fourier-encoded, diagonal-free experiment to simplify homonuclear 2D NMR correlations

    Science.gov (United States)

    Huang, Zebin; Guan, Quanshuai; Chen, Zhong; Frydman, Lucio; Lin, Yulan

    2017-07-01

    Nuclear magnetic resonance (NMR) spectroscopy has long served as an irreplaceable, versatile tool in physics, chemistry, biology, and materials sciences, owing to its ability to study molecular structure and dynamics in detail. In particular, the connectivity of chemical sites within molecules, and thereby molecular structure, becomes visible by multi-dimensional NMR. Homonuclear correlation experiments are a powerful tool for identifying coupled spins. Generally, diagonal peaks in these correlation spectra display the strongest intensities and do not offer any new information beyond the standard one-dimensional spectrum, whereas weaker, symmetrically placed cross peaks contain most of the coupling information. The cross peaks near the diagonal are often affected by the tails of strong diagonal peaks or even obscured entirely by the diagonal. In this paper, we demonstrate a homonuclear encoding approach based on imparting a discrete phase modulation of the targeted cross peaks and combine it with a site-selective sculpting scheme, capable of simplifying the patterns arising in these 2D correlation spectra. The theoretical principles of the new methods are laid out, and experimental observations are rationalized on the basis of theoretical analyses. The ensuing techniques provide a new way to retrieve 2D coupling information within homonuclear spin systems, with enhanced sensitivity, speed, and clarity.

  2. Diatomées

    African Journals Online (AJOL)

    Impact environnemental et évaluation de la qualité des eaux par des méthodes chimiques et biologiques « Diatomées » ... possèdent un caractère alcaliphyle prononcé avec une abondance des espèces résistantes à la pollution organique. Mots clés : Diatomées, qualité de l'eau, bio-indicateur, IDL, IPO, Merja Fouarat.

  3. The Microscopic World of Diatoms

    Science.gov (United States)

    Sultany, Molly; Bixby, Rebecca

    2016-01-01

    For students in biology, chemistry, or environmental science, diatoms offer excellent insight into watershed health and human impact on the environment. Diatoms are found globally in virtually every habitat that has sunlight and moisture, including polar seas, tropical streams, and on moist soils and mosses. Studying diatoms as biological…

  4. Coherence Transfer in Dipolar-Coupled Homonuclear Spin Systems in Solids Rotating at the Magic Angle

    Science.gov (United States)

    Weintraub, O.; Vega, S.; Hoelger, C.; Limbach, H. H.

    Two routes for the exploitation of the t-SEDRA pulse scheme, which induces coherence transfer in dipolar-coupled homonuclear spin systems in rotating samples, are demonstrated and discussed. This sequence is utilized to deduce intramolecular connectivities by creating an initial coherence of one spin only, applying the t-SEDRA sequence, and monitoring the signal enhancement of the coupled spin. Probing the signal amplitude variations of the two spins and comparing them to simulations can also yield molecular distances. Using 2D spectroscopy, t-SEDRA can also be utilized to establish spin correlations. In this case, the t-SEDRA sequence is applied during the mixing time of a 2D dipolar-correlation experiment. These two approaches are demonstrated by performing 15N CPMAS NMR experiments on a 15N-doubly labeled sample of 3(5)-methyl-5(3)-phenylpyrazole.

  5. Compound

    Indian Academy of Sciences (India)

    UV-vis spectra showing solvent effects on compounds (6). Figure S4. UV-vis spectra showing solvent effects on compounds (9). Figure S5. UV-vis spectra showing solvent ___, acidic--- and basic -□- effects on compound (8) in CH2Cl2 solution. Table S1. 1H and 13C NMR spectral data of salicylaldimine Schiff bases (5-8).

  6. Designer diatom episomes delivered by bacterial conjugation

    National Research Council Canada - National Science Library

    Karas, Bogumil J; Diner, Rachel E; Lefebvre, Stephane C; McQuaid, Jeff; Phillips, Alex P R; Noddings, Chari M; Brunson, John K; Valas, Ruben E; Deerinck, Thomas J; Jablanovic, Jelena; Gillard, Jeroen T F; Beeri, Karen; Ellisman, Mark H; Glass, John I; Hutchison, 3rd, Clyde A; Smith, Hamilton O; Venter, J Craig; Allen, Andrew E; Dupont, Christopher L; Weyman, Philip D

    2015-01-01

    .... Here we describe the first nuclear episomal vector for diatoms and a plasmid delivery method via conjugation from Escherichia coli to the diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana...

  7. Interactions between Diatoms and Bacteria

    Science.gov (United States)

    Amin, Shady A.; Parker, Micaela S.

    2012-01-01

    Summary: Diatoms and bacteria have cooccurred in common habitats for hundreds of millions of years, thus fostering specific associations and interactions with global biogeochemical consequences. Diatoms are responsible for one-fifth of the photosynthesis on Earth, while bacteria remineralize a large portion of this fixed carbon in the oceans. Through their coexistence, diatoms and bacteria cycle nutrients between oxidized and reduced states, impacting bioavailability and ultimately feeding higher trophic levels. Here we present an overview of how diatoms and bacteria interact and the implications of these interactions. We emphasize that heterotrophic bacteria in the oceans that are consistently associated with diatoms are confined to two phyla. These consistent bacterial associations result from encounter mechanisms that occur within a microscale environment surrounding a diatom cell. We review signaling mechanisms that occur in this microenvironment to pave the way for specific interactions. Finally, we discuss known interactions between diatoms and bacteria and exciting new directions and research opportunities in this field. Throughout the review, we emphasize new technological advances that will help in the discovery of new interactions. Deciphering the languages of diatoms and bacteria and how they interact will inform our understanding of the role these organisms have in shaping the ocean and how these interactions may change in future oceans. PMID:22933565

  8. Interactions between diatoms and bacteria.

    Science.gov (United States)

    Amin, Shady A; Parker, Micaela S; Armbrust, E Virginia

    2012-09-01

    Diatoms and bacteria have cooccurred in common habitats for hundreds of millions of years, thus fostering specific associations and interactions with global biogeochemical consequences. Diatoms are responsible for one-fifth of the photosynthesis on Earth, while bacteria remineralize a large portion of this fixed carbon in the oceans. Through their coexistence, diatoms and bacteria cycle nutrients between oxidized and reduced states, impacting bioavailability and ultimately feeding higher trophic levels. Here we present an overview of how diatoms and bacteria interact and the implications of these interactions. We emphasize that heterotrophic bacteria in the oceans that are consistently associated with diatoms are confined to two phyla. These consistent bacterial associations result from encounter mechanisms that occur within a microscale environment surrounding a diatom cell. We review signaling mechanisms that occur in this microenvironment to pave the way for specific interactions. Finally, we discuss known interactions between diatoms and bacteria and exciting new directions and research opportunities in this field. Throughout the review, we emphasize new technological advances that will help in the discovery of new interactions. Deciphering the languages of diatoms and bacteria and how they interact will inform our understanding of the role these organisms have in shaping the ocean and how these interactions may change in future oceans.

  9. Controlling dynamics in diatomic systems

    Indian Academy of Sciences (India)

    Keywords. Iterative method; optimal control theory; diatomic systems; quantum control. Abstract. Controlling molecular energetics using laser pulses is exemplified for nuclear motion in two different diatomic systems. The problem of finding the optimized field for maximizing a desired quantum dynamical target is formulated ...

  10. Homonuclear 1H NMR and circular dichroism study of the HIV-1 Tat Eli variant

    Science.gov (United States)

    Watkins, Jennifer D; Campbell, Grant R; Halimi, Hubert; Loret, Erwann P

    2008-01-01

    Background The HIV-1 Tat protein is a promising target to develop AIDS therapies, particularly vaccines, due to its extracellular role that protects HIV-1-infected cells from the immune system. Tat exists in two different lengths, 86 or 87 residues and 99 or 101 residues, with the long form being predominant in clinical isolates. We report here a structural study of the 99 residue Tat Eli variant using 2D liquid-state NMR, molecular modeling and circular dichroism. Results Tat Eli was obtained from solid-phase peptide synthesis and the purified protein was proven biologically active in a trans-activation assay. Circular dichroism spectra at different temperatures up to 70°C showed that Tat Eli is not a random coil at 20°C. Homonuclear 1H NMR spectra allowed us to identify 1639 NMR distance constraints out of which 264 were interresidual. Molecular modeling satisfying at least 1474 NMR constraints revealed the same folding for different model structures. The Tat Eli model has a core region composed of a part of the N-terminus including the highly conserved Trp 11. The extra residues in the Tat Eli C-terminus protrude from a groove between the basic region and the cysteine-rich region and are well exposed to the solvent. Conclusion We show that active Tat variants share a similar folding pattern whatever their size, but mutations induce local structural changes. PMID:18808674

  11. Determination of proton transverse relaxation times in homonuclear-coupled Spin Systems

    Science.gov (United States)

    Gochin, Miriam

    A new method is described for obtaining proton transverse relaxation times in homonuclear-coupled systems. The oscillatory effect of the coupling on the T2 decay was removed by using the attached heteronucleus as a filter. A BIRD pulse (J. R. Garbow, D. P. Weitekamp, and A. Pines, Chem. Phys. Lett.93, 504, 1982) was applied in the center of the T2 decay period, causing protons directly and remotely connected to the heteronucleus to be decoupled from each other. Protons directly bound to the heteronucleus were inverted, leaving remote protons unaffected. Thus the method works well in natural-abundance 13C and 15N systems or for 15N-enriched biological materials, where no NN connectivities exist. The importance of obtaining proton T2 values pertains to their usefulness and sensitivity in quantitating structure and mobility in molecules. Sequences for obtaining proton T2 values were described and demonstrated on formate, alcohol, and gramicidin S. The accuracy of the measured T2 as a function of X-nucleus offset and heteronuclear coupling constant was assessed.

  12. Improved Narrowband Dipolar Recoupling for Homonuclear Distance Measurements in Rotating Solids

    Science.gov (United States)

    Goobes, G.; Vega, S.

    2002-02-01

    Recovery of the magnetic dipolar interaction between nuclei bearing the same gyromagnetic ratio in rotating solids can be promoted by synchronous rf irradiation. Determination of the dipolar interaction strength can serve as a tool for structural elucidation in polycrystalline powders. Spinning frequency dependent narrow-band (nb) RFDR and SEDRA experiments are utilized as simple techniques for the determination of dipolar interactions between the nuclei in coupled homonuclear spin pairs. The magnetization exchange and coherence dephasing due to a fixed number of rotor-synchronously applied π-pulses is monitored at spinning frequencies in the vicinity of the rotational resonance (R2) conditions. The powder nbRFDR and nbSEDRA decay curves of spin magnetizations and coherences, respectively, as a function of the spinning frequency can be measured and analyzed using simple rate equations providing a quantitative measure of the dipolar coupling. The effects of the phenomenological relaxation parameters in these rate equations are discussed and an improved methodology is suggested for analyzing nbRFDR data for small dipolar couplings. The distance between the labeled nuclei in the 1,3-13C2-hydroxybutyric acid molecule is rederived using existing nbRFDR results and the new simulation procedure. A nbSEDRA experiment has been performed successfully on a powder sample of singly labeled 1-13C-L-leucine measuring the dipolar interaction between the labeled carboxyl carbon and the natural abundant β-carbon. Both narrowband techniques are employed for the determination of the nuclear distances between the side-chain carbons of leucine and its carbonyl carbon in a tripeptide Leu-Gly-Phe that is singly 13C-labeled at the leucine carbonyl carbon position.

  13. Synthesis of Ag nanoparticles using diatom cells for ammonia sensing

    Directory of Open Access Journals (Sweden)

    Lakhi Chetia

    2017-11-01

    Full Text Available Growth of silver nanoparticles through photo induced bioreduction mechanism on the surface of diatom cells, which is a kind of photosensitive fresh water organism containing hydrated amorphous silica structure, has been found to be a cost-effective, rapid, non-toxic, eco-friendly, photo-induced bottom-up process. This material shows broad absorbance in the visible light spectra. Light sensitive fucoxanthin pigment of diatoms that contain hydroxyl (−OH groups, play a vital role in the formation of silver cluster on the surface of diatom cells and its growth process. Involvement of the compounds and proteins of the diatoms which are responsible for reduction of metal ions and stabilization of the grown nanoparticles on diatom cells, are confirmed by FTIR analysis. Investigations are done to see if the synthesized samples acted as sensing material in the fabrication of a room temperature sensor of dissolved ammonia. With increase in ammonia concentration the visible light absorption peaks tend to higher intensity with blue shift due to the formation of [Ag(NH32]+ complexes causing repulsion between the Ag nanoparticles and consequently lead to the formation of smaller Ag nanoparticles. The intensity of absorption of the as-synthesized material is linearly correlated with the concentration of dissolved ammonia as observed from 0 to 100ppm. The use of naturally occurring diatoms for Ag nanoparticles synthesis has the benefits of amenability for large-scale easy production. Also the experimental findings indicate that the as-synthesized material can act as fast and reliable sensing material. Keywords: Diatoms, Fucoxanthin, Silver nanoparticles, Ammonia sensor

  14. Stuart R. Stidolph diatom atlas

    Science.gov (United States)

    Stidolph, S.R.; Sterrenburg, F.A.S.; Smith, K.E.L.; Kraberg, A.

    2012-01-01

    The "Stuart R. Stidolph Diatom Atlas" is a comprehensive volume of diatom taxa identified and micrographed by Stuart R. Stidoph during the 1980s and 1990s. The samples were collected from marine coasts of various geographic regions within tropical and subtropical climates. The plates included within this report have never been published and are being published by the USGS as an online reference so that others may have access to this incredible collection.

  15. Diatom Milking: A Review and New Approaches

    Science.gov (United States)

    Vinayak, Vandana; Manoylov, Kalina M.; Gateau, Hélène; Blanckaert, Vincent; Hérault, Josiane; Pencréac’h, Gaëlle; Marchand, Justine; Gordon, Richard; Schoefs, Benoît

    2015-01-01

    The rise of human populations and the growth of cities contribute to the depletion of natural resources, increase their cost, and create potential climatic changes. To overcome difficulties in supplying populations and reducing the resource cost, a search for alternative pharmaceutical, nanotechnology, and energy sources has begun. Among the alternative sources, microalgae are the most promising because they use carbon dioxide (CO2) to produce biomass and/or valuable compounds. Once produced, the biomass is ordinarily harvested and processed (downstream program). Drying, grinding, and extraction steps are destructive to the microalgal biomass that then needs to be renewed. The extraction and purification processes generate organic wastes and require substantial energy inputs. Altogether, it is urgent to develop alternative downstream processes. Among the possibilities, milking invokes the concept that the extraction should not kill the algal cells. Therefore, it does not require growing the algae anew. In this review, we discuss research on milking of diatoms. The main themes are (a) development of alternative methods to extract and harvest high added value compounds; (b) design of photobioreactors; (c) biodiversity and (d) stress physiology, illustrated with original results dealing with oleaginous diatoms. PMID:25939034

  16. Diatom Milking: A Review and New Approaches

    Directory of Open Access Journals (Sweden)

    Vandana Vinayak

    2015-04-01

    Full Text Available The rise of human populations and the growth of cities contribute to the depletion of natural resources, increase their cost, and create potential climatic changes. To overcome difficulties in supplying populations and reducing the resource cost, a search for alternative pharmaceutical, nanotechnology, and energy sources has begun. Among the alternative sources, microalgae are the most promising because they use carbon dioxide (CO2 to produce biomass and/or valuable compounds. Once produced, the biomass is ordinarily harvested and processed (downstream program. Drying, grinding, and extraction steps are destructive to the microalgal biomass that then needs to be renewed. The extraction and purification processes generate organic wastes and require substantial energy inputs. Altogether, it is urgent to develop alternative downstream processes. Among the possibilities, milking invokes the concept that the extraction should not kill the algal cells. Therefore, it does not require growing the algae anew. In this review, we discuss research on milking of diatoms. The main themes are (a development of alternative methods to extract and harvest high added value compounds; (b design of photobioreactors; (c biodiversity and (d stress physiology, illustrated with original results dealing with oleaginous diatoms.

  17. Biochemical and Genetic Engineering of Diatoms for Polyunsaturated Fatty Acid Biosynthesis

    Directory of Open Access Journals (Sweden)

    Hong-Ye Li

    2014-01-01

    Full Text Available The role of diatoms as a source of bioactive compounds has been recently explored. Diatom cells store a high amount of fatty acids, especially certain polyunsaturated fatty acids (PUFAs. However, many aspects of diatom metabolism and the production of PUFAs remain unclear. This review describes a number of technical strategies, such as modulation of environmental factors (temperature, light, chemical composition of culture medium and culture methods, to influence the content of PUFAs in diatoms. Genetic engineering, a newly emerging field, also plays an important role in controlling the synthesis of fatty acids in marine microalgae. Several key points in the biosynthetic pathway of PUFAs in diatoms as well as recent progresses are also a critical part and are summarized here.

  18. Biochemical and genetic engineering of diatoms for polyunsaturated fatty acid biosynthesis.

    Science.gov (United States)

    Li, Hong-Ye; Lu, Yang; Zheng, Jian-Wei; Yang, Wei-Dong; Liu, Jie-Sheng

    2014-01-07

    The role of diatoms as a source of bioactive compounds has been recently explored. Diatom cells store a high amount of fatty acids, especially certain polyunsaturated fatty acids (PUFAs). However, many aspects of diatom metabolism and the production of PUFAs remain unclear. This review describes a number of technical strategies, such as modulation of environmental factors (temperature, light, chemical composition of culture medium) and culture methods, to influence the content of PUFAs in diatoms. Genetic engineering, a newly emerging field, also plays an important role in controlling the synthesis of fatty acids in marine microalgae. Several key points in the biosynthetic pathway of PUFAs in diatoms as well as recent progresses are also a critical part and are summarized here.

  19. Towards a representative periphytic diatom sample

    Directory of Open Access Journals (Sweden)

    2007-01-01

    Full Text Available The need to acquire a representative periphytic diatom sample for river water quality monitoring has been recognised in the development of existing diatom indices, important in the development and employment of diatom monitoring tools for the Water Framework Directive. In this study, a nested design with replication is employed to investigate the magnitude of variation in diatom biomass, composition and Trophic Diatom Index at varying scales within a small chalk river. The study shows that the use of artificial substrates may not result in diatom communities that are typical of the surrounding natural substrates. Periphytic diatom biomass and composition varies between artificial and natural substrates, riffles and glides and between two stretches of the river channel. The study also highlights the existence of high variation in diatom frustule frequency and biovolume at the individual replicate scale which may have implications for the use of diatoms in routine monitoring.

  20. Metabolomic Profiling of 13 Diatom Cultures and Their Adaptation to Nitrate-Limited Growth Conditions

    Science.gov (United States)

    Bromke, Mariusz A.; Sabir, Jamal S.; Alfassi, Fahad A.; Hajarah, Nahid H.; Kabli, Saleh A.; Al-Malki, Abdulrahman L.; Ashworth, Matt P.; Méret, Michaël; Jansen, Robert K.; Willmitzer, Lothar

    2015-01-01

    Diatoms are very efficient in their use of available nutrients. Changes in nutrient availability influence the metabolism and the composition of the cell constituents. Since diatoms are valuable candidates to search for oil producing algae, measurements of diatom-produced compounds can be very useful for biotechnology. In order to explore the diversity of lipophilic compounds produced by diatoms, we describe the results from an analysis of 13 diatom strains. With the help of a lipidomics platform, which combines an UPLC separation with a high resolution/high mass accuracy mass spectrometer, we were able to measure and annotate 142 lipid species. Out of these, 32 were present in all 13 cultures. The annotated lipid features belong to six classes of glycerolipids. The data obtained from the measurements were used to create lipidomic profiles. The metabolomic overview of analysed cultures is amended by the measurement of 96 polar compounds. To further increase the lipid diversity and gain insight into metabolomic adaptation to nitrogen limitation, diatoms were cultured in media with high and low concentrations of nitrate. The growth in nitrogen-deplete or nitrogen-replete conditions affects metabolite accumulation but has no major influence on the species-specific metabolomic profile. Thus, the genetic component is stronger in determining metabolic patterns than nitrogen levels. Therefore, lipid profiling is powerful enough to be used as a molecular fingerprint for diatom cultures. Furthermore, an increase of triacylglycerol (TAG) accumulation was observed in low nitrogen samples, although this trend was not consistent across all 13 diatom strains. Overall, our results expand the current understanding of metabolomics diversity in diatoms and confirm their potential value for producing lipids for either bioenergy or as feed stock. PMID:26440112

  1. Metabolomic Profiling of 13 Diatom Cultures and Their Adaptation to Nitrate-Limited Growth Conditions.

    Directory of Open Access Journals (Sweden)

    Mariusz A Bromke

    Full Text Available Diatoms are very efficient in their use of available nutrients. Changes in nutrient availability influence the metabolism and the composition of the cell constituents. Since diatoms are valuable candidates to search for oil producing algae, measurements of diatom-produced compounds can be very useful for biotechnology. In order to explore the diversity of lipophilic compounds produced by diatoms, we describe the results from an analysis of 13 diatom strains. With the help of a lipidomics platform, which combines an UPLC separation with a high resolution/high mass accuracy mass spectrometer, we were able to measure and annotate 142 lipid species. Out of these, 32 were present in all 13 cultures. The annotated lipid features belong to six classes of glycerolipids. The data obtained from the measurements were used to create lipidomic profiles. The metabolomic overview of analysed cultures is amended by the measurement of 96 polar compounds. To further increase the lipid diversity and gain insight into metabolomic adaptation to nitrogen limitation, diatoms were cultured in media with high and low concentrations of nitrate. The growth in nitrogen-deplete or nitrogen-replete conditions affects metabolite accumulation but has no major influence on the species-specific metabolomic profile. Thus, the genetic component is stronger in determining metabolic patterns than nitrogen levels. Therefore, lipid profiling is powerful enough to be used as a molecular fingerprint for diatom cultures. Furthermore, an increase of triacylglycerol (TAG accumulation was observed in low nitrogen samples, although this trend was not consistent across all 13 diatom strains. Overall, our results expand the current understanding of metabolomics diversity in diatoms and confirm their potential value for producing lipids for either bioenergy or as feed stock.

  2. S(3) HMBC: Spin-State-Selective HMBC for accurate measurement of homonuclear coupling constants. Application to strychnine yielding thirteen hitherto unreported J(HH).

    Science.gov (United States)

    Kjaerulff, Louise; Benie, Andrew J; Hoeck, Casper; Gotfredsen, Charlotte H; Sørensen, Ole W

    2016-02-01

    A novel method, Spin-State-Selective (S(3)) HMBC, for accurate measurement of homonuclear coupling constants is introduced. As characteristic for S(3) techniques, S(3) HMBC yields independent subspectra corresponding to particular passive spin states and thus allows determination of coupling constants between detected spins and homonuclear coupling partners along with relative signs. In the presented S(3) HMBC experiment, spin-state selection occurs via large one-bond coupling constants ensuring high editing accuracy and unequivocal sign determination of the homonuclear long-range relative to the associated one-bond coupling constant. The sensitivity of the new experiment is comparable to that of regular edited HMBC and the accuracy of the J/RDC measurement is as usual for E.COSY and S(3)-type experiments independent of the size of the homonuclear coupling constant of interest. The merits of the method are demonstrated by an application to strychnine where thirteen J(HH) coupling constants not previously reported could be measured. Copyright © 2015 Elsevier Inc. All rights reserved.

  3. Diatom genomics: genetic acquisitions and mergers.

    Science.gov (United States)

    Nisbet, R Ellen R; Kilian, Oliver; McFadden, Geoffrey I

    2004-12-29

    Diatom algae arose by two-step endosymbiosis. The complete genome of the diatom Thalassiosira pseudonana has now been sequenced, allowing us to reconstruct the remarkable intracellular gene transfers that occurred during this convoluted cellular evolution.

  4. Diatoms and drowning--once more.

    Science.gov (United States)

    Foged, N

    1983-01-01

    The content of diatoms in 5 samples: lung-, kidney- and liver-tissue plus columna- and femur-marrow from each of four drowned and four non-drowned persons has been investigated. Diatom valves were found in all the samples. It seems, however, impossible to point out any characteristic differences between the composition of the diatom 'flora' in drowned and non-drowned persons. Consequently it will not be possible by means of diatoms to prove that a person died by drowning.

  5. On the age of fossil diatoms

    Directory of Open Access Journals (Sweden)

    Siemińska Jadwiga

    2015-06-01

    Full Text Available The finding of fossil freshwater diatoms in late Cretaceous chert in Mexico suggests - together with all the discoveries of fossil freshwater diatoms known from positions older than the Cretaceous - that the extinct marine Cretaceous diatom taxa cannot be considered to be the oldest.

  6. Diatomic interaction potential theory applications

    CERN Document Server

    Goodisman, Jerry

    2013-01-01

    Diatomic Interaction Potential Theory, Volume 2: Applications discusses the variety of applicable theoretical material and approaches in the calculations for diatomic systems in their ground states. The volume covers the descriptions and illustrations of modern calculations. Chapter I discusses the calculation of the interaction potential for large and small values of the internuclear distance R (separated and united atom limits). Chapter II covers the methods used for intermediate values of R, which in principle means any values of R. The Hartree-Fock and configuration interaction schemes des

  7. In vivo exposure to northern diatoms arrests sea urchin embryonic development.

    Science.gov (United States)

    Gudimova, Elena; Eilertsen, Hans C; Jørgensen, Trond Ø; Hansen, Espen

    2016-01-01

    There are numerous reports indicating that marine diatoms may act harmful to early developmental stages of invertebrates. It is believed that the compounds responsible for these detrimental effects are oxylipins resulting from oxidized polyunsaturated fatty acids, and that they may function as grazing deterrents. Most studies reporting these effects have exposed test organisms to diatom extracts or purified toxins, but data from in vivo exposure to intact diatoms are scarce. We have conducted sea urchin egg incubation and plutei feeding experiments to test if intact diatom cells affected sea urchin embryo development and survival. This was done by exposing the common northern sea urchins Strongylocentrotus droebachiensis and Echinus acutus to northern strains of the diatoms Chaetoceros socialis, Skeletonema marinoi, Chaetoceros furcellatus, Attheya longicornis, Thalassiosira gravida and Porosira glacialis. The intact diatom cell suspensions were found to inhibit sea urchin egg hatching and embryogenesis. S. marinoi was the most potent one as it caused acute mortality in S. droebachiensis eggs after only four hours exposure to high (50 μg/L Chla) diatom concentrations, as well as 24 h exposure to normal (20 μg/L Chla) and high diatom concentrations. The second most potent species was T. gravida that caused acute mortality after 24 h exposure to both diatom concentrations. A. longicornis was the least harmful of the diatom species in terms of embryo development arrestment, and it was the species that was most actively ingested by S. droebachiensis plutei. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  8. Biophotonics of diatoms

    DEFF Research Database (Denmark)

    Gössling, Johannes Wilhelm

    is the encasement of the cell in a silicate frustule compounded of two valves and corresponding girdle bands. Photonic structures in the frustule, i.e. pores and chambers on the micro- to nanoscale, interact with electromagnetic radiation in the visible spectrum of light. It has therefore been proposed...

  9. (Ln=La-Lu) Diatom

    Indian Academy of Sciences (India)

    LnSi diatoms is carried out taking relativistic effect into account. In order to reveal the unusual properties of the rare earth Ln and silicon clusters, the main objective of this research, therefore, is to provide a detailed investigation of equilibrium geometries, charge-transfer properties, ionization potentials (IPs), electron affinitie ...

  10. Automated measurement of diatom size

    Science.gov (United States)

    Spaulding, Sarah A.; Jewson, David H.; Bixby, Rebecca J.; Nelson, Harry; McKnight, Diane M.

    2012-01-01

    Size analysis of diatom populations has not been widely considered, but it is a potentially powerful tool for understanding diatom life histories, population dynamics, and phylogenetic relationships. However, measuring cell dimensions on a light microscope is a time-consuming process. An alternative technique has been developed using digital flow cytometry on a FlowCAM® (Fluid Imaging Technologies) to capture hundreds, or even thousands, of images of a chosen taxon from a single sample in a matter of minutes. Up to 30 morphological measures may be quantified through post-processing of the high resolution images. We evaluated FlowCAM size measurements, comparing them against measurements from a light microscope. We found good agreement between measurement of apical cell length in species with elongated, straight valves, including small Achnanthidium minutissimum (11-21 µm) and largeDidymosphenia geminata (87–137 µm) forms. However, a taxon with curved cells, Hannaea baicalensis (37–96 µm), showed differences of ~ 4 µm between the two methods. Discrepancies appear to be influenced by the choice of feret or geodesic measurement for asymmetric cells. We describe the operating conditions necessary for analysis of size distributions and present suggestions for optimal instrument conditions for size analysis of diatom samples using the FlowCAM. The increased speed of data acquisition through use of imaging flow cytometers like the FlowCAM is an essential step for advancing studies of diatom populations.

  11. Proteomics studies on stress responses in diatoms.

    Science.gov (United States)

    Muhseen, Ziyad Tariq; Xiong, Qian; Chen, Zhuo; Ge, Feng

    2015-12-01

    Diatoms are a highly diverse group of eukaryotic phytoplankton that are distributed throughout marine and freshwater environments and are believed to be responsible for approximately 40% of the total marine primary productivity. The ecological success of diatoms suggests that they have developed a range of strategies to cope with various biotic and abiotic stress factors. It is of great interest to understand the adaptive responses of diatoms to different stresses in the marine environment. Proteomic technologies have been applied to the adaptive responses of marine diatoms under different growth conditions in recent years such as nitrogen starvation, iron limitation and phosphorus deficiency. These studies have provided clues to elucidate the sophisticated sensing mechanisms that control their adaptive responses. Although only a very limited number of proteomic studies were conducted in diatoms, the obtained data have led to a better understanding of the biochemical processes that contribute to their ecological success. This review presents the current status of proteomic studies of diatom stress responses and discusses the novel developments and applications for the analysis of protein post-translational modification in diatoms. The potential future application of proteomics could contribute to a better understanding of the physiological mechanisms underlying diatom acclimation to a given stress and the acquisition of an enhanced diatom stress tolerance. Future challenges and research opportunities in the proteomics studies of diatoms are also discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Colloquium on diatom-copepod interactions

    DEFF Research Database (Denmark)

    Paffenhofer, G.A.; Ianora, A.; Miralto, A.

    2005-01-01

    From 3 to 6 November 2002, a colloquium was convened at the Benthos Laboratory of the Stazione Zoologica Anton Dohrn on Ischia, Italy, with the goal of evaluating the present status of the effects of diatoms on their main consumers, planktonic copepods, and to develop future research strategies...... to enhance our understanding of such interactions. These included (1) toxic effects of diatom metabolites on copepods, particularly reproduction, and (2) nutritional effects of diatoms on juvenile to adult copepods. Key issues involved in the impact of diatoms on the dynamics of natural plankton communities...... in situ were also addressed. During the plenary session, the most recent advances on this topic were presented. The plenary session was followed by 3 working groups on (1) production of aldehydes by phytoplankton, (2) toxic and nutritional effects of diatoms on zooplankton, and (3) the chemistry of diatom...

  13. Expanding the 2, 2’-bipyrimidine bridged 1D homonuclear coordination polymers family: [MIIbpymCl2] (M=Fe, Co) magnetic and structural characterization

    OpenAIRE

    Alborés, Pablo; Rentschler, Eva

    2015-01-01

    One pot reaction of hydrated chloride salts of Fe(II) and Co(II) with stoichiometric amounts of 2, 2’-bipyrimidine (bpym) in a methanol/ acetonitrile mixture afforded the corresponding 1D homonuclear coordination polymers, [μ-(bpym)MCl2]n. Crystal structures of both complexes are isomorphous in the highly symmetric orthorhombic space group Fddd. The 1D coordination polymers are composed of almost orthogonal alternating bipyrimidine bridges linking the {MCl2} units. The magnetic behaviour of t...

  14. Diatom-Based Material Production Demonstration

    Science.gov (United States)

    2016-03-14

    The vast majority of these researchers have little or no experience in diatom cultivation or cell wall purification. Ready availability of a wider...there is a little bit of a ‘chicken and egg’ phenomena in that limited availability of diatom cell walls constrains the research on GAI Final...based on application of these unique materials. Such a project would not only advance current research on diatom cell wall applications, but could be

  15. Diatom-inspired templates for 3D replication: natural diatoms versus laser written artificial diatoms.

    Science.gov (United States)

    Belegratis, M R; Schmidt, V; Nees, D; Stadlober, B; Hartmann, P

    2014-03-01

    The diatoms are ubiquitous, exist in large numbers and show a great diversity of features on their porous silica structures. Therefore, they inspire the fabrication of nanostructured templates for nanoimprint processes (NIL), where large structured areas with nanometer precision are required. In this study, two approaches regarding the respective challenges and potential exploitations are followed and discussed: the first one takes advantage of a template that is directly made of natural occurring diatoms. Here, two replication steps via soft lithography are needed to obtain a template which is subsequently used for NIL. The second approach exploits the technical capabilities of the precise 3D laser lithography (3DLL) based on two-photon polymerization of organic materials. This method enables the fabrication of arbitrary artificial diatom-inspired micro- and nanostructures and the design of an inverse structure. Therefore, only one replication step is needed to obtain a template for NIL. In both approaches, a replication technique for true 3D structures is shown.

  16. Structural identification of long-chain polyamines associated with diatom biosilica in a Southern Ocean sediment core

    Science.gov (United States)

    Bridoux, Maxime C.; Ingalls, Anitra E.

    2010-07-01

    Long-chain polyamines (LCPAs) constitute a new family of natural organic compounds that have recently been isolated and characterized from the biosilicified cell walls of diatom cultures. To date, diatom-specific polyamines have not been investigated from the marine environment and their fate in the environment is entirely unknown. Here, we report a series of LCPAs in a diatom frustule-rich sediment core (TNO57-13 PC4), originating from the Atlantic sector of the Southern Ocean and spanning from the Holocene to the Last Glacial Maximum (LGM). Liquid chromatography with electrospray ionization mass spectrometry (LC-ESI-MS) revealed a complex mixture of linear polyamines with at least 28 individual molecular species. Ion trap mass fragmentation studies, combined with high resolution Time of Flight (TOF) mass spectrometry showed that the polyamine pool consisted of a series of N-methylated propylamine compounds attached to a putrescine moiety, with individual LCPAs varying in chain length and degree of methylation. The structural similarity between LCPAs extracted from the diatom-rich sediment core and those extracted from the frustules of cultured diatoms suggests that sedimentary LCPAs are derived from diatom frustules. We hypothesize that these intrinsically labile organic molecular fossils are protected from diagenesis by encapsulation within the frustule. These compounds constitute a new class of biomarkers that could potentially be indicators of diatom species distribution. Isotopic analysis of LCPAs could be used to improve age models for sediment cores that lack calcium carbonate and to improve current interpretations of diatom-based paleoproxies, including diatom-bound nitrogen isotopes.

  17. Toward Chemical Accuracy in ab Initio Thermochemistry and Spectroscopy of Lanthanide Compounds: Assessing Core-Valence Correlation, Second-Order Spin-Orbit Coupling, and Higher Order Effects in Lanthanide Diatomics.

    Science.gov (United States)

    Solomonik, Victor G; Smirnov, Alexander N

    2017-11-14

    The higher order (HO) correlation beyond the coupled-cluster single double (triple) CCSD(T) level of theory, second-order spin-orbit coupling (SOC), and core-valence (CV) correlation effects on bond length, re, vibrational frequency, ωe, and dissociation energy, De, are studied for a set of 17 lanthanide containing diatomics, including lanthanum, europium, ytterbium, and lutetium oxides and halides. Convergence in the magnitudes of the SOC, CV, and HO corrections with respect to basis set size is examined using a sequence of double, triple, and quadruple-ζ basis sets, with the complete basis set (CBS) limit estimates provided in most cases. The CV effects on De, re, and ωe are calculated to amount up to 1.3 kcal·mol(-1), 0.008 Å, and 5 cm(-1), respectively. A detailed analysis of the origin of the CV effect with a particular accounting for various subvalence shells reveals that, generally, the Ln 4d correlation makes a major contribution, although in some instances the lower-lying 4sp shells contribute largely and even more substantially than 4d. The second-order SOC effect evaluated via two-component and four-component relativistic techniques proves to be non-negligible, especially for heavier species, e.g., LaI, in which it is as large as 0.8 kcal·mol(-1) in De, 0.002 Å in re, and 1.3 cm(-1) in ωe. Higher order correlation effects assessed through the CCSDT(Q) level are mostly less than 0.8 kcal·mol(-1), 0.004 Å, and 5 cm(-1); however, in species with prominence of nondynamical correlation, e.g., EuO, YbF, and LuO, the HO correction can amount to 1.2-1.6 kcal·mol(-1), 0.005-0.008 Å, and 8-30 cm(-1) in De, re, and ωe, respectively. In general, the [CCSD(T)+CV]/CBS + SOC + HO composite results are in good agreement with the available experimental data, exhibiting a mean absolute deviation of 1.8 kcal·mol(-1) in De, 0.0023 Å in re, and 3.5 cm(-1) in ωe. A significant experimental outlier, the bond length in YbI, is revealed, implying the need for re

  18. DDD: Dynamic Database for Diatomics

    Science.gov (United States)

    Schwenke, David

    2004-01-01

    We have developed as web-based database containing spectra of diatomic moiecuies. All data is computed from first principles, and if a user requests data for a molecule/ion that is not in the database, new calculations are automatically carried out on that species. Rotational, vibrational, and electronic transitions are included. Different levels of accuracy can be selected from qualitatively correct to the best calculations that can be carried out. The user can view and modify spectroscopic constants, view potential energy curves, download detailed high temperature linelists, or view synthetic spectra.

  19. Automatic segmentation of diatom images for classification

    NARCIS (Netherlands)

    Jalba, Andrei C.; Wilkinson, Michael H.F.; Roerdink, Jos B.T.M.

    A general framework for automatic segmentation of diatom images is presented. This segmentation is a critical first step in contour-based methods for automatic identification of diatoms by computerized image analysis. We review existing results, adapt popular segmentation methods to this difficult

  20. Relationship between diatom communities and environmental ...

    African Journals Online (AJOL)

    The relationship between diatom species and measured environmental variables was explored at different sites of Honghe wetland region located in northeastern China. Planktonic and epiphytic diatom assemblages in the wetland were identified from May to October of 2007 and 2008. Their relationships with ...

  1. Thermodynamics properties of diatomic molecules with general ...

    Indian Academy of Sciences (India)

    AKPAN N IKOT

    2018-01-10

    Jan 10, 2018 ... S and vibrational specific heat capacity C. These thermodynamic functions are studied for the electronic state X1 + g of K2 diatomic molecules. Keywords. Asymptotic iteration method; diatomic molecules; general molecular potential; partition function. PACS Nos 03.65.Ge; 03.65.Ca. 1. Introduction.

  2. Deep carbon export from a Southern Ocean iron-fertilized diatom bloom

    NARCIS (Netherlands)

    Smetacek, V.; Klaas, C.; Strass, V.H.; Assmy, P.; Montresor, M.; Cisewski, B.; Savoye, N.; Webb, A.; d'Ovidio, F.; Arrieta, J.M.; Bathmann, U.; Bellerby, R.; Berg, G.M.; Croot, P.; Gonzalez, S.; Henjes, J.; Herndl, G.J.; Hoffmann, L.J.; Leach, H.; Losch, M.; Mills, M.M.; Neill, C.; Peeken, I.; Röttgers, R.; Sachs, O.; Sauter, E.; Schmidt, M.M.; Schwarz, J.; Terbrüggen, A.; Wolf-Gladrow, D.

    2012-01-01

    Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of

  3. Characterization of marine diatom-infecting virus promoters in the model diatom Phaeodactylum tricornutum

    OpenAIRE

    Kadono, Takashi; Miyagawa-Yamaguchi, Arisa; Kira, Nozomu; Tomaru, Yuji; Okami, Takuma; Yoshimatsu, Takamichi; Hou, Liyuan; Ohama, Takeshi; Fukunaga, Kazunari; Okauchi, Masanori; Yamaguchi, Haruo; Ohnishi, Kohei; Falciatore, Angela; Adachi, Masao

    2015-01-01

    International audience; Viruses are considered key players in phytoplankton population control in oceans. However, mechanisms that control viral gene expression in prominent microalgae such as diatoms remain largely unknown. In this study, potential promoter regions isolated from several marine diatom-infecting viruses (DIVs) were linked to the egfp reporter gene and transformed into the Pennales diatom Phaeodactylum tricornutum. We analysed their activity in cells grown under different condi...

  4. Digitisation of the South African diatom collection

    CSIR Research Space (South Africa)

    Van der Molen, J

    2008-06-01

    Full Text Available This presentation gives the background of the Diatom collection as well as an overview of the collection content. The two phases of the digitisation process are described in detail...

  5. Oceanographic and Biogeochemical Insights from Diatom Genomes

    Science.gov (United States)

    Bowler, Chris; Vardi, Assaf; Allen, Andrew E.

    2010-01-01

    Diatoms are the most successful group of eukaryotic phytoplankton in the modern ocean and have risen to dominance relatively quickly over the last 100 million years. Recently completed whole genome sequences from two species of diatom, Thalassiosira pseudonana and Phaeodactylum tricornutum, have revealed a wealth of information about the evolutionary origins and metabolic adaptations that have led to their ecological success. A major finding is that they have incorporated genes both from their endosymbiotic ancestors and by horizontal gene transfer from marine bacteria. This unique melting pot of genes encodes novel capacities for metabolic management, for example, allowing the integration of a urea cycle into a photosynthetic cell. In this review we show how genome-enabled approaches are being leveraged to explore major phenomena of oceanographic and biogeochemical relevance, such as nutrient assimilation and life histories in diatoms. We also discuss how diatoms may be affected by climate change-induced alterations in ocean processes.

  6. Selective silicate-directed motility in diatoms

    DEFF Research Database (Denmark)

    Bondoc, Karen Grace V.; Heuschele, Jan; Gillard, Jeroen

    2016-01-01

    Diatoms are highly abundant unicellular algae that often dominate pelagic as well as benthic primary production in the oceans and inland waters. Being strictly dependent on silica to build their biomineralized cell walls, marine diatoms precipitate 240 × 10(12) mol Si per year, which makes them...... the major sink in the global Si cycle. Dissolved silicic acid (dSi) availability frequently limits diatom productivity and influences species composition of communities. We show that benthic diatoms selectively perceive and behaviourally react to gradients of dSi. Cell speed increases under d......Si-limited conditions in a chemokinetic response and, if gradients of this resource are present, increased directionality of cell movement promotes chemotaxis. The ability to exploit local and short-lived dSi hotspots using a specific search behaviour likely contributes to micro-scale patch dynamics in biofilm...

  7. The evolution of silicon transporters in diatoms.

    Science.gov (United States)

    Durkin, Colleen A; Koester, Julie A; Bender, Sara J; Armbrust, E Virginia

    2016-10-01

    Diatoms are highly productive single-celled algae that form an intricately patterned silica cell wall after every cell division. They take up and utilize silicic acid from seawater via silicon transporter (SIT) proteins. This study examined the evolution of the SIT gene family to identify potential genetic adaptations that enable diatoms to thrive in the modern ocean. By searching for sequence homologs in available databases, the diversity of organisms found to encode SITs increased substantially and included all major diatom lineages and other algal protists. A bacterial-encoded gene with homology to SIT sequences was also identified, suggesting that a lateral gene transfer event occurred between bacterial and protist lineages. In diatoms, the SIT genes diverged and diversified to produce five distinct clades. The most basal SIT clades were widely distributed across diatom lineages, while the more derived clades were lineage-specific, which together produced a distinct repertoire of SIT types among major diatom lineages. Differences in the predicted protein functional domains encoded among SIT clades suggest that the divergence of clades resulted in functional diversification among SITs. Both laboratory cultures and natural communities changed transcription of each SIT clade in response to experimental or environmental growth conditions, with distinct transcriptional patterns observed among clades. Together, these data suggest that the diversification of SITs within diatoms led to specialized adaptations among diatoms lineages, and perhaps their dominant ability to take up silicic acid from seawater in diverse environmental conditions. © 2016 The Authors. Journal of Phycology published by Wiley Periodicals, Inc. on behalf of Phycological Society of America.

  8. The genome of the diatom Thalassiosira pseudonana: Ecology,evolution, and metabolism

    Energy Technology Data Exchange (ETDEWEB)

    Ambrust, E.V.; Berges, J.; Bowler, C.; Green, B.; Martinez, D.; Putnam, N.; Zhou, S.; Allen, A.; Apt, K.; Bechner, M.; Brzezinski, M.; Chaal, B.; Chiovitti, A.; Davis, A.; Goodstein, D.; Hadi, M.; Hellsten,U.; Hildebrand, M.; Jenkins, B.; Jurka, J.; Kapitonov, V.; Kroger, N.; Lau, W.; Lane, T.; Larimer, F.; Lippmeier, J.; Lucas, S.; Medina, M.; Montsant, A.; Obornik, M.; Parker, M. Schnitzler; Palenik, B.; Pazour,G.; Richardson, P.; Rynearson, T.; Saito, M.; Schwartz, D.; Thamatrakoln,K.; Valentin, K.; Vardi, A.; Wilkerson, F.; Rokhsar, D.; Vardi, A.; Wilkerson, F.P.; Rokhsar, D.S.

    2004-09-01

    Diatoms are unicellular algae with plastids acquired by secondary endosymbiosis. They are responsible for {approx}20% of global carbon fixation. We report the 34 Mbp draft nuclear genome of the marine diatom, Thalassiosira pseudonana and its 129 Kbp plastid and 44 Kbp mitochondrial genomes. Sequence and optical restriction mapping revealed 24 diploid nuclear chromosomes. We identified novel genes for silicic acid transport and formation of silica-based cell walls, high-affinity iron uptake, biosynthetic enzymes for several types of polyunsaturated fatty acids, utilization of a range of nitrogenous compounds and a complete urea cycle, all attributes that allow diatoms to prosper in the marine environment. Diatoms are unicellular, photosynthetic, eukaryotic algae found throughout the world's oceans and freshwater systems. They form the base of short, energetically-efficient food webs that support large-scale coastal fisheries. Photosynthesis by marine diatoms generates as much as 40% of the 45-50 billion tonnes of organic carbon produced each year in the sea (1), and their role in global carbon cycling is predicted to be comparable to that of all terrestrial rainforests combined (2, 3). Over geological time, diatoms may have influenced global climate by changing the flux of atmospheric carbon dioxide into the oceans (4). A defining feature of diatoms is their ornately patterned silicified cell wall or frustule, which displays species-specific nano-structures of such fine detail that diatoms have long been used to test the resolution of optical microscopes. Recent attention has focused on biosynthesis of these nano-structures as a paradigm for future silica nanotechnology (5). The long history (over 180 million years) and dominance of diatoms in the oceans is reflected by their contributions to vast deposits of diatomite, most cherts and a significant fraction of current petroleum reserves (6). As photosynthetic heterokonts, diatoms reflect a fundamentally

  9. The Genome of the Diatom Thalassiosira Pseudonana: Ecology, Evolution and Metabolism

    Energy Technology Data Exchange (ETDEWEB)

    Armbrust, E V; Berges, J A; Bowler, C; Green, B R; Martinez, D; Putnam, N H; Zhou, S; Allen, A E; Apt, K E; Bechner, M; Brzezinski, M A; Chaal, B K; Chiovitti, A; Davis, A K; Demarest, M S; Detter, J C; del Rio, T G; Goodstein, D; Hadi, M Z; Hellsten, U; Hildebrand, M; Jenkins, B D; Jurka, J; Kapitonov, V V; Kroger, N; Lau, W Y; Lane, T W; Larimer, F W; Lippmeier, J C; Lucas, S; Medina, M; Montsant, A; Obornik, M; Parker, M S; Palenik, B; Pazour, G J; Richardson, P M; Rynearson, T A; Saito, M A; Schwartz, D C; Thamatrakoln, K; Valentin, K; Vardi, A; Wilkerson, F P; Rokhsar, D S

    2005-11-14

    Diatoms are unicellular algae with plastids acquired by secondary endosymbiosis. They are responsible for {approx}20% of global carbon fixation. We report the 34 Mbp draft nuclear genome of the marine diatom, Thalassiosira pseudonana and its 129 Kbp plastid and 44 Kbp mitochondrial genomes. Sequence and optical restriction mapping revealed 24 diploid nuclear chromosomes. We identified novel genes for silicic acid transport and formation of silica-based cell walls, high-affinity iron uptake, biosynthetic enzymes for several types of polyunsaturated fatty acids, utilization of a range of nitrogenous compounds and a complete urea cycle, all attributes that allow diatoms to prosper in the marine environment. Diatoms are unicellular, photosynthetic, eukaryotic algae found throughout the world's oceans and freshwater systems. They form the base of short, energetically-efficient food webs that support large-scale coastal fisheries. Photosynthesis by marine diatoms generates as much as 40% of the 45-50 billion tonnes of organic carbon produced each year in the sea (1), and their role in global carbon cycling is predicted to be comparable to that of all terrestrial rainforests combined (2, 3). Over geological time, diatoms may have influenced global climate by changing the flux of atmospheric carbon dioxide into the oceans (4). A defining feature of diatoms is their ornately patterned silicified cell wall or frustule, which displays species-specific nano-structures of such fine detail that diatoms have long been used to test the resolution of optical microscopes. Recent attention has focused on biosynthesis of these nano-structures as a paradigm for future silica nanotechnology (5). The long history (over 180 million years) and dominance of diatoms in the oceans is reflected by their contributions to vast deposits of diatomite, most cherts and a significant fraction of current petroleum reserves (6). As photosynthetic heterokonts, diatoms reflect a fundamentally

  10. The Glass Menagerie: diatoms for novel applications in nanotechnology.

    Science.gov (United States)

    Gordon, Richard; Losic, Dusan; Tiffany, Mary Ann; Nagy, Stephen S; Sterrenburg, Frithjof A S

    2009-02-01

    Diatoms are unicellular, eukaryotic, photosynthetic algae that are found in aquatic environments. Diatoms have enormous ecological importance on this planet and display a diversity of patterns and structures at the nano- to millimetre scale. Diatom nanotechnology, a new interdisciplinary area, has spawned collaborations in biology, biochemistry, biotechnology, physics, chemistry, material science and engineering. We survey diatom nanotechnology since 2005, emphasizing recent advances in diatom biomineralization, biophotonics, photoluminescence, microfluidics, compustat domestication, multiscale porosity, silica sequestering of proteins, detection of trace gases, controlled drug delivery and computer design. Diatoms might become the first organisms for which the gap in our knowledge of the relationship between genotype and phenotype is closed.

  11. Extremophile Diatoms: Implications to the Drake Equation

    Science.gov (United States)

    Sterrenburg, Frithjof A. S.; Hoover, Richard B.

    2011-01-01

    Diatoms are unicellular Eukaryotes that (as a group and phylogenetically) are not strictly regarded as extremophiles , since the vast majority of diatoms are mesophilic photoautotrophs. However, among the terrestrial Eukaryotes, diatoms are by far the single group of organisms with the ability to inhabit the greatest range of hostile environments on Earth. They are the dominant eukaryotes in the polar regions; in fumaroles, hot springs and geysers; and in hypersaline and hyperalkaline lakes and pools. Cryophilic species such as Fragilaria sublinearis and Chaetoceras fragilis are able to carry out respiration at extremely low rates at low temperatures in darkness. The Drake Equation refers to the likelihood of there being intelligent life at the technological level of electromagnetic communication. However, consideration of the range of conditions suitable for the habitability of eukaryotic diatoms and prokaryotic extremophiles, the likelihood that life exists elsewhere in the cosmos becomes many orders of magnitude greater than that predicted by the classical Drake Equation. In this paper we review the characteristics of diatoms as eukaryotic extremophiles and consider the implications to adjustments needed to the Drake Equation to assess the possibility that life exists elsewhere in the Universe.

  12. Effect of ageing on survival of benthic diatom propagules

    Digital Repository Service at National Institute of Oceanography (India)

    Anil, A.C.; Mitbavkar, S.; DeSilva, M.S.; Hegde, S.; DeCosta, P.M.; Meher, S.S.; Banerjee, D.

    A comparison of viable benthic diatom propagules based on the observations recorded immediately and after 5 years of ageing at 5oC is presented. The number of viable benthic diatom propagules decreased with ageing. However, they exhibited...

  13. Quantification of diatoms in biofilms: Standardisation of methods

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, J.S.; Anil, A.C.

    of the difficulty in sampling and enumeration. Scraping or brushing are the traditional methods used for removal of diatoms from biofilms developed on solid substrata. The method of removal is the most critical step in enumerating the biofilm diatom community...

  14. Characterization of marine diatom-infecting virus promoters in the model diatom Phaeodactylum tricornutum.

    Science.gov (United States)

    Kadono, Takashi; Miyagawa-Yamaguchi, Arisa; Kira, Nozomu; Tomaru, Yuji; Okami, Takuma; Yoshimatsu, Takamichi; Hou, Liyuan; Ohama, Takeshi; Fukunaga, Kazunari; Okauchi, Masanori; Yamaguchi, Haruo; Ohnishi, Kohei; Falciatore, Angela; Adachi, Masao

    2015-12-22

    Viruses are considered key players in phytoplankton population control in oceans. However, mechanisms that control viral gene expression in prominent microalgae such as diatoms remain largely unknown. In this study, potential promoter regions isolated from several marine diatom-infecting viruses (DIVs) were linked to the egfp reporter gene and transformed into the Pennales diatom Phaeodactylum tricornutum. We analysed their activity in cells grown under different conditions. Compared to diatom endogenous promoters, novel DIV promoter (ClP1) mediated a significantly higher degree of reporter transcription and translation. Stable expression levels were observed in transformants grown under both light and dark conditions, and high levels of expression were reported in cells in the stationary phase compared to the exponential phase of growth. Conserved motifs in the sequence of DIV promoters were also found. These results allow the identification of novel regulatory regions that drive DIV gene expression and further examinations of the mechanisms that control virus-mediated bloom control in diatoms. Moreover, the identified ClP1 promoter can serve as a novel tool for metabolic engineering of diatoms. This is the first report describing a promoter of DIVs that may be of use in basic and applied diatom research.

  15. Diatoms: a fossil fuel of the future.

    Science.gov (United States)

    Levitan, Orly; Dinamarca, Jorge; Hochman, Gal; Falkowski, Paul G

    2014-03-01

    Long-term global climate change, caused by burning petroleum and other fossil fuels, has motivated an urgent need to develop renewable, carbon-neutral, economically viable alternatives to displace petroleum using existing infrastructure. Algal feedstocks are promising candidate replacements as a 'drop-in' fuel. Here, we focus on a specific algal taxon, diatoms, to become the fossil fuel of the future. We summarize past attempts to obtain suitable diatom strains, propose future directions for their genetic manipulation, and offer biotechnological pathways to improve yield. We calculate that the yields obtained by using diatoms as a production platform are theoretically sufficient to satisfy the total oil consumption of the US, using between 3 and 5% of its land area. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Designer diatom episomes delivered by bacterial conjugation.

    Science.gov (United States)

    Karas, Bogumil J; Diner, Rachel E; Lefebvre, Stephane C; McQuaid, Jeff; Phillips, Alex P R; Noddings, Chari M; Brunson, John K; Valas, Ruben E; Deerinck, Thomas J; Jablanovic, Jelena; Gillard, Jeroen T F; Beeri, Karen; Ellisman, Mark H; Glass, John I; Hutchison, Clyde A; Smith, Hamilton O; Venter, J Craig; Allen, Andrew E; Dupont, Christopher L; Weyman, Philip D

    2015-04-21

    Eukaryotic microalgae hold great promise for the bioproduction of fuels and higher value chemicals. However, compared with model genetic organisms such as Escherichia coli and Saccharomyces cerevisiae, characterization of the complex biology and biochemistry of algae and strain improvement has been hampered by the inefficient genetic tools. To date, many algal species are transformable only via particle bombardment, and the introduced DNA is integrated randomly into the nuclear genome. Here we describe the first nuclear episomal vector for diatoms and a plasmid delivery method via conjugation from Escherichia coli to the diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana. We identify a yeast-derived sequence that enables stable episome replication in these diatoms even in the absence of antibiotic selection and show that episomes are maintained as closed circles at copy number equivalent to native chromosomes. This highly efficient genetic system facilitates high-throughput functional characterization of algal genes and accelerates molecular phytoplankton research.

  17. Periphytic diatom communities in tributaries around Lake Ichkeul ...

    African Journals Online (AJOL)

    Diatoms were stressed mostly by the influence of temperature and salinity, which drove species composition and increased mortality. Further research is required on the ecology of diatoms in Ichkeul thermal springs. The use of diatoms as indicators of ecosystem health in the Ichkeul area requires additional knowledge of ...

  18. Isolation of diatom Navicula cryptocephala and characterization of ...

    African Journals Online (AJOL)

    Over the past decade diatoms are screened for high lipid content. Geologists claim that much of crude oil comes from diatoms. In this study diatom Navicula cryptocephala, isolated from fresh water source was grown on suitable media for extracting and characterizing the oil for biodiesel production. Three methods namely ...

  19. Antibacterial constituents of the diatom Navicula delognei.

    Science.gov (United States)

    Findlay, J A; Patil, A D

    1984-01-01

    The novel ester (E)-phytol (5Z,8Z,11Z,14Z,17Z)-eicosapentaenoate++ + (1); (6Z,9Z,12Z,15Z)-hexadecatetraenoic acid; (6Z,9Z,12Z,15Z)-octadecatetraenoic acid; and (6Z,9Z,12Z)-hexadecatrienoic acid isolated from the diatom Navicula delognei f. elliptica, show significant antibacterial activity against Staphylococcus aureus, Staphylococcus epidermidis, Salmonella typhimurium, and Proteus vulgaris. beta-Carotene, alpha-cryptoxanthin, fucoxanthin, lutein, trans-phytol, and plastoquinone-9 were also isolated from this diatom.

  20. Oxylipin Diversity in the Diatom Family Leptocylindraceae Reveals DHA Derivatives in Marine Diatoms

    Directory of Open Access Journals (Sweden)

    Deepak Nanjappa

    2014-01-01

    Full Text Available Marine planktonic organisms, such as diatoms, are prospective sources of novel bioactive metabolites. Oxygenated derivatives of fatty acids, generally referred to as oxylipins, in diatoms comprise a highly diverse and complex family of secondary metabolites. These molecules have recently been implicated in several biological processes including intra- and inter-cellular signaling as well as in defense against biotic stressors and grazers. Here, we analyze the production and diversity of C20 and C22 non-volatile oxylipins in five species of the family Leptocylindraceae, which constitute a basal clade in the diatom phylogeny. We report the presence of species-specific lipoxygenase activity and oxylipin patterns, providing the first demonstration of enzymatic production of docosahexaenoic acid derivatives in marine diatoms. The differences observed in lipoxygenase pathways among the species investigated broadly reflected the relationships observed with phylogenetic markers, thus providing functional support to the taxonomic diversity of the individual species.

  1. Epibiotic Diatoms Are Universally Present on All Sea Turtle Species.

    Science.gov (United States)

    Robinson, Nathan J; Majewska, Roksana; Lazo-Wasem, Eric A; Nel, Ronel; Paladino, Frank V; Rojas, Lourdes; Zardus, John D; Pinou, Theodora

    2016-01-01

    The macro-epibiotic communities of sea turtles have been subject to growing interest in recent years, yet their micro-epibiotic counterparts are almost entirely unknown. Here, we provide the first evidence that diatoms are epibionts for all seven extant species of sea turtle. Using Scanning Electron Microscopy, we inspected superficial carapace or skin samples from a single representative of each turtle species. We distinguished 18 diatom taxa from these seven individuals, with each sea turtle species hosting at least two diatom taxa. We recommend that future research is undertaken to confirm whether diatom communities vary between sea turtle species and whether these diatom taxa are facultative or obligate commensals.

  2. Deep carbon export from a Southern Ocean iron-fertilized diatom bloom.

    Science.gov (United States)

    Smetacek, Victor; Klaas, Christine; Strass, Volker H; Assmy, Philipp; Montresor, Marina; Cisewski, Boris; Savoye, Nicolas; Webb, Adrian; d'Ovidio, Francesco; Arrieta, Jesús M; Bathmann, Ulrich; Bellerby, Richard; Berg, Gry Mine; Croot, Peter; Gonzalez, Santiago; Henjes, Joachim; Herndl, Gerhard J; Hoffmann, Linn J; Leach, Harry; Losch, Martin; Mills, Matthew M; Neill, Craig; Peeken, Ilka; Röttgers, Rüdiger; Sachs, Oliver; Sauter, Eberhard; Schmidt, Maike M; Schwarz, Jill; Terbrüggen, Anja; Wolf-Gladrow, Dieter

    2012-07-18

    Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of carbon sequestration from the atmosphere are uncertain. Here we report the results of a five-week experiment carried out in the closed core of a vertically coherent, mesoscale eddy of the Antarctic Circumpolar Current, during which we tracked sinking particles from the surface to the deep-sea floor. A large diatom bloom peaked in the fourth week after fertilization. This was followed by mass mortality of several diatom species that formed rapidly sinking, mucilaginous aggregates of entangled cells and chains. Taken together, multiple lines of evidence-although each with important uncertainties-lead us to conclude that at least half the bloom biomass sank far below a depth of 1,000 metres and that a substantial portion is likely to have reached the sea floor. Thus, iron-fertilized diatom blooms may sequester carbon for timescales of centuries in ocean bottom water and for longer in the sediments.

  3. Intracellular metabolic pathway distribution in diatoms and tools for genome-enabled experimental diatom research.

    Science.gov (United States)

    Gruber, Ansgar; Kroth, Peter G

    2017-09-05

    Diatoms are important primary producers in the oceans and can also dominate other aquatic habitats. One reason for the success of this phylogenetically relatively young group of unicellular organisms could be the impressive redundancy and diversity of metabolic isoenzymes in diatoms. This redundancy is a result of the evolutionary origin of diatom plastids by a eukaryote-eukaryote endosymbiosis, a process that implies temporary redundancy of functionally complete eukaryotic genomes. During the establishment of the plastids, this redundancy was partially reduced via gene losses, and was partially retained via gene transfer to the nucleus of the respective host cell. These gene transfers required re-assignment of intracellular targeting signals, a process that simultaneously altered the intracellular distribution of metabolic enzymes compared with the ancestral cells. Genome annotation, the correct assignment of the gene products and the prediction of putative function, strongly depends on the correct prediction of the intracellular targeting of a gene product. Here again diatoms are very peculiar, because the targeting systems for organelle import are partially different to those in land plants. In this review, we describe methods of predicting intracellular enzyme locations, highlight findings of metabolic peculiarities in diatoms and present genome-enabled approaches to study their metabolism.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'. © 2017 The Author(s).

  4. A new diatom growth inhibition assay using the XTT colorimetric method.

    Science.gov (United States)

    Jiang, Weina; Akagi, Takuya; Suzuki, Hidekazu; Takimoto, Ayaka; Nagai, Hiroshi

    2016-01-01

    Marine biofouling, which leads to significant operational stress and economic damage on marine infrastructures, is a major problem in marine related industries. Currently, the most common way to avoid marine biofouling involves the use of biocidal products in surface coatings. However, the need for environmentally friendly antibiofouling compounds has increased rapidly with the recent global prohibition of harmful antifoulants, such as tributyltin (TBT). In particular, periphytic diatoms have been shown to contribute significantly to biofilms, which play an important role in biofouling. Therefore, inhibiting the proliferation of fouling diatoms is a very important step in the prevention of marine biofouling. In this study, we developed a new, rapid, accurate, and convenient growth inhibition assay using the XTT colorimetric method to prevent the growth of the fouling periphytic diatom, Nitzschia amabilis Hidek. Suzuki (replaced synonym, Nitzschia laevis Hustedt). The feasibility of this method was verified by determining the growth inhibition activities of two standard photosynthetic inhibitors, DCMU and CuSO4. However, neither inhibitor had any cytotoxic activities at the range of concentrations tested. Moreover, this method was applied by screening and purification of herbicidic but non-cytotoxic compounds from cyanobacteria extracts. Our results demonstrate the utility of this newly established growth inhibition assay for the identification of marine anti-biofouling compounds. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Molecular evidence of the toxic effects of diatom diets on gene expression patterns in copepods.

    Directory of Open Access Journals (Sweden)

    Chiara Lauritano

    Full Text Available BACKGROUND: Diatoms are dominant photosynthetic organisms in the world's oceans and are considered essential in the transfer of energy through marine food chains. However, these unicellular plants at times produce secondary metabolites such as polyunsaturated aldehydes and other products deriving from the oxidation of fatty acids that are collectively termed oxylipins. These cytotoxic compounds are responsible for growth inhibition and teratogenic activity, potentially sabotaging future generations of grazers by inducing poor recruitment in marine organisms such as crustacean copepods. PRINCIPAL FINDINGS: Here we show that two days of feeding on a strong oxylipin-producing diatom (Skeletonema marinoi is sufficient to inhibit a series of genes involved in aldehyde detoxification, apoptosis, cytoskeleton structure and stress response in the copepod Calanus helgolandicus. Of the 18 transcripts analyzed by RT-qPCR at least 50% were strongly down-regulated (aldehyde dehydrogenase 9, 8 and 6, cellular apoptosis susceptibility and inhibitor of apoptosis IAP proteins, heat shock protein 40, alpha- and beta-tubulins compared to animals fed on a weak oxylipin-producing diet (Chaetoceros socialis which showed no changes in gene expression profiles. CONCLUSIONS: Our results provide molecular evidence of the toxic effects of strong oxylipin-producing diatoms on grazers, showing that primary defense systems that should be activated to protect copepods against toxic algae can be inhibited. On the other hand other classical detoxification genes (glutathione S-transferase, superoxide dismutase, catalase, cytochrome P450 were not affected possibly due to short exposure times. Given the importance of diatom blooms in nutrient-rich aquatic environments these results offer a plausible explanation for the inefficient use of a potentially valuable food resource, the spring diatom bloom, by some copepod species.

  6. [Research advances in heavy metals pollution ecology of diatom].

    Science.gov (United States)

    Ding, Teng-Da; Ni, Wan-Min; Zhang, Jian-Ying

    2012-03-01

    Diatom, due to its high sensitivity to environmental change, is one of the bio-indicators of aquatic ecosystem health, and some typical diatom species have been applied to indicate the heavy metals pollution of water body. With the focus on the surface water heavy metals pollution, this paper reviewed the research advances in the toxic effect of heavy metals pollution on diatom, biosorption and bioaccumulation of heavy metals by diatom, ecological adaptation mechanisms of diatom to heavy metals pollution, and roles of diatom as bio-indicator and in ecological restoration of heavy metals pollution. The growth tendency of diatom and the morphological change of frustule under heavy metals pollution as well as the differences in heavy metals biosorption and bioaccumulation by diatom, the ecological adaptation mechanisms of diatom on heavy metals surface complexation and ion exchange, and the roles of diatom as bio-indicator and in ecological restoration of heavy metals polluted water body were also discussed. This review could provide scientific evidences for the prevention of aquatic ecosystems heavy metals pollution and related early warning techniques.

  7. Addressed immobilization of biofunctionalized diatoms on electrodes by gold electrodeposition.

    Science.gov (United States)

    Leonardo, S; Garibo, D; Fernández-Tejedor, M; O'Sullivan, C K; Campàs, M

    2017-03-23

    Diatoms are single cell microalgae with a silica shell (frustule), which possess a micro/nanoporous pattern of unparalleled diversity far beyond the possibilities of current micro- and nanofabrication techniques. To explore diatoms as natural three-dimensional nanostructured supports in sensing and biosensing devices, a simple, rapid and stable method to immobilize diatoms via gold electrodeposition is described. In this process, gold microstructures are formed, immobilizing diatoms by entrapment or crossing their nanopores. Varying the applied potential, time and HAuCl 4 concentration, gold deposits of different morphologies and roughness are obtained, thereby determining the diatom immobilization process. Optical and scanning electron microscopy have been used to characterize diatom immobilization yields, the morphology of the gold microstructures, and the morphological integrity of diatoms. Cyclic voltammetry has been performed to characterize the gold deposits and to demonstrate the enhanced electrocatalytic activity of the gold-diatom electrodes. Electro-addressed immobilization of different diatoms on specific bands of interdigitated electrode arrays has been achieved, highlighting the potential application of diatoms for site-specific immobilization on microarrays. The feasibility to combine tailored immobilization with diatom biofunctionalization has also been demonstrated. Antibody-functionalized diatoms were immobilized on electrodes retaining their ability to detect its cognate antigen. The reported method exploits the natural three-dimensional nanostructures of diatoms together with their easy modification with biomolecules and the simplicity of gold electrodeposition to produce micro/nanostructured and highly electrocatalytic electrodes, providing low-cost and eco-friendly platforms and arrays with potential application in biosensing devices.

  8. Photo-Oxidative Stress-Driven Mutagenesis and Adaptive Evolution on the Marine Diatom Phaeodactylum tricornutum for Enhanced Carotenoid Accumulation

    Directory of Open Access Journals (Sweden)

    Zhiqian Yi

    2015-09-01

    Full Text Available Marine diatoms have recently gained much attention as they are expected to be a promising resource for sustainable production of bioactive compounds such as carotenoids and biofuels as a future clean energy solution. To develop photosynthetic cell factories, it is important to improve diatoms for value-added products. In this study, we utilized UVC radiation to induce mutations in the marine diatom Phaeodactylum tricornutum and screened strains with enhanced accumulation of neutral lipids and carotenoids. Adaptive laboratory evolution (ALE was also used in parallel to develop altered phenotypic and biological functions in P. tricornutum and it was reported for the first time that ALE was successfully applied on diatoms for the enhancement of growth performance and productivity of value-added carotenoids to date. Liquid chromatography-mass spectrometry (LC-MS was utilized to study the composition of major pigments in the wild type P. tricornutum, UV mutants and ALE strains. UVC radiated strains exhibited higher accumulation of fucoxanthin as well as neutral lipids compared to their wild type counterpart. In addition to UV mutagenesis, P. tricornutum strains developed by ALE also yielded enhanced biomass production and fucoxanthin accumulation under combined red and blue light. In short, both UV mutagenesis and ALE appeared as an effective approach to developing desired phenotypes in the marine diatoms via electromagnetic radiation-induced oxidative stress.

  9. Bulk Sediment and Diatom Silica Carbon Isotope Composition from Coastal Marine Sediments off East Antarctica

    NARCIS (Netherlands)

    Berg, S.; Leng, M.J.; Kendrick, C.P.; Cremer, H.; Wagner, B.

    2013-01-01

    Organic carbon occluded in diatom silica is assumed to be protected from degradation in the sediment. δ13C from diatom carbon (δ13C(diatom)) therefore potentially provides a signal of conditions during diatom growth. However, there have been few studies based on δ13C(diatom). Numerous variables can

  10. An Investigation Into the Molecular and Isotopic Composition of Diatom Frustule-Bound Organic Matter: Method Development for New Proxies

    Science.gov (United States)

    Bridoux, M. C.; Ingalls, A. E.

    2009-12-01

    Diatoms are single cell phytoplankton that are ubiquitous in marine ecosystems and are responsible for up to 40% of the carbon fixed annually in the ocean. Their intricately nanopatterned siliceous frustules are formed under the control of template organic molecules, some of which are incorporated into the frustule during growth. Several diatom frustule-based paleoproxies have been developed to exploit these microfossils because they are from a known phytoplankton source that is relatively unaltered from diagenesis. Among these proxies, diatom frustule-bound organic matter (OM) is recognized as a potentially important material for use in paleoreconstructions of past productivity (13C/12C), nutrient utilization (15N/14N) as well as to determine the radiocarbon age of sedimentary frustules (Δ14C). Despite numerous advances, diatom frustule-bound OM remains poorly characterized. Here we focus on the chemical characterization of diatom frustule-bound OM with the goal of developing molecular and compound-specific isotope methods to better reconstruct the past environments of diatom rich regions such as the Southern Ocean and the North Pacific. To do this, we 1) chemically cleaned diatom frustules, 2) dissolve them in HF to release organic compounds embedded in the frustules and 3) unambiguously characterized this organic matter by ion pairing reversed phase liquid chromatography coupled to diode array, electrospray ionization - ion trap mass spectrometry (ESI/IT-MSn) and accurate mass quadrupole time of flight mass spectrometry (Q-TOF). These analyses reveal the presence of low molecular weight, UV light absorbing compounds called mycosporine-like amino acids (MAAs) and a series of long chain polyamines (LCPAs) consisting of N-methylated derivatives of polypropyleneimine units attached to putrescine. LCPAs are known to direct silicification, while MAAs are thought to provide sunscreen to many marine organisms. The presence of these specific biomarkers in sediment

  11. Diatoms of the Mystery Lake, Taiwan (III

    Directory of Open Access Journals (Sweden)

    Jiunn-Tzong Wu

    2009-09-01

    Full Text Available This is the last part of study about the diatom flora found in the Mystery Lake, a slightly acidic lake situated within a hardwood nature preserve in northeastern Taiwan. In this article, we reported 17 species, belonging to 4 genera, 4 families, and 2 orders, based on scanning electron microscopic observations. The species described here, 9 are newly recorded in Taiwan. They are: Navicula cryptotenella, Navicula ingrata, Navicula subfasciata, Pinnularia borealis var. rectangularis, Pinnularia interrupta, Pinnularia maior, Sellaphora laevissima, S. vitabunda, and Nitzschia perminuta. In total, we found 76 diatom species in the surface sediments of this lake. Among them, 33 (43% are newly recorded to Taiwan. The present study indicates that this lake is characterized by high species diversity and high species richness, which are related to the oligotrophic and non-polluted environmental conditions.

  12. Morse basis expansion applied to diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Emanuel F. de, E-mail: eflima@rc.unesp.br [Departamento de Estatística, Matemática Aplicada e Computação, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista – UNESP, Rio Claro, São Paulo 13506-900 (Brazil)

    2012-02-20

    This work explores the use of the eigenfunctions of the Morse potential with a infinite barrier at long range to solve the radial Schrödinger equation for diatomic molecules. Analytical formulas are obtained for the kinetic energy operator matrix elements in the Morse basis. The Morse basis expansion is applied to find the vibrational–rotational levels of the sodium molecule in the electronic ground state. -- Highlights: ► The Morse potential basis is invoked to find the rovibrational levels of diatomic molecules. ► Analytical formulas for the kinetic energy operator in the Morse basis are obtained. ► The results of the Morse basis expansion show good agreement with the Fourier Grid technique.

  13. Silicon diatom frustules as nanostructured photoelectrodes.

    Science.gov (United States)

    Chandrasekaran, Soundarrajan; Sweetman, Martin J; Kant, Krishna; Skinner, William; Losic, Dusan; Nann, Thomas; Voelcker, Nicolas H

    2014-09-18

    In the quest for solutions to meeting future energy demands, solar fuels play an important role. A particularly promising example is photocatalysis since even incremental improvements in performance in this process are bound to translate into significant cost benefits. Here, we report that semiconducting and high surface area 3D silicon replicas prepared from abundantly available diatom fossils sustain photocurrents and enable solar energy conversion.

  14. Benthic diatom response to changing environmental conditions

    Science.gov (United States)

    Cibic, Tamara; Comici, Cinzia; Bussani, Andrea; Del Negro, Paola

    2012-12-01

    In the Gulf of Trieste (northern Adriatic Sea, Italy) the benthic diatom community dynamics has been studied for seven years (1999-2005) at two sublittoral stations and related to variations of temperature, salinity, nutrient concentrations, freshwater inflow and mucilage. Bin-averaged temperature versus abundance of the main genera revealed that Nitzschia and Navicula presented a positive stepped trend with increasing temperature. An increase of ca. 860 ± 150 cells per cm3 per °C was calculated for Navicula and up to 590 ± 170 cells per cm3 per °C for Nitzschia. The genus Pleurosigma revealed a negative trend with increasing temperature, with a calculated decrease of ca. 140 ± 60 cells per cm3 per °C. A negative relation between Diploneis and temperature was found only in the shallower site. A peak of the tychopelagic genus Cylindrotheca was observed in correspondence with high salinity, but no significant results between bin-averaged salinity and benthic diatom abundance were found. Significant negative relations were obtained between bin-averaged abundance of Pleurosigma and H4SiO4 and NO3- at the deeper station and between the bin-averaged abundance of Gyrosigma and NH4+ at the coastal station. In this site the abundance of Gyrosigma showed a significant increasing trend over the study period. Navicula and Nitzschia seemed to suffer from the presence of mucilage events occurred in summer 2000 and 2004 whereas Diploneis occupied the ecological niche which remained temporarily uncovered by Navicula and Nitzschia. An exceptional freshwater plume with extremely high terrigenous input in November 2000 completely covered the benthic diatom community, causing a remarkable decrease in its total abundance in late autumn and winter 2000-01. The Gulf of Trieste may be considered a natural megacosm due to its geomorphologic characteristics and therefore the benthic diatom response to changing environmental conditions observed in this site could be extended beyond the

  15. Influence of illumination on settlement of diatom Navicula sp.

    Science.gov (United States)

    Cao, Shan; Wang, Jiadao; Chen, Darong

    2011-11-01

    Diatoms are responsible for biofouling, which causes many problems in various marine industries. This study examined the effects of different light conditions (intensity, incident direction, time of illumination) on the settling behavior of the marine diatom Navicula sp. on glass surfaces. The density of this diatom's settlement on glass was strongly influenced by light conditions. Moreover, very weak light emitted on the bottom of the culture dish could also rapidly inhibit diatom settlement. These phenomena were explained by spatial interference between chloroplast and holdfast-like structures inside the thecae. The holdfast-like structure is observed to be responsible for diatom locomotion and hence the settlement behavior. It was proposed that the interrelation of illumination and attachment of diatoms allowed them to better adapt to the habitat with higher efficiency of attachment and successive reproduction.

  16. Applications of Diatoms as Potential Microalgae in Nanobiotechnology

    OpenAIRE

    Jamali, Ali Akbar; Akbari, Fariba; Ghorakhlu, Mohamad Moradi; de la Guardia, Miguel; Yari Khosroushahi, Ahmad

    2012-01-01

    Introduction: Diatoms are single cell eukaryotic microalgae, which present in nearly every water habitat make them ideal tools for a wide range of applications such as oil explora­tion, forensic examination, environmental indication, biosilica pattern generation, toxicity testing and eutrophication of aqueous ecosystems. Methods: Essential information on diatoms were reviewed and discussed towards impacts of diatoms on biosynthesis and bioremediation. Results: In this review, we present the ...

  17. Diatom flora in subterranean ecosystems: a review

    Directory of Open Access Journals (Sweden)

    Elisa Falasco

    2014-09-01

    Full Text Available In scarcity of light and primary producers, subterranean ecosystems are generally extremely oligotrophic habitats, receiving poor supplies of degradable organic matter from the surface. Human direct impacts on cave ecosystems mainly derive from intensive tourism and recreational caving, causing important alterations to the whole subterranean environment. In particular, artificial lighting systems in show caves support the growth of autotrophic organisms (the so-called lampenflora, mainly composed of cyanobacteria, diatoms, chlorophytes, mosses and ferns producing exocellular polymeric substances (EPSs made of polysaccharides, proteins, lipids and nucleic acids. This anionic EPSs matrix mediates to the intercellular communications and participates to the chemical exchanges with the substratum, inducing the adsorption of cations and dissolved organic molecules from the cave formations (speleothems. Coupled with the metabolic activities of heterotrophic microorganisms colonising such layer (biofilm, this phenomenon may lead to the corrosion of the mineral surfaces. In this review, we investigate the formation of biofilms, especially of diatom-dominated ones, as a consequence of artificial lighting and its impacts on speleothems. Whenever light reaches the subterranean habitat (both artificially and naturally a relative high number of species of diatoms may indeed colonise it. Cave entrances, artificially illuminated walls and speleothems inside the cave are generally the preferred substrates. This review focuses on the diatom flora colonising subterranean habitats, summarizing the information contained in all the scientific papers published from 1900 up to date. In this review we provide a complete checklist of the diatom taxa recorded in subterranean habitats, including a total of 363 taxa, belonging to 82 genera. The most frequent and abundant species recorded in caves and other low light subterranean habitats are generally aerophilic and

  18. Seasonal variations in fouling diatom communities on the Yantai coast

    Science.gov (United States)

    Yang, Cuiyun; Wang, Jianhua; Yu, Yang; Liu, Sujing; Xia, Chuanhai

    2015-03-01

    Fouling diatoms are a main component of biofilm, and play an important role in marine biofouling formation. We investigated seasonal variations in fouling diatom communities that developed on glass slides immersed in seawater, on the Yantai coast, northern Yellow Sea, China, using microscopy and molecular techniques. Studies were conducted during 2012 and 2013 over 3, 7, 14, and 21 days in each season. The abundance of attached diatoms and extracellular polymeric substances increased with exposure time of the slides to seawater. The lowest diatom density appeared in winter and the highest species richness and diversity were found in summer and autumn. Seasonal variation was observed in the structure of fouling diatom communities. Pennate diatoms Cylindrotheca, Nitzschia, Navicula, Amphora, Gomphonema, and Licmophora were the main fouling groups. Cylindrotheca sp. dominated in the spring. Under laboratory culture conditions, we found that Cylindrotheca grew very fast, which might account for the highest density of this diatom in spring. The lower densities in summer and autumn might result from the emergence of fouling animals and environmental factors. The Cylindrotheca sp. was identified as Cylindrotheca closterium using18S rDNA sequencing. The colonization process of fouling diatoms and significant seasonal variation in this study depended on environmental and biological factors. Understanding the basis of fouling diatoms is essential and important for developing new antifouling techniques.

  19. Metabolic analysis of adaptation to short-term changes in culture conditions of the marine diatom Thalassiosira pseudonana.

    Directory of Open Access Journals (Sweden)

    Mariusz A Bromke

    Full Text Available This report describes the metabolic and lipidomic profiling of 97 low-molecular weight compounds from the primary metabolism and 124 lipid compounds of the diatom Thalassiosira pseudonana. The metabolic profiles were created for diatoms perturbed for 24 hours with four different treatments: (I removal of nitrogen, (II lower iron concentration, (III addition of sea salt, (IV addition of carbonate to their growth media. Our results show that as early as 24 hours after nitrogen depletion significant qualitative and quantitative change in lipid composition as well as in the primary metabolism of Thalassiosira pseudonana occurs. So we can observe the accumulation of several storage lipids, namely triacylglycerides, and TCA cycle intermediates, of which citric acid increases more than 10-fold. These changes are positively correlated with expression of TCA enzymes genes. Next to the TCA cycle intermediates and storage lipid changes, we have observed decrease in N-containing lipids and primary metabolites such as amino acids. As a measure of counteracting nitrogen starvation, we have observed elevated expression levels of nitrogen uptake and amino acid biosynthetic genes. This indicates that diatoms can fast and efficiently adapt to changing environment by altering the metabolic fluxes and metabolite abundances. Especially, the accumulation of proline and the decrease of dimethylsulfoniopropionate suggest that the proline is the main osmoprotectant for the diatom in nitrogen rich conditions.

  20. Partial localization in coherent electron emission from asymmetric diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Tachino, C A; Galassi, M E; Rivarola, R D [Instituto de FIsica Rosario, Consejo Nacional de Investigaciones CientIficas y Tecnicas - Universidad Nacional de Rosario, Av. Pellegrini 250, 2000 Rosario (Argentina); MartIn, F, E-mail: rivarola@fceia.unr.edu.a [Departamento de QuImica, Modulo 13, Universidad Autonoma de Madrid, 28049 Madrid (Spain)

    2010-07-14

    The presence of interference patterns in doubly differential cross sections is investigated for single electron ionization of a heteronuclear system, the HeH{sup +} molecular ion, produced by highly energetic protons. These interferences, which are due to coherent electron emission from the vicinity of the target nuclei, are preserved even after averaging over all molecular orientations. However, when compared with the homonuclear H{sub 2} target case, the effect appears to be less pronounced due to the partial localization of the target electrons around the alpha particle centre. Similarities and differences with the case of photon beams are also discussed.

  1. Influence of diatom exopolymers and biofilms on metamorphosis in the barnacle Balanus amphitrite

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, J.S.; Anil, A.C.

    Natural biofilms constitute a complex network of microorganisms (bacteria, diatoms, protozoa, fungi) and their extracellular polymeric substances (EPS), which influence settlement inbenthic invertebrates. The influence of diatom (Bacillariophyceae...

  2. Impact of nutrient starvation on the biochemical composition of the marine diatom Thalassiosira weissflogii: from the whole cell to the frustule fraction

    Science.gov (United States)

    Soler, C.; Claquin, P.; Goutx, M.; Ragueneau, O.; Moriceau, B.

    2010-08-01

    Interactions between carbon and silica in the diatom frustule play an important role in carbon export through their impact on diatom remineralization (carbon degradation and biogenic silica dissolution). To ameliorate model prediction of the fate of Si and organic matter during sedimentation, there is a need to first understand the origin and nature of Si-OC interactions, their impact on diatom remineralization and their variability with environmental conditions. In this study we focus on the impact of nutrient starvations on the formation and nature of these interactions in an ubiquitous diatom, Thalassiosira weissflogii. Fluorescence reveals the strong impact of all starvations on diatom metabolism while Fourier transformed infrared (FTIR) spectroscopy clearly showed that starvations altered the composition of the different diatom fractions. The relative compositions of whole cells were almost not impacted by starvations except Si(OH)4 starvation that slightly increased proteins relative contribution while decreasing carbohydrate. Starvation impacts became obvious looking at the composition of the different part of the diatom. The relative biochemical composition of the organic coating, protecting the frustule from the environment, was strongly affected by starvation. Under nitrate starvation, carbohydrate contribution increased while protein contribution decreased. Inversely, phosphate starvation increased the proportion of proteins and decreased carbohydrates contribution. Starvations also modified the different frustule phases. bSiO2 contribution decreased in the less reactive phase under silicate and phosphate starvation whereas nitrate starvation rather increased carbohydrate and protein pools. Phosphate starvation also led to an important shift of dominance among protein groups between amide I and amide II which compounds are suspected to play a key role in the frustule synthesis and architecture. Nutrient starvations affected the relative biochemical

  3. Periodic Traveling Waves in Diatomic Granular Chains

    Science.gov (United States)

    Betti, Matthew; Pelinovsky, Dmitry E.

    2013-10-01

    We study bifurcations of periodic traveling waves in diatomic granular chains from the anti-continuum limit, when the mass ratio between the light and heavy beads is zero. We show that every limiting periodic wave is uniquely continued with respect to the mass ratio parameter, and the periodic waves with a wavelength larger than a certain critical value are spectrally stable. Numerical computations are developed to study how this solution family is continued to the limit of equal mass ratio between the beads, where periodic traveling waves of homogeneous granular chains exist.

  4. Diatom-based water quality monitoring in southern Africa ...

    African Journals Online (AJOL)

    Much work still needs to be carried out on diatom tolerances, ecological preferences and ecophysiology. It is recommended that past research pertaining to African diatom taxonomy should be made readily accessible to all through electronic media for use as a reference point. Moreover, following the same approach as for ...

  5. A contribution to the epipsammic diatom flora of Estonia

    NARCIS (Netherlands)

    Cremer, H.

    2006-01-01

    A study of the modern epipsammic diatom flora in Lake Karujärv, Saaremaa Island, Estonia revealed seventy-one taxa representing thirty-one genera. The identity of all taxa is documented with light micrographs. Most abundant taxa of the epipsammic diatom community were Achnanthidium minutissimum

  6. Preparation and method of study of fossil diatoms

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G.A.P.

    to be exercised during the preparation of the samples A method for the preparation of strewn slides is then explained A detailed procedure for the study of diatom-strewn slides under the microscope, using the "England finder", is described, and a note on diatom...

  7. Records of Diatoms and Physicochemical Parameters of Seasonal ...

    African Journals Online (AJOL)

    A study of diatoms species composition, associated with four ponds in Zaria, Northern Nigeria was carried out between November 2005–January 2006 and June–August 2006. Twenty three taxa of diatoms were recorded in the study. Multivariate analysis showed that there were significant positive and negative ...

  8. Interference patterns and extinction ratio of the diatom Coscinodiscus granii

    DEFF Research Database (Denmark)

    Maibohm, Christian; Friis, Søren Michael Mørk; Ellegaard, M.

    2015-01-01

    We report experimental and theoretical verification of the nature and position of multiple interference points of visible light transmitted through the valve of the centric diatom species Coscinodiscus granii. Furthermore, by coupling the transmitted light into an optical fiber and moving the dia...... the diatom valve between constructive and destructive interference points, an extinction ratio of 20 dB is shown...

  9. Spatial And Temporal Distribution Of Epiphytic Diatoms On ...

    African Journals Online (AJOL)

    The important components in the flora of the epiphytic diatoms were belonging to the genera: Achnanthes, Achnanthidium, Fragilaria, Gyrosigma, Licmophora, Navicula, Pleurosigma, Synedra and Tabellaria. The rest recorded epiphytic diatoms were considered rare and of no significance in defining the epiphytic flora on ...

  10. The Central Carbon and Energy Metabolism of Marine Diatoms

    Directory of Open Access Journals (Sweden)

    Adriano Nunes-Nesi

    2013-05-01

    Full Text Available Diatoms are heterokont algae derived from a secondary symbiotic event in which a eukaryotic host cell acquired an eukaryotic red alga as plastid. The multiple endosymbiosis and horizontal gene transfer processes provide diatoms unusual opportunities for gene mixing to establish distinctive biosynthetic pathways and metabolic control structures. Diatoms are also known to have significant impact on global ecosystems as one of the most dominant phytoplankton species in the contemporary ocean. As such their metabolism and growth regulating factors have been of particular interest for many years. The publication of the genomic sequences of two independent species of diatoms and the advent of an enhanced experimental toolbox for molecular biological investigations have afforded far greater opportunities than were previously apparent for these species and re-invigorated studies regarding the central carbon metabolism of diatoms. In this review we discuss distinctive features of the central carbon metabolism of diatoms and its response to forthcoming environmental changes and recent advances facilitating the possibility of industrial use of diatoms for oil production. Although the operation and importance of several key pathways of diatom metabolism have already been demonstrated and determined, we will also highlight other potentially important pathways wherein this has yet to be achieved.

  11. Applications of diatoms as potential microalgae in nanobiotechnology.

    Science.gov (United States)

    Jamali, Ali Akbar; Akbari, Fariba; Ghorakhlu, Mohamad Moradi; de la Guardia, Miguel; Yari Khosroushahi, Ahmad

    2012-01-01

    Diatoms are single cell eukaryotic microalgae, which present in nearly every water habitat make them ideal tools for a wide range of applications such as oil explora-tion, forensic examination, environmental indication, biosilica pattern generation, toxicity testing and eutrophication of aqueous ecosystems. Essential information on diatoms were reviewed and discussed towards impacts of diatoms on biosynthesis and bioremediation. In this review, we present the recent progress in this century on the application of diatoms in waste degradation, synthesis of biomaterial, biomineraliza-tion, toxicity and toxic effects of mineral elements evaluations. Diatoms can be considered as metal toxicity bioindicators and they can be applied for biomineralization, synthesis of biomaterials, and degradation of wastes.

  12. Applications of Diatoms as Potential Microalgae in Nanobiotechnology

    Directory of Open Access Journals (Sweden)

    Ahmad Yari Khosroushahi

    2012-05-01

    Full Text Available Introduction: Diatoms are single cell eukaryotic microalgae, which present in nearly every water habitat make them ideal tools for a wide range of applications such as oil explora­tion, forensic examination, environmental indication, biosilica pattern generation, toxicity testing and eutrophication of aqueous ecosystems. Methods: Essential information on diatoms were reviewed and discussed towards impacts of diatoms on biosynthesis and bioremediation. Results: In this review, we present the recent progress in this century on the application of diatoms in waste degradation, synthesis of biomaterial, biomineraliza­tion, toxicity and toxic effects of mineral elements evaluations. Conclusion: Diatoms can be considered as metal toxicity bioindicators and they can be applied for biomineralization, synthesis of biomaterials, and degradation of wastes.

  13. Variation partitioning of diatom species data matrices: Understanding the influence of multiple factors on benthic diatom communities in tropical streams

    Energy Technology Data Exchange (ETDEWEB)

    Bere, Taurai, E-mail: tbere2015@gmail.com; Mangadze, Tinotenda; Mwedzi, Tongai

    2016-10-01

    Elucidating the confounding influence of multiple environmental factors on benthic diatom communities is important in developing water quality predictive models for better guidance of stream management efforts. The objective of this study was to explore the relative impact of metal pollution and hydromorphological alterations in, addition to nutrient enrichment and organic pollution, on diatom taxonomic composition with the view to improve stream diatom-based water quality inference models. Samples were collected twice at 20 sampling stations in the tropical Manyame Catchment, Zimbabwe. Diatom, macroinvertebrate communities and environmental factors were sampled and analysed. The variations in diatom community composition explained by different categories of environmental factors were analysed using canonical correspondence analysis using variance partitioning (partial CCA). The following variations were explained by the different predictor matrices: nutrient levels and organic pollution - 10.4%, metal pollution - 8.3% and hydromorphological factors - 7.9%. Thus, factors other than nutrient levels and organic pollution explain additional significant variation in these diatom communities. Development of diatom-based stream water quality inference models that incorporate metal pollution and hydromorphological alterations, where these are key issues, is thus deemed necessary. - Highlights: • Confounding influences of multiple environmental factors on diatom communities are elucidated. • Variation explained: nutrients + organic pollution - 10.4%, metals - 8.3% and hydromorphological factors - 7.9%. • Calibration of existing or development of new indices may be necessary.

  14. Importance of sampling frequency when collecting diatoms

    Science.gov (United States)

    Wu, Naicheng; Faber, Claas; Sun, Xiuming; Qu, Yueming; Wang, Chao; Ivetic, Snjezana; Riis, Tenna; Ulrich, Uta; Fohrer, Nicola

    2016-11-01

    There has been increasing interest in diatom-based bio-assessment but we still lack a comprehensive understanding of how to capture diatoms’ temporal dynamics with an appropriate sampling frequency (ASF). To cover this research gap, we collected and analyzed daily riverine diatom samples over a 1-year period (25 April 2013-30 April 2014) at the outlet of a German lowland river. The samples were classified into five clusters (1-5) by a Kohonen Self-Organizing Map (SOM) method based on similarity between species compositions over time. ASFs were determined to be 25 days at Cluster 2 (June-July 2013) and 13 days at Cluster 5 (February-April 2014), whereas no specific ASFs were found at Cluster 1 (April-May 2013), 3 (August-November 2013) (>30 days) and Cluster 4 (December 2013 - January 2014) (<1 day). ASFs showed dramatic seasonality and were negatively related to hydrological wetness conditions, suggesting that sampling interval should be reduced with increasing catchment wetness. A key implication of our findings for freshwater management is that long-term bio-monitoring protocols should be developed with the knowledge of tracking algal temporal dynamics with an appropriate sampling frequency.

  15. Importance of sampling frequency when collecting diatoms

    KAUST Repository

    Wu, Naicheng

    2016-11-14

    There has been increasing interest in diatom-based bio-assessment but we still lack a comprehensive understanding of how to capture diatoms’ temporal dynamics with an appropriate sampling frequency (ASF). To cover this research gap, we collected and analyzed daily riverine diatom samples over a 1-year period (25 April 2013–30 April 2014) at the outlet of a German lowland river. The samples were classified into five clusters (1–5) by a Kohonen Self-Organizing Map (SOM) method based on similarity between species compositions over time. ASFs were determined to be 25 days at Cluster 2 (June-July 2013) and 13 days at Cluster 5 (February-April 2014), whereas no specific ASFs were found at Cluster 1 (April-May 2013), 3 (August-November 2013) (>30 days) and Cluster 4 (December 2013 - January 2014) (<1 day). ASFs showed dramatic seasonality and were negatively related to hydrological wetness conditions, suggesting that sampling interval should be reduced with increasing catchment wetness. A key implication of our findings for freshwater management is that long-term bio-monitoring protocols should be developed with the knowledge of tracking algal temporal dynamics with an appropriate sampling frequency.

  16. Combined zero-quantum and spin-diffusion mixing for efficient homonuclear correlation spectroscopy under fast MAS: broadband recoupling and detection of long-range correlations.

    Science.gov (United States)

    Lu, Xingyu; Guo, Changmiao; Hou, Guangjin; Polenova, Tatyana

    2015-01-01

    Fast magic angle spinning (MAS) NMR spectroscopy is emerging as an essential analytical and structural biology technique. Large resolution and sensitivity enhancements observed under fast MAS conditions enable structural and dynamics analysis of challenging systems, such as large macromolecular assemblies and isotopically dilute samples, using only a fraction of material required for conventional experiments. Homonuclear dipolar-based correlation spectroscopy constitutes a centerpiece in the MAS NMR methodological toolbox, and is used essentially in every biological and organic system for deriving resonance assignments and distance restraints information necessary for structural analysis. Under fast MAS conditions (rotation frequencies above 35-40 kHz), dipolar-based techniques that yield multi-bond correlations and non-trivial distance information are ineffective and suffer from low polarization transfer efficiency. To overcome this limitation, we have developed a family of experiments, CORD-RFDR. These experiments exploit the advantages of both zero-quantum RFDR and spin-diffusion based CORD methods, and exhibit highly efficient and broadband dipolar recoupling across the entire spectrum, for both short-range and long-range correlations. We have verified the performance of the CORD-RFDR sequences experimentally on a U-(13)C,(15)N-MLF tripeptide and by numerical simulations. We demonstrate applications of 2D CORD-RFDR correlation spectroscopy in dynein light chain LC8 and HIV-1 CA tubular assemblies. In the CORD-RFDR spectra of LC8 acquired at the MAS frequency of 40 kHz, many new intra- and inter-residue correlations are detected, which were not observed with conventional dipolar recoupling sequences. At a moderate MAS frequency of 14 kHz, the CORD-RFDR experiment exhibits excellent performance as well, as demonstrated in the HIV-1 CA tubular assemblies. Taken together, the results indicate that CORD-RFDR experiment is beneficial in a broad range of conditions

  17. Diatoms as indicators of water quality in the Jukskei-Crocodile river ...

    African Journals Online (AJOL)

    South Africa has a long legacy of diatom research. The eminent diatomist Dr BJ Cholnoky spent much of his working life examining and enumerating diatom communities found in Southern Africa. Most if not all of Cholnoky's collected diatom material in the form of mounted material on glass slides accompanied by diatom ...

  18. Diatoms from a peat bog on the Pešter plateau (southwestern Serbia: New records for diatom flora of Serbia

    Directory of Open Access Journals (Sweden)

    Vidaković Danijela

    2016-01-01

    Full Text Available The distribution of diatoms was studied in three types of diatom communities (epiphytes, benthos and plankton of a peat bog on the Pešter plateau. The observed diatom flora inhabited all investigated communities, comprising in total 250 taxa in 53 genera. Among them, 45 taxa were new records for the Serbian diatom flora. Identified taxa belonged to different groups of algae, however alkaliphile diatoms were dominant. New ecological data for Encyonopsis minuta, Pinnularia isostauron and P. marchica are presented here. All the diatoms were documented by light micrographs, and brief notes on their morphology, distribution and ecology are provided. [Projekat Ministarstva nauke Republike Srbije, br. TR 037009

  19. Diatom auxospore scales and early stages in diatom frustule morphogenesis: their potential for use in nanotechnology.

    Science.gov (United States)

    Tiffany, Mary Ann

    2005-01-01

    Incomplete, forming diatom cell wall components have potential uses in nanotechnology that differ from those of mature frustules. Diminutive, discoid auxospore scales, produced after sexual reproduction, could also be evaluated for their value. The structure of developing diatom valves and girdle bands is generally simple, since features such as cribra and other ornamentation have yet to be added. They are also more lightly silicified. Bullulae and honeycomb structures give strength to the final framework of some species using a minimal amount of silica. The morphogenesis of girdle bands is shown to be unidirectional in a marine centric species, forming open-ended cylinders, another potential shape for the arsenal of structures useful to nanotechnologists.

  20. Molecular Detection of a Potentially Toxic Diatom Species

    Directory of Open Access Journals (Sweden)

    Bidhan Chandra Dhar

    2015-05-01

    Full Text Available A few diatom species produce toxins that affect human and animal health. Among these, members of the Pseudo-nitzschia genus were the first diatoms unambiguously identified as producer of domoic acid, a neurotoxin affecting molluscan shell-fish, birds, marine mammals, and humans. Evidence exists indicating the involvement of another diatom genus, Amphora, as a potential producer of domoic acid. We present a strategy for the detection of the diatom species Amphora coffeaeformis based on the development of species-specific oligonucleotide probes and their application in microarray hybridization experiments. This approach is based on the use of two marker genes highly conserved in all diatoms, but endowed with sufficient genetic divergence to discriminate diatoms at the species level. A region of approximately 450 bp of these previously unexplored marker genes, coding for elongation factor 1-a (eEF1-a and silicic acid transporter (SIT, was used to design oligonucleotide probes that were tested for specificity in combination with the corresponding fluorescently labeled DNA targets. The results presented in this work suggest a possible use of this DNA chip technology for the selective detection of A. coffeaeformis in environmental settings where the presence of this potential toxin producer may represent a threat to human and animal health. In addition, the same basic approach can be adapted to a wider range of diatoms for the simultaneous detection of microorganisms used as biomarkers of different water quality levels.

  1. Spatial paradigms of lotic diatom distribution: A landscape ecology perspective

    Science.gov (United States)

    Passy, S.I.

    2001-01-01

    Spatial distributional patterns of benthic diatoms and their relation to current velocity were investigated in an unshaded cobble-bottom reach of White Creek (Washington County, NY). On 27 August 1999, diatoms were sampled and current velocity and depth were measured on a regular square sampling grid with a grain size of 0.01 m2, interval of 0.5 m, and extent of 16 m2. The relative abundance of the 18 common diatom species enumerated in the 81 samples was subjected to detrended correspondence analysis (DCA). The first axis (DCA1) explained 51% of the variance in diatom data and separated the samples according to current regimes. The spatial autocorrelation of DCA1 sample scores in deposition and erosion regions of White Creek was determined by Moran's I statistic to indicate patch size. In White Creek the patch length of all diatom communities was more than 3.1 m, whereas the patch width was 1 m in the deposition region and 0.5 m in the erosion region. There were 5 dominant diatom taxa, Achnanthes minutissima Ku??tz. et vars, Fragilaria capucina Dezmazie??res et vars, F. crotonensis Kitt., Diatoma vulgaris Bory, and Synedra ulna (Nitz.) Ehr. et vars. The patch length of the dominant species varied from 1 to more than 4.1 m, whereas the patch width, if defined, was 0.5 m. Achnanthes minutissima and F. capucina, the two diatom species with the highest relative abundance, displayed spatially structured patches of low abundance and comparatively random patches of high abundance, suggesting broad scale abiotic control of species performance in low abundance regions and finer scale biotic control of high abundance areas. Another objective of this study was to test the hypothesis that higher current velocities, which generally impede immigration, would increase randomness and complexity (i.e. homogeneity of diatom distributional patterns). The spatial complexity in low versus high velocity transects was determined by calculating the respective fractal dimension (D) of DCA

  2. Some new and rare diatoms from South Africa 2. Diatoms from lake Sibayi and lake Nhlange in Tongaland (Natal)

    CSIR Research Space (South Africa)

    Archibald, REM

    1966-01-01

    Full Text Available ~-t~6SDI NOVA HEDWIGIA ZEITSCHRIFT FUR KRYPTOGAMENKUNDE HERAUSGEGEBEN VON J. GERLOFF, F. MATTICK & J. POELT (BERLIN-DANLEM) SONDERABDRUCK AUS BAND XII, 3+4 Some New and Rare Diatoms from South Africa 2 by R. B. M. ARCHIBALD QL1 j NC~ iii... verpfiichtet aum Bezug des gesamten Werkea. i I Some New and Rare Diatoms from South Africa 2. Diatoms from Lake Sibayi and Lake Nlilange in Tongalanri (Natal). By R. E. il. ARGIIEBALD?) With Plate 97(V In January, 1966, the Zoology Department of Rhodes...

  3. Acidification counteracts negative effects of warming on diatom silicification

    KAUST Repository

    Coello-Camba, Alexandra

    2016-10-24

    Diatoms are a significant group contributing up to 40 % of annual primary production in the oceans. They have a special siliceous cell wall that, acting as a ballast, plays a key role in the sequestration of global carbon and silica. Diatoms dominate primary production in the Arctic Ocean, where global climate change is causing increases in water temperature and in the partial pressure of CO2 (pCO2). Here we show that as water temperature increases diatoms become stressed, grow to smaller sizes, and decrease their silicification rates. But at higher pCO2, as the pH of seawater decreases, silica incorporation rates are increased. In a future warmer Arctic ocean diatoms may have a competitive advantage under increased ocean acidification, as increased pCO2 counteracts the adverse effects of increasing temperature on silicification and buffers its consequences in the biogeochemical cycles of carbon and silica.

  4. Diatoms - nature materials with great potential for bioapplications

    Directory of Open Access Journals (Sweden)

    Medarević Đorđe P.

    2016-01-01

    Full Text Available Diatoms are widespread unicellular photosynthetic algae that produce unique highly ordered siliceous cell wall, called frustule. Micro- to nanoporous structure with high surface area that can be easily modified, high mechanical resistance, unique optical features (light focusing and luminescence and biocompatibility make diatom frustule as a suitable raw material for the development of devices such as bio- and gas sensors, microfluidic particle sorting devices, supercapacitors, batteries, solar cells, electroluminescent devices and drug delivery systems. Their wide availability in the form of fossil remains (diatomite or diatomaceous earth as well as easy cultivation in the artificial conditions further supports use of diatoms in many different fields of application. This review focused on the recent achievements in the diatom bioapplications such as drug delivery, biomolecules immobilization, bio- and gas sensing, since great progress was made in this field over the last several years.

  5. Light Manipulation by Single Cells: The Case of Diatoms

    Directory of Open Access Journals (Sweden)

    Edoardo De Tommasi

    2016-01-01

    Full Text Available Diatoms are ubiquitous monocellular microalgae, responsible for about 20–25% of the global oxygen produced by photosynthesis. Living in environments where sunlight is not so easily accessible, evolution shaped diatoms in order to exploit light with high efficiency. In particular, diatoms are provided with an external, micro- and nanopatterned silica shell, the frustule, surprisingly similar to artificial photonic crystals and able to manipulate light in many different ways. The present paper reviews the most relevant studies on optical and photonic properties of diatoms that have been performed throughout the last years making use of SEM characterizations, transmittance measurements at different wavelengths, holographic microscopy, Raman spectroscopy and imaging, photoluminescence spectroscopy, and the predictive support of different numerical simulation algorithms.

  6. Lake warming favours small-sized planktonic diatom species

    National Research Council Canada - National Science Library

    Monika Winder; John E Reuter; S. Geoffrey Schladow

    2009-01-01

    ... were not responsible for the change. The increase in small-celled species was sufficient to decrease the average diatom size and thus sinking velocity, which strongly influences energy transfer through the food web and carbon cycling...

  7. Modified Ribose Receptor Response in Isolated Diatom Frustules

    Energy Technology Data Exchange (ETDEWEB)

    Fairbanks, Carly R.

    2011-08-26

    Diatoms are a distinctive group of microalgae with the unique ability to produce a highly-ordered biosilica matrix, known as the frustule. Diatoms hold significant potential in the biotechnology field as a silica scaffold for embedding proteins. In this study, we analyzed the funtionalization of biosilica with a receptor complex through genetic modification of the diatom, Thalassiosira pseudonana. Through the use of Foerster Resonance Energy Transfer (FRET), the receptor was shown to remain active in transformed frustules after the inner cellular contents were removed. In addition to protein functionality, growth conditions for T. pseudonana were optimized. Untransformed cultures receiving aeration grew more rapidly than stagnant untransformed cultures. Surprisingly, transformed cultures grew more quickly than untransformed cultures. This study demonstrates isolated diatom frustules provide an effective scaffold for embedded receptor complexes. Through this research, we provide the groundwork for the development of new biosensors for use in diagnostics and environmental remediation.

  8. Abundance of bacterial and diatom fouling on various surfaces

    Digital Repository Service at National Institute of Oceanography (India)

    PrabhaDevi

    Abundance of bacterial and diatom fouling on aluminium, fibreglass and stainless steel were studied from Dona Paula waters of the Zuari Estuary. Both these forms were reversibly attached in large numbers to surfaces during the initial 24 hr...

  9. Improvement of Neutral Lipid and Polyunsaturated Fatty Acid Biosynthesis by Overexpressing a Type 2 Diacylglycerol Acyltransferase in Marine Diatom Phaeodactylum tricornutum

    Directory of Open Access Journals (Sweden)

    Ying-Fang Niu

    2013-11-01

    Full Text Available Microalgae have been emerging as an important source for the production of bioactive compounds. Marine diatoms can store high amounts of lipid and grow quite quickly. However, the genetic and biochemical characteristics of fatty acid biosynthesis in diatoms remain unclear. Glycerophospholipids are integral as structural and functional components of cellular membranes, as well as precursors of various lipid mediators. In addition, diacylglycerol acyltransferase (DGAT is a key enzyme that catalyzes the last step of triacylglyceride (TAG biosynthesis. However, a comprehensive sequence-structure and functional analysis of DGAT in diatoms is lacking. In this study, an isoform of diacylglycerol acyltransferase type 2 of the marine diatom Phaeodactylum tricornutum was characterized. Surprisingly, DGAT2 overexpression in P. tricornutum stimulated more oil bodies, and the neutral lipid content increased by 35%. The fatty acid composition showed a significant increase in the proportion of polyunsaturated fatty acids; in particular, EPA was increased by 76.2%. Moreover, the growth rate of transgenic microalgae remained similar, thereby maintaining a high biomass. Our results suggest that increased DGAT2 expression could alter fatty acid profile in the diatom, and the results thus represent a valuable strategy for polyunsaturated fatty acid production by genetic manipulation.

  10. Production of silver nanoparticles by the diatom Phaeodactylum tricornutum

    Science.gov (United States)

    Wishkerman, Asher; Arad (Malis), Shoshana

    2017-05-01

    Diatoms (Bacillariophyceae) are the most species-rich group of algae, they are single-celled characterized by a silicified cell wall called a frustule. Diatoms are diverse in shape with many distinct features like raphe and fultoportulae. The diatom cell wall morphology and its hierarchy structure make it a unique unicellular organism for nanotechnology research and applications. Diatom cells are a promising system for green synthesis of nanomaterials like metallic nanoparticles (NPs), nanostructured polymers and other nanomaterials. The production of NPs is achieved today by using methods like attrition or pyrolysis. The cost and the toxic substances often used in these common methods of NPs synthesis limit their applications. Therefore, NPs biosynthesis by diatom cultures, which can be done at ambient CO2 concentrations, temperature and pressure, offers a sustainable alternative solution. In this work, we examined the formation of silver NPs (AgNPs) by the diatom Phaeodactylum tricornutum cultivated at 25°C for a period of 8 days. Using this approach, diatom cultures were either grown throughout the duration of the experiment in an artificial seawater (ASW)-f/2 medium enriched with 1 ppm Ag+ or grown in an ASW-f/2 medium where similar silver ion concentrations were added on experimental day 4. We found that 1 ppm Ag+ reduces the P. tricornutum growth by up to 50% as compared with the control. Moreover, scanning electron microscopy (SEM) in combination with Energy-Dispersive X-ray (EDX) showed the presence of AgNPs nanoparticles with different sizes and chemical composition associated with the diatom frustules and extracellular polymeric substances.

  11. Diversity and Evolutionary History of Iron Metabolism Genes in Diatoms.

    Directory of Open Access Journals (Sweden)

    Ryan D Groussman

    Full Text Available Ferroproteins arose early in Earth's history, prior to the emergence of oxygenic photosynthesis and the subsequent reduction of bioavailable iron. Today, iron availability limits primary productivity in about 30% of the world's oceans. Diatoms, responsible for nearly half of oceanic primary production, have evolved molecular strategies for coping with variable iron concentrations. Our understanding of the evolutionary breadth of these strategies has been restricted by the limited number of species for which molecular sequence data is available. To uncover the diversity of strategies marine diatoms employ to meet cellular iron demands, we analyzed 367 newly released marine microbial eukaryotic transcriptomes, which include 47 diatom species. We focused on genes encoding proteins previously identified as having a role in iron management: iron uptake (high-affinity ferric reductase, multi-copper oxidase, and Fe(III permease; iron storage (ferritin; iron-induced protein substitutions (flavodoxin/ferredoxin, and plastocyanin/cytochrome c6 and defense against reactive oxygen species (superoxide dismutases. Homologs encoding the high-affinity iron uptake system components were detected across the four diatom Classes suggesting an ancient origin for this pathway. Ferritin transcripts were also detected in all Classes, revealing a more widespread utilization of ferritin throughout diatoms than previously recognized. Flavodoxin and plastocyanin transcripts indicate possible alternative redox metal strategies. Predicted localization signals for ferredoxin identify multiple examples of gene transfer from the plastid to the nuclear genome. Transcripts encoding four superoxide dismutase metalloforms were detected, including a putative nickel-coordinating isozyme. Taken together, our results suggest that the majority of iron metabolism genes in diatoms appear to be vertically inherited with functional diversity achieved via possible neofunctionalization of

  12. Diatoms and Water Quality of Telaga Warna Dieng, Java Indonesia

    Science.gov (United States)

    Retnaningsih Soeprobowati, Tri; Widodo Agung Suedy, Sri; Hadiyanto

    2017-02-01

    Diatoms are popular name for Bacillariophyte, the microalgae with the specific characteristic of silicious cell walls that well preserved in the sediments. The different diatoms assemblage in the sediment layers indicate different environment at the time of the diatoms live and deposited. Telaga Warna is small lake in Dieng Plateau. Telaga means lake, Warna means colour. It is called Telaga Warna because previously have 4 colours i.e. red, white, blue, and yellow which was influenced by weather, time, and site of view. This study aims to analysis the diatoms communities and water quality of Telaga Warna Dieng, Java, Indonesia. Coring conducted at three different locations. Water sampling carried out on all three spots. Analysis of diatoms consist of three stages: digestion, preparation, and identification of diatoms. There were 59 diatoms species found in Telaga Warna Dieng that were belong to 9 groups diatoms of centric, arafid, eunotoid, birafid, monorafid, birafid, epitemid, nitzschioid, and surirelloid. Eunotia, Pinnularia, and Melosira were the dominant genus from Telaga Warna. The water quality parameters that exceeded Indonesia Water Quality Standard were pH (2.2 - 5.4), Pb, Cd, Cr, Cu. Based on the abundance of species Eunotia and Pinnularia in Telaga Warna Dieng indicates that water tends to be acidic. The dominance of Melosira indicates waters rich in nitrogen. Based on the total concentration of nitrogen and phosphorous, Telaga Warna was in an eutrophic - hipereutrophic conditions with total nitrogen concentration > 1.9 mg/L and total phosphorus concentration > 0.1 mg/L.

  13. Fast Regulation of Photosynthesis in Diatoms: Mechanisms, Evolution and Ecophysiology

    OpenAIRE

    Lavaud, Johann

    2007-01-01

    International audience; Diatoms (Bacillariophyceae, Heterokontophytes) are essential aquatic eukaryotes. Their role in the structure and ecology of most of the aquatic ecosystems is crucial. Especially, their photosynthetic activity is responsible for about a quarter of the Earth's primary productivity as large as the most productive terrestrial ecosystems, even though they represent only few percents of the total plant biomass on the planet. Both planktonic and benthic diatoms tend to domina...

  14. Information on Gas-Phase Diatomic Molecules from Magnetically Induced Current Densities.

    Science.gov (United States)

    Alvarez-Thon, Luis; Mammino, Liliana

    2018-01-05

    Magnetically induced current densities are different for different types of chemical bonds, and may help highlight some of their characteristics and stress their main differences. The present work considers magnetically induced current densities in the bonds of diatomic molecules bonded by covalent bonds as well as the gas phase molecules of 1:1 ionic compounds, comparing the current strength values and visualizing current density maps. The results show clear-cut differences for the different types of bonds (non-polar covalent, polar covalent, and ionic), and can also be related to the extent of the covalent or ionic character of a bond. For ionic compounds, the results also show relevant differences depending on the charges of the ions and on their electron configuration (including significant effects from the presence of d electrons in the outer shell of the ions). The article presents and analyses the results in detail. It is concluded that the magnetically induced current densities contribute to the description and interpretation of chemical bonding in diatomic molecules. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  15. Marine Polysaccharide Networks and Diatoms at the Nanometric Scale

    Directory of Open Access Journals (Sweden)

    Tea Mišić Radić

    2013-10-01

    Full Text Available Despite many advances in research on photosynthetic carbon fixation in marine diatoms, the biophysical and biochemical mechanisms of extracellular polysaccharide production remain significant challenges to be resolved at the molecular scale in order to proceed toward an understanding of their functions at the cellular level, as well as their interactions and fate in the ocean. This review covers studies of diatom extracellular polysaccharides using atomic force microscopy (AFM imaging and the quantification of physical forces. Following a brief summary of the basic principle of the AFM experiment and the first AFM studies of diatom extracellular polymeric substance (EPS, we focus on the detection of supramolecular structures in polysaccharide systems produced by marine diatoms. Extracellular polysaccharide fibrils, attached to the diatom cell wall or released into the surrounding seawater, form distinct supramolecular assemblies best described as gel networks. AFM makes characterization of the diatom polysaccharide networks at the micro and nanometric scales and a clear distinction between the self-assembly and self-organization of these complex systems in marine environments possible.

  16. Adsorption of diatoms at the oil-water interface

    Science.gov (United States)

    Fathollahi, Niloofar; Sheng, Jian

    2013-11-01

    Statistically robust experimental observations on 3D trajectory of diatoms approaching an oil-water interface is crucial for understanding sorption mechanisms of active particles, and interfacial rheology with over-arching implications in interfacial dynamics, droplet break and coalescence. Digital Holographic Cinematography is utilized to measure 3-D trajectories of diatoms, Thalassiosira pseudomona and T. weissflogii and simultaneously track the interface. Experiments are conducted in a 300 × 100 × 100 mm chamber containing 32 ppt artificial seawater. A stationary pendant drop is created on the tip of a needle located at the center of the chamber. Three oil samples, Louisiana crude, hexadecane, and mineral oil, are used. Diatoms are injected at a height above the drop with a negligible velocity, where Diatom precipitates freely on its excess weight. Holograms of diatom and drop are recorded at 5 fps with a magnification of 1.3X and are streamed in real time allowing for long-term study of sorption onto a slowly aging interface. A novel autofocus algorithm enables us to determine 3D locations within an uncertainty of 0.05 particle diameter. This allows us to perform super-resolution measurement to determine the effects of location and orientation of diatoms on the adsorption rate at the oil-water interface. Funded by GoMRI.

  17. Growth form defines physiological photoprotective capacity in intertidal benthic diatoms.

    Science.gov (United States)

    Barnett, Alexandre; Méléder, Vona; Blommaert, Lander; Lepetit, Bernard; Gaudin, Pierre; Vyverman, Wim; Sabbe, Koen; Dupuy, Christine; Lavaud, Johann

    2015-01-01

    In intertidal marine sediments, characterized by rapidly fluctuating and often extreme light conditions, primary production is frequently dominated by diatoms. We performed a comparative analysis of photophysiological traits in 15 marine benthic diatom species belonging to the four major morphological growth forms (epipelon (EPL), motile epipsammon (EPM-M) and non-motile epipsammon (EPM-NM) and tychoplankton (TYCHO)) found in these sediments. Our analyses revealed a clear relationship between growth form and photoprotective capacity, and identified fast regulatory physiological photoprotective traits (that is, non-photochemical quenching (NPQ) and the xanthophyll cycle (XC)) as key traits defining the functional light response of these diatoms. EPM-NM and motile EPL showed the highest and lowest NPQ, respectively, with EPM-M showing intermediate values. Like EPL, TYCHO had low NPQ, irrespective of whether they were grown in benthic or planktonic conditions, reflecting an adaptation to a low light environment. Our results thus provide the first experimental evidence for the existence of a trade-off between behavioural (motility) and physiological photoprotective mechanisms (NPQ and the XC) in the four major intertidal benthic diatoms growth forms using unialgal cultures. Remarkably, although motility is restricted to the raphid pennate diatom clade, raphid pennate species, which have adopted a non-motile epipsammic or a tychoplanktonic life style, display the physiological photoprotective response typical of these growth forms. This observation underscores the importance of growth form and not phylogenetic relatedness as the prime determinant shaping the physiological photoprotective capacity of benthic diatoms.

  18. THE INFLUENCE OF SUBMERGED MACROPHYTES ON SEDIMENTARY DIATOM ASSEMBLAGES(1).

    Science.gov (United States)

    Vermaire, Jesse C; Prairie, Yves T; Gregory-Eaves, Irene

    2011-12-01

    Submerged macrophytes are a central component of lake ecosystems; however, little is known regarding their long-term response to environmental change. We have examined the potential of diatoms as indicators of past macrophyte biomass. We first sampled periphyton to determine whether habitat was a predictor of diatom assemblage. We then sampled 41 lakes in Quebec, Canada, to evaluate whether whole-lake submerged macrophyte biomass (BiomEpiV) influenced surface sediment diatom assemblages. A multivariate regression tree (MRT) was used to construct a semiquantitative model to reconstruct past macrophyte biomass. We determined that periphytic diatom assemblages on macrophytes were significantly different from those on wood and rocks (ANOSIM R = 0.63, P macrophyte, nutrient-limited lakes (BiomEpiV ≥525 μg · L(-1) ; total phosphorus [TP] macrophyte, nutrient-limited lakes (BiomEpiV eutrophic lakes (TP ≥35 μg · L(-1) ; six lakes). A semiquantitative model correctly predicted the MRT group of the lake 71% of the time (P macrophytes have a significant influence on diatom community structure and that sedimentary diatom assemblages can be used to infer past macrophyte abundance. © 2011 Phycological Society of America.

  19. Responses of diatom communities to hydrological processes during rainfall events

    Science.gov (United States)

    Wu, Naicheng; Faber, Claas; Ulrich, Uta; Fohrer, Nicola

    2015-04-01

    The importance of diatoms as a tracer of hydrological processes has been recently recognized (Pfister et al. 2009, Pfister et al. 2011, Tauro et al. 2013). However, diatom variations in a short-term scale (e.g., sub-daily) during rainfall events have not been well documented yet. In this study, rainfall event-based diatom samples were taken at the outlet of the Kielstau catchment (50 km2), a lowland catchment in northern Germany. A total of nine rainfall events were caught from May 2013 to April 2014. Non-metric multidimensional scaling (NMDS) revealed that diatom communities of different events were well separated along NMDS axis I and II, indicating a remarkable temporal variation. By correlating water level (a proxy of discharge) and different diatom indices, close relationships were found. For example, species richness, biovolume (μm3), Shannon diversity and moisture index01 (%, classified according to van Dam et al. 1994) were positively related with water level at the beginning phase of the rainfall (i.e. increasing limb of discharge peak). However, in contrast, during the recession limb of the discharge peak, diatom indices showed distinct responses to water level declines in different rainfall events. These preliminary results indicate that diatom indices are highly related to hydrological processes. The next steps will include finding out the possible mechanisms of the above phenomena, and exploring the contributions of abiotic variables (e.g., hydrologic indices, nutrients) to diatom community patterns. Based on this and ongoing studies (Wu et al. unpublished data), we will incorporate diatom data into End Member Mixing Analysis (EMMA) and select the tracer set that is best suited for separation of different runoff components in our study catchment. Keywords: Diatoms, Rainfall event, Non-metric multidimensional scaling, Hydrological process, Indices References: Pfister L, McDonnell JJ, Wrede S, Hlúbiková D, Matgen P, Fenicia F, Ector L, Hoffmann L

  20. Seasonal changes of diatom species in the Hooghly estuary, India

    Science.gov (United States)

    Goswami, P. K.

    2013-12-01

    The Hooghly estuary is considered as one of the most important fishing ground of north-east India which is mainly because presence of large shallow parts of Bays, which provide extensive growths for benthic and planktonic community and also makes it a highly productive area .Anthropogenic effects induce intensive pressure to this ecosystem ;and consequently results in the eutrophication followed by rapid plankton growth, sometimes even bloom. Diatom comprises one of the most diverse and significant part of the biota of aquatic habitats. Ecologically they are of immense importance since they constitute the podium of food chain and are at pinnacle of the biomass pyramid. The present study was based on the diversity of most dominant diatom species found in the brackish waters of Hooghly estuarine region in three locations of Sagar islands - Gangasagar, Chemaguri and Kachuberia. In this study diatom distribution from post monsoon - pre monsoon period was studied on the specific assemblages of them.. There was wide diversity of diatom species in different locations and in different seasons. Maximum number of diatom species was found in post-monsoon period in Gangasagar and Chemaguri, while in Kachuberia maximum number was found in pre-monsoon period. In Gangasagar, Navicula socialis, Coscinodiscus spp. and Biddulphia spp. were the predominant species in early, mid and late post monsoon period respectively and Biddulphia spp. also continues as the predominant diatom in pre-monsoon period. In Chemaguri, Amphora ostrearia, Coscinodiscus perforatus and Nitzschia acuminate were the predominant species in early, mid and late post monsoon period respectively while Coscinodiscus radiates was the stable predominant diatom species in pre-monsoon period while Thalassionema spp., Ditylum spp., Proboscia spp. and Biddulphia spp. were also found in significantly increased numbers at different times of pre-monsoon period. In Kachuberia area although a wide range of diatoms are present

  1. Temporal changes of diatoms in marine biofilm developed on acrylic panels submerged in a tropical coast

    Science.gov (United States)

    Satheesh, Sathianeson; Wesley, Samuel Godwin

    2012-12-01

    The colonization of diatom groups on the acrylic panels submerged in Kudankulam coastal waters, east coast of India, was studied for one year from October 2004 to August 2005. Results showed temporal variability in the abundance of dominant diatom groups. Diatoms belonging to 19 genera colonized the panels. Navicula and Nitzschia were the dominant diatoms observed throughout the present study. The abundance of diatoms on test panels increased with the length of exposure. Significant variations in the abundance of Navicula and Nitzschia were observed between the sampling months. Temporal changes in biofilm diatom community composition in this study attain significance from the view point of macrofouling community recruitment on marine structures.

  2. The evolution of diatoms and their biogeochemical functions.

    Science.gov (United States)

    Benoiston, Anne-Sophie; Ibarbalz, Federico M; Bittner, Lucie; Guidi, Lionel; Jahn, Oliver; Dutkiewicz, Stephanie; Bowler, Chris

    2017-09-05

    In contemporary oceans diatoms are an important group of eukaryotic phytoplankton that typically dominate in upwelling regions and at high latitudes. They also make significant contributions to sporadic blooms that often occur in springtime. Recent surveys have revealed global information about their abundance and diversity, as well as their contributions to biogeochemical cycles, both as primary producers of organic material and as conduits facilitating the export of carbon and silicon to the ocean interior. Sequencing of diatom genomes is revealing the evolutionary underpinnings of their ecological success by examination of their gene repertoires and the mechanisms they use to adapt to environmental changes. The rise of the diatoms over the last hundred million years is similarly being explored through analysis of microfossils and biomarkers that can be traced through geological time, as well as their contributions to seafloor sediments and fossil fuel reserves. The current review aims to synthesize current information about the evolution and biogeochemical functions of diatoms as they rose to prominence in the global ocean.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'. © 2017 The Author(s).

  3. Modelling diatom life forms and ecological guilds for river biomonitoring

    Directory of Open Access Journals (Sweden)

    Marcel Rémy

    2017-01-01

    Full Text Available Biomonitoring is central to the European Union's Water Framework Directive (WFD and to the French water and aquatic environmental law, but most diatom indices do not separate different anthropogenic impacts. To address this gap, the effect of water chemistry on diatom ecological guilds and life forms was assessed in order to indicate stream perturbations. Generalised additive models (GAMs were built on a large-scale data set of 1571 samples from the French monitoring network. The relationships between diatom ecological guild and life form metrics were investigated by Principal components analysis and the results predicted by GAMs. The models characterised eight chemical parameters that modified adaptive strategies (ecological guilds and growth morphology (life forms. Total phosphorus, conductivity, nitrate and pH are the main influencing factors, followed by temperature, dissolved oxygen and organic matter. The findings confirm three groups of diatoms with different adaptive strategies: 1 – fast moving species, 2 – species growing close to the substrate and 3 – species extending to the surface layers of the biofilm. Thirteen diatom metrics displayed a variety of responses to different ranges of the eight chemical parameters. These metrics could be used to help to identify and quantify which chemical alterations are caused by polluted effluents in rivers.

  4. Postglacial diatom stratigraphy of Kirchner Marsh, Minnesota*1

    Science.gov (United States)

    Brugam, Richard B.

    1980-01-01

    Fossil diatom assemblages from a 12-m core from Kirchner Marsh were compared with modern surface assemblages from 159 Minnesota and labrador lakes using cluster analysis. The deepest levels of the core (spruce pollen zone 13,000 to 10,200 yr B.P.) resemble modern diatom assemblages from deep oligotrophic lakes of northeastern Minnesota. Diatom assemblages of the pine pollen zone (about 10,200 to 9500 yr B.P.) have few modern analogs. In the oak zone (9500 yr B.P. to present) after a brief pulse of diatom species indicative of eutrophication, the assemblages are dominated by species characteristic of shallow lakes, suggesting a drop in the lake water level during the prairie period (5500 to 7500 yr B.P.). Macrofossil data of W. A. Watts and T. C. Winter (1966, Geological Society of America Bulletin77, 1339-1360) show that this shift to shallow-water diatoms occurred when aquatic macrophytes appeared at the site in abundance.

  5. Growth inhibition of periphytic diatoms by methanol extracts of sponges and holothurians

    Digital Repository Service at National Institute of Oceanography (India)

    Mokashe, S.S.; Garg, A; Anil, A; Wagh, A

    Crude methanol extracts of a holothurian Holothuria leucospilota, and two sponges Craniella sp. and Ircinia ramosa were tested for their inhibitory effects on the growth of two marine diatoms, Navicula subinflata and N. crucicula, by diatom plating...

  6. Diatoms of the microphytobenthic community: Population structure in a tropical intertidal sand flat

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Anil, A.C

    Temporal and spatial variations were investigated in the viable diatom population of the microphytobenthic community from an intertidal sand flat of a tropical environment. The presence of diatoms to a sediment depth of 15 cm and their rejuvenation...

  7. Genotoxicity of cadmium in marine diatom Chaetoceros tenuissimus using the alkaline Comet assay

    Digital Repository Service at National Institute of Oceanography (India)

    Desai, S.R.; Verlecar, X.N.; Nagarajappa; Goswami

    of Cd increased growth of the diatom decreased. Alkaline single-cell gel electrophoresis (Comet assay) method, which is highly sensitive in detection of DNA damage in eukaryotic cells, was used to observe genomic changes in marine diatom cells. DNA...

  8. Fouling diatom community with reference to substratum variability in tropical marine environment

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Desai, D.V.; Khandeparker, L.; Anil, A.C.; Wagh, A.B.

    form encountered. The paper deals with the qualitative and quantitative aspects of diatom colonization, their community structure, and correlation between the prevailing diatom population in the environment and that in the fouling community...

  9. Palaeoecology of fossil diatoms (the thermometers of salinity) of lake Bonneville, Utah, USA

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G.A.P.

    Kolbe (1927) described diatoms as indicators of salinity hence the fossil diatoms can yield paleoecological information considerable importance to the geologist regarding the environment in which their enclosing sediments were deposited...

  10. Diatom diet selectivity by early post-larval abalone Haliotis diversicolor supertexta under hatchery conditions

    Science.gov (United States)

    Zhang, Yuyu; Gao, Yahui; Liang, Junrong; Chen, Changping; Zhao, Donghai; Li, Xuesong; Li, Yang; Wu, Wenzhong

    2010-11-01

    Benthic diatoms constitute the primary diet of abalone during their early stages of development. To evaluate the dietary preferences of early post-larval abalone, Haliotis diversicolor supertexta, we analyzed the gut contents of post-larvae that settled on diatom films. We compared the abundance and species diversity of diatom assemblages in the gut to those of the epiphytic diatom assemblages on the attachment films, and identified 40 benthic diatom species in the gut contents of post-larvae 12 to 24 d after settlement. The most abundant taxa in the gut contents were Navicula spp., Amphora copulate, and Amphora coffeaeformis. Navicula spp. accounted for 64.0% of the cell density. In the attachment films, we identified 110 diatom species belonging to 38 genera. Pennate diatoms were the dominant members including the species Amphiprora alata, Cocconeis placentula var. euglypta, Cylindrotheca closterium, Navicula sp. 2, and A. coffeaeformis. Nano-diatoms (Navicula and Amphora during the month after settlement.

  11. Allelopathic Effects of Cyanobacterial Filtrates on Baltic Diatom

    Science.gov (United States)

    Śliwińska, Sylwia; Latała, Adam

    2012-01-01

    Allelopathy may be one of the factors affecting the formation of massive and harmful algal blooms in aquatic environments. Recent studies indicate that blooms of cyanobacteria in the Baltic Sea has grown significantly in last decades, so it is important to determine the allelopathic interactions between the dominant species of cyanobacteria and microalgae. In this work we investigated the influence of allelopathic compounds on the growth of Skeletonema marinoi by addition of cell-free filtrate of the Baltic cyanobacterium Nodularia spumigena cultures grown under different temperature (15-25°C). Additionally the effects of filtrates of both an exponential and a stationary growing culture of N. spumigena were tested on diatom. These studies indicate that high temperature affected the donor species by increasing its production of allelochemicals. The highest drop of growth of analyzed diatom were observed after the addition of cell-free filtrate obtained from N. spumigena grown at 25°C and constituted 70% of their control. N. spumigena was only allelopathic in exponential growth phase, whereas the cyanobacteria filtrate from stationary phase have any effect on S. marinoi. These findings suggest that N. spumigena may reveal allelopathic activity and that the production of allelopathic substances is influenced by the temperature and growth phase of cyanobacteria. Allelopatia może być kluczowym czynnikiem wpływającym na tworzenie się masowych zakwitów sinic w wielu wodnych ekosystemach. Badania pokazują, że zakwity sinic w Morzu Bałtyckim w ostatnich dekadach znacznie się nasiliły, dlatego tak ważne jest określenie stopnia oddziaływania allelopatycznego dominujących w tym akwenie gatunków fitoplanktonu. W przeprowadzonych badaniach określono wpływ związków allelopatycznych produkowanych przez bałtycką sinicę Nodularia spumigena hodowaną w różnych temperaturach (15-25°C) na wzrost okrzemki Skeletonema marinoi. Dodatkowo w niniejszej pracy por

  12. Specificity of lipoxygenase pathways supports species delineation in the marine diatom genus Pseudo-nitzschia.

    Directory of Open Access Journals (Sweden)

    Nadia Lamari

    Full Text Available Oxylipins are low-molecular weight secondary metabolites derived from the incorporation of oxygen into the carbon chains of polyunsaturated fatty acids (PUFAs. Oxylipins are produced in many prokaryotic and eukaryotic lineages where they are involved in a broad spectrum of actions spanning from stress and defense responses, regulation of growth and development, signaling, and innate immunity. We explored the diversity in oxylipin patterns in the marine planktonic diatom Pseudo-nitzschia. This genus includes several species only distinguishable with the aid of molecular markers. Oxylipin profiles of cultured strains were obtained by reverse phase column on a liquid chromatograph equipped with UV photodiode detector and q-ToF mass spectrometer. Lipoxygenase compounds were mapped on phylogenies of the genus Pseudo-nitzschia inferred from the nuclear encoded hyper-variable region of the LSU rDNA and the plastid encoded rbcL. Results showed that the genus Pseudo-nitzschia exhibits a rich and varied lipoxygenase metabolism of eicosapentaenoic acid (EPA, with a high level of specificity for oxylipin markers that generally corroborated the genotypic delineation, even among genetically closely related cryptic species. These results suggest that oxylipin profiles constitute additional identification tools for Pseudo-nitzschia species providing a functional support to species delineation obtained with molecular markers and morphological traits. The exploration of the diversity, patterns and plasticity of oxylipin production across diatom species and genera will also provide insights on the ecological functions of these secondary metabolites and on the selective pressures driving their diversification.

  13. Sedimentation of phytoplankton during a diatom bloom : Rates and mechanisms

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Hansen, J.L.S.; Alldredge, A.L.

    1996-01-01

    velocities, settling of cells attached to marine snow aggregates formed from discarded larvacean houses or pteropod feeding webs, and packaging of cells into rapidly falling zooplankton fecal pellets. We quantified the relative significance of these different mechanisms during a diatom bloom in a temperate...... recorded in the water column (by divers) nor in sediment traps. The low coagulation rates were due to a very low 'stickiness' of suspended particles. The dominant diatom, Thalassiosira mendiolana, that accounted for up to 75% of the phytoplankton biomass, was not sticky at al, and did not turn sticky upon...... nutrient depletion in culture experiments. The low particle stickiness recorded may be related to low formation rates by diatoms of transparent exopolymeric particles (TEP), that occurred in low concentrations throughout the study period. Zooplankton grazing rate did not respond to the development...

  14. Bioactive glass 45S5 from diatom biosilica

    Directory of Open Access Journals (Sweden)

    Luqman A. Adams

    2017-12-01

    Full Text Available A major draw-back to large scale production of bioactive glasses is the high cost of the standard silica precursor, usually tetraethyl orthosilicate (TEOS. The current study describes a novel sol–gel preparation of 45S5 bioactive glass using diatom biosilica from cultured cells of the diatom, Aulacoseira granulata as substitute to TEOS. The glass formed was characterized using mechanical tester, scanning electron microscopy (SEM, energy dispersive X-ray analysis (EDX, X-ray diffraction (XRD and Fourier transform infrared (FTIR spectroscopy. Results showed that the glass possessed a compressive strength of 3.75 ± 0.18 and formed carbonated hydroxyapatite (HCA within 7 days in simulated body fluid (SBF, attributable to good surface chemistry. The performance of the glass was compared with that of those formed using TEOS. Diatom biosilica could be a potential economically friendly starting material for large scale fabrication of bioactive glasses.

  15. Genome engineering empowers the diatom Phaeodactylum tricornutum for biotechnology.

    Science.gov (United States)

    Daboussi, Fayza; Leduc, Sophie; Maréchal, Alan; Dubois, Gwendoline; Guyot, Valérie; Perez-Michaut, Christophe; Amato, Alberto; Falciatore, Angela; Juillerat, Alexandre; Beurdeley, Marine; Voytas, Daniel F; Cavarec, Laurent; Duchateau, Philippe

    2014-05-29

    Diatoms, a major group of photosynthetic microalgae, have a high biotechnological potential that has not been fully exploited because of the paucity of available genetic tools. Here we demonstrate targeted and stable modifications of the genome of the marine diatom Phaeodactylum tricornutum, using both meganucleases and TALE nucleases. When nuclease-encoding constructs are co-transformed with a selectable marker, high frequencies of genome modifications are readily attained with 56 and 27% of the colonies exhibiting targeted mutagenesis or targeted gene insertion, respectively. The generation of an enhanced lipid-producing strain (45-fold increase in triacylglycerol accumulation) through the disruption of the UDP-glucose pyrophosphorylase gene exemplifies the power of genome engineering to harness diatoms for biofuel production.

  16. Circular random motion in diatom gliding under isotropic conditions.

    Science.gov (United States)

    Gutiérrez-Medina, Braulio; Guerra, Andrés Jiménez; Maldonado, Ana Iris Peña; Rubio, Yadiralia Covarrubias; Meza, Jessica Viridiana García

    2014-11-13

    How cells migrate has been investigated primarily for the case of trajectories composed by joined straight segments. In contrast, little is known when cellular motion follows intrinsically curved paths. Here, we use time-lapse optical microscopy and automated trajectory tracking to investigate how individual cells of the diatom Nitzschia communis glide across surfaces under isotropic environmental conditions. We find a distinct kind of random motion, where trajectories are formed by circular arcs traveled at constant speed, alternated with random stoppages, direction reversals and changes in the orientation of the arcs. Analysis of experimental and computer-simulated trajectories show that the circular random motion of diatom gliding is not optimized for long-distance travel but rather for recurrent coverage of limited surface area. These results suggest that one main biological role for this type of diatom motility is to efficiently build the foundation of algal biofilms.

  17. Palaeoecological reconstruction of Komořany Lake in Late Glacial based on diatom analysis

    OpenAIRE

    Poštulková, Anna

    2016-01-01

    Diatom analysis of basal part of profile PK-1-L contributes to multi-proxy research of former Lake Komořany. At this part of profile radiocarbon dating (dates sediments into Late Glacial and Early Holocene) and LOI (loss on ignition) had been conducted before, of which results have been utilized to more accurate interpretation of diatom analysis conclusions. Apart from diatom valves, presence of stomatocysts of Chrysophyceae has been observed. Having separated diatom valves from 32 sediment s...

  18. Molecular fossils of diatoms: Applications in petroleum geochemistry and palaeoenvironmental studies

    OpenAIRE

    Rampen, S.W.

    2009-01-01

    Diatoms are one of the major groups of algae which originated relatively recently and evolved in the Late Jurassic/Cretaceous. This thesis presents the results of a comprehensive study of diatom lipids in cultures and in the environment and their applications in the age determination of petroleum and in palaeoenvironmental studies. Diatom DNA sequences were analyzed in order to relate the phylogenetic positions of diatoms to the lipid chemotaxonomy. Forty four different sterols were identifie...

  19. Cenozoic planktonic marine diatom diversity and correlation to climate change.

    Directory of Open Access Journals (Sweden)

    David Lazarus

    Full Text Available Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂(18O (climate and carbon cycle records (∂(13C, and 20-0 Ma pCO2. Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p.9, detrended r>.6, all p<.001, but only weakly over the earlier Cenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls.

  20. Diatom data from Bradley Lake, Oregon: downcore analyses

    Science.gov (United States)

    Hemphill-Haley, Eileen; Lewis, Roger C.

    2003-01-01

    Displaced marine diatoms provide biostratigraphic evidence for tsunami inundation at Bradley Lake, a small freshwater lake on the south-central Oregon coast. During the past 7,200 years, fine-grained lacustrine deposits in the deep axis of the lake were disturbed 17 times by the erosion and emplacement of coarse-grained gyttja and, in some cases, sand. By identifying diatoms in closely spaced core samples, we determined that 13 of the 17 events (termed idisturbance eventsi) record prehistoric tsunamis in Bradley Lake. We consider the evidence strong for 11 events, based on numbers and diversity of marine taxa: De1, De2, De4, De5, De6, De7, De8, De11, De12, De13, and De17. The evidence is less compelling for an additional 2 events (De9 and De10), although tsunami inundation is likely. Finally, we identified 4 events (De3, De14, De15 and De16) in which there were no marine diatoms to support tsunami inundation, although stratigraphic data shows that the lake bottom was disturbed. Freshwater diatoms dominate throughout the Bradley Lake record, showing that the lake has remained a freshwater habitat throughout its existence. However, anomalous occurrences of three species of brackish diatoms (Thalassiosira bramaputrae, Cyclotella meneghiniana, and Mastogloia smithii) may be evidence for short-lived periods of slightly elevated salinities in the lake following De16, De13, De12, De11, De9, De8, and De5. With the exception of De12, increased abundances of one or more of the brackish species is coincident with decreased numbers of freshwater diatoms. A temporary rise in salinity, as evidenced by short-lived increases in abundances of brackish species and decreases in abundances of freshwater species, is consistent with tsunami inundation into the lake.

  1. Cenozoic planktonic marine diatom diversity and correlation to climate change.

    Science.gov (United States)

    Lazarus, David; Barron, John; Renaudie, Johan; Diver, Patrick; Türke, Andreas

    2014-01-01

    Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂(18)O (climate) and carbon cycle records (∂(13)C, and 20-0 Ma pCO2). Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p.9, detrended r>.6, all pCenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls.

  2. Methodological aspects of paleo-ecological diatom research in coastal areas of the Netherlands

    NARCIS (Netherlands)

    Vos, P.C.; Wolf, H. de

    2007-01-01

    A major problem in paleo-ecological research of diatoms in tidal environments is the distinction of autochthonous and allochthonous diatom valves. A new approach applying several diatom- and non-diatomrelated criteria is introduced in order to solve the autochthonous/allochthonous problem. A

  3. Moss-inhabiting diatom communities from Heard Island, sub-Antarctic

    NARCIS (Netherlands)

    VandeVijver, B.; Beyens, L.; Vincke, S.; Gremmen, N.J.M.

    2004-01-01

    In this paper, we list 192 diatom taxa, collected from bryophyte samples from Heard Island (52degrees05'S, 73degrees30'E). The Heard Island diatom flora shows a marked similarity to those of the Crozet and Kerguelen archipelagos, and is quite dissimilar to the moss-dwelling diatom flora of Macquarie

  4. Parasitic chytrids could promote copepod survival by mediating material transfer from inedible diatoms

    NARCIS (Netherlands)

    Kagami, M.; Helmsing, N.R.; Van Donk, E.

    2011-01-01

    Diatoms form large spring blooms in lakes and oceans, providing fuel for higher trophic levels at the start of the growing season. Some of the diatom blooms, however, are not grazed by filter-feeding zooplankton like Daphnia due to their large size. Several of these large diatoms are susceptible to

  5. Freshwater diatoms as environmental indicators: evaluating the effects of eutrophication using species morphology and biological indices.

    Science.gov (United States)

    Vilmi, Annika; Karjalainen, Satu Maaria; Landeiro, Victor L; Heino, Jani

    2015-05-01

    Anthropogenic eutrophication is a major form of perturbation in freshwaters, and several approaches aim to recognise its effects on lake ecosystems. We compared the responses of diatom species morphology, diversity indices and diatom indices to total phosphorus, total nitrogen and distance from a point stressor causing eutrophication in a large lake. We specifically examined the degree to which extent nutrients and distance to the stressor affect variation in the values of various biological indices and diatom valve size. In addition, special attention was given to the adequate repetition of diatom valve width measurements in the context of environmental assessment. Our results showed that diatom valve width was a better indicator of nutrient concentrations than any of the diatom and diversity indices examined. However, the results varied between the two study transects, suggesting that the diatom-based variables not only respond to nutrients but also to other environmental factors (e.g. shoreline morphology). We also found that when using the method based on diatom morphology, one should measure more valves than has been originally suggested to provide a more reliable picture of response to eutrophication. We argue that diatom morphology could be considered as an additional environmental assessment tool, because it may complement the information provided by the traditional diatom indices. Diatom valve width may also be more sensitive to early phases of the eutrophication process and its effects on freshwater ecosystems than various diatom indices that were developed in regional contexts with wide ranges in nutrient levels.

  6. Assessment of water quality based on diatom indices in a small ...

    African Journals Online (AJOL)

    Multivariate data analyses were performed on the diatom community dataset to specify the main gradients of floristic variation and to detect and visualize similarities in diatom samples in relation to land-use patterns within the catchment. One hundred and twelve (112) diatom species belonging to 36 genera were recorded ...

  7. Identification automatique des diatomées de la Merja fouarate : Une ...

    African Journals Online (AJOL)

    SARAH

    30 sept. 2015 ... Université Ibn Tofail, Faculté des Sciences,. Laboratoire de Botanique et de Protection des Plantes, B. P. 133, Kénitra, Maroc. ... mathématique, Fouarate, Kenitra, Maroc. Automatic identification of Fouarate Merja diatoms: An ..... Human error and quality assurance in diatom analysis. In Automatic Diatom.

  8. Establishing an Historic Baseline of Diatom Diversity in Southern California

    OpenAIRE

    Lange, Carina

    2004-01-01

    Diatoms are single-celled, microscopic algae with intricately built, often beautiful, silicon shells. As the sea’s primary producers, they provide food directly or indirectly for nearly all the sea’s fishes and marine mammals. They are the base of the marine food chain, and as such their abundance is a good indicator of the ocean’s productivity—the more diatoms, the greater the ocean’s productivity. Ocean productivity has profound implications for marine biodiversity and for commercial fisher...

  9. Diatoms of the concrete embankment of the Zegrze Lake

    Directory of Open Access Journals (Sweden)

    Hanna Borzyńska

    2015-01-01

    Full Text Available It has been established that conditions for the development of diatoms on a concrete embankment are favourable. Beside organisms permanently or periodically connected with the solid substrate, typical planktons also occurred. The following species were most numerous: Cymbella affinis, Nitzschia kützingiana, Amphora ovalis var. pediculus and Navicula gracilis. The most intensive development of diatoms was observed in April, May, July and October. The total number of organisms depended on pollution of water in the Żerań Canal, increased water temperature in autumn in the section between the Canal and Białobrzegi and intensity of waves.

  10. R-Syst::diatom: an open-access and curated barcode database for diatoms and freshwater monitoring.

    Science.gov (United States)

    Rimet, Frédéric; Chaumeil, Philippe; Keck, François; Kermarrec, Lenaïg; Vasselon, Valentin; Kahlert, Maria; Franc, Alain; Bouchez, Agnès

    2016-01-01

    Diatoms are micro-algal indicators of freshwater pollution. Current standardized methodologies are based on microscopic determinations, which is time consuming and prone to identification uncertainties. The use of DNA-barcoding has been proposed as a way to avoid these flaws. Combining barcoding with next-generation sequencing enables collection of a large quantity of barcodes from natural samples. These barcodes are identified as certain diatom taxa by comparing the sequences to a reference barcoding library using algorithms. Proof of concept was recently demonstrated for synthetic and natural communities and underlined the importance of the quality of this reference library. We present an open-access and curated reference barcoding database for diatoms, called R-Syst::diatom, developed in the framework of R-Syst, the network of systematic supported by INRA (French National Institute for Agricultural Research), see http://www.rsyst.inra.fr/en. R-Syst::diatom links DNA-barcodes to their taxonomical identifications, and is dedicated to identify barcodes from natural samples. The data come from two sources, a culture collection of freshwater algae maintained in INRA in which new strains are regularly deposited and barcoded and from the NCBI (National Center for Biotechnology Information) nucleotide database. Two kinds of barcodes were chosen to support the database: 18S (18S ribosomal RNA) and rbcL (Ribulose-1,5-bisphosphate carboxylase/oxygenase), because of their efficiency. Data are curated using innovative (Declic) and classical bioinformatic tools (Blast, classical phylogenies) and up-to-date taxonomy (Catalogues and peer reviewed papers). Every 6 months R-Syst::diatom is updated. The database is available through the R-Syst microalgae website (http://www.rsyst.inra.fr/) and a platform dedicated to next-generation sequencing data analysis, virtual_BiodiversityL@b (https://galaxy-pgtp.pierroton.inra.fr/). We present here the content of the library regarding the

  11. Colonisation and community structure of benthic diatoms on artificial ...

    African Journals Online (AJOL)

    A major flooding event that occurred during October–November 2012 caused major changes in the Kowie River hydromorphology and aquatic communities. The aim of our study was to identify the environmental variables that structure riverine benthic diatom communities at upstream and downstream locations 25 km apart ...

  12. Diatom as an alternative for biostratigraphy research in Karangsambung

    Science.gov (United States)

    Ridwan, Januar

    2018-02-01

    Paleogene stratigraphy of Karangsambung consists of Karangsambung and Totogan olistostrome deposit. The previous biostratigraphy research for those formations used the olistostrome matrix as the main sample. In fact, the olistostrome matrix is also a mixed material that might consist of the mixed material of the older and young sediment, making this sample unrepresentative for biostratigraphy analysis. The previous biostratigraphy research based on the matrix sample should be evaluated and should also consider new criteria for the representative sample. The most suitable biostratigraphy analysis sample from the olistostrome deposit is soft fraction sediment and laminated sediment which represent the suspension deposition phase in the part of olistostrome depositional process. On the other hand, diatom biostratigraphy could be applied in the representative sample related to the diatom living strategy in deep marine as lamination form and also their progressive spreading in Cenozoic. However, the application of diatom biostratigraphy in olistostrome deposit is still new and it lacks of reference, especially for diatom research in Indonesia. Though the application would be difficult to realize, it might open the chance for new research and discovery in Karangsambung biostratigraphy.

  13. Isolation of diatom Navicula cryptocephala and characterization of ...

    African Journals Online (AJOL)

    sjce

    Full Length Research Paper. Isolation of diatom Navicula cryptocephala and characterization of oil extracted for biodiesel production. Sanjay K. R.*, Nagendra Prasad M. N., Anupama S.#, Yashaswi B. R.# and Deepak B.#. Department of Biotechnology, Sri Jayachamarajendra College of Engineering, Mysore- 570006, India ...

  14. Structure and dynamics of exopolymers in an intertidal diatom biofilm

    NARCIS (Netherlands)

    Stal, L.J.; Défarge, C.

    2005-01-01

    Diatom biofilms growing at the surface of the intertidal mudflat of Marennes Oléron, France, were incubated for 48 h in the laboratory under simulated conditions of high- and low tide (immersed and emersed in seawater) and day and night (illuminated or dark conditions). The biofilms were

  15. Diatom centromeres suggest a mechanism for nuclear DNA acquisition.

    Science.gov (United States)

    Diner, Rachel E; Noddings, Chari M; Lian, Nathan C; Kang, Anthony K; McQuaid, Jeffrey B; Jablanovic, Jelena; Espinoza, Josh L; Nguyen, Ngocquynh A; Anzelmatti, Miguel A; Jansson, Jakob; Bielinski, Vincent A; Karas, Bogumil J; Dupont, Christopher L; Allen, Andrew E; Weyman, Philip D

    2017-07-18

    Centromeres are essential for cell division and growth in all eukaryotes, and knowledge of their sequence and structure guides the development of artificial chromosomes for functional cellular biology studies. Centromeric proteins are conserved among eukaryotes; however, centromeric DNA sequences are highly variable. We combined forward and reverse genetic approaches with chromatin immunoprecipitation to identify centromeres of the model diatom Phaeodactylum tricornutum We observed 25 unique centromere sequences typically occurring once per chromosome, a finding that helps to resolve nuclear genome organization and indicates monocentric regional centromeres. Diatom centromere sequences contain low-GC content regions but lack repeats or other conserved sequence features. Native and foreign sequences with similar GC content to P. tricornutum centromeres can maintain episomes and recruit the diatom centromeric histone protein CENH3, suggesting nonnative sequences can also function as diatom centromeres. Thus, simple sequence requirements may enable DNA from foreign sources to persist in the nucleus as extrachromosomal episomes, revealing a potential mechanism for organellar and foreign DNA acquisition.

  16. Evolutionary genomics of the cold-adapted diatom Fragilariopsis cylindrus

    KAUST Repository

    Mock, Thomas

    2017-01-17

    The Southern Ocean houses a diverse and productive community of organisms. Unicellular eukaryotic diatoms are the main primary producers in this environment, where photosynthesis is limited by low concentrations of dissolved iron and large seasonal fluctuations in light, temperature and the extent of sea ice. How diatoms have adapted to this extreme environment is largely unknown. Here we present insights into the genome evolution of a cold-adapted diatom from the Southern Ocean, Fragilariopsis cylindrus, based on a comparison with temperate diatoms. We find that approximately 24.7 per cent of the diploid F. cylindrus genome consists of genetic loci with alleles that are highly divergent (15.1 megabases of the total genome size of 61.1 megabases). These divergent alleles were differentially expressed across environmental conditions, including darkness, low iron, freezing, elevated temperature and increased CO2. Alleles with the largest ratio of non-synonymous to synonymous nucleotide substitutions also show the most pronounced condition-dependent expression, suggesting a correlation between diversifying selection and allelic differentiation. Divergent alleles may be involved in adaptation to environmental fluctuations in the Southern Ocean.

  17. Light manipulation and photonics applications of diatom frustules

    DEFF Research Database (Denmark)

    Su, Yanyan

    their applications, manipulation or control of the nanostructure of frustules is desirable. The effect of different light spectra (six different wavelengths throughout the visible range at two light intensities) on the morphology of centric diatom Coscinodiscus granii has been investigated. It has been shown...

  18. Colonization of diatom aggregates by the dinoflagellate Noctiluca scintillans

    DEFF Research Database (Denmark)

    Tiselius, P.; Kiørboe, Thomas

    1998-01-01

    . The attached N. scintillans were feeding on the diatoms in the aggregates, as revealed by food-vacuole content. In the particular environment studied, N, scintillans appeared not to depend on aggregate feeding since shipboard experiments showed that clearance rates (10-20 mu l h(-1)) on unaggregated cells were...

  19. Copepod reproduction is unaffected by diatom aldehydes or lipid composition

    DEFF Research Database (Denmark)

    Dutz, Jörg; Koski, Marja; Jonasdottir, Sigrun

    2008-01-01

    We investigated whether reduced reproductive success of copepods fed with diatoms was related to nutritional imbalances with regard to essential lipids or to the production of inhibitory aldehydes. In 10-d laboratory experiments, feeding, egg production, egg hatching success, and fecal pellet...

  20. Functionalized diatom silica microparticles for removal of mercury ions

    Science.gov (United States)

    Yu, Yang; Addai-Mensah, Jonas; Losic, Dusan

    2012-01-01

    Diatom silica microparticles were chemically modified with self-assembled monolayers of 3-mercaptopropyl-trimethoxysilane (MPTMS), 3-aminopropyl-trimethoxysilane (APTES) and n-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS), and their application for the adsorption of mercury ions (Hg(II)) is demonstrated. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses revealed that the functional groups (–SH or –NH2) were successfully grafted onto the diatom silica surface. The kinetics and efficiency of Hg(II) adsorption were markedly improved by the chemical functionalization of diatom microparticles. The relationship among the type of functional groups, pH and adsorption efficiency of mercury ions was established. The Hg(II) adsorption reached equilibrium within 60 min with maximum adsorption capacities of 185.2, 131.7 and 169.5 mg g−1 for particles functionalized with MPTMS, APTES and AEAPTMS, respectively. The adsorption behavior followed a pseudo-second-order reaction model and Langmuirian isotherm. These results show that mercapto- or amino-functionalized diatom microparticles are promising natural, cost-effective and environmentally benign adsorbents suitable for the removal of mercury ions from aqueous solutions. PMID:27877475

  1. Functionalized diatom silica microparticles for removal of mercury ions

    Directory of Open Access Journals (Sweden)

    Yang Yu, Jonas Addai-Mensah and Dusan Losic

    2012-01-01

    Full Text Available Diatom silica microparticles were chemically modified with self-assembled monolayers of 3-mercaptopropyl-trimethoxysilane (MPTMS, 3-aminopropyl-trimethoxysilane (APTES and n-(2-aminoethyl-3-aminopropyl-trimethoxysilane (AEAPTMS, and their application for the adsorption of mercury ions (Hg(II is demonstrated. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses revealed that the functional groups (–SH or –NH2 were successfully grafted onto the diatom silica surface. The kinetics and efficiency of Hg(II adsorption were markedly improved by the chemical functionalization of diatom microparticles. The relationship among the type of functional groups, pH and adsorption efficiency of mercury ions was established. The Hg(II adsorption reached equilibrium within 60 min with maximum adsorption capacities of 185.2, 131.7 and 169.5 mg g-1 for particles functionalized with MPTMS, APTES and AEAPTMS, respectively. The adsorption behavior followed a pseudo-second-order reaction model and Langmuirian isotherm. These results show that mercapto- or amino-functionalized diatom microparticles are promising natural, cost-effective and environmentally benign adsorbents suitable for the removal of mercury ions from aqueous solutions.

  2. CHECKLIST OF DIATOMS FROM THE LAURENTIAN GREAT LAKES

    Science.gov (United States)

    An updated diatom (Bacillariophyta) checklist for the Great Lakes has been completed (J. Great Lakes Res. 1999) and supplants the preliminary checklist (J. Great Lakes Res. 1978). The present list is effectively a 20-year update. The updated list is based upon: 1) the 1978 checkl...

  3. Four new freshwater diatom species (Bacillariophyceae) from Antarctica

    Czech Academy of Sciences Publication Activity Database

    Zidarova, R.; Van de Vijver, B.; Mataloni, G.; Kopalová, K.; Nedbalová, Linda

    2009-01-01

    Roč. 30, č. 4 (2009), s. 295-310 ISSN 0181-1568 Institutional research plan: CEZ:AV0Z60050516 Keywords : Antarctica * diatoms * James Ross Island Subject RIV: EF - Botanics Impact factor: 0.574, year: 2009

  4. A SYSTEMATIC ACCOUNT OF SOME SOUTH INDIAN DIATOMS*

    Indian Academy of Sciences (India)

    THE number of papers dealing With systematic accounts of, Diatoins from the different parts of India has been so far very few. The first important account of the diatom flora of the Indian region was given by Grunow (1865) in a paper on the Diatomaceae and Desmidiaceae of the Island of Banka near. Singapore.

  5. The Kinker diatom collection: discovery – exploration – exploitation

    NARCIS (Netherlands)

    Sterrenburg, F.A.S.; Wolf, de H.

    2004-01-01

    Johannes Kinker (1823-1900) was a typical representative of the Victorian ‘amateur-savant’. As a wellto- do stockbroker he was able to invest considerable time and money into studies of nature, first entomology and subsequently diatoms. The latter subject flourished in the late 19th century and,

  6. Does sediment grain size affect diatom grazing by harpacticoid copepods?

    Science.gov (United States)

    De Troch, Marleen; Houthoofd, Lieven; Chepurnov, Victor; Vanreusel, Ann

    2006-04-01

    Estuarine soft sediments support a diverse group of eukaryotic and prokaryotic organisms though the role of the sediment per se for the functioning of these organisms remains largely unknown. The present study aimed to test the effect of sediment grain size on the grazing activities of harpacticoid copepods. In controlled experiments, two common intertidal harpacticoid species (Paramphiascella fulvofasciata and Nitokra spinipes) were each offered a mix of two benthic diatom species (Navicula phyllepta and Seminavis robusta) in different sedimentary conditions. Several microcosms were created using a variety of sediment types, including fine silt (grained sands (125-250, 250-450, 100-300 microm), artificial 'sediments' of glass beads (250-500, 2000 microm) and even the absence of sediment was tested. The diatoms were enriched in the stable carbon (13)C to facilitate tracing in the harpacticoids. Both copepod species were able to graze on the diatoms with highest uptake when sediment was absent. In contrast, both harpacticoid species showed no uptake in silty conditions. In general, grazing was favoured when mean sediment grain size increased. The strong negative effect of fine grains on the grazer's efficiency can be explained by the resulting differences in the structure (and accessibility) of the diatom biofilm on the one hand and the mobility of the grazer on the other hand. In view of the subtle equilibrium between primary producers and grazers, these results might have important implications for the effect of siltation of tidal flats due to, e.g., human activities.

  7. Decay of delayed light with the diatom Phaeodactylum tricornutum

    NARCIS (Netherlands)

    Goedheer, J.C.; Swart, J.

    Intact cells of the diatom Phaeodactylum tricornutum do not show a smooth afterglow decay curve. After a sharp decline (0–150 msec), a maximum may occur after 4 sec at 17° or after 22 sec at 2°. This maximum is present after excitation with far red light of low intensity, which is absorbed primarily

  8. Enhancement of the reactive iron pool by marine diatoms

    NARCIS (Netherlands)

    Rijkenberg, Micha J. A.; Gerringa, Loes J. A.; Timmermans, Klaas R.; Fischer, Astrid C.; Kroon, Koos J.; Buma, Anita G. J.; Wolterbeek, Bert Th.; de Baar, Hein J. W.

    2008-01-01

    Short term (2 days) laboratory experiments were performed to study the change in irradiance induced production of Fe(II) in seawater in the presence of two open oceanic Southern Ocean diatom species, Thalassiosira sp. and Chaetoceros brevis. Three irradiance conditions were applied: 1) UVB+UVA+VIS,

  9. Determining the possible application value of diatoms as indicators ...

    African Journals Online (AJOL)

    driniev

    of Van Dam et al. (1994), could not be transposed directly to South. African conditions. For this reason the current study investigates the potential use of another ...... WERNER D (ed.) (1977) The Biology of Diatoms.University of California. Press. Berkeley, CA. WILLEMSEN GD, GAST HF, FRANKEN ROG and CUPPEN JGM.

  10. Temperature affects the silicate morphology in a diatom

    NARCIS (Netherlands)

    Javaheri, N.; Dries, R; Burson, A.; Stal, L.J.; Sloot, P.M.A.; Kaandorp, J.A.

    2015-01-01

    Silica deposition by diatoms, a common component of the phytoplankton, has attracted considerable interest given the importance in ecology and materials science. There has recently been a great deal of research into the biological control of biosilicifcation, yet the in vivo physical and chemical

  11. Temperature affects the silicate morphology in a diatom

    NARCIS (Netherlands)

    Javaheri, N.; Dries, R.; Burson, A.; Stal, L.J.; Sloot, P.M.A.; Kaandorp, J.A.

    2015-01-01

    Silica deposition by diatoms, a common component of the phytoplankton, has attracted considerable interest given the importance in ecology and materials science. There has recently been a great deal of research into the biological control of biosilicifcation, yet the in vivo physical and

  12. Freshwater diatoms as a source of lipids for biofuels.

    Science.gov (United States)

    Graham, James M; Graham, Linda E; Zulkifly, Shahrizim B; Pfleger, Brian F; Hoover, Spencer W; Yoshitani, Jun

    2012-03-01

    Until recently, biodiesel production has been derived from terrestrial plants such as soybean and canola, leading to competition between biodiesel production and agricultural production for source materials. Microalgae have the potential to synthesize 30 times more oil per hectare than terrestrial plants without competing for agricultural land. We examined four genera (Cyclotella, Aulacoseira, Fragilaria, Synedra) of common freshwater diatoms (Bacillariophyceae) for growth and lipid content in defined medium (sD11) that replicates hypereutrophic conditions in lakes and wastewater treatment plant effluents and optimized the medium for silicon content. Cyclotella and Aulacoseira produced the highest levels of total lipids, 60 and 43 μg total lipids/ml, respectively. Both diatoms are rich in fatty acids C14, C16, C16:1, C16:2,7,10, and C22:5n3. Of the diatoms examined, Cyclotella reached the highest population density (>2.5 × 10(6) cells/ml) in stationary phase when many of the cells appeared to be filled entirely with oil. Silicon enrichment studies indicated that for optimal utilization of phosphorus and nitrogen by diatoms growing in wastewater effluent, the amount of silicon present or added to the effluent should be 17.5 times the mass of phosphorus in the effluent. With high growth rates, high lipid contents, and rapid settling rates, Cyclotella and Aulacoseira are candidates for biodiesel production.

  13. Immunocytochemical evidence for acidic thylakoids in intact diatom cells

    NARCIS (Netherlands)

    Vrieling, EG; Lee, RE

    2002-01-01

    Using the weak base 3-(2,4-dinitroanilino)-3'-amino-N-methyI propylamine (DAMP) in in situ probing experiments, ultrastructural evidence for the acidic nature of the thylakoids in whole cells has been obtained in three unicellular pennate diatom species, with special emphasis on Navicula salinarum.

  14. Cenozoic planktonic marine diatom diversity and correlation to climate change

    Science.gov (United States)

    Lazarus, David; Barron, John; Renaudie, Johan; Diver, Patrick; Türke, Andreas

    2014-01-01

    Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂18O (climate) and carbon cycle records (∂13C, and 20-0 Ma pCO2). Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p2 were only moderately higher than today. Diversity is strongly correlated to both ∂13C and pCO2 over the last 15 my (for both: r>.9, detrended r>.6, all pwarm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls.

  15. Effects of eutrophication on diatom abundance, biovolume and diversity in tropical coastal waters.

    Science.gov (United States)

    Lim, Joon Hai; Lee, Choon Weng

    2017-08-03

    Diatom abundance, biovolume and diversity were measured over a 2-year period along the Straits of Malacca at two stations with upper (Klang) and lower (Port Dickson) states of eutrophication. Diatom abundance, which ranged from 0.2 × 10 4 to 21.7 × 10 4  cells L -1 at Klang and 0.9 × 10 3 - 41.3 × 10 3  cells L -1 at Port Dickson, was influenced partly by nutrient concentrations. At Klang, the diatoms were generally smaller and less diverse (H' = 0.77 ± 0.48) and predominated by Skeletonema spp. (60 ± 32% of total diatom biomass). In contrast, diatoms were larger and more diverse (H' = 1.40 ± 0.67) at Port Dickson. Chaetoceros spp. were the most abundant diatoms at Port Dickson but attributed only 48 ± 30% of total diatom biomass. Comparison of both Klang and Port Dickson showed that their diatom community structure differed and that eutrophication reduced diatom diversity at Klang. We also observed how Si(OH) 4 affected the abundance of Skeletonema spp. which in turn influenced the temporal variation of diatom community at Klang. Our results highlighted how eutrophication affects diatom diversity and community structure.

  16. Haloperoxidase Mediated Quorum Quenching by Nitzschia cf pellucida: Study of the Metabolization of N-Acyl Homoserine Lactones by a Benthic Diatom

    Directory of Open Access Journals (Sweden)

    Michail Syrpas

    2014-01-01

    Full Text Available Diatoms are known to produce a variety of halogenated compounds, which were recently shown to have a role in allelopathic interactions between competing species. The production of these compounds is linked to haloperoxidase activity. This research, has shown that this system may also be involved in diatom-bacteria interactions via the H2O2 dependent inactivation of a type of quorum sensing (QS molecule, i.e., N-β-ketoacylated homoserine lactones (AHLs, by a natural haloperoxidase system from the benthic diatom Nitzschia cf pellucida. The AHL degradation pathway towards corresponding halogenated derivatives was elucidated via HPLC-MS analysis and the synthesis of a broad series of novel halogenated AHL analogues as reference compounds. Furthermore, their biological activity as quorum sensing modulators was directly compared and evaluated against a series of naturally occurring β-keto-AHLs. It has been demonstrated that the loss of the QS activity results from the final cleavage of the halogenated N-acyl chain of the signal molecules.

  17. Toxicity of dissolved and precipitated aluminium to marine diatoms.

    Science.gov (United States)

    Gillmore, Megan L; Golding, Lisa A; Angel, Brad M; Adams, Merrin S; Jolley, Dianne F

    2016-05-01

    Localised aluminium contamination can lead to high concentrations in coastal waters, which have the potential for adverse effects on aquatic organisms. This research investigated the toxicity of 72-h exposures of aluminium to three marine diatoms (Ceratoneis closterium (formerly Nitzschia closterium), Minutocellus polymorphus and Phaeodactylum tricornutum) by measuring population growth rate inhibition and cell membrane damage (SYTOX Green) as endpoints. Toxicity was correlated to the time-averaged concentrations of different aluminium size-fractions, operationally defined as aluminium exposure varied between diatom species. C. closterium was the most sensitive species (10% inhibition of growth rate (72-h IC10) of 80 (55-100)μg Al/L (95% confidence limits)) while M. polymorphus (540 (460-600)μg Al/L) and P. tricornutum (2100 (2000-2200)μg Al/L) were less sensitive (based on measured total aluminium). Dissolved aluminium was the primary contributor to toxicity in C. closterium, while a combination of dissolved and precipitated aluminium forms contributed to toxicity in M. polymorphus. In contrast, aluminium toxicity to the most tolerant diatom P. tricornutum was due predominantly to precipitated aluminium. Preliminary investigations revealed the sensitivity of C. closterium and M. polymorphus to aluminium was influenced by initial cell density with aluminium toxicity significantly (paluminium toxicity to diatoms do not involve compromising the plasma membrane. These results indicate that marine diatoms have a broad range in sensitivity to aluminium with toxic mechanisms related to both dissolved and precipitated aluminium. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Diatoms and diatomaceous earth as novel poultry vaccine adjuvants.

    Science.gov (United States)

    Nazmi, A; Hauck, R; Davis, A; Hildebrand, M; Corbeil, L B; Gallardo, R A

    2017-02-01

    Diatoms are single cell eukaryotic microalgae; their surface possesses a porous nanostructured silica cell wall or frustule. Diatomaceous earth (DE) or diatomite is a natural siliceous sediment of diatoms. Since silica has been proved to have adjuvant capabilities, we propose that diatoms and DE may provide an inexpensive and abundant source of adjuvant readily available to use in livestock vaccines.In a first experiment, the safety of diatoms used as an adjuvant for in-ovo vaccination was investigated. In a second experiment, we assessed the humoral immune response after one in-ovo vaccination with inactivated Newcastle Disease Virus (NDV) and DE as adjuvant followed by 2 subcutaneous boosters on d 21 and 29 of age. In both experiments, results were compared to Freund's incomplete adjuvant and aluminum hydroxide.No detrimental effects on hatchability and chick quality were detected after in-ovo inoculation of diatoms and DE in experiments 1 and 2 respectively. In experiment 2 no humoral responses were detected after the in-ovo vaccination until 29 d of age. Seven d after the second subcutaneous booster an antibody response against NDV was detected in chickens that had received vaccines adjuvanted with Freund's incomplete adjuvant, aluminum hydroxide, and DE. These responses became significantly higher 10 d after the second booster. Finally, 15 d after the second booster, the humoral responses induced by the vaccine with Freund's incomplete adjuvant were statistically higher, followed by comparable responses induced by vaccines containing DE or aluminum hydroxide that were significantly higher than DE+PBS, PBS+INDV and PBS alone. From an applied perspective, we can propose that DE can serve as a potential adjuvant for vaccines against poultry diseases. Published by Oxford University Press on behalf of Poultry Science Association 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.

  19. Understanding amine catalyzed silica polymerization : diatoms as bioarchitects.

    Energy Technology Data Exchange (ETDEWEB)

    Spoerke, Erik David; Aubry, Sylvie; Lane, Pamela; Robinson, David B; Bauer, Christina A.; Zendejas, Frank; Tran, Huu; Lane, Todd W.; Simmons, Blake Alexander

    2007-10-01

    Current state-of-the-art biomimetic methodologies employed worldwide for the realization of self-assembled nanomaterials are adequate for certain unique applications, but a major breakthrough is needed if these nanomaterials are to obtain their true promise and potential. These routes typically utilize a 'top-down' approach in terms of controlling the nucleation, growth, and deposition of structured nanomaterials. Most of these techniques are inherently limited to primarily 2D and simple 3D structures, and are therefore limited in their ultimate functionality and field of use. Zeolites, one of the best-known and understood synthetic silica structures, typically possess highly ordered silica domains over very small length scales. The development of truly organized and hierarchical zeolites over several length scales remains an intense area of research world wide. Zeolites typically require high-temperature and complex synthesis routes that negatively impact certain economic parameters and, therefore, the ultimate utility of these materials. Nonetheless, zeolite usage is in the tons per year worldwide and is quickly becoming ubiquitous in its applications. In addition to these more mature aspects of current practices in materials science, one of the most promising fields of nanotechnology lies in the advent and control of biologically self-assembled materials, especially those involved with silica and other ceramics such as hydroxyapatite. Nature has derived, through billions of years of evolutionary steps, numerous methods by which fault-tolerant and mechanically robust structures can be created with exquisite control and precision at relatively low temperature ranges and pressures. Diatoms are one of the best known examples that exhibit this degree of structure and control known that is involved with the biomineralization of silica. Diatoms are eukaryotic algae that are ubiquitous in marine and freshwater environments. They are a dominant form of

  20. Effect of Bacterial Microbiota on the Silica Uptake of the Marine Diatom, Odontella sp.

    Science.gov (United States)

    Hughes, E. J.; Kempnich, M.; Sison-Mangus, M.

    2016-12-01

    Diatoms are the most prolific primary producers in the ocean and are known to dominate the phytoplankton community when nutrients become available. Diatoms require silica for growth in order to produce their silica wall frustules. Studies pertaining to silica uptake in diatoms have recently become possible with the use of PDMPO [2-(4-pyridyl)-5{[4-dimethylaminoethyl-aminocarbamoyl]-methoxy}phenyl]oxazole], a dye which selectively binds to free silica and can effectively be used to demonstrate silica uptake and deposition in diatoms. Many factors affect the growth of diatoms, including their bacterial associates or microbiome. Some members of their microbiota can increase diatom growth while others stunt their growth and eventually lyse them. Bacteria-free diatoms, on the other hand, have significantly lower growth than diatoms associating with bacteria. Here we ask if the silica uptake of Odontella sp. was influenced by co-culture with various types of bacteria. Silicification was measured using spectrophotometry to calculate PDMPO concentration as a proxy for silica uptake. We found that axenic cultures have the lowest silica uptake while non-axenic diatoms and diatoms co-cultured with the bacteria from Bacteroidetes (Cellulophaga), Firmicutes (Planococcus) and Gamma-proteobacteria (Vibrio) have varying effects on the silica uptake of the 3 diatoms. This study adds another piece of evidence that bacteria can play an important role on the growth and development of the diatoms. This work suggests that different types of bacteria can have a profound effect on the survival and ecological success of diatoms and bacterial associates should be considered when studying diatom's biology and ecology.

  1. The structure and diversity of freshwater diatom assemblages from Franz Josef Land Archipelago: a northern outpost for freshwater diatoms

    Directory of Open Access Journals (Sweden)

    Sergi Pla-Rabés

    2016-02-01

    Full Text Available We examined diatom assemblages from 18 stream and pond samples in the Franz Josef Land Archipelago (FJL, the most northern land of Eurasia. More than 216 taxa were observed, revealing a rich circumpolar diatom flora, including many undescribed taxa. Widely distributed taxa were the most abundant by cell densities, while circumpolar taxa were the most species rich. Stream and pond habitats hosted different assemblages, and varied along a pH gradient. Diatoma tenuis was the most abundant and ubiquitous taxon. However, several circumpolar taxa such as Chamaepinnularia gandrupii, Cymbella botellus, Psammothidium sp. and Humidophila laevissima were also found in relatively high abundances. Aerophilic taxa were an important component of FJL diatom assemblages (Humidophila spp., Caloneis spp. and Pinnularia spp., reflecting the large and extreme seasonal changes in Arctic conditions. We predict a decrease in the abundance of circumpolar taxa, an increase in local (α- freshwater diatom diversity, but a decrease in regional diversity (circumpolar homogenization as a result of current warming trends and to a lesser extent the increasing human footprint in the region.

  2. Kinetic control on Zn isotope signatures recorded in marine diatoms

    Science.gov (United States)

    Köbberich, Michael; Vance, Derek

    2017-08-01

    Marine diatoms dominate the oceanic cycle of the essential micronutrient zinc (Zn). The stable isotopes of zinc and other metals are increasingly used to understand trace metal micronutrient cycling in the oceans. One clear feature of the early isotope data is the heavy Zn isotope signature of the average oceanic dissolved pool relative to the inputs, potentially driven by uptake of light isotopes into phytoplankton cells and export to sediments. However, despite the fact that diatoms strip Zn from surface waters across the Antarctic polar front in the Southern Ocean, the local upper ocean is not isotopically heavy. Here we use culturing experiments to quantify the extent of Zn isotope fractionation by diatoms and to elucidate the mechanisms driving it. We have cultured two different open-ocean diatom species (T. oceanica and Chaetoceros sp.) in a series of experiments at constant medium Zn concentration but at bioavailable medium Fe ranging from limiting to replete. We find that T. oceanica can maintain high growth rates and Zn uptake rates over the full range of bioavailable iron (Fe) investigated, and that the Zn taken up has a δ66Zn that is unfractionated relative to that of the bioavailable free Zn in the medium. The studied representative of the genus Chaetoceros, on the other hand, shows more significantly reduced Zn uptake rates at low Fe and records more variable biomass δ66Zn signatures, of up to 0.85‰ heavier than the medium. We interpret the preferential uptake of heavy isotopes at extremely low Zn uptake rates as potentially due to either of the following two mechanisms. First, the release of extracellular polymeric substances (EPS), at low Fe levels, may preferentially scavenge heavy Zn isotopes. Second, the Zn uptake rate may be slow enough to establish pseudo-equilibrium conditions at the transporter site, with heavy Zn isotopes forming more stable surface complexes. Thus we find that, in our experiments, Fe-limitation exerts a key control that

  3. Using benthic diatom assemblages to assess human impacts on streams across a rural to urban gradient.

    Science.gov (United States)

    Yang, Ying; Cao, Jin-Xiang; Pei, Guo-Feng; Liu, Guo-Xing

    2015-11-01

    Benthic diatom assemblages on the natural substrata were investigated at 21 sites of the Ganhe River watershed (China) once per season and in addition, early spring in 2013. A total of 487 diatom taxa from 36 genera were identified during five investigations. The assemblages were dominated by Achnanthidium minutissimum (Kützing) Czarnecki and Cocconeis placentula in the rural reach, whereas Navicula, Nitzschia, and Gomphonema species were characteristic of urbanized sites. Our results suggest that biodiversity was positively related to high nutrient levels and strongly negatively related to diatom-based indices. The periphyton biomass (expressed as chlorophyll a and ash-free dry mass) was not related to water quality. Canonical correspondence analysis (CCA) showed that the nutrient concentration gradient was the most important factor that affected the diatom assemblage composition and species distribution. The diatom-based indices (specific pollution sensitivity index (IPS), biological diatom index (IBD), and trophic diatom index (TDI)) were significantly positively correlated with water quality and are adequate for use in China. Slight changes in the biodiversity and diatom-based indices followed a temporal pattern. The species composition was less related to the season or hydrological characteristics of the river but more strongly related to differences in the trophic status. In this region, urbanization masked the impact of rural land use on benthic diatoms. The research will expand the understanding of using benthic diatom assemblages for water quality monitoring in urban streams and improve watershed-scale management and conservation efforts in the Ganhe River, China.

  4. Using diatom indices for water quality assessment in a subtropical river, China.

    Science.gov (United States)

    Tan, Xiang; Sheldon, Fran; Bunn, Stuart E; Zhang, Quanfa

    2013-06-01

    Diatoms have been regularly used as bioindicators to assess water quality of surface waters. However, diatom-based indices developed for a specific geographic region may not be appropriate elsewhere. We sampled benthic diatom assemblages in the upper Han River, a subtropical river in China, to evaluate applicability of 14 diatom-based indices used worldwide for water quality assessment. A total of 194 taxa from 31 genera were identified in the dry season and 139 taxa from 23 genera in the wet season. During the dry season, significant relationships were found for all but one of the diatom-based indices (Index Diatom Artois-Picardie) with one or more physical and chemical variables including nutrients and ion concentrations in river waters. The Biological Diatom Index (IBD) and diatom-based eutrophication/pollution index (EPI-D) were strongly related to trophic status and ionic content, while Watanabe's Index was related to organic pollution and conductivity. Yet, the diatom indices showed weak relationships with physical and chemical variables during the wet season. It suggests that diatom-based indices developed in Europe can be applied with confidence as bioindicators of water quality in subtropical rivers of China, at least during base-flow conditions.

  5. Do diatoms run downhill? Using biodiversity of terrestrial and aquatic diatoms to identify hydrological connectivity between aquatic zones in Luxembourg

    Science.gov (United States)

    Pfister, L.; Wetzel, C. E.; Martinez-Carreras, N.; Frentress, J.; Ector, L.; Hoffmann, L.; McDonnell, J. J.

    2011-12-01

    Diatoms are siliceous unicellular algae, and range in size between a few and more than 500 micrometers. Diatoms are spread worldwide, live in many aquatic habitats, have many life forms and their short generation time make them respond rapidly to environmental changes. Their taxonomic diversity represents a valuable tool to assess water quality as each taxon has specific responses to environmental factors. Recently, diatoms have been used as tracers to detect the onset/cessation of surface runoff through binary classification of terrestrial and aquatic species in the Attert basin in Luxembourg. In order to continue the validation of these first results, we have collected samples during rain events at different seasons of the year using automatic stream water samplers, grab samples of diatoms from various terrestrial and subaerial substrates (bryophytes, litter and leaves), as well as from aquatic habitats (epilithon, epipelon and drift samples). This new type of information will be used to constrain assumptions of the conventional tracer-based hydrograph separation technique (i.e. using geochemistry and stable isotopes). The first results concerning the diatom flora, based on 39 samples, revealed 152 species belonging to 38 genera. The most species-rich genera were Pinnularia (15.8% - 24 taxa), Eunotia (13.2% - 20 taxa), Gomphonema (8.6% - 13 taxa), Navicula (7.2% - 11 taxa) and Stauroneis (5.3% - 8 taxa). The flora are mainly composed of oligotrophic and/or acidophilic taxa (32.0%), ubiquitous (14.0%) or poorly known ecologically species (43.0%). The most important taxa found in drift samples were Fragilariforma virescens, Fragilaria capucina sensu lato, Planothidium lanceolatum, Eunotia minor, Achnanthidium kranzii, Karayevia oblongella and Eunotia incisa. In the riparian zone (n = 10), 102 species were observed, with Eunotia exigua var. tenella, Eunotia botuliformis and Pinnularia perirrorata being among the most frequent. Epilithic samples from the main channel

  6. Coulomb-stable triply charged diatomic: HeY3+

    Science.gov (United States)

    Wesendrup, Ralf; Pernpointner, Markus; Schwerdtfeger, Peter

    1999-11-01

    Accurate relativistic coupled-cluster calculations show that the triply charged species HeY3+ is a stable molecule and represents the lightest diatomic trication that does not undergo a Coulomb fragmentation into charged fragments. The diatomic potential-energy curve is approximated by an extended Morse potential, and vibrational-rotational constants for HeY3+ are predicted (Re=224.3 pm, D0=0.394 eV, ωe=437 cm-1, ωexe=15.8 cm-1, Be=0.877 cm-1). It is further shown that the He-Y3+ bond can basically be described as a charge-induced dipole interaction.

  7. Arctic Diatoms - Diversity, Plankton Interactions and Poulation Dynamics

    DEFF Research Database (Denmark)

    Tammilehto, Anna

    Oceans produce nearly half of the global net primary production annually. Most productive marine areas are found along coasts and, contrary to the terrestrial ecosystems, at high latitudes. In these areas most primary production is done by phytoplankton. In the Arctic, phytoplankton communities...... are often dominated by diatoms. They are single-celled, eukaryotic algae, which play an essential role in ocean carbon and silica cycles. Many species of the diatom genus Pseudo-nitzschia Peragallo produce a neurotoxin, domoic acid (DA), which can be transferred to higher levels in food webs causing amnesic...... that blooming behavior may be beneficial for F. cylindrus. High genetic diversity found in F. cylindrus coupled with high ecophysiological variability (i.e. variation among the strains and phenotypic plasticity) with regard to projected increase in temperature and decrease in pH due to climate change suggests...

  8. Momentum autocorrelation function of a classic diatomic chain

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Ming B., E-mail: mingbyu@gmail.com

    2016-10-23

    A classical harmonic diatomic chain is studied using the recurrence relations method. The momentum autocorrelation function results from contributions of acoustic and optical branches. By use of convolution theorem, analytical expressions for the acoustic and optical contributions are derived as even-order Bessel function expansions with coefficients given in terms of integrals of elliptic functions in real axis and a contour parallel to the imaginary axis, respectively. - Highlights: • Momentum autocorrelation function of a classic diatomic chain is studied. • It is derived as even-order Bessel function expansion using the convolution theorem. • The expansion coefficients are integrals of elliptic functions. • Addition theorem is used to reduce complex elliptic function to complex sum of real ones.

  9. Molecular level characterization of diatom-associated biopolymers that bind 234Th, 233Pa, 210Pb, and 7Be in seawater: A case study with Phaeodactylum tricornutum

    Science.gov (United States)

    Chuang, Chia-Ying; Santschi, Peter H.; Xu, Chen; Jiang, Yuelu; Ho, Yi-Fang; Quigg, Antonietta; Guo, Laodong; Hatcher, Patrick G.; Ayranov, Marin; Schumann, Dorothea

    2015-09-01

    In order to investigate the importance of biogenic silica associated biopolymers on the scavenging of radionuclides, the diatom Phaeodactylum tricornutum was incubated together with the radionuclides 234Th, 233Pa, 210Pb, and 7Be during their growth phase. Normalized affinity coefficients were determined for the radionuclides bound with different organic compound classes (i.e., proteins, total carbohydrates, uronic acids) in extracellular (nonattached and attached exopolymeric substances), intracellular (ethylene diamine tetraacetic acid and sodium dodecyl sulfate extractable), and frustule embedded biopolymeric fractions (BF). Results indicated that radionuclides were mostly concentrated in frustule BF. Among three measured organic components, Uronic acids showed the strongest affinities to all tested radionuclides. Confirmed by spectrophotometry and two-dimensional heteronuclear single quantum coherence-nuclear magnetic resonance analyses, the frustule BF were mainly composed of carboxyl-rich, aliphatic-phosphoproteins, which were likely responsible for the strong binding of many of the radionuclides. Results from this study provide evidence for selective absorption of radionuclides with different kinds of diatom-associated biopolymers acting in concert rather than as a single compound. This clearly indicates the importance of these diatom-related biopolymers, especially frustule biopolymers, in the scavenging and fractionation of radionuclides used as particle tracers in the ocean.

  10. Chytridiomycosis of Marine Diatoms-The Role of Stress Physiology and Resistance in Parasite-Host Recognition and Accumulation of Defense Molecules.

    Science.gov (United States)

    Scholz, Bettina; Küpper, Frithjof C; Vyverman, Wim; Ólafsson, Halldór G; Karsten, Ulf

    2017-01-25

    Little is known about the role of chemotaxis in the location and attachment of chytrid zoospores to potential diatom hosts. Hypothesizing that environmental stress parameters affect parasite-host recognition, four chytrid-diatom tandem cultures (Chytridium sp./Navicula sp., Rhizophydium type I/Nitzschia sp., Rhizophydium type IIa/Rhizosolenia sp., Rhizophydium type IIb/Chaetoceros sp.) were used to test the chemotaxis of chytrid zoospores and the presence of potential defense molecules in a non-contact-co-culturing approach. As potential triggers in the chemotaxis experiments, standards of eight carbohydrates, six amino acids, five fatty acids, and three compounds known as compatible solutes were used in individual and mixed solutions, respectively. In all tested cases, the whole-cell extracts of the light-stressed (continuous light exposure combined with 6 h UV radiation) hosts attracted the highest numbers of zoospores (86%), followed by the combined carbohydrate standard solution (76%), while all other compounds acted as weak triggers only. The results of the phytochemical screening, using biomass and supernatant extracts of susceptible and resistant host-diatom cultures, indicated in most of the tested extracts the presence of polyunsaturated fatty acids, phenols, and aldehydes, whereas the bioactivity screenings showed that the zoospores of the chytrid parasites were only significantly affected by the ethanolic supernatant extract of the resistant hosts.

  11. Biological monitoring of lotic ecosystems: the role of diatoms

    OpenAIRE

    T. Bere; JG. Tundisi

    2010-01-01

    Increasing anthropogenic influence on lotic environments as a result of civilisation has captured public interest because of the consequent problems associated with deterioration of water quality. Various biological monitoring methods that provide a direct measure of ecological integrity by using the response of biota to environmental changes have been developed to monitor the ecological status of lotic environments. Diatoms have been used extensively in this regard and this review attempts t...

  12. Novel sex cells and evidence for sex pheromones in diatoms.

    Science.gov (United States)

    Sato, Shinya; Beakes, Gordon; Idei, Masahiko; Nagumo, Tamotsu; Mann, David G

    2011-01-01

    Diatoms belong to the stramenopiles, one of the largest groups of eukaryotes, which are primarily characterized by a presence of an anterior flagellum with tubular mastigonemes and usually a second, smooth flagellum. Based on cell wall morphology, diatoms have historically been divided into centrics and pennates, of which only the former have flagella and only on the sperm. Molecular phylogenies show the pennates to have evolved from among the centrics. However, the timing of flagellum loss--whether before the evolution of the pennate lineage or after--is unknown, because sexual reproduction has been so little studied in the 'araphid' basal pennate lineages, to which Pseudostaurosira belongs. Sexual reproduction of an araphid pennate, Pseudostaurosira trainorii, was studied with light microscopy (including time lapse observations and immunofluorescence staining observed under confocal scanning laser microscopy) and SEM. We show that the species produces motile male gametes. Motility is mostly associated with the extrusion and retrieval of microtubule-based 'threads', which are structures hitherto unknown in stramenopiles, their number varying from one to three per cell. We also report experimental evidence for sex pheromones that reciprocally stimulate sexualization of compatible clones and orientate motility of the male gametes after an initial 'random walk'. The threads superficially resemble flagella, in that both are produced by male gametes and contain microtubules. However, one striking difference is that threads cannot beat or undulate and have no motility of their own, and they do not bear mastigonemes. Threads are sticky and catch and draw objects, including eggs. The motility conferred by the threads is probably crucial for sexual reproduction of P. trainorii, because this diatom is non-motile in its vegetative stage but obligately outbreeding. Our pheromone experiments are the first studies in which gametogenesis has been induced in diatoms by cell

  13. Novel sex cells and evidence for sex pheromones in diatoms.

    Directory of Open Access Journals (Sweden)

    Shinya Sato

    Full Text Available BACKGROUND: Diatoms belong to the stramenopiles, one of the largest groups of eukaryotes, which are primarily characterized by a presence of an anterior flagellum with tubular mastigonemes and usually a second, smooth flagellum. Based on cell wall morphology, diatoms have historically been divided into centrics and pennates, of which only the former have flagella and only on the sperm. Molecular phylogenies show the pennates to have evolved from among the centrics. However, the timing of flagellum loss--whether before the evolution of the pennate lineage or after--is unknown, because sexual reproduction has been so little studied in the 'araphid' basal pennate lineages, to which Pseudostaurosira belongs. METHODS/PRINCIPAL FINDING: Sexual reproduction of an araphid pennate, Pseudostaurosira trainorii, was studied with light microscopy (including time lapse observations and immunofluorescence staining observed under confocal scanning laser microscopy and SEM. We show that the species produces motile male gametes. Motility is mostly associated with the extrusion and retrieval of microtubule-based 'threads', which are structures hitherto unknown in stramenopiles, their number varying from one to three per cell. We also report experimental evidence for sex pheromones that reciprocally stimulate sexualization of compatible clones and orientate motility of the male gametes after an initial 'random walk'. CONCLUSIONS/SIGNIFICANCE: The threads superficially resemble flagella, in that both are produced by male gametes and contain microtubules. However, one striking difference is that threads cannot beat or undulate and have no motility of their own, and they do not bear mastigonemes. Threads are sticky and catch and draw objects, including eggs. The motility conferred by the threads is probably crucial for sexual reproduction of P. trainorii, because this diatom is non-motile in its vegetative stage but obligately outbreeding. Our pheromone experiments

  14. Automated Diatom Classification (Part B: A Deep Learning Approach

    Directory of Open Access Journals (Sweden)

    Anibal Pedraza

    2017-05-01

    Full Text Available Diatoms, a kind of algae microorganisms with several species, are quite useful for water quality determination, one of the hottest topics in applied biology nowadays. At the same time, deep learning and convolutional neural networks (CNN are becoming an extensively used technique for image classification in a variety of problems. This paper approaches diatom classification with this technique, in order to demonstrate whether it is suitable for solving the classification problem. An extensive dataset was specifically collected (80 types, 100 samples/type for this study. The dataset covers different illumination conditions and it was computationally augmented to more than 160,000 samples. After that, CNNs were applied over datasets pre-processed with different image processing techniques. An overall accuracy of 99% is obtained for the 80-class problem and different kinds of images (brightfield, normalized. Results were compared to previous presented classification techniques with different number of samples. As far as the authors know, this is the first time that CNNs are applied to diatom classification.

  15. Microfluidic accumulation assay probes attachment of biofilm forming diatom cells.

    Science.gov (United States)

    Nolte, Kim A; Schwarze, Jana; Rosenhahn, Axel

    2017-08-01

    Testing of fouling release (FR) technologies is of great relevance for discovery of the next generation of protective marine coatings. In this paper, an accumulation assay to test diatom interaction under laminar flow with the model organism Navicula perminuta is introduced. Using time lapse microscopy with large area sampling allows determination of the accumulation kinetics of the diatom on three model surfaces with different surface properties at different wall shear stresses. The hydrodynamic conditions within the flow cell are described and a suitable shear stress range to perform accumulation experiments is identified at which statistically significant discrimination of surfaces is possible. The observed trends compare well to published adhesion preferences of N. perminuta. Also, previously determined trends of critical wall shear stresses required for cell removal from the same set of functionalized interfaces shows consistent trends. Initial attachment mediated by extracellular polymeric substances (EPS) present outside the diatoms leads to the conclusion that the FR potential of the tested coating candidates can be deducted from dynamic accumulation experiments under well-defined hydrodynamic conditions. As well as testing new coating candidates for their FR properties, monitoring of the adhesion process under flow provides additional information on the mechanism and geometry of attachment and the population kinetics.

  16. The use of diatoms in ecotoxicology and bioassessment: Insights, advances and challenges.

    Science.gov (United States)

    Pandey, Lalit K; Bergey, Elizabeth A; Lyu, Jie; Park, Jihae; Choi, Soyeon; Lee, Hojun; Depuydt, Stephen; Oh, Young-Tae; Lee, Sung-Mo; Han, Taejun

    2017-07-01

    Diatoms are regularly used for bioassessment and ecotoxicological studies in relation to environmental and anthropogenic disturbances. Traditional taxonomical diatom parameters (cell counts, biovolume estimates, species richness, diversity indices and metrics using sensitive and tolerant diatom species) are regularly used for these studies. In the same context, very less focus was given on new endpoints of diatoms (life-forms, nuclear anomalies, alteration in photosynthetic apparatus shape, motility, lipid bodies, size reduction and deformities), in spite of their numerous merits, such as, their easiness, quickness, cheapness, global acceptation and no especial training in diatom taxonomy. In this review we analyzed 202 articles (from lab and field studies), with the aim to investigate the bioassessment and ecotoxicological advancement taken place in diatom research especially in terms of exploring new endpoints along with the traditional taxonomical parameters in a perspective which can greatly enhance the evaluation of fluvial ecosystem quality for biomonitoring practices. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Intracellular nitrate of marine diatoms as a driver of anaerobic nitrogen cycling in sinking aggregates

    DEFF Research Database (Denmark)

    Kamp, Anja; Stief, Peter; Bristow, Laura A.

    2016-01-01

    Diatom-bacteria aggregates are key for the vertical transport of organic carbon in the ocean. Sinking aggregates also represent pelagic microniches with intensified microbial activity, oxygen depletion in the center, and anaerobic nitrogen cycling. Since some of the aggregate-forming diatom species...... store nitrate intracellularly, we explored the fate of intracellular nitrate and its availability for microbial metabolism within anoxic diatom-bacteria aggregates. The ubiquitous nitrate-storing diatom Skeletonema marinoi was studied as both axenic cultures and laboratory-produced diatom...... in concentrations > 60 mmol L-1 both as free-living cells and associated to aggregates. Intracellular nitrate concentrations exceeded extracellular concentrations by three orders of magnitude. Intracellular nitrate was used up within 2-3 days after shifting diatom-bacteria aggregates to dark and anoxic conditions...

  18. Intracellular nitrate of marine diatoms as a driver of anaerobic nitrogen cycling in sinking aggregates

    DEFF Research Database (Denmark)

    Kamp, Anja; Stief, Peter; Bristow, Laura A.

    2016-01-01

    Diatom-bacteria aggregates are key for the vertical transport of organic carbon in the ocean. Sinking aggregates also represent pelagic microniches with intensified microbial activity, oxygen depletion in the center, and anaerobic nitrogen cycling. Since some of the aggregate-forming diatom species...... store nitrate intracellularly, we explored the fate of intracellular nitrate and its availability for microbial metabolism within anoxic diatom-bacteria aggregates. The ubiquitous nitrate-storing diatom Skeletonema marinoi was studied as both axenic cultures and laboratory-produced diatom-bacteria...... in concentrations > 60 mmol L-1 both as free-living cells and associated to aggregates. Intracellular nitrate concentrations exceeded extracellular concentrations by three orders of magnitude. Intracellular nitrate was used up within 2-3 days after shifting diatom-bacteria aggregates to dark and anoxic conditions...

  19. Diatoms in acid mine drainage and their role in the formation of iron-rich stromatolites

    Energy Technology Data Exchange (ETDEWEB)

    Brake, S.S.; Hasiotis, S.T.; Dannelly, H.K. [Indiana State University, Terre Haute, IN (United States)

    2004-08-01

    Adverse conditions in the acid mine drainage (AMD) system at the Green Valley mine, Indiana, limit diatom diversity to one species, Nitzschia tubicola. It is present in three distinct microbial consortia: Euglena mutabilis-dominated biofilm, diatom-dominated biofilm, and diatom-exclusive biofilm. E. mutabilis dominates the most extensive biofilm, with lesser numbers of N. tubicola, other eukaryotes, and bacteria. Diatom-dominated biofilm occurs as isolated patches containing N. tubicola with minor fungal hyphae, filamentous algae, E. mutabilis, and bacteria. Diatom-exclusive biofilm is rare, composed entirely of N. tubicola. Diatom distribution is influenced by seasonal and intraseasonal changes in water temperature and chemistry. Diatoms are absent in winter due to cool water temperatures. In summer, isolated patchy communities are present due to warmer water temperatures. In 2001, the diatom community expanded its distribution following a major rainfall that temporarily diluted the effluent, creating hospitable conditions for diatom growth. After several weeks when effluent returned to preexisting conditions, the diatom biofilm retreated to isolated patches, and E. mutabilis biofilm flourished. Iron-rich stromatolites underlie the biofilms and consist of distinct laminae, recording spatial and temporal oscillations in physicochemical conditions and microbial activity. The stromatolites are composed of thin, wavy laminae with partially decayed E. mutabilis biofilm, representing microbial activity and iron precipitation under normal AMD conditions. Alternating with the wavy layers are thicker, porous, spongelike laminae composed of iron precipitated on and incorporated into radiating colonies of diatoms. These layers indicate episodic changes in water chemistry, allowing diatoms to temporarily dominate the system.

  20. Short- and long-term conditioning of a temperate marine diatom community to acidification and warming

    OpenAIRE

    Tatters, A. O.; Roleda, M.Y.; Schnetzer, A; Fu, F.; Hurd, C. L.; Boyd, P. W.; CARON D.A.; Lie, A. A. Y.; Hoffmann, Linn J.; Hutchins, D. A.

    2013-01-01

    Ocean acidification and greenhouse warming will interactively influence competitive success of key phytoplankton groups such as diatoms, but how long-term responses to global change will affect community structure is unknown. We incubated a mixed natural diatom community from coastal New Zealand waters in a short-term (two-week) incubation experiment using a factorial matrix of warming and/or elevated pCO2 and measured effects on community structure. We then isolated the dominant diatoms in c...

  1. Distribution patterns of epilithic diatoms along climatic, spatial and physicochemical variables in the Baltic Sea

    OpenAIRE

    Virta, Leena; Soininen, Janne

    2017-01-01

    The species richness and community composition of the diatom communities were studied in the Baltic Sea, Northern Europe, to enhance knowledge about the diversity of these organisms in a brackish water ecosystem. Many organisms in the Baltic Sea have been studied extensively, but studies investigating littoral diatoms are scarce. The goal of this study was to examine the importance of climatic, spatial and water physicochemical variables as drivers of epilithic diatoms in the Gulf of Finland ...

  2. Classification des diatomées par les descripteurs de Fourier du contour

    Directory of Open Access Journals (Sweden)

    Fathallah Nouboud

    2007-07-01

    Full Text Available We present in this paper an automatic system for the classification of diatoms based on the extraction of the normal angles of an anticlockwise 8-connected contour. For that, we used a parametric model that consists in characterizing the contour of the diatoms according to a vector of the Fourier descriptors. The correct classification rate is around 97% of the 450 diatom images examined.

  3. The Life Cycle of the Centric Diatom Thalassiosira Weissflogii: Control of Gametogenesis and Cell Size

    Science.gov (United States)

    1990-06-01

    Engineering . DOCTORAL DISSERTATION The Life Cycle of the Centric Diatom "Thalassiosira weissflogii: Control of Gametogenesis and Cell Size by by OTIC...Cycle of the Centric Diatom Thalassiosira weissflogii: Control of Gametogenesis and Cell Size by E. Virginia Armbrust Woods Hole Oceanographic...Cycle of the Centric Diatom Thalassiosira weissflogii: Control of Gametogenesis and Cell Size. Ph.D. Thesis. MIT/WHOI, WHO1-90-16. "Approved for

  4. Distribution of non-marine diatoms in surface sediments of streams in Socotra Island, Yemen

    OpenAIRE

    Abdelfattah A. Zalat; Mohammed A. Al-Wosabi

    2011-01-01

    Abundance and species composition of non-marine benthic diatom assemblages were studied from surface sediments samples of 11 streams distributed in Socotra Island, located in the northwest Indian Ocean. A total of 145 diatom species, representing 44 genera, were identified. The overall diatom communities appear to be the first recorded off the island. Pennales and non-planktonic taxa were most dominant over centrales and planktonic forms, both in diversity of genera and species. The majority ...

  5. A simple DNA coprecipitation method for the detection of diatoms in heart blood.

    Science.gov (United States)

    Seo, Yasuhisa; Sato, Shingo; Kuroki, Kohji; Kishida, Tetsuko

    2013-10-10

    We developed a method for detecting and enumerating diatoms in the heart blood of drowning victims and evaluate its utility for diagnosing death by drowning. For purification of diatoms from blood, the DNA binding ability of the diatom frustule in the presence of a chaotropic agent was utilized. The procedure is basically the same as the commonly used method for DNA purification from blood using Proteinase K treatment and denaturation by a chaotropic agent. DNA adsorbed to the diatom (DNA/diatom complex) is recovered by ethanol precipitation, and the DNA is subsequently digested using DNase. Purified diatoms could be clearly observed under a microscope. Diatoms spiked in the blood of non-drowned cadavers (n=15) were well recovered, and were detected in heart blood from all drowning victims (n=22). The mean number of diatoms found in 5 ml of blood from drowning victims was 7.8±5.8 (mean±SD), and the number of diatoms detected in the blood of the left ventricle (6.1±5.8) was approximately two times higher than that of the right ventricle (3.0±2.7, p<0.05). These results suggest that this simple and safe method can become an effective tool for diagnosing the cause of death as drowning. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  6. How-to-Do-It: Diatoms: The Ignored Alga in High School Biology.

    Science.gov (United States)

    Hungerford, James J.

    1988-01-01

    Provides historical background, descriptions, uses and basis for identification of diatoms. Explains collection, dry-mount cleaning, and preparation procedures of the algae. Cites additional resources. (RT)

  7. All New Faces of Diatoms: Potential Source of Nanomaterials and Beyond

    Directory of Open Access Journals (Sweden)

    Meerambika Mishra

    2017-07-01

    Full Text Available Nature’s silicon marvel, the diatoms have lately astounded the scientific community with its intricate designs and lasting durability. Diatoms are a major group of phytoplanktons involved in the biogeochemical cycling of silica and are virtually inherent in every environment ranging from water to ice to soil. The usage of diatoms has proved prudently cost effective and its handling neither requires costly materials nor sophisticated instruments. Diatoms can easily be acquired from the environment, their culture requires ambient condition and does not involve any costly media or expensive instruments, besides, they can be transported in small quantities and proliferated to a desirable confluence from that scratch, thus are excellent cost effective industrial raw material. Naturally occurring diatom frustules are a source of nanomaterials. Their silica bio-shells have raised curiosity among nanotechnologists who hope that diatoms will facilitate tailoring minuscule structures which are beyond the capabilities of material scientists. Additionally, there is a colossal diversity in the dimensions of diatoms as the frustule shape differs from species to species; this provides a scope for the choice of a particular species of diatom to be tailored to an exacting requisite, thus paving the way to create desired three dimensional nanocomposites. The present article explores the use of diatoms in various arenas of science, may it be in nanotechnology, biotechnology, environmental science, biophysics or biochemistry and summarizes facets of diatom biology under one umbrella. Special emphasis has been given to biosilicification, biomineralization and use of diatoms as nanomaterials’, drug delivery vehicles, optical and immune-biosensors, filters, immunodiagnostics, aquaculture feeds, lab-on-a-chip, metabolites, and biofuels.

  8. Growth inhibition of fouling bacteria and diatoms by extract of terrestrial plant, Derris scandens (Dicotyledonae:Leguminocae)

    Digital Repository Service at National Institute of Oceanography (India)

    Sawant, S.S.; Sonak, S.; Garg, A.

    Methanol extract of terrestrial plant, Derris scandens Benth, was found to inhibit growth of four diatoms and 7 bacterial species of fouling community. The concentrations required to bring about 100% inhibition of growth of the diatoms ranged...

  9. Growth inhibition of fouling bacteria and diatoms by extract of terrestrial plant, @iDerris scandens@@ (Dicotyledonae:Leguminocae)

    Digital Repository Service at National Institute of Oceanography (India)

    Sawant, S.S.; Sonak, S.; Garg, A.

    Methanol extract of terrestrial plant, @iDerris scandens@@ Benth, was found to inhibit growth of four diatoms and 7 bacterial species of fouling community. The concentrations required to bring about 100% inhibition of growth of the diatoms ranged...

  10. Diatom Communities and Metrics as Indicators of Urbanization Effects on Streams and Potential Moderation by Landscape Green Infrastructure

    Science.gov (United States)

    Diatoms are very useful and important indicators of anthropogenic impacts on streams because they are the foundation of primary production and are responsive to nutrients, conductivity, and habitat conditions. We characterized relationships of diatom assemblages with water chemis...

  11. The diatom-produced polyunsaturated aldehydes can induce trophic cascades in the planktonic food web in productive coastal waters.

    Science.gov (United States)

    Franzè, G.; Stoecker, D. K.; Pierson, J. J.; Lavrentyev, P.

    2016-02-01

    Allelopathy is wide spread among marine phytoplankton, including diatoms that produce cytotoxic secondary metabolites such as polyunsaturated aldehydes (PUA). Most published PUA studies focused on the reproduction and development of specific marine invertebrates under laboratory conditions. In this study, we examined the effect of PUA on the trophic interactions between the copepod Acartia tonsa and natural microplankton collected from the Chesapeake Bay and the Virginia coastal waters. A set of bottle incubation experiments was conducted using the environmentally realistic concentrations of dissolved 2E, 4E-heptadienal and 2E, 4E-octadienal. Although PUA did not change phytoplankton growth, microzooplankton growth was affected at the species-specific level and their community herbivory rates declined. At the same time, the rates of copepod herbivory and predation on ciliates increased in the PUA treatments. These preliminary results suggest that production of cytotoxic compounds by diatoms may be a defense mechanism primarily against microzooplankton. The cascading effects induced by PUA can alter the composition and dynamics of microbial plankton communities, which in turn could have strong implication for the carbon cycling in productive coastal ecosystems.

  12. Comparing optical properties of different species of diatoms

    DEFF Research Database (Denmark)

    Maibohm, Christian; Friis, Søren Michael Mørk; Su, Y.

    2015-01-01

    analysis software. The software uses parameters which are extracted from experimental im ages as basis for simulation and allows us to extract the influence of the different elements of the frustule. The information could be used both for predicting optical properties of diatoms and by changing frustule...... frustules. We have observed, when incident light interacts w ith the micro-structured frustule it is multiple diffracted giving rise to wavelength dependent multiple focal points and other optical effects. Experimental results have been simulated and well confirmed by free space FFT propagation routine...

  13. Evanescent-wave mirror for ultracold diatomic polar molecules.

    Science.gov (United States)

    Kallush, S; Segev, B; Côté, R

    2005-10-14

    We describe the interaction of an ultracold diatomic polar molecule with an evanescent-wave mirror. Several features of this system are explored, such as the coupling between internal rovibrational states of the molecule and the laser field. Numerical simulations show quantum reflection and state selection under attainable physical conditions. Such molecular optics components will facilitate the manipulation and trapping of ultracold molecules, and might serve in future applications in several fields, e.g., as devices to filter and select a state for ultracold chemistry, to measure extremely low temperatures of molecules, or to manipulate states for quantum information processing.

  14. Dissociation rate of bromine diatomics in an argon heat bath

    Science.gov (United States)

    Razner, R.; Hopkins, D.

    1973-01-01

    The evolution of a collection of 300 K bromine diatomics embedded in a heat bath of argon atoms at 1800 K was studied by computer, and a dissociation-rate constant for the reaction Br2 + BR + Ar yields Br + Ar was determined. Previously published probability distributions for energy and angular momentum transfers in classical three-dimensional Br2-Ar collisions were used in conjunction with a newly developed Monte Carlo scheme for this purpose. Results are compared with experimental shock-tube data and the predictions of several other theoretical models. A departure from equilibrium is obtained which is significantly greater than that predicted by any of these other theories.

  15. Thermodynamics properties of diatomic molecules with general molecular potential

    Science.gov (United States)

    Ikot, Akpan N.; Chukwuocha, E. O.; Onyeaju, M. C.; Onate, C. A.; Ita, B. I.; Udoh, M. E.

    2018-02-01

    In this paper, the energy spectra of the general molecular potential are obtained using the asymptotic iteration method within the framework of non-relativistic quantum mechanics.With the energy spectrum obtained, the vibrational partition function is calculated in a closed form and is used to obtain an expression for other thermodynamic functions such as vibrational mean energy U, vibrational mean free energy F, vibrational entropy S and vibrational specific heat capacity C. These thermodynamic functions are studied for the electronic state X1Σ _g^+ of K_2 diatomic molecules.

  16. Diatoms in peat – dominant producers in a changing environment?

    DEFF Research Database (Denmark)

    Kokfelt, Ulla; Struyf, Eric; Randsalu, Linda

    2009-01-01

    Changes in hydrology and temperature can induce rapid changes in boreal wetland ecosystems. Factors such as hydrosere, permafrost, climate and human interference may disturb the prevailing mire vegetation, whereby a new dominant assemblage can develop. At the transition from one vegetation type...... to another, the old vegetation may be suppressed, die out or start to decay, and some time may pass until a new mire vegetation is fully established. Here, we demonstrate that diatoms may thrive during such transitions, creating isolated and shallow peat layers with significantly elevated biogenic silica...

  17. Dissociation curves of diatomic molecules: A DC-DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Sim, Eunji; Kim, Min-Cheol [Department of Chemistry and Institute of Nano-Bio Molecular Assemblies, Yonsei University, Seoul 120-749 (Korea, Republic of); Burke, Kieron [Department of Chemistry, University of California, Irvine, CA, 92697 (United States)

    2015-12-31

    We investigate dissociation of diatomic molecules using standard density functional theory (DFT) and density-corrected density functional theory (DC-DFT) compared with CCSD(T) results as reference. The results show the difference between the HOMO values of dissociated atomic species often can be used as an indicator whether DFT would predict the correct dissociation limit. DFT predicts incorrect dissociation limits and charge distribution in molecules or molecular ions when the fragments have large HOMO differences, while DC-DFT and CCSD(T) do not. The criteria for large HOMO difference is about 2 ∼ 4 eV.

  18. The influence of land use on water quality and diatom community ...

    African Journals Online (AJOL)

    Epilithic diatom communities offer a holistic and integrated approach for assessing water quality as they remain in one place for a number of months and reflect an ecological memory of water quality over a period of time. The objective of this study is to use diatom assemblages to distinguish between particular land types ...

  19. Influence of land-use patterns on benthic diatom communities and ...

    African Journals Online (AJOL)

    The objective of this study was to determine the effects of land-use patterns on both diatom community composition and water quality in tropical streams during the dry season. Benthic diatom collections and water quality sampling were done 4 times at 10 sites. A suite of environmental variables that varied with human ...

  20. Challenges of diatom-based biological monitoring and assessment of streams in developing countries.

    Science.gov (United States)

    Bere, Taurai

    2016-03-01

    Stream biomonitoring tools are largely lacking for many developing countries, resulting in adoption of tools developed from other countries/regions. In many instances, however, the applicability of adopted tools to the new system has not been explicitly evaluated. The objective of this study was to test the applicability of foreign diatom-based water quality assessment indices to streams in Zimbabwe, with the view to highlight challenges being faced in diatom-based biological monitoring in this developing country. The study evaluated the relationship between measured water quality variables and diatom index scores and observed some degree of concordance between water quality variables and diatom index scores emphasising the importance of diatom indices in characterisation and monitoring of stream ecological conditions in developing countries. However, ecological requirements of some diatom species need to be clarified and incorporated in a diatom-based water quality assessment protocol unique to these regions. Resources should be channelled towards tackling challenges associated with diatom-based biological monitoring, principally taxonomic studies, training of skilled labour and acquiring and maintaining the necessary infrastructure. Meanwhile, simpler coarse taxonomy-based rapid bioassessment protocol, which is less time and resource consuming and requires less specialised manpower, can be developed for the country.

  1. Actin, actin-related proteins and profilin in diatoms: a comparative genomic analysis.

    Science.gov (United States)

    Aumeier, Charlotte; Polinski, Ellen; Menzel, Diedrik

    2015-10-01

    Diatoms are heterokont unicellular algae with a widespread distribution throughout all aquatic habitats. Research on diatoms has advanced significantly over the last decade due to available genetic transformation methods and publicly available genome databases. Yet up to now, proteins involved in the regulation of the cytoskeleton in diatoms are largely unknown. Consequently, this work focuses on actin and actin-related proteins (ARPs) encoded in the diatom genomes of Thalassiosira pseudonana, Thalassiosira oceanica, Phaeodactylum tricornutum, Fragilariopsis cylindrus and Pseudo-nitzschia multiseries. Our comparative genomic study revealed that most diatoms possess only a single conventional actin and a small set of ARPs. Among these are the highly conserved cytoplasmic Arp1 protein and the nuclear Arp4 as well as Arp6. Diatom genomes contain genes coding for two structurally different homologues of Arp4 that might serve specific functions. All diatom species examined here lack ARP2 and ARP3 proteins, suggesting that diatoms are not capable of forming the Arp2/3 complex, which is essential in most eukaryotes for actin filament branching and plus-end dynamics. Interestingly, none of the sequenced representatives of the Bacillariophyta phylum code for profilin. Profilin is an essential actin-binding protein regulating the monomer actin pool and is involved in filament plus-end dynamics. This is the first report of organisms not containing profilin. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. The health of benthic diatom assemblages in lower stretch of a ...

    Indian Academy of Sciences (India)

    This study examines the ecological state of epilithic diatom assemblages along the lower stretch of. Mandakini, a glacier-fed Himalayan river. The diatoms were sampled at four stations during winter and summer, only once in each season. ...... ary 19–21 2007: Board of Research in Nuclear Sciences,. Department of Atomic ...

  3. Monitoring rapid valve formation in the pennate diatom Navicula salinarum (Bacillariophyceae)

    NARCIS (Netherlands)

    Hazelaar, S; van der Strate, HJ; Gieskes, WWC; Vrieling, EG

    After each division of a diatom cell, a new siliceous hypovalve is formed inside the silica deposition vesicle (SDV). We present the sequence of this early formation of the new valve in the pennate marine diatom Navicula salinarum (Grunow) Hustedt, visualized by using the fluorescent probe

  4. Diatoms as a source for 4-desmethyl-23,24-dimethyl steroids in sediments and petroleum

    Science.gov (United States)

    Rampen, Sebastiaan W.; Schouten, Stefan; Hopmans, Ellen C.; Abbas, Ben; Noordeloos, Anna A. M.; van Bleijswijk, Judith D. L.; Geenevasen, Jan A. J.; Sinninghe Damsté, Jaap S.

    2009-01-01

    Analysis of the sterol composition of more than 100 diatom cultures, representing all major marine diatom orders, indicates that this group of algae may be an important source for 4-desmethyl-23,24-dimethyl steroids in sediments and petroleum, as their precursors, i.e. 4-desmethyl-23,24-dimethyl sterols, were present in 22 of the cultures. The phylogenetic positions of diatom species that produce 4-desmethyl-23,24-dimethyl sterols show that, within the centric diatoms, only a specific group of diatoms is able to produce these sterols, while within the pennate diatoms, a phylogenetic relationship between 4-desmethyl-23,24-dimethyl sterol-producing diatoms is less apparent. Based on the phylogenetic relationship, it is suggested that diatoms inherited the ability of producing these sterols from a single common ancestor, which originated between 150 and 100 Ma ago. Co-injection of an authentic 23R,24R-dimethyl-5α-cholestane standard with extracts confirmed its presence in sediments. We also tentatively identified three other 4-desmethyl-23,24-dimethyl sterane isomers having different side-chain stereo-configurations and observed that some of the isomers co-elute with other steranes including 24-ethyl-5α-cholestane.

  5. Adaptive significance of phytoplankton stickiness with emphasis on the diatom Skeletonema costatum

    DEFF Research Database (Denmark)

    Hansen, J.L.S.; Timm, U.; Kiørboe, Thomas

    1995-01-01

    -most pronounced in eutrophic and hydro-graphically isolated environments. The sticking properties of the diatom Skeletonema costatum are discussed in an evolutionary context; we suggest that mutual coagulation increases the abundance of S. costatum relative to other diatom species in coastal areas. The model...

  6. Fluxes of diatoms in the Dona Paula Bay, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Garg, A.; Bhaskar, P.V.

    ) and particulate organic carbon (POC). The highest diatom flux was recorded in April-May for both the years. Fluxes of diatoms varied from 0.6 x 10 sup(4) cells m sup(-2) day sup(-1) (November 1995) to 121.47 x 10 sup(4) cells m sup(-2) day sup(-1) (December 1996...

  7. An integrated analysis of molecular acclimation to high light in the marine diatom Phaeodactylum tricornutum

    DEFF Research Database (Denmark)

    Nymark, Marianne; Valle, Kristin C; Brembu, Tore

    2009-01-01

    Photosynthetic diatoms are exposed to rapid and unpredictable changes in irradiance and spectral quality, and must be able to acclimate their light harvesting systems to varying light conditions. Molecular mechanisms behind light acclimation in diatoms are largely unknown. We set out to investiga...

  8. A stress surveillance system based on calcium and nitric oxide in marine diatoms

    NARCIS (Netherlands)

    Vardi, A.; Formiggini, F.; Casotti, R.; De Martino, A.; Ribalet, F.; Miralto, A.; Bowler, C.

    2006-01-01

    Diatoms are an important group of eukaryotic phytoplankton, responsible for about 20% of global primary productivity. Study of the functional role of chemical signaling within phytoplankton assemblages is still in its infancy although recent reports in diatoms suggest the existence of chemical-based

  9. A stress surveillance system based on calcium and nitric oxide in marine diatoms.

    NARCIS (Netherlands)

    Vardi, A.; Formiggini, F.; Casotti, R.; De Martino, A.; Ribalet, F.; Miralto, A.; Bowler, C.

    2006-01-01

    Diatoms are an important group of eukaryotic phytoplankton, responsible for about 20% of global primary productivity. Study of the functional role of chemical signaling within phytoplankton assemblages is still in its infancy although recent reports in diatoms suggest the existence of chemical-based

  10. The health of benthic diatom assemblages in lower stretch of a ...

    Indian Academy of Sciences (India)

    This study examines the ecological state of epilithic diatom assemblages along the lower stretch of Mandakini, a glacier-fed Himalayan river. The diatoms were sampled at four stations during winter and summer, only once in each season. Valve counts were obtained from Naphrax mounts prepared from each sample.

  11. Rotation-vibrational spectra of diatomic molecules and nuclei with Davidson interactions

    CERN Document Server

    Rowe, D J

    1998-01-01

    Complete rotation-vibrational spectra and electromagnetic transition rates are obtained for Hamiltonians of diatomic molecules and nuclei with Davidson interactions. Analytical results are derived by dynamical symmetry methods for diatomic molecules and a liquid-drop model of the nucleus. Numerical solutions are obtained for a many-particle nucleus with quadrupole Davidson interactions within the framework of the microscopic symplectic model. (author)

  12. $\\Delta I=4$ and $\\Delta I=8$ bifurcations in rotational bands of diatomic molecules

    CERN Document Server

    Bonatsos, Dennis; Lalazissis, G A; Drenska, S B; Minkov, N; Raychev, P P; Roussev, R P; Bonatsos, Dennis

    1996-01-01

    It is shown that the recently observed $\\Delta I=4$ bifurcation seen in superdeformed nuclear bands is also occurring in rotational bands of diatomic molecules. In addition, signs of a $\\Delta I=8$ bifurcation, of the same order of magnitude as the $\\Delta I=4$ one, are observed both in superdeformed nuclear bands and rotational bands of diatomic molecules.

  13. Long-term pigment dynamics and diatom survival in dark sediment

    NARCIS (Netherlands)

    Veuger, B.; Van Oevelen, D.

    2011-01-01

    In order to investigate survival of diatoms and long-term pigment dynamics in dark sediment, we incubated samples of homogenized, sieved, tidal-flat sediment for 1 yr in darkness. Microscopic observations revealed that some diatoms survived the full year in darkness and retained their pigments.

  14. Diatoms as water quality indicators in the upper reaches of the Great ...

    African Journals Online (AJOL)

    All index scores showed the Great Fish River to be impacted, and showed significant correlations of diatom species abundance with pH, NO3-N, electrical conductivity, NH4-N and CaCO3. Analysis revealed EC and NO3-N as the main environmental drivers affecting diatom commnity composition, followed by pH and ...

  15. A diatom record of recent environmental change in Lake Duluti, northern Tanzania

    DEFF Research Database (Denmark)

    Öberg, Helena; Andersen, Thorbjørn Joest; Westerberg, Lars-Ove

    2012-01-01

    ) Simonsen, Gomphonema parvulum (Kützing) Grunow and Nitzschia amphibia Grunow. All three cores display similar stratigraphic succession, but the relative ratio of habitats represented by the diatoms varies substantially between cores. Diatoms indicate that the oldest part of the record is characterized...

  16. Paleoceanographic, and paleoclimatic constraints on the global Eocene diatom and silicoflagellate record

    Science.gov (United States)

    Barron, John A.; Stickley, Catherine E.; Bukry, David

    2015-01-01

    Eocene diatom and silicoflagellate biostratigraphy are summarized and correlated with the most recent geologic time scale as well as with the global oxygen isotope and eustatic sea level curves. The global distribution of Eocene diatom/silicoflagellate-bearing sediments varies considerably, reflecting changing oceanic gateways and paleoceanography with changing patterns that are punctuated by four major depositional events.

  17. Molecular fossils of diatoms: Applications in petroleum geochemistry and palaeoenvironmental studies

    NARCIS (Netherlands)

    Rampen, S.W.

    2009-01-01

    Diatoms are one of the major groups of algae which originated relatively recently and evolved in the Late Jurassic/Cretaceous. This thesis presents the results of a comprehensive study of diatom lipids in cultures and in the environment and their applications in the age determination of petroleum

  18. Molecular fossils of diatoms : Applications in petroleum geochemistry and palaeoenvironmental studies

    NARCIS (Netherlands)

    Rampen, S.W.|info:eu-repo/dai/nl/330221574

    2009-01-01

    Diatoms are one of the major groups of algae which originated relatively recently and evolved in the Late Jurassic/Cretaceous. This thesis presents the results of a comprehensive study of diatom lipids in cultures and in the environment and their applications in the age determination of petroleum

  19. Further contribution to the diatom flora of sewage enriched waters in southern Africa

    CSIR Research Space (South Africa)

    Schoeman, FR

    1972-01-01

    Full Text Available The systematics and autecology of the diatoms observed in an algal sample from a maturation pond of the Walvis Bay (south west African coast) sewage works are discussed. Fourteen diatoms species are recorded. A new specie, Amphora subacutiuscula...

  20. Seasonal effects of cadmium accumulation in periphytic diatom communities of freshwater biofilms

    Energy Technology Data Exchange (ETDEWEB)

    Thi Thuy Duong [Institute of Environmental Technology, Vietnamese Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi (Viet Nam); Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France)], E-mail: duongthuy0712@yahoo.com; Morin, Soizic [Cemagref, UR REBX, 50 avenue de Verdun, F-33612 Cestas cedex (France); Herlory, Olivier [Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France); Feurtet-Mazel, Agnes [Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France)], E-mail: a.feurtet-mazel@epoc.u-bordeaux1.fr; Coste, Michel [Cemagref, UR REBX, 50 avenue de Verdun, F-33612 Cestas cedex (France); Boudou, Alain [Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France)

    2008-10-20

    The relationships between diatom species and cadmium (Cd) accumulated in biofilms of the Riou-Mort River (SW, France) were studied in July 2004 and March 2005. Biofilms were sampled from artificial substrates immersed along a metallic pollution gradient during 20 days. Dynamics of diatom communities and cadmium accumulation were followed by collecting samples after 4, 7, 14 and 20 days of biofilm colonization. Cd accumulation in biofilms during experiment was significantly higher in Cd polluted station (Joanis) than in reference station (Firmi) for both seasons. Periphytic diatom composition varied between sites and seasons. At Firmi station, seasonal dynamics of diatom communities were stable with the dominance of Cyclotella meneghiniana and Melosira varians in July and Surirellabrebissonnii and Navicula gregaria in March. At Joanis station, diatom communities mainly responded to high levels of metal by a high proportion of small, adnate species. Positive correlations between Eolimna minima, Nitzschia palea, Encyonema minutum, Surirella angusta, and Gomphonema parvulum and cadmium accumulation were observed, indicating that these species are tolerant to high levels of cadmium. On the other hand, negative correlations of C. meneghiniana, N. gregaria, Navicula lanceolata, M. varians and Nitzschia dissipata with cadmium qualify them as sensitive diatom species. Periphytic diatom composition through the presence of specific species highlight metal tolerant indicator diatom groups which will be meaningful for biomonitoring pollution in natural aquatic systems.

  1. Ciona intestinalis as a Marine Model System to Study Some Key Developmental Genes Targeted by the Diatom-Derived Aldehyde Decadienal

    Directory of Open Access Journals (Sweden)

    Anna Lettieri

    2015-03-01

    Full Text Available The anti-proliferative effects of diatoms, described for the first time in copepods, have also been demonstrated in benthic invertebrates such as polychaetes, sea urchins and tunicates. In these organisms PUAs (polyunsaturated aldehydes induce the disruption of gametogenesis, gamete functionality, fertilization, embryonic mitosis, and larval fitness and competence. These inhibitory effects are due to the PUAs, produced by diatoms in response to physical damage as occurs during copepod grazing. The cell targets of these compounds remain largely unknown. Here we identify some of the genes targeted by the diatom PUA 2-trans-4-trans-decadienal (DD using the tunicate Ciona intestinalis. The tools, techniques and genomic resources available for Ciona, as well as the suitability of Ciona embryos for medium-to high-throughput strategies, are key to their employment as model organisms in different fields, including the investigation of toxic agents that could interfere with developmental processes. We demonstrate that DD can induce developmental aberrations in Ciona larvae in a dose-dependent manner. Moreover, through a preliminary analysis, DD is shown to affect the expression level of genes involved in stress response and developmental processes.

  2. The influence of reduced light intensity on the response of benthic diatoms to herbicide exposure.

    Science.gov (United States)

    Wood, Rebecca J; Mitrovic, Simon M; Lim, Richard P; Kefford, Ben J

    2016-09-01

    Herbicide pollution events in aquatic ecosystems often coincide with increased turbidity and reduced light intensity. It is therefore important to determine whether reduced light intensity can influence herbicide toxicity, especially to primary producers such as benthic diatoms. Benthic diatoms collected from 4 rivers were exposed to herbicides in 48 h rapid toxicity tests under high light (100 µmol m(-2)  s(-1) ) and low light (20 µmol m(-2)  s(-1) ) intensities. The effects of 2 herbicides (atrazine and glyphosate) were assessed on 26 freshwater benthic diatom taxa. There was no significant interaction of light and herbicide effects at the community level or on the majority (22 of 26) of benthic diatom taxa. This indicates that low light levels will likely have only a minor influence on the response of benthic diatoms to herbicides. Environ Toxicol Chem 2016;35:2252-2260. © 2016 SETAC. © 2016 SETAC.

  3. Growth of fouling diatoms from the Zuari estuary, Goa (west coast of India) under different salinities in the laboratory

    Digital Repository Service at National Institute of Oceanography (India)

    Redekar, P.D.; Wagh, A.B.

    Diatoms take part in the initial process of fouling i.e. primary film formation. In order to understand the growth of the diatoms under different salinity conditions in the laboratory, this work was undertaken. Fouling diatoms on glass slides were...

  4. HUBUNGAN ANTARA KANDUNGAN SILIKA DENGAN KELIMPAHAN DIATOM BENTHIK DI SEPANJANG SUNGAI PELUS KABUPATEN BANYUMAS

    Directory of Open Access Journals (Sweden)

    Siti Umiatun

    2017-03-01

    Full Text Available Silica is an element that is useful to the organism especially Diatoms (Chrysophyta: Bacillariophyceae. The sources of Silica in waters derive from weathering rock-containing silica. Diatoms are a phytoplankton that able to live as a phytobenthos distributed globally in all types of waters. The purpose of this study was to determine; the silica content, the abundance of diatoms, and the relationship between the content of silica and the abundance of diatoms in the Pelus River Banyumas. This research was conducted as a survey and samples were collected using composite sampling technique at 5 stations. Samples were collected three times with 2 weeks intervals. Two main parameters (diatoms abundance and silica content and ten supporting parameters (temperature, current velocity, pH, DO, BOD, COD, TSS, TDS, nitrate, and ortofosfat of waters were measured. Data of analysis calculated in this study including regression correlation analysis to determine the relationship of the silica content and the abundance of diatoms. The silica concentration in the Pelus River waters varies between 112.48-175.00 mg.l-1 with an average of 146 mg.l-1. The total abundance of benthic diatoms was 44,442 ind.cm-2. The highest diatoms abundance was at station II (11,128 ind.cm-2, the lowest was at Station IV (6,828 ind.cm-2. The relationship between silica contained in the waters and abundance of diatoms indicated by the value of R2 (coefficient of determination by 0.38 or 38%. The abundance of Diatoms are affected 62% by the available silica in the environment, and the rest 38% e rest are determined by other factors.

  5. Investigation of mechanical properties of diatom frustules using nanoindentation.

    Science.gov (United States)

    Subhash, G; Yao, S; Bellinger, B; Gretz, M R

    2005-01-01

    Diatom frustules have been identified as potential candidate materials for nanotechnology applications. However, for successful engineering applications, their mechanical properties must be fully determined. Toward this end, indentation hardness and elastic properties frustules of the centric diatom Coscinodiscus concinnus were evaluated using nanoindentation. A series of nanoindentation tests were performed on the outer surfaces of frustules at various locations. Analysis of the indentations revealed that the Young's modulus and hardness values appear to be strongly dependent on the location of the indentation. The modulus varied from 0.591 to 2.768 GPa in the center and 0.347 to 2.446 GPa at locations away from the center. Similarly, frustule hardness varied between 0.033 and 0.116 GPa in the center and between 0.076 and 0.12 GPa away from the center. Another series of nanoindentation tests were performed on the frustules (positioned in both concave and convex orientations) at various locations to analyze the failure mode. It was found that the failure modes in each of the orientations were also drastically different. In convex orientation, cracks initiated along the sharp edges of the indentation were followed by circular ring cracks, whereas in concave orientation only cracks along the sharp edges (corresponding to the three edges of the indenter) were revealed. The porosity and the nonplanar nature of the frustules make it difficult to extract the mechanical properties accurately at each location.

  6. Sex allocation pattern of the diatom Cyclotella meneghiniana.

    Science.gov (United States)

    Shirokawa, Y; Shimada, M

    2013-06-22

    Sex allocation is one of the most successful applications of evolutionary game theory. This theory has usually been applied to multicellular organisms; however, conditional sex allocation in unicellular organisms remains an unexplored field of research. Observations at the cellular level are indispensable for an understanding of the phenotypic sex allocation strategy among individuals within clonal unicellular organisms. The diatom Cyclotella meneghiniana, in which the sexes are generated from vegetative cells, is suitable for investigating effects of phenotypic plasticity factors on sex allocation while excluding genetic differences. We designed a microfluidic system that allowed us to trace the fate of individual cells. Sex allocation by individual mother cells was affected by cell lineage, cell size and cell density. Sibling cell pairs tended to differentiate into the same fates (split sex ratio). We found a significant negative correlation between the cell area of the mother cell and sex ratio of the two sibling cells. The male-biased sex ratio declined with higher local cell population density, supporting the fertility insurance hypothesis. Our results characterize multiple non-genetic factors that affect the phenotypic single cell-level sex allocation. Sex allocation in diatoms may provide a model system for testing evolutionary game theory in unicellular organisms.

  7. Underwater locomotion strategy by a benthic pennate diatom Navicula sp.

    Science.gov (United States)

    Wang, Jiadao; Cao, Shan; Du, Chuan; Chen, Darong

    2013-10-01

    The mechanism of diatom locomotion has been widely researched but still remains a hypothesis. There are several questionable points on the prevailing model proposed by Edgar, and some of the observed phenomena cannot be completely explained by this model. In this paper, we undertook detailed investigations of cell structures, locomotion, secreted mucilage, and bending deformation for a benthic pennate diatom Navicula species. According to these broad evidences, an updated locomotion model is proposed. For Navicula sp., locomotion is realized via two or more pseudopods or stalks protruded out of the frustules. The adhesion can be produced due to the pull-off of one pseudopod or stalk from the substratum through extracellular polymeric substances. And the positive pressure is generated to balance the adhesion because of the push-down of another pseudopod or stalk onto the substratum. Because of the positive pressure, friction is generated, acting as a driving force of locomotion, and the other pseudopod or stalk can detach from the substratum, resulting in the locomotion. Furthermore, this model is validated by the force evaluation and can better explain observed phenomena. This updated model would provide a novel aspect on underwater locomotion strategy, hence can be useful in terms of artificial underwater locomotion devices.

  8. Processing and characterization of diatom nanoparticles and microparticles as potential source of silicon for bone tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Le, Thi Duy Hanh [Department of Industrial Engineering, University of Trento, Trento (Italy); BIOtech Research Center and European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Trento (Italy); Bonani, Walter [Department of Industrial Engineering, University of Trento, Trento (Italy); BIOtech Research Center and European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Trento (Italy); Interuniversity Consortium for Science and Technology of Materials, Trento Research Unit, Trento (Italy); Speranza, Giorgio [Center for Materials and Microsystems, PAM-SE, Fondazione Bruno Kessler, Trento (Italy); Sglavo, Vincenzo; Ceccato, Riccardo [Department of Industrial Engineering, University of Trento, Trento (Italy); Maniglio, Devid; Motta, Antonella [Department of Industrial Engineering, University of Trento, Trento (Italy); BIOtech Research Center and European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Trento (Italy); Interuniversity Consortium for Science and Technology of Materials, Trento Research Unit, Trento (Italy); Migliaresi, Claudio, E-mail: claudio.migliaresi@unitn.it [Department of Industrial Engineering, University of Trento, Trento (Italy); BIOtech Research Center and European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Trento (Italy); Interuniversity Consortium for Science and Technology of Materials, Trento Research Unit, Trento (Italy)

    2016-02-01

    Silicon plays an important role in bone formation and maintenance, improving osteoblast cell function and inducing mineralization. Often, bone deformation and long bone abnormalities have been associated with silica/silicon deficiency. Diatomite, a natural deposit of diatom skeleton, is a cheap and abundant source of biogenic silica. The aim of the present study is to validate the potential of diatom particles derived from diatom skeletons as silicon-donor materials for bone tissue engineering applications. Raw diatomite (RD) and calcined diatomite (CD) powders were purified by acid treatments, and diatom microparticles (MPs) and nanoparticles (NPs) were produced by fragmentation of purified diatoms under alkaline conditions. The influence of processing on the surface chemical composition of purified diatomites was evaluated by X-ray photoelectron spectroscopy (XPS). Diatoms NPs were also characterized in terms of morphology and size distribution by transmission electron microscopy (TEM) and Dynamic light scattering (DLS), while diatom MPs morphology was analyzed by scanning electron microscopy (SEM). Surface area and microporosity of the diatom particles were evaluated by nitrogen physisorption methods. Release of silicon ions from diatom-derived particles was demonstrated using inductively coupled plasma optical emission spectrometry (ICP/OES); furthermore, silicon release kinetic was found to be influenced by diatomite purification method and particle size. Diatom-derived microparticles (MPs) and nanoparticles (NPs) showed limited or no cytotoxic effect in vitro depending on the administration conditions. - Highlights: • Diatomite is a natural source of silica and has a potential as silicon-donor for bone regenerative applications. • Diatom particles derived from purified diatom skeletons were prepared by fragmentation under extreme alkaline condition. • Dissolution of diatom particles derived from diatom skeletons in DI water depend on purification method

  9. Controlling the invasive diatom Didymosphenia geminata: an ecotoxicity assessment of four potential biocides.

    Science.gov (United States)

    Jellyman, P G; Clearwater, S J; Clayton, J S; Kilroy, C; Blair, N; Hickey, C W; Biggs, B J F

    2011-07-01

    In 2004, an invasive mat-forming freshwater diatom, Didymosphenia geminata (didymo), was found in New Zealand causing concern with regard to potential consequences for local freshwater ecosystems. A four-stage research program was initiated to identify methods to control D. geminata. This article reports the results of Stage 2, in which four potential control compounds [Gemex™ (a chelated copper formulation), EDTA, Hydrothol®191, and Organic Interceptor™ (a pine oil formulation)] selected in Stage 1 were evaluated for their biocidal efficacy on D. geminata and effects on non-target organisms using both artificial stream and laboratory trials. Artificial stream trials evaluated the mortality rates of D. geminata and fishes to three concentrations of the four biocides, whereas laboratory toxicity trials tested the response of green alga and cladocera to a range of biocide concentrations and exposure times. In artificial stream trials, Gemex and Organic Interceptor were the most effective biocides against D. geminata for a number of measured indices; however, exposure of fishes to Organic Interceptor resulted in high mortality rates. Laboratory toxicity testing indicated that Gemex might negatively affect sensitive stream invertebrates, based on the cladoceran sensitivity at the proposed river control dose. A decision support matrix evaluated the four biocides based on nine criteria stipulated by river stakeholders (effectiveness, non-target species impacts, stalk removal, degradation profile, risks to health and safety, ease of application, neutralization potential, cost, and local regulatory requirements) and Gemex was identified as the product warranting further refinement prior to an in-river trial.

  10. Limnological record inferred from diatoms in sediments of Lake Skaliska (north-eastern Poland

    Directory of Open Access Journals (Sweden)

    Sienkiewicz Elwira

    2013-06-01

    Full Text Available Subfossil diatoms analysis was employed to reconstruct past environmental changes in Lake Skaliska. This lake, presently a palaeolake, is located on a wide plain called the Skaliska Basin (northern part of Mazury Lake District, north-eastern Poland. Changes in terrestrial vegetation suggest that the initial phase of the lake was in the early Holocene. In the sediments a total of 176 diatom species belonging to 35 genera were identified. The majority of diatoms are alkaliphilous and alkalibiontic, occurring mainly in meso-eutrophic water. Diatom flora development suggests that the best conditions for diatom growth prevailed throughout the Boreal and in the early Atlantic, a suggestion supported by the increased frequency of planktonic diatoms living in nutrient-rich water. A water pH reconstruction (DIpH based on diatoms points to alkalinity during the lake’s existence. Since roughly the mid-Atlantic the lake was shallowing, and at the beginning of the Subboreal peat sedimentation led to complete overgrowth of the lake.

  11. Factors affecting diatom dynamics in the alpine lakes of Colbricon (Northern Italy: a 10-year survey

    Directory of Open Access Journals (Sweden)

    Andrea SQUARTINI

    2010-08-01

    Full Text Available Planktonic diatom fluctuations, their diversity and relationships with environmental variables were analyzed for ten consecutive years in Colbricon Superiore and Inferiore, two small high-mountain lakes located in the Paneveggio-Pale di S. Martino Natural Park (Trento, Italy offering the rare opportunity to study two lakes differing only by area and volume and being in this respect in a ratio of 2:1 and 3:1 respectively. The lakes were monitored and sampled monthly, during ten ice-free periods, from 1998 to 2007, to correlate water chemical and physical characteristics with the recorded diversity and abundance of planktonic diatoms. 55 taxa of Bacillariophyceae were found, among which Cyclotella spp., Tabellaria flocculosa and Fragilaria spp. were dominant. Both chemical data and diatom community composition are consistent with well buffered mesotrophic lakes. We found statistical evidence that the development of diatoms was strongly related to the variation of water temperature. Furthermore, several different signatures of the diatom-enviroment relationships arose between the two lakes as e.g., a negative correlation between diatom development and water transparency was occurring in the larger lake only. As a result, the average diatom density recorded over the 10 years period were 1.17 fold higher than in the lower lake which corresponds to a 1.65 fold higher biomass. A size-dependent tighter response of the phytoplankton to chemical parameters appears to operate in the smaller waterbody compared to the larger one.

  12. Diagnosis of the Diatom Community upon Biofilm Development on Stainless Steels in Natural Freshwater

    Directory of Open Access Journals (Sweden)

    Caroline Richard

    2017-01-01

    Full Text Available This paper reports the development of biofilms on stainless steels (SS upon exposure in a natural freshwater ecosystem for about six months and focuses on the composition of diatom populations. By using environmental scanning electron microscopy (ESEM technique, we provide a detailed description regarding diatom identification at species level as well as their main characteristics, including type, morphology, ability to form colony, and motility. Results reveal the presence of both prostrate (initial colonizers and stalked (late colonizers forms. Pennate diatoms, Cocconeis placentula and Amphora coffeaeformis, and a centric diatom, Melosira varians, are shown to be the abundant forms regardless of the SS type. Pennate diatoms dominate the community and are directly attached to the substratum, whereas the centric form is entangled in the biofilm matrix in a significant number. The dominance of adnate forms suggests that these cells are sturdy and successfully maintaining their population. In situ monitoring of the electrochemical response of immersed materials showed ennoblement of the open circuit potential, which seems to be due to the biogenic production of H2O2, detected in a significant amount within the biofilms. The substantial enrichment of biofilms with diatoms potentially suggests the implication of these microorganisms in the process of ennoblement. A mechanism is proposed in this paper describing the possible interactions of diatom community with SS in the studied ecosystem.

  13. Freshwater diatom influx in intertropical Atlantic: Relationships with continental records from Africa

    Science.gov (United States)

    Gasse, Françoise; Stabell, Bjørg; Fourtanier, Elizabeth; van Iperen, Yolanda

    1989-09-01

    Diatom assemblages from modern West African rivers and from lacustrine sediments subjected to deflation represent the present-day sources of continental diatoms to the sea. Diatom productivity in large rivers is high, especially for the genus Melosira. Windblown diatoms derive mainly from the central and northern Sahara (summer dust plume) where saline chloride-water assemblages are widespread, or from the southern edge of the Sahara (winter dust plume) where Melosira-rich assemblages of dilute water predominate. Freshwater diatom peaks in Atlantic cores may reflect (1) phases of increased river influx, correlated with humid episodes on the continent or (2) phases of enhanced deflation and wind transport during arid episodes (the single hypothesis for fine sediments from mid-ocean sites). Genus Melosira dominates the freshwater assemblages of many modern and fossil marine samples, whatever the transport agent is. Therefore, it is not an accurate paleoclimate indicator by itself, but associated taxa may provide information on the environmental and geographical origin of the displaced diatoms. This tentative approach shows that freshwater diatoms in Atlantic cores may be a good tool for reconstructing paleoclimates and for establishing continent-ocean correlations if species analyses are made and if the continental distribution of the taxa encountered is considered.

  14. Relationships between benthic diatom assemblages’ structure and selected environmental parameters in Slovak water reservoirs (Slovakia, Europe

    Directory of Open Access Journals (Sweden)

    Fidlerová D.

    2016-01-01

    Full Text Available The main objective of the present study is to describe the structure of benthic diatom communities in 23 water reservoirs in Slovakia classified as heavily modified water bodies. Environmental variables together with biological data obtained during the routine biomonitoring of water reservoirs in Slovakia were explored and analysed to understand variability of benthic diatom communities and their relationships with environmental variables in order to obtain an integrated knowledge about their relevance as bioindicators for the Water Framework Directive-compliant ecological potential assessment. This study summarizes results from a four-year monitoring programme of water reservoirs surveyed during the period of 2011–2014. The performed survey and statistical analyses revealed the following: (i two main groups of reservoirs could be distinguished based on the purpose of their main use (multipurpose or drinking water-supply use; (ii multipurpose and drinking water-supply reservoirs differed in benthic diatom community structure, diatom water quality indices as well as in the principal environmental gradients structuring the diatom communities; (iii 5 distinct sub-groups of reservoirs could be identified differing in terms of diatom species composition and several environmental parameters; (iv the most significant environmental variables in explaining differences in diatom species composition in multipurpose reservoirs were mean depth and mean annual flow; in drinking water-supply reservoirs conductivity and water transparency.

  15. Diatoms dominate the eukaryotic metatranscriptome during spring in coastal 'dead zone' sediments.

    Science.gov (United States)

    Broman, Elias; Sachpazidou, Varvara; Dopson, Mark; Hylander, Samuel

    2017-10-11

    An important characteristic of marine sediments is the oxygen concentration that affects many central metabolic processes. There has been a widespread increase in hypoxia in coastal systems (referred to as 'dead zones') mainly caused by eutrophication. Hence, it is central to understand the metabolism and ecology of eukaryotic life in sediments during changing oxygen conditions. Therefore, we sampled coastal 'dead zone' Baltic Sea sediment during autumn and spring, and analysed the eukaryotic metatranscriptome from field samples and after incubation in the dark under oxic or anoxic conditions. Bacillariophyta (diatoms) dominated the eukaryotic metatranscriptome in spring and were also abundant during autumn. A large fraction of the diatom RNA reads was associated with the photosystems suggesting a constitutive expression in darkness. Microscope observation showed intact diatom cells and these would, if hatched, represent a significant part of the pelagic phytoplankton biomass. Oxygenation did not significantly change the relative proportion of diatoms nor resulted in any major shifts in metabolic 'signatures'. By contrast, diatoms rapidly responded when exposed to light suggesting that light is limiting diatom development in hypoxic sediments. Hence, it is suggested that diatoms in hypoxic sediments are on 'standby' to exploit the environment if they reach suitable habitats. © 2017 The Author(s).

  16. Distribution of non-marine diatoms in surface sediments of streams in Socotra Island, Yemen

    Directory of Open Access Journals (Sweden)

    Abdelfattah A. Zalat

    2011-11-01

    Full Text Available Abundance and species composition of non-marine benthic diatom assemblages were studied from surface sediments samples of 11 streams distributed in Socotra Island, located in the northwest Indian Ocean. A total of 145 diatom species, representing 44 genera, were identified. The overall diatom communities appear to be the first recorded off the island. Pennales and non-planktonic taxa were most dominant over centrales and planktonic forms, both in diversity of genera and species. The majority of recognized diatoms are of cosmopolitan distribution. The predominant diatom flora in the surface sediment samples follow: Synedra ulna, Synedra longissima, Encyonema caespitosum, Encyonema silesiacum, Encyonemopsis microcephala, Mastogloia braunii, Mastogloia dansei, Mastogloia elliptica, Navicula cryptocephala, Navicula cryptotenella, Navicula rhynchocephala, Navicula cincta, Nitzschia amphibian, Nitzschia frustulum, Nitzschia perminuta, Cocconeis placentula, Pleurosira laevis and Staurosirella pinnata. These are found in addition to the common occurrence of Amphora coffeaeformis, Amphora Montana, Anomoeoneis sphaerophora, Cyclotella meneghiniana, Cymbella affinis, Diploneis elliptica, Encyonema mesianum, Diploneis smithii, Gomphonema gracile, Gomphonema parvulum, Kobayasia subtilissima, Mastogloia smithii, Navicula minuscule, Navicula notha, Navicula tenelloides, Nitzschia obtuse, Nitzschia palea, Nitzschia scalaris, Synedra nana, Tryblionella acuminate, Tryblionella granulate and Tryblionella punctata. Multivariate statistical techniques including detrended correspondence and cluster analyses were used to summarize changes in the diatom assemblages present in the examined streams. The results indicated six major diatom assemblages with a variation in dominant species. Each assemblage reflects distinctive environmental conditions based on salinity preference of the recognized and dominant.

  17. A diatom record of CO2 decline since the late Miocene

    Science.gov (United States)

    Mejía, Luz María; Méndez-Vicente, Ana; Abrevaya, Lorena; Lawrence, Kira T.; Ladlow, Caroline; Bolton, Clara; Cacho, Isabel; Stoll, Heather

    2017-12-01

    Extratropical sea surface temperature records from alkenones record a dramatic cooling of up to 17 °C over the last ∼14 Ma, but the relationship between this cooling and greenhouse gas forcing has been elusive due to sparse and contrasting reconstructions of atmospheric CO2 for the time period. Alkenone carbon isotopic fractionation during photosynthesis has previously been used to estimate changes in pCO2 over this interval, but is complicated by significant changes in cell size of the alkenone-producing coccolithophorids over this time period. In this study, we reconstruct carbon isotopic fractionation during photosynthesis (εp) using organic compounds trapped within the frustules of pennate diatoms in sediments from the Eastern Equatorial Pacific Ocean at Ocean Drilling Program Site 846 over the last ∼13 Ma. Physical separation of pennate diatoms prior to measuring carbon isotopic fractionation enables us to obtain a record with constant cell geometry, eliminating this factor of uncertainty in our pCO2 reconstruction. In the past ∼11 Ma, εp declines from 15.5 to 10.3‰. Using the classic diffusive model and taking into account variations in opal content, alkenone concentration and coccolith Sr/Ca as indicators of past productivity and growth rate, and sea surface temperature records from the site, we estimate a decline in pCO2 from 454 (+ / - 41) to 250 (+ / - 15) ppmv between ∼11 and 6 Ma. Models accounting for changing the significance of active carbon uptake for photosynthesis, which likely produce more accurate CO2 estimates, suggest a significant larger pCO2 decline of up to twice that shown by the classic diffusive model (in average from 794 (+ / - 233) ppmv at ∼11 Ma to 288 (+/-25) ppmv at ∼6 Ma, considering growth rates varying between 0.5 and 1.7 day-1). Large uncertainties in the pCO2 estimated between ∼8 and 11 Ma using the active uptake model are related to the growth rate used for calculations. Together, these results suggest CO2

  18. Diatom Transcriptional and Physiological Responses to Changes in Iron Bioavailability across Ocean Provinces

    Directory of Open Access Journals (Sweden)

    Natalie R. Cohen

    2017-11-01

    Full Text Available Changes in iron (Fe bioavailability influence diatom physiology and community composition, and thus have a profound impact on primary productivity and ecosystem dynamics. Iron limitation of diatom growth rates has been demonstrated in both oceanic and coastal waters of the Northeast Pacific Ocean and is predicted to become more pervasive in future oceans. However, it is unclear how the strategies utilized by phytoplankton to cope with low Fe bioavailability and resupply differ across these ocean provinces. We investigated the response of diatom communities to variable Fe conditions through incubation experiments performed in the Fe mosaic of the California Upwelling Zone and along a natural Fe gradient in the Northeast Pacific Ocean. Through coupling gene expression of two dominant diatom taxa (Pseudo-nitzschia and Thalassiosira with biological rate process measurements, we provide an in-depth examination of the physiological and molecular responses associated with varying Fe status. Following Fe enrichment, oceanic diatoms showed distinct differential expression of gene products involved in nitrogen assimilation, photosynthetic carbon fixation, and vitamin production compared to diatoms from low-Fe coastal sites, possibly driven by the chronic nature of Fe stress at the oceanic site. Genes of interest involved in Fe and N metabolism additionally exhibited divergent expression patterns between the two diatom taxa investigated, demonstrating that diverse diatoms may invoke alternative strategies when dealing with identical changes in their environment. We report here several mechanisms used distinctly by coastal or oceanic diatom communities as well as numerous taxa-specific strategies for coping with Fe stress and rearranging nutrient metabolism following Fe enrichment.

  19. Diatoms and bacteria diversity: study of their relationships in the Southern Adriatic Sea

    Directory of Open Access Journals (Sweden)

    C. CAROPPO

    2003-12-01

    Full Text Available In the Southern Adriatic Sea (Italian coasts bacterial and diatom diversity was studied over an annual cycle and the relationships between these two microbial components were analyzed. As regards the culturable heterotrophic bacteria, Aeromonas was the predominant genus among the Gram-negative bacteria. The presence of Enterobacteriaceae, Cytophaga, Pseudomonas, Acinetobacterand Photobacteriumwas also remarkable. Flexibacter, Moraxella, Chromobacterium, Flavobacteriumand Vibriowere present at less than 5%. Of the 92 diatom species determined, 16 were the most abundant representing the 96% of this phytoplankton group. The results obtained demonstrated that several bacterial genera were significantly related to the most abundant and representative diatoms ( Chaetocerosspp., Pseudo-nitzschia pseudodelicatissimaand Rhizosoleniaspp..

  20. THE RESPONSE OF THE PERIPHYTIC DIATOM COMMUNITY TO ACID MINE DRAINAGE POLLUTION

    Directory of Open Access Journals (Sweden)

    Andreea Ciorba

    2004-01-01

    Full Text Available This paper proposes to relate the principal characteristics of diatom community (species richness, biodiversity, community biomass, diatom indices to the stress induced by acidification and high levels of metal. The study was done in a mine drainage affected area in Galicia (NW Spain by comparing periphytic diatom communities from polluted streams to ones in supposedly clean waters. The change in the dominant species was the clearest response to AMD pollution while species richness and diversity were sensitive only to high levels of pollution.

  1. On the Occurrence of Four Diatom Taxa from Eastern India with a Taxonomic Note

    Directory of Open Access Journals (Sweden)

    Jai Prakash Keshri

    2016-01-01

    Full Text Available Diatoms were collected from the Kotulpur area of West Bengal. Four diatom taxa, namely, Eunotia minor (Kützing Grunow, Achnanthidium minutissimum (Kützing Czarnecki, Lemnicola hungarica (Grunow Round and Basson, and Navicula radiosa Kützing were observed using scanning electron microscopy (SEM and identified in light of modern diatom taxonomic trends. Except Eunotia minor, all these taxa are new records to Eastern India. A note on the taxonomy of Achnanthes pseudobiasolletiana as described by Gandhi and Eunotia serrata var. diadema (Ehr. R. M. Patrick as reported by Dwivedi and Misra has been added.

  2. Asymmetric wave transmission in a diatomic acoustic/elastic metamaterial

    Energy Technology Data Exchange (ETDEWEB)

    Li, Bing; Tan, K. T., E-mail: ktan@uakron.edu [Department of Mechanical Engineering, The University of Akron, Akron, Ohio 44325-3903 (United States)

    2016-08-21

    Asymmetric acoustic/elastic wave transmission has recently been realized using nonlinearity, wave diffraction, or bias effects, but always at the cost of frequency distortion, direction shift, large volumes, or external energy. Based on the self-coupling of dual resonators, we propose a linear diatomic metamaterial, consisting of several small-sized unit cells, to realize large asymmetric wave transmission in low frequency domain (below 1 kHz). The asymmetric transmission mechanism is theoretically investigated, and numerically verified by both mass-spring and continuum models. This passive system does not require any frequency conversion or external energy, and the asymmetric transmission band can be theoretically predicted and mathematically controlled, which extends the design concept of unidirectional transmission devices.

  3. Relation between properties of long-range diatomic bound states

    DEFF Research Database (Denmark)

    Spirko, Vladimir; Sauer, Stephan P. A.; Szalewicz, Krzysztof

    2013-01-01

    Long-range states of diatomic molecules have average values of internuclear separations at least one order of magnitude larger than the equilibrium value of R. For example, the helium dimer 4He2 has a single bound state with of about 50 Å. We show that the properties of these states, such as ...>, the dissociation energy, or the s-wave scattering length, can be related by simple, yet very accurate formulas if a potential energy curve is known. By examining a range of ab initio and empirical helium dimer potentials, as well as scaling these potentials, we found that the formulas remain accurate even if very...

  4. Global Expression for Representing Diatomic Potential-Energy Curves

    Science.gov (United States)

    Ferrante, John; Schlosser, Herbert; Smith, John R.

    1991-01-01

    A three-parameter expression that gives an accurate fit to diatomic potential curves over the entire range of separation for charge transfers between 0 and 1. It is based on a generalization of the universal binding-energy relation of Smith et al. (1989) with a modification that describes the crossover from a partially ionic state to the neutral state at large separations. The expression is tested by comparison with first-principles calculations of the potential curves ranging from covalently bonded to ionically bonded. The expression is also used to calculate spectroscopic constants form a curve fit to the first-principles curves. A comparison is made with experimental values of the spectroscopic constants.

  5. Stable Langmuir solitons in plasma with diatomic ions

    Directory of Open Access Journals (Sweden)

    M. Dvornikov

    2013-08-01

    Full Text Available We study stable axially and spherically symmetric spatial solitons in plasma with diatomic ions. The stability of a soliton against collapse is provided by the interaction of induced electric dipole moments of ions with the rapidly oscillating electric field of a plasmoid. We derive the new cubic-quintic nonlinear Schrödinger equation, which governs the soliton dynamics and numerically solve it. Then we discuss the possibility of implementation of such plasmoids in realistic atmospheric plasma. In particular, we suggest that spherically symmetric Langmuir solitons, described in the present work, can be excited at the formation stage of long-lived atmospheric plasma structures. The implication of our model for the interpretation of the results of experiments for the plasmoids generation is discussed.

  6. Fatty Acid Synthesis by Indonesian Marine Diatom, Chaetoceros gracilis

    Directory of Open Access Journals (Sweden)

    ALBERTA RIKA PRATIWI

    2009-12-01

    Full Text Available Since the primary storage nutrients in diatoms consist of lipid, they are potential for the industrial fatty acid production. High value fatty acids include arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid. This study aimed to analyze fatty acid synthesis by Chaetoceros gracilis diatom during growth. There was a large increase in lipid yield from 4pg cell−1 mass of lipid per cell at the exponential phase to 283pg cell−1 at stationary phase. The lipid concentrations also increased significantly from the stationary phase to the death phase, but not significantly from the end exponential phase to the stationary phase. The relative percentage of saturated fatty acid (SAFA of the total fatty acid was higher than that of monounsaturated fatty acid (MUFA and polyunsaturated fatty acid (PUFA at all of growth phase. The highest PUFA was found at stationary phase at the same time when SAFA was being the lowest. The majority of SAFA was palmitic acid (24.03–40.35%. MUFA contained significant proportion of oleic acid (19.6–20.9%. Oleic acid, linoleic acid and á-linolenic acid were found at every stage growth. These fatty acids are considered as precursor for production of long chain PUFA-Docosahexaenoic acid (DHA/22:6ù3 through series of desaturation and elongation step with all of desaturase enzyme (Ä8-D, Ä9-D, Ä12-D, Ä15-D, Ä17-D, Ä6-D, Ä5-D, and Ä4-D and elongase enzyme (E.

  7. Laboratory Rotational Spectroscopy of Astrophysical Interesting Diatomic Hydrides

    Science.gov (United States)

    Halfen, DeWayne; Ziurys, L.

    2008-05-01

    Diatomic hydride are among the most common molecular species in the interstellar medium (ISM). The low molecular mass and thus moments of inertia cause their rotational spectra to lie entirely in the submillimeter and far-infrared regions. Hence, the future airborne and space-borne platforms, such as SOFIA and Herschel, are primed to explore these prevalent molecules. However, in order to detect these species in the ISM, their rotational spectra must first be measured in the laboratory. Using submillimeter direct absorption methods in the Ziurys laboratory, we have recorded the spectra of several diatomic hydrides of astrophysical interest. We have measured the pure rotational spectrum of MnH (X7Σ+: N = 0 - 1) and MnD (N = 2 - 3), as well as the deuterium and carbon-13 isotopologues of CH, CD (X2Πr: N = 1 - 1 and 1 - 2) and 13CH (N = 1 - 1). Manganese hydride and deuteride were created in a DC discharge of H2 or D2 and manganese vapor, generated in a Broida-type oven. CD and 13CH were produced in an AC discharge of argon and CD4 or 13CH4. For MnH, the five strongest manganese hyperfine transitions were recorded in its N = 0 - 1 transition, each of which are additionally split by hydrogen hyperfine interactions. CD and 13CH also have multiple hyperfine components due to the D, 13C, and/or H atoms. The direct measurement of these fundamental transitions will allow for unambiguous astronomical detections. The results of these studies will be presented.

  8. The thylakoid membrane proteome of two marine diatoms outlines both diatom-specific and species-specific features of the photosynthetic machinery.

    Science.gov (United States)

    Grouneva, Irina; Rokka, Anne; Aro, Eva-Mari

    2011-12-02

    The thylakoid membrane of photoautotrophic organisms contains the main components of the photosynthetic electron transport chain. Detailed proteome maps of the thylakoid protein complexes of two marine diatoms, Thalassiosira pseudonana and Phaeodactylum tricornutum, were created by means of two-dimensional blue native (BN)/SDS-PAGE coupled with mass spectrometry analysis. One novel diatom-specific photosystem I (PS I)-associated protein was identified. A second plastid-targeted protein with possible PS I interaction was discovered to be restricted to the centric diatom species T. pseudonana. PGR5/PGRL homologues were found to be the only protein components of PS I-mediated cyclic electron transport common to both species. For the first time, evidence for a possible PS I localization of LI818-like light harvesting proteins (Lhcx) is presented. This study also advances the current knowledge on the light harvesting antenna composition and Lhcx expression in T. pseudonana on the protein level and presents details on the molecular distribution of Lhcx in diatoms. Above mentioned proteins and several others with unknown function provide a broad basis for further mutagenesis analysis, aiming toward further understanding of the composition and function of the photosynthetic apparatus of diatoms. The proteomics approach of this study further served as a tool to confirm and improve genome-derived protein models.

  9. Relationships between diatoms and tidal environments in Oregon and Washington, USA

    Science.gov (United States)

    Sawai, Yuki; Horton, Benjamin P.; Kemp, Andrew C.; Hawkes, Andrea D.; Nagumo, Tamostsu; Nelson, Alan R.

    2016-01-01

    A new regional dataset comprising 425 intertidal diatom taxa from 175 samples from 11 ecologically diverse Oregon and Washington estuaries illustrates the importance of compiling a large modern dataset from a range of sites. Cluster analyses and detrended correspondence analysis of the diatom assemblages identify distinct vertical zones within supratidal, intertidal and subtidal environments at six of the 11 study sites, but the abundance of some of the most common species varies widely among and within sites. Canonical correspondence analysis of the regional dataset shows relationships between diatom species and tidal exposure, salinity and substratum (grain size and organic content). Correspondence analyses of local datasets show higher values of explained variation than the analysis of the combined regional dataset. Our results emphasize that studies of the autecology of diatom species require many samples from a range of modern environments to adequately characterize species–environment relationships.

  10. Account of the littoral diatoms from Langebaan, Saldanha bay, Cape province, South Africa

    CSIR Research Space (South Africa)

    Giffen, MH

    1975-01-01

    Full Text Available The diatom flora from several stations on the eastern shore of Saldanha Bay (South Africa) has been studied. Saldanha bay is situated on the western coast of South Africa 110Km north of Cape Town....

  11. South African diatom collection - a future for historic data [SAMSS 2008

    CSIR Research Space (South Africa)

    Van der Molen, J

    2008-07-01

    Full Text Available Diatoms are an important group of micro algae occurring in marine, estuarine and freshwater habitats as phytoplankton and phytobenthos. The species composition at any given time and place is indicative of the prevailing environmental conditions...

  12. Autofluorescence imaging system to discriminate and quantify the distribution of benthic cyanobacteria and diatoms

    DEFF Research Database (Denmark)

    Carreira, Cátia; Staal, Marc Jaap; Middelboe, Mathias

    2015-01-01

    Observation of benthic photoautotrophs on sediment surfaces shows a single algal layer without distinction between photosynthetic groups. Until now it has not been possible to distinguish between benthic photosynthetic microorganisms, i.e. cyanobacteria and diatoms, at μm to mm scales using...... a single nondisruptive system. Chlorophyll autofluorescence can be used to distinguish different photoautotrophic groups if the correct excitation light is applied. Using this principle, a nonintrusive technique was developed to study the spatial distribution of benthic cyanobacteria and diatoms. By means...... of a charge coupled device camera, diatoms and cyanobacteria could be identified by blue light (470 nm) excitation and amber light (600 nm) excitation, respectively. By this approach, diatom or cyanobacterial dominance could be easily distinguished using the blue over amber ratio. We applied this method...

  13. Aulacoseira kruegeriana (Bacillariophyta, Coscinodiscophyceae): a new centric diatom from high-elevation Andean streams of Bolivia

    Czech Academy of Sciences Publication Activity Database

    Morales, E. A.; Rivera, S. F.; Rubin, S. D. C.; Vis, M. L.; Houk, Václav

    2015-01-01

    Roč. 30, č. 3 (2015), s. 269-277 ISSN 0269-249X Institutional support: RVO:67985939 Keywords : centric diatom s * taxonomy * valve ultrastructure Subject RIV: EF - Botanics Impact factor: 1.868, year: 2015

  14. Diatoms: A Novel Source for the Neurotoxin BMAA in Aquatic Environments

    Science.gov (United States)

    Lage, Sandra; Jonasson, Sara; Shams, Shiva; Mehine, Martin; Ilag, Leopold L.; Rasmussen, Ulla

    2014-01-01

    Amyotrophic lateral sclerosis (ALS) or Lou Gehrig’s disease is a neurological disorder linked to environmental exposure to a non-protein amino acid, β-N-methylamino-L-alanine (BMAA). The only organisms reported to be BMAA-producing, are cyanobacteria – prokaryotic organisms. In this study, we demonstrate that diatoms – eukaryotic organisms – also produce BMAA. Ultra-high-performance liquid chromatography coupled with tandem mass spectrometry revealed the occurrence of BMAA in six investigated axenic diatom cultures. BMAA was also detected in planktonic field samples collected on the Swedish west coast that display an overrepresentation of diatoms relative to cyanobacteria. Given the ubiquity of diatoms in aquatic environments and their central role as primary producers and the main food items of zooplankton, the use of filter and suspension feeders as livestock fodder dramatically increases the risk of human exposure to BMAA-contaminated food. PMID:24392143

  15. Phenotypic plasticity of southern ocean diatoms: key to success in the sea ice habitat?

    Directory of Open Access Journals (Sweden)

    Olivia Sackett

    Full Text Available Diatoms are the primary source of nutrition and energy for the Southern Ocean ecosystem. Microalgae, including diatoms, synthesise biological macromolecules such as lipids, proteins and carbohydrates for growth, reproduction and acclimation to prevailing environmental conditions. Here we show that three key species of Southern Ocean diatom (Fragilariopsis cylindrus, Chaetoceros simplex and Pseudo-nitzschia subcurvata exhibited phenotypic plasticity in response to salinity and temperature regimes experienced during the seasonal formation and decay of sea ice. The degree of phenotypic plasticity, in terms of changes in macromolecular composition, was highly species-specific and consistent with each species' known distribution and abundance throughout sea ice, meltwater and pelagic habitats, suggesting that phenotypic plasticity may have been selected for by the extreme variability of the polar marine environment. We argue that changes in diatom macromolecular composition and shifts in species dominance in response to a changing climate have the potential to alter nutrient and energy fluxes throughout the Southern Ocean ecosystem.

  16. Wetland Paleoecological Study of Coastal Louisiana: Sediment Cores and Diatom Samples Dataset

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Wetland sediment data was collected from coastal Louisiana as part of a pilot study to develop a diatom-based proxy for past wetland water chemistry and the...

  17. Photophysiological variability of microphytobenthic diatoms after growth in different types of culture conditions

    NARCIS (Netherlands)

    Forster, R.M.; Martin-Jézéquel, V.R.

    2005-01-01

    Microphytobenthic diatoms have great ecological importance in estuarine and coastal marine ecosystenis, yet many aspects of their physiology have not been investigated under controlled conditions. This work describes patterns in growth rates and photosynthesis in different types of culture for

  18. Diatoms in water quality assessment: to count or not to count them?

    Czech Academy of Sciences Publication Activity Database

    Brabcová, B.; Marvan, P.; Opatřilová, L.; Brabec, K.; Fránková, Markéta; Heteša, J.

    2017-01-01

    Roč. 795, č. 1 (2017), s. 113-127 ISSN 0018-8158 Institutional support: RVO:67985939 Keywords : diatoms * quantification * streams Subject RIV: EH - Ecology, Behaviour Impact factor: 2.056, year: 2016

  19. The characteristics of the diatom' s ecological preferences in the lakes of the Danube Delta

    Directory of Open Access Journals (Sweden)

    TÖRÖK Liliana

    2006-09-01

    Full Text Available During five years of investigation there have been carried out observation on ecological value of the diatoms from Danube Delta’s lakes. The present study provide new data on their sensitivity to environmental conditions.

  20. Effect of holothurian and zoanthid extracts on growth of some bacterial and diatom species

    Digital Repository Service at National Institute of Oceanography (India)

    Gonsalves, C.

    The antifouling properties of the extracts from two zoanthids, viz. Zoanthus sp, Protopalythoa sp and one holothurian species, viz. Holothuria leucospilota occurring in the coastal waters off Goa were tested against 5 bacteria and 2 diatom species...

  1. Diatom silicon biomineralization as an inspirational source of new approaches to silica production

    NARCIS (Netherlands)

    Vrieling, EG; Beelen, TPM; van Santen, RA; Gieskes, WWC

    1999-01-01

    The demand for new materials and products is still growing and the interest in naturally formed biopolymers and biominerals, such as chitin, calcium precipitates and silica is increasing. Photosynthesizing microalgae of the family Bacillariophyceae (diatoms) produce silica exoskeletons with a

  2. Toxic diatoms and domoic acid in natural and iron enriched waters of the oceanic Pacific

    National Research Council Canada - National Science Library

    Mary W. Silver; Sibel Bargu; Susan L. Coale; Claudia R. Benitez-Nelson; Ana C. Garcia; Kathryn J. Roberts; Emily Sekula-Wood; Kenneth W. Bruland; Kenneth H. Coale; M. M. Morel

    2010-01-01

    ...°S) contain the neurotoxin domoic acid (DA), associated with the diatom Pseudo-nitzschia. Of the 35 stations sampled, including ones from historic iron fertilization experiments (SOFeX, IronEx II...

  3. A diatom functional-based approach to assess changing environmental conditions in temporary depressional wetlands

    CSIR Research Space (South Africa)

    Riato, L

    2017-07-01

    Full Text Available factors, wetland depth and total relative evapotranspiration (ETo), were good predictors of diatom species and functional group composition. Low profile guilds dominated by pioneer life-forms showed the strongest relationship with higher disturbance levels...

  4. New and interesting small-celled naviculoid diatoms (Bacillariophyta) from the Maritime Antarctic Region

    Czech Academy of Sciences Publication Activity Database

    Van de Vijver, B.; Kopalová, Kateřina; Zidarova, R.; Cox, E. J.

    2013-01-01

    Roč. 97, 1-2 (2013), s. 189-208 ISSN 0029-5035 Institutional support: RVO:67985939 Keywords : Bacillariophyta * Diatoms * Maritime Antarctic Region Subject RIV: EF - Botanics Impact factor: 0.989, year: 2013

  5. Diatom-based models for inferring water chemistry and hydrology in temporary depressional wetlands

    CSIR Research Space (South Africa)

    Riato, L

    2017-08-01

    Full Text Available Information on the response of temporary depressional wetland diatoms to human-induced disturbances is a limited and important component for the development of temporary wetland biological assessments in human-modified landscapes. Establishing a...

  6. Molecular dynamics of the diatom thylakoid membrane under different light conditions.

    Science.gov (United States)

    Lepetit, Bernard; Goss, Reimund; Jakob, Torsten; Wilhelm, Christian

    2012-03-01

    During the last years significant progress was achieved in unraveling molecular characteristics of the thylakoid membrane of different diatoms. With the present review it is intended to summarize the current knowledge about the structural and functional changes within the thylakoid membrane of diatoms acclimated to different light conditions. This aspect is addressed on the level of the organization and regulation of light-harvesting proteins, the dissipation of excessively absorbed light energy by the process of non-photochemical quenching, and the lipid composition of diatom thylakoid membranes. Finally, a working hypothesis of the domain formation of the diatom thylakoid membrane is presented to highlight the most prominent differences of heterokontic thylakoids in comparison to vascular plants and green algae during the acclimation to low and high light conditions.

  7. Aquatic macroinvertebrate and diatom survey in Tetlin National Wildlife Refuge, AK

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the results from macroinvertebrate and diatom surveys conducted in Desper, Gardiner, and Scottie creeks; lowland streams in Tetlin National...

  8. Molecular fossils of diatoms. Applications in petroleum geochemistry and palaeoenvironmental studies

    Energy Technology Data Exchange (ETDEWEB)

    Rampen, S.W.

    2009-06-11

    Diatoms are one of the major groups of algae which originated relatively recently and evolved in the Late Jurassic/Cretaceous. This thesis presents the results of a comprehensive study of diatom lipids in cultures and in the environment and their applications in the age determination of petroleum and in palaeoenvironmental studies. Diatom DNA sequences were analyzed in order to relate the phylogenetic positions of diatoms to the lipid chemotaxonomy. Forty four different sterols were identified in diatoms, with 24-methylcholesta-5,24(28)-dien-3-beta-ol being most common. 24-Methylcholesta-5,22E-dien-3-beta-ol, previously described as a diatom biomarker, was only the fifth most common sterol and absent in some major diatom groups. All identified sterols have been reported in other algae, but within the diatoms, some sterols and sterol compositions seem to be specific for specific phylogenetic clusters. Sterol compositions confirmed the separate phylogenetic position of the genus Attheya, as also indicated by molecular phylogeny and microscopy. 23-Methyl and 23,24-dimethyl sterols, often associated with dinoflagellate algae, were present in a substantial number of diatoms, suggesting that diatoms may also be a major source. Their phylogenetic position suggests that these diatoms originated from a single common ancestor which evolved in the late Jurassic. In addition to 23-methyl and 23,24-dimethyl sterols, the unusual sterol gorgosterol was found in two diatom cultures of the genus Delphineis. 24-Norsterols were found in the diatom species Thalassiosira aff. antarctica and in dinoflagellate cultures. The evolutionary history of dinoflagellates and diatoms explains the stepwise increases of 24-norsterane concentrations, diagenetic products of 24-norsterols, in petroleum. Long-chain 1,14-diols and 12-hydroxy methyl alkanoates were detected in Proboscia diatoms and may be used as indicators for high-nutrient conditions and upwelling. Their distributions varied between

  9. Diatoms (Bacillariophyceae from the Valley of the Great Lakes in Western Mongolia

    Directory of Open Access Journals (Sweden)

    Mark B. Edlund

    2010-06-01

    Full Text Available T he Valley of the Great Lakes (VOGL in western Mongolia is dominated by two main (Uvs, Khyargas and many minor closed basin lake systems. In 2004 and 2005, we sampled diatom communities from the surfi cial sediment of 64 lakes in the western Mongolian provinces of Uvs, Khovd, Zavkhan, and Bayan-Ulgii. Lakes ranged in water chemistry from fresh to hypersaline, oligotrophic to hypertrophic, and from low elevation VOGL lakes to high elevation lakes in the Altai Mountains. Over 300 diatom species were identifi ed in the sediment samples including a diverse fl ora limited to saline lakes, many widespread taxa, many new reports for the Mongolian diatom fl ora, and several new and possibly endemic species. We also review recent diatom literature from Mongolia including fl oristic surveys, paleo-ecology, and water quality studies.

  10. Diatom community structure along physicochemical gradients in upland river segments of Tamiraparani river system, South India

    Directory of Open Access Journals (Sweden)

    Meenakshisundaram Amutha

    2017-01-01

    Full Text Available This study examines the diversity and distributional patterns of benthic diatom assemblages in the upland streams of Tamiraparani River system, southern part of Western Ghats of Peninsular India. A total of 168 benthic diatoms representing 16 orders, 32 families, and 47 genera were enumerated. Structuring of diatom community was dependent on the environmental conditions of the respective habitats. Canonical correspondence analysis described both physical habitat quality and water parameter gradient and factors that correlated significantly were substrate type, water temperature, dissolved oxygen and nitrate content. Gomphonema gandhii, Cocconeis placentula and Navicula cuspidate were strongly associated with sites with embedded substrates and clear water. Diatoms could be effective in assessing physical habitat alterations in streams.

  11. Allelopathic effects of diatom filtrates on the toxic benthic dinoflagellate Ostreopsis cf. ovata.

    Science.gov (United States)

    Pichierri, Salvatore; Accoroni, Stefano; Pezzolesi, Laura; Guerrini, Franca; Romagnoli, Tiziana; Pistocchi, Rossella; Totti, Cecilia

    2017-10-01

    Ostreopsis blooms regularly occur in many Mediterranean coastal areas in late summer-autumn. In the northern Adriatic Sea, Ostreopsis blooms affect diatom-dominated microphytobenthic communities. In this study, the effects of the filtrates of some diatom species, both benthic (Tabularia affinis, Proschkinia complanatoides and Navicula sp.) and planktonic (Thalassiosira sp. and Skeletonema marinoi) on cell morphology, cytological features and growth of O. cf. ovata were investigated. Our results showed a marked decrease of O. cf. ovata growth when cells were exposed to all diatom filtrates tested. The highest inhibitions were observed for exposures to P. complanatoides and Navicula sp. filtrates (92.5% and 80%, respectively) and increased with the age of diatom culture. Moreover, a clear DNA degradation and abnormal forms of O. cf. ovata cells (83.8% of the total) were found at the highest concentrations using Navicula sp. filtrate after 10 days of the inoculum. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. USE OF DIATOMS TO ASSES WATER QUALITY OF ANTHROPOGENICALLY MODIFIED MATYSÓWKA STREAM

    Directory of Open Access Journals (Sweden)

    Teresa Noga

    2013-04-01

    Full Text Available Matysówka stream is small, under 6 km long watercourse, which is a right-bank tributary of Strug River. In 2009–2011studies on the subject of diversity of diatom communities using diatom indices IPS, GDI and TDI for water quality assessment were conducted. On the stream 271 diatom taxa were identified, among which: Achnanthidium minutissimum var. minutissimum, Navicula cryptotenella, N. gregaria, N. lanceolata, N. tripunctata, Nitzschia linearis, N. pusilla, N. recta, Planothidium frequentissimum, Rhoicosphenia abbreviata were the most frequent. Middle and lower section of Matysówka stream was characterized by increased concentrations of phosphates, nitrites, ammonium, total phosphorus and nitrogen, BOD5. On the basis of diatom indices IPS and GDI waters were characterized as III–IV quality classes, while the TDI index revealed the worst water quality classes (IV–V.

  13. Modern Diatom Distributions in Guanabara Bay Sediment and Oceanic Areas, Rio de Janeiro (Brazil

    Directory of Open Access Journals (Sweden)

    Frederico S. Silva

    2011-01-01

    Full Text Available One hundred and fifty three superficial sediments were collected in Guanabara Bay to physical-chemistry and diatom analyses in the ambit to Monitoring Project (CENPES/PETROBRAS. A total of 146 taxa of diatoms were identified where the most frequent taxa in Guanabara Bay were Amphora spp., Coscinodiscus spp. and Navicula yarrensis var. yarrensis. These species are potentially harmful that might harm fisheries and mariculture during blooms. The values of ecological indexes like richness and diversity followed the estuarine gradient were the higher values were found in the mouth and de low in the inner part. The multivariate analyzes permitted recognize seven diatom assemblages in the bay. The DCA analyze shows the most influence in the distribution of assemblages were the depth and pH. The diatom assemblages analyze proved to be an efficient tool in the environmental diagnosis of Guanabara Bay.

  14. Diatom species composition in the Raška river (Southwestern Serbia

    Directory of Open Access Journals (Sweden)

    Vidaković Danijela P.

    2015-01-01

    Full Text Available The paper presents data on the composition of epilithic diatoms in the Raška River. Samples were collected by scraping stone surfaces with a brush from 5 localities along the Raška River in April, June, August and November 2011 and March and May 2012. Diatom frustules were cleaned using cold acid method, and mounted on permanent slides. An investigation of the Raška River resulted in description of 106 diatom taxa. The most species rich genera are Navicula (10, Gomphonema (10 and Nitzschia (9, while other genera are presented with one or more species. Detailed floristic analysis of the benthic diatom flora in this river has not been conducted before. Therefore, this paper provides a groundwork for future researches. [Projekat Ministarstva nauke Republike Srbije, br. TR 037009

  15. Diatoms as indicators of water quality in the Jukskei-Crocodile river ...

    African Journals Online (AJOL)

    2005-04-02

    Apr 2, 2005 ... provide a reflection of water quality based on the specific pollu- tion tolerances .... modern diatom pollution indices that have been developed and tested over ...... Publishing Company, Houston, Texas. pp 251-281. ZELINKA M ...

  16. Marine diatoms in polar and sub-polar environments and their application to Late Pleistocene paleoclimate reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Crosta, Xavier, E-mail: x.crosta@epoc.u-bordeaux1.fr [UMR-CNRS 5805 EPOC, Universite Bordeaux 1, Avenue des Facultes, 33405 Talence Cedex (France)

    2011-05-15

    Diatoms are one of the major phytoplankton groups in polar and sub-polar marine environments along with green algae and chrysophytes. Diatoms are composed of two components, a two-valve test made of amorphous silica and an organic cell encapsulated into the test. Mucilage covering the test and proteins embedded in the silica lattice of the test completes the organic pool of the diatoms. The preservation of these two components into deep-sea sediments allows for a large set of diatom-based proxies to infer past oceanographic and climatic changes in polar and sub-polar marine environments. Most diatom species in polar and sub-polar marine environments exhibit a narrow range of ecological preferences, especially in terms of sea-surface temperature and sea ice conditions. Preserved diatom assemblages in deep-sea sediments mirror the diatom assemblages in the phytoplankton. It is subsequently possible to extrapolate the relationships between diatom assemblages in surface sediments and modern parameters to down-core fossil assemblages to document past changes in sea-surface temperatures and sea ice conditions. Congruent analysis of biogenic silica and organic carbon and stable isotope ratios (O, Si in the silica matrix and C, N in the diatom-intrinsic organic matter) provides information on siliceous productivity, nutrient cycling and water mass circulation. Measurements of diatom biomarkers give complementary information on sea ice conditions and siliceous productivity.

  17. Processing and characterization of diatom nanoparticles and microparticles as potential source of silicon for bone tissue engineering.

    Science.gov (United States)

    Le, Thi Duy Hanh; Bonani, Walter; Speranza, Giorgio; Sglavo, Vincenzo; Ceccato, Riccardo; Maniglio, Devid; Motta, Antonella; Migliaresi, Claudio

    2016-02-01

    Silicon plays an important role in bone formation and maintenance, improving osteoblast cell function and inducing mineralization. Often, bone deformation and long bone abnormalities have been associated with silica/silicon deficiency. Diatomite, a natural deposit of diatom skeleton, is a cheap and abundant source of biogenic silica. The aim of the present study is to validate the potential of diatom particles derived from diatom skeletons as silicon-donor materials for bone tissue engineering applications. Raw diatomite (RD) and calcined diatomite (CD) powders were purified by acid treatments, and diatom microparticles (MPs) and nanoparticles (NPs) were produced by fragmentation of purified diatoms under alkaline conditions. The influence of processing on the surface chemical composition of purified diatomites was evaluated by X-ray photoelectron spectroscopy (XPS). Diatoms NPs were also characterized in terms of morphology and size distribution by transmission electron microscopy (TEM) and Dynamic light scattering (DLS), while diatom MPs morphology was analyzed by scanning electron microscopy (SEM). Surface area and microporosity of the diatom particles were evaluated by nitrogen physisorption methods. Release of silicon ions from diatom-derived particles was demonstrated using inductively coupled plasma optical emission spectrometry (ICP/OES); furthermore, silicon release kinetic was found to be influenced by diatomite purification method and particle size. Diatom-derived microparticles (MPs) and nanoparticles (NPs) showed limited or no cytotoxic effect in vitro depending on the administration conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Diatoms as an indicator for tile drainage flow in a German lowland catchment

    Science.gov (United States)

    Wu, Naicheng; Faber, Claas; Ulrich, Uta; Schmalz, Britta; Fohrer, Nicola

    2014-05-01

    The separation of flow components within a model simulation is of great importance for a successful implementation of management measures. Tracers are commonly used to identify and assess runoff-generating processes and to detect sources of stream flow components within a target catchment. Diatoms could be an ideal tracer due to their diverse preferences to different aquatic habitats (van Dam et al. 1994, Pfister et al. 2009). As a part of a DFG (Deutsche Forschungsgemeinschaft) project, we collected diatom samples of 9 sites (4 tile drainage, and 5 river sites) weekly or biweekly from March to July 2013 in a German lowland catchment (the Kielstau catchment). First results showed that diatom species Achnanthes lanceolata, Fragilaria biceps and Navicula ingapirca dominated in tile drainage flow with relative abundances of 22.2%, 21.5% and 10.9%, respectively. For river sites, the most abundant species was Navicula cryptocephala (20.5%), followed by Fragilaria biceps (12.9%), Cyclotella meneghiniana (9.5%) and Achnanthes lanceolata (9.3%). Compared with river sites, tile drainage flow had lower diatom density, biomass, species richness and percentage of Aquatic/Riparian diatoms (AqRi%). However, the proportion of Riparian diatoms (RiZo%) increased at tile drainage flow. Indicator value method (IndVal) revealed that the two water types were characterized by different indicator species. Fifteen taxa (e.g. Cocconeis placentula, Cyclotella meneghiniana, Navicula cryptocephala and Fragilaria biceps) were significant indicators for river sites. Achnanthes lanceolata, Achnanthes minutissima and Navicula ingapirca were significant indicators for tile drainage flow. These results highlight the suitability of diatoms as an indicator for tile drainage flow. Spatial and temporal variations of diatom community should be considered in future surveys. Keywords: Diatoms, Flow components, Indicator value method, Tracer References: Pfister, L., J. J. McDonnell, S. Wrede, D. Hl

  19. Intracellular Nitrate of Marine Diatoms as a Driver of Anaerobic Nitrogen Cycling in Sinking Aggregates

    Science.gov (United States)

    Kamp, Anja; Stief, Peter; Bristow, Laura A.; Thamdrup, Bo; Glud, Ronnie N.

    2016-01-01

    Diatom-bacteria aggregates are key for the vertical transport of organic carbon in the ocean. Sinking aggregates also represent pelagic microniches with intensified microbial activity, oxygen depletion in the center, and anaerobic nitrogen cycling. Since some of the aggregate-forming diatom species store nitrate intracellularly, we explored the fate of intracellular nitrate and its availability for microbial metabolism within anoxic diatom-bacteria aggregates. The ubiquitous nitrate-storing diatom Skeletonema marinoi was studied as both axenic cultures and laboratory-produced diatom-bacteria aggregates. Stable 15N isotope incubations under dark and anoxic conditions revealed that axenic S. marinoi is able to reduce intracellular nitrate to ammonium that is immediately excreted by the cells. When exposed to a light:dark cycle and oxic conditions, S. marinoi stored nitrate intracellularly in concentrations >60 mmol L-1 both as free-living cells and associated to aggregates. Intracellular nitrate concentrations exceeded extracellular concentrations by three orders of magnitude. Intracellular nitrate was used up within 2–3 days after shifting diatom-bacteria aggregates to dark and anoxic conditions. Thirty-one percent of the diatom-derived nitrate was converted to nitrogen gas, indicating that a substantial fraction of the intracellular nitrate pool of S. marinoi becomes available to the aggregate-associated bacterial community. Only 5% of the intracellular nitrate was reduced to ammonium, while 59% was recovered as nitrite. Hence, aggregate-associated diatoms accumulate nitrate from the surrounding water and sustain complex nitrogen transformations, including loss of fixed nitrogen, in anoxic, pelagic microniches. Additionally, it may be expected that intracellular nitrate not converted before the aggregates have settled onto the seafloor could fuel benthic nitrogen transformations. PMID:27847498

  20. Role of Diatoms in the Spatial-Temporal Distribution of Intracellular Nitrate in Intertidal Sediment

    Science.gov (United States)

    Stief, Peter; Kamp, Anja; de Beer, Dirk

    2013-01-01

    Intracellular nitrate storage allows microorganisms to survive fluctuating nutrient availability and anoxic conditions in aquatic ecosystems. Here we show that diatoms, ubiquitous and highly abundant microalgae, represent major cellular reservoirs of nitrate in an intertidal flat of the German Wadden Sea and are potentially involved in anaerobic nitrate respiration. Intracellular nitrate (ICNO3) was present year-round in the sediment and was spatially and temporally correlated with fucoxanthin, the marker photopigment of diatoms. Pyrosequencing of SSU rRNA genes of all domains of life confirmed that ICNO3 storage was most likely due to diatoms rather than other known nitrate-storing microorganisms (i.e., large sulfur bacteria and the eukaryotic foraminifers and gromiids). Sedimentary ICNO3 concentrations reached up to 22.3 µmol dm-3 at the sediment surface and decreased with sediment depth to negligible concentrations below 5 cm. Similarly, the ICNO3/fucoxanthin ratio and porewater nitrate (PWNO3) concentrations decreased with sediment depth, suggesting that ICNO3 of diatoms is in equilibrium with PWNO3, but is enriched relative to PWNO3 by 2-3 orders of magnitude. Cell-volume-specific ICNO3 concentrations in a diatom mat covering the sediment surface during spring were estimated at 9.3-46.7 mmol L-1. Retrieval of 18S rRNA gene sequences related to known nitrate-storing and nitrate-ammonifying diatom species suggested that diatoms in dark and anoxic sediment layers might be involved in anaerobic nitrate respiration. Due to the widespread dominance of diatoms in microphytobenthos, the total nitrate pool in coastal marine sediments may generally be at least two times larger than derived from porewater measurements and partially be recycled to ammonium. PMID:24023845

  1. The effect of bacteria on diatom community structure - The 'antibiotics' approach

    Digital Repository Service at National Institute of Oceanography (India)

    DeCosta, P.M.; Anil, A.C.

    adhere to a substratum (Wigglesworth- Cooksey and Cooksey, 2005), and sediment stabilization by diatoms (Gerbersdorf et al., 2008; Wigglesworth-Cooksey et al., 2001). Though a lot of information is available about the relevance of bacteria to diatoms... (Guillard and Ryther, 1962) prepared in autoclaved, artificial seawater (MBL) (Cavanaugh, 1975) was used as the control diluent (CONT). Nutrient-enriched f/2 medium prepared in autoclaved, 0.45 µm-filtered, aged seawater [f/2(ASW)] was used...

  2. Eco-biology of marine diatoms with emphasis on the influence of physico-chemical parameters

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.

    role in the benthic community (Fig. 6.1). Vertical migratory behavior of benthic diatoms is one of the adaptive strategies employed for a life in intertidal habitats. This self-initiated migration helps diatoms to move to the surface during low tides... of microphytobenthos to migrate vertically within the surface sediment when their requirements are fulfilled may be considered as a form of behavioral photoacclimation, allowing cells to avoid potentially 166 damaging irradiance and temperature conditions (Kromkamp...

  3. Efficiency of copper and cupronickel substratum to resist development of diatom biofilms

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, J.S.; Anil, A.C.

    coatings are widely used as component in the marine structures because of their biofouling and corrosion resistance (Stanczak 2004).At present there are several reports that describe the diatoms colonization/communities on Cu based antifouling surfaces... nature of the substratum (Chamberlain and Garner, 1988; French and Evans, 1988) and (iii) different sensitivities of diatoms towards toxic panels (Molino et al., 2009). Earlier study by Sawant et al. (1995) on corrosion and microfouling of Cu and Cu...

  4. Intracellular Nitrate of Marine Diatoms as a Driver of Anaerobic Nitrogen Cycling in Sinking Aggregates

    Directory of Open Access Journals (Sweden)

    Anja Kamp

    2016-11-01

    Full Text Available Diatom-bacteria aggregates are key for the vertical transport of organic carbon in the ocean. Sinking aggregates also represent pelagic microniches with intensified microbial activity, oxygen depletion in the center, and anaerobic nitrogen cycling. Since some of the aggregate-forming diatom species store nitrate intracellularly, we explored the fate of intracellular nitrate and its availability for microbial metabolism within anoxic diatom-bacteria aggregates. The ubiquitous nitrate-storing diatom Skeletonema marinoi was studied as both axenic cultures and laboratory-produced diatom-bacteria aggregates. Stable 15N isotope incubations under dark and anoxic conditions revealed that axenic S. marinoi is able to reduce intracellular nitrate to ammonium that is immediately excreted by the cells. When exposed to a light:dark cycle and oxic conditions, S. marinoi stored nitrate intracellularly in concentrations > 60 mmol L-1 both as free-living cells and associated to aggregates. Intracellular nitrate concentrations exceeded extracellular concentrations by three orders of magnitude. Intracellular nitrate was used up within 2-3 days after shifting diatom-bacteria aggregates to dark and anoxic conditions. Thirty-one percent of the diatom-derived nitrate was converted to nitrogen gas, indicating that a substantial fraction of the intracellular nitrate pool of S. marinoi becomes available to the aggregate-associated bacterial community. Only 5% of the intracellular nitrate was reduced to ammonium, while 59% was recovered as nitrite. Hence, aggregate-associated diatoms accumulate nitrate from the surrounding water and sustain complex nitrogen transformations, including loss of fixed nitrogen, in anoxic, pelagic microniches. Additionally, it may be expected that intracellular nitrate not converted before the aggregates have settled onto the seafloor could fuel benthic nitrogen transformations.

  5. Decadal variations in diatoms and dinoflagellates on the inner shelf of the East China Sea, China

    Science.gov (United States)

    Abate, Rediat; Gao, Yahui; Chen, Changping; Liang, Junrong; Mu, Wenhua; Kifile, Demeke; Chen, Yanghang

    2017-11-01

    Diatoms and dinoflagellates are two major groups of phytoplankton that flourish in the oceans, particularly in coastal zone and upwelling systems, and their contrasting production have been reported in several world seas. However, this information is not available in the coastal East China Sea (ECS). Thus, to investigate and compare the decadal trends in diatoms and dinoflagellates, a sediment core, 47 cm long, was collected from the coastal zone of the ECS. Sediment chlorophyll- a (Chl- a), phytoplankton-group specific pigment signatures of diatoms and dinoflagellates, and diatom valve concentrations were determined. The sediment core covered the period from 1961 to 2011 AD. The chlorophyll- a contents ranged from 2.32 to 73 µg/g dry sediment (dw) and averaged 9.81 µg/g dw. Diatom absolute abundance ranged from 29152 to 177501 valve/gram (v/g) dw and averaged 72137 v/g dw. Diatom valve and diatom specific pigment marker concentrations were not significantly correlated. Peridinin increased after the 1980s in line with intensified use of fertilizer and related increases in nutrient inputs into the marine environment. The increased occurrence of dinoflagellate dominance after the 1980s can be mostly explained by the increase in nutrients. However, the contribution of dinoflagellates to total phytoplankton production (Chl- a) decreased during the final decade of this study, probably because of the overwhelming increase in diatom production that corresponded with the construction of the Three Gorges Dam (TGD) and related light availability. Similarly, the mean ratio of fucoxanthin/peridinin for the period from 1982 to 2001 was 6% less than for 1961 to 1982, while the ratio for 2001 to 2011 was 45.3% greater than for 1982 to 2001. The decadal variation in the fucoxanthin/peridinin ratio implies that dinoflagellate production had been gradually increasing until 2001. We suggest that the observed changes can be explained by anthropogenic impacts, such as nutrient

  6. Distribution patterns of epilithic diatoms along climatic, spatial and physicochemical variables in the Baltic Sea

    OpenAIRE

    Virta, Leena; Soininen, Janne

    2017-01-01

    Abstract The species richness and community composition of the diatom communities were studied in the Baltic Sea, Northern Europe, to enhance knowledge about the diversity of these organisms in a brackish water ecosystem. Many organisms in the Baltic Sea have been studied extensively, but studies investigating littoral diatoms are scarce. The goal of this study was to examine the importance of climatic, spatial and water physicochemical variables as drivers of epilithic diato...

  7. Large centric diatoms allocate more cellular nitrogen to photosynthesis to counter slower RUBISCO turnover rates

    Directory of Open Access Journals (Sweden)

    Yaping eWu

    2014-12-01

    Full Text Available Diatoms contribute ~40% of primary production in the modern ocean and encompass the largest cell size range of any phytoplankton group. Diatom cell size influences their nutrient uptake, photosynthetic light capture, carbon export efficiency, and growth responses to increasing pCO2. We therefore examined nitrogen resource allocations to the key protein complexes mediating photosynthesis across six marine centric diatoms, spanning 5 orders of magnitude in cell volume, under past, current and predicted future pCO2 levels, in balanced growth under nitrogen repletion. Membrane bound photosynthetic protein concentrations declined with cell volume in parallel with cellular concentrations of total protein, total nitrogen and chlorophyll. Larger diatom species, however, allocated a greater fraction (by 3.5 fold of their total cellular nitrogen to the soluble RUBISCO carbon fixation complex than did smaller species. Carbon assimilation per unit of RUBISCO large subunit (C RbcL-1 s-1 decreased with cell volume, from ~8 to ~2 C RbcL-1 s-1 from the smallest to the largest cells. Whilst a higher allocation of cellular nitrogen to RUBISCO in larger cells increases the burden upon their nitrogen metabolism, the higher RUBISCO allocation buffers their lower achieved RUBISCO turnover rate to enable larger diatoms to maintain carbon assimilation rates per total protein comparable to small diatoms. Individual species responded to increased pCO2, but cell size effects outweigh pCO2 responses across the diatom species size range examined. In large diatoms a higher nitrogen cost for RUBISCO exacerbates the higher nitrogen requirements associated with light absorption, so the metabolic cost to maintain photosynthesis is a cell size-dependent trait.

  8. Refinement of the Diatom Episome Maintenance Sequence and Improvement of Conjugation-based DNA Delivery Methods

    Directory of Open Access Journals (Sweden)

    Rachel E Diner

    2016-08-01

    Full Text Available Conjugation of episomal plasmids from bacteria to diatoms advances diatom genetic manipulation by simplifying transgene delivery and providing a stable and consistent gene expression platform. To reach its full potential, this nascent technology requires new optimized expression vectors and a deeper understanding of episome maintenance. Here we present the development of an additional diatom vector (pPtPBR1, based on the parent plasmid pBR322, to add a plasmid maintained at medium copy number in E. coli to the diatom genetic toolkit. Using this new vector, we evaluated the contribution of individual yeast DNA elements comprising the 1.4-kb tripartite CEN6-ARSH4-HIS3 sequence that enables episome maintenance in P. tricornutum. While various combinations of these individual elements enable efficient conjugation and high ex-conjugant yield in P. tricornutum, individual elements alone do not. Conjugation of episomes containing CEN6-ARSH4 and a small sequence from the low GC content 3’ end of HIS3 produced the highest number of diatom ex-conjugant colonies, resulting in a smaller and more efficient vector design. Our findings suggest that the CEN6 and ARSH4 sequences function differently in yeast and diatoms, and that low GC content regions of greater than ~500 bp are a potential indicator of a functional diatom episome maintenance sequence. Additionally, we have developed improvements to the conjugation protocol including a higher-throughput option utilizing 12-well plates, and plating methods that improve ex-conjugant yield and reduce time and materials required for the conjugation protocol. The data presented offer additional information regarding the mechanism by which the yeast-derived sequence enables diatom episome maintenance, and demonstrate options for flexible vector design.

  9. An experiment to assess the effects of diatom dissolution on oxygen isotope ratios.

    Science.gov (United States)

    Smith, Andrew C; Leng, Melanie J; Swann, George E A; Barker, Philip A; Mackay, Anson W; Ryves, David B; Sloane, Hilary J; Chenery, Simon R N; Hems, Mike

    2016-01-30

    Current studies which use the oxygen isotope composition from diatom silica (δ(18) Odiatom ) as a palaeoclimate proxy assume that the δ(18) Odiatom value reflects the isotopic composition of the water in which the diatom formed. However, diatoms dissolve post mortem, preferentially losing less silicified structures in the water column and during/after burial into sediments. The impact of dissolution on δ(18) Odiatom values and potential misinterpretation of the palaeoclimate record are evaluated. Diatom frustules covering a range of ages (6 samples from the Miocene to the Holocene), environments and species were exposed to a weak alkaline solution for 48 days at two temperatures (20 °C and 4 °C), mimicking natural dissolution post mucilage removal. Following treatment, dissolution was assessed using scanning electron microscope images and a qualitative diatom dissolution index. The diatoms were subsequently analysed for their δ(18) O values using step-wise fluorination and isotope ratio mass spectrometry. Variable levels of diatom dissolution were observed between the six samples; in all cases higher temperatures resulted in more frustule degradation. Dissolution was most evident in younger samples, probably as a result of the more porous nature of the silica. The degree of diatom dissolution does not directly equate to changes in the isotope ratios; the δ(18) Odiatom value was, however, lower after dissolution, but in only half the samples was this reduction outside the analytical error (2σ analytical error = 0.46‰). We have shown that dissolution can have a small negative impact on δ(18) Odiatom values, causing reductions of up to 0.59‰ beyond analytical error (0.46‰) at natural environmental temperatures. These findings need to be considered in palaeoenvironmental reconstructions using δ(18) Odiatom values, especially when interpreting variations in these values of <1‰. Copyright © 2015 John Wiley & Sons, Ltd.

  10. Marennine, Promising Blue Pigments from a Widespread Haslea Diatom Species Complex

    OpenAIRE

    Romain Gastineau; François Turcotte; Jean-Bernard Pouvreau; Michèle Morançais; Joël Fleurence; Eko Windarto; Fiddy Semba Prasetiya; Sulastri Arsad; Pascal Jaouen; Mathieu Babin; Laurence Coiffard; Céline Couteau; Jean-François Bardeau; Boris Jacquette; Vincent Leignel

    2014-01-01

    In diatoms, the main photosynthetic pigments are chlorophylls a and c, fucoxanthin, diadinoxanthin and diatoxanthin. The marine pennate diatom Haslea ostrearia has long been known for producing, in addition to these generic pigments, a water-soluble blue pigment, marennine. This pigment, responsible for the greening of oysters in western France, presents different biological activities: allelopathic, antioxidant, antibacterial, antiviral, and growth-inhibiting. A method to extract and purify ...

  11. Solid self-emulsifying phospholipid suspension (SSEPS) with diatom as a drug carrier.

    Science.gov (United States)

    Milović, Mladen; Simović, Spomenka; Lošić, Dušan; Dashevskiy, Andriy; Ibrić, Svetlana

    2014-10-15

    We report the application of diatom as a solid carrier for water insoluble drugs applied in oral drug delivery system based on the self-emulsifying drug delivery system (SEDDS) caprylocaproyl macrogol-8 glycerides/lecithin/propylene glycol/caprylic/capric triglyceride. Diatoms are fossilized skeletons of photosynthetic algae with complex 3-dimensional (3D), porous structure consisting of amorphous silica, obtained by purification of diatomaceous earth. Different solid samples of carbamazepine (CBZ) suspension in SEDDS, called solid self-emulsifying phospholipid suspension (SSEPS), were prepared using two methods: adsorption of CBZ dispersion in SEDDS by gentle mixing with diatoms in mortar with pestle (Method A) or dispersion of diatoms in ethanol solution of CBZ and SEDDS components, followed by ethanol evaporation (Method B). Release rate of CBZ from SSEPS was significantly higher in comparison to pure drug, physical mixture of diatoms and CBZ as well as solid dispersion of pure CBZ and diatoms obtained by ethanol evaporation. The dissolution of CBZ from SSEPS sample prepared using method B was faster than from the sample prepared by the method A. Higher dissolution for sample prepared by the method B can be attributed to the partial adsorption (deeper localization) of liquid material inside the pores of diatoms. Upon storage of the samples under accelerated conditions (40°C and 70% RH) for 10 weeks no significant changes in CBZ crystallinity and dissolution was in case of SSEPS, contrary to solid dispersion with increased crystallinity, indicating that diatoms with adsorbed liquid CBZ-loaded SEPS can maintain initial CBZ characteristics. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. A model for carbohydrate metabolism in the diatom Phaeodactylum tricornutum deduced from comparative whole genome analysis.

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    Peter G Kroth

    Full Text Available BACKGROUND: Diatoms are unicellular algae responsible for approximately 20% of global carbon fixation. Their evolution by secondary endocytobiosis resulted in a complex cellular structure and metabolism compared to algae with primary plastids. METHODOLOGY/PRINCIPAL FINDINGS: The whole genome sequence of the diatom Phaeodactylum tricornutum has recently been completed. We identified and annotated genes for enzymes involved in carbohydrate pathways based on extensive EST support and comparison to the whole genome sequence of a second diatom, Thalassiosira pseudonana. Protein localization to mitochondria was predicted based on identified similarities to mitochondrial localization motifs in other eukaryotes, whereas protein localization to plastids was based on the presence of signal peptide motifs in combination with plastid localization motifs previously shown to be required in diatoms. We identified genes potentially involved in a C4-like photosynthesis in P. tricornutum and, on the basis of sequence-based putative localization of relevant proteins, discuss possible differences in carbon concentrating mechanisms and CO(2 fixation between the two diatoms. We also identified genes encoding enzymes involved in photorespiration with one interesting exception: glycerate kinase was not found in either P. tricornutum or T. pseudonana. Various Calvin cycle enzymes were found in up to five different isoforms, distributed between plastids, mitochondria and the cytosol. Diatoms store energy either as lipids or as chrysolaminaran (a beta-1,3-glucan outside of the plastids. We identified various beta-glucanases and large membrane-bound glucan synthases. Interestingly most of the glucanases appear to contain C-terminal anchor domains that may attach the enzymes to membranes. CONCLUSIONS/SIGNIFICANCE: Here we present a detailed synthesis of carbohydrate metabolism in diatoms based on the genome sequences of Thalassiosira pseudonana and Phaeodactylum tricornutum

  13. STUDY OF THE DIATOM COMMUNITIES UPSTREAM THE BÂRZAVA RIVER

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    Bianca CÎRJEU

    2013-12-01

    Full Text Available This study aimed the qualitative and quantitative determination of the diatom community, and for this it was necessary to identify and monitor the diatom flora of the Bârzava river. Further processing, targeted specific abundance and genres, as well as synthetic assessment of their saprobic preferences. Following determinations resulted 89 species divided into 25 genres. The richest in species, is the Cymbella genre, followed by Navicula and Achnanthes.

  14. Evolutionary origins and functions of the carotenoid biosynthetic pathway in marine diatoms.

    Directory of Open Access Journals (Sweden)

    Sacha Coesel

    Full Text Available Carotenoids are produced by all photosynthetic organisms, where they play essential roles in light harvesting and photoprotection. The carotenoid biosynthetic pathway of diatoms is largely unstudied, but is of particular interest because these organisms have a very different evolutionary history with respect to the Plantae and are thought to be derived from an ancient secondary endosymbiosis between heterotrophic and autotrophic eukaryotes. Furthermore, diatoms have an additional xanthophyll-based cycle for dissipating excess light energy with respect to green algae and higher plants. To explore the origins and functions of the carotenoid pathway in diatoms we searched for genes encoding pathway components in the recently completed genome sequences of two marine diatoms. Consistent with the supplemental xanthophyll cycle in diatoms, we found more copies of the genes encoding violaxanthin de-epoxidase (VDE and zeaxanthin epoxidase (ZEP enzymes compared with other photosynthetic eukaryotes. However, the similarity of these enzymes with those of higher plants indicates that they had very probably diversified before the secondary endosymbiosis had occurred, implying that VDE and ZEP represent early eukaryotic innovations in the Plantae. Consequently, the diatom chromist lineage likely obtained all paralogues of ZEP and VDE genes during the process of secondary endosymbiosis by gene transfer from the nucleus of the algal endosymbiont to the host nucleus. Furthermore, the presence of a ZEP gene in Tetrahymena thermophila provides the first evidence for a secondary plastid gene encoded in a heterotrophic ciliate, providing support for the chromalveolate hypothesis. Protein domain structures and expression analyses in the pennate diatom Phaeodactylum tricornutum indicate diverse roles for the different ZEP and VDE isoforms and demonstrate that they are differentially regulated by light. These studies therefore reveal the ancient origins of several

  15. Iron Availability Influences Silicon Isotope Fractionation in Two Southern Ocean Diatoms (Proboscia inermis and Eucampia antarctica and a Coastal Diatom (Thalassiosira pseudonana

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    Scott Meyerink

    2017-07-01

    Full Text Available The fractionation of silicon (Si isotopes was measured in two Southern Ocean diatoms (Proboscia inermis and Eucampia Antarctica and a coastal diatom (Thalassiosira pseudonana that were grown under varying iron (Fe concentrations. Varying Fe concentrations had no effect on the Si isotope enrichment factor (ε in T. pseudonana, whilst E. Antarctica and P. inermis exhibited significant variations in the value of ε between Fe-replete and Fe-limited conditions. Mean ε values in P. inermis and E. Antarctica decreased from (± 1SD −1.11 ± 0.15‰ and −1.42 ± 0.41 ‰ (respectively under Fe-replete conditions, to −1.38 ± 0.27 ‰ and −1.57 ± 0.5 ‰ (respectively under Fe-limiting conditions. These variations likely arise from adaptations in diatoms arising from the nutrient status of their environment. T. pseudonana is a coastal clone typically accustomed to low Si but high Fe conditions whereas E. Antarctica and P. inermis are typically accustomed to High Si, High nitrate low Fe conditions. Growth induced variations in silicic acid (Si(OH4 uptake arising from Fe-limitation is the likely mechanism leading to Si-isotope variability in E. Antarctica and P. inermis. The multiplicative effects of species diversity and resource limitation (e.g., Fe on Si-isotope fractionation in diatoms can potentially alter the Si-isotope composition of diatom opal in diatamaceous sediments and sea surface Si(OH4. This work highlights the need for further in vitro studies into intracellular mechanisms involved in Si(OH4 uptake, and the associated pathways for Si-isotope fractionation in diatoms.

  16. Antifouling agents against the benthic marine diatom,Navicula salinicola Homarine from the gorgoniansLeptogorgia virgulata andL. setacea and analogs.

    Science.gov (United States)

    Targett, N M; Bishop, S S; McConnell, O J; Yoder, J A

    1983-07-01

    At concentrations found in the gorgonian corals,Leptogorgia virgulata (L.) andL. setacea (L.), homarine (N-methyl-2-carboxypyridine) and water-soluble extracts from the gorgonians that contained homarine inhibited the growth of the potential fouling diatom.Navicula salinicola Hust., by 50-60%. Homarine comprised 0.3 and 0.25% of the fresh weight ofL. virgulata andL. setacea, respectively, and the water-soluble extracts comprised 4.0 and 3.0% of the fresh weight of the gorgonians, respectively. Three compounds structurally related to homarine including, in order of most to least active, nicotinic acid, picolinic acid, and pyridine, also reduced growth ofN. salinicola. The activity of these compounds in the diatom assay suggests that the carboxyl group at the 2 position of the pyridine ring is important for activity and thatN-methylation is not important. We conclude that chemical defense against fouling is operative inLeptogorgia species. Evidence from the literature for combined chemical and mechanical defenses byLeptogorgia and other organisms against fouling is presented.

  17. Diatom culture media contain extracellular silica nanoparticles which form opalescent films

    Science.gov (United States)

    Losic, Dusan; Mitchell, James G.; Voelcker, Nicolas H.

    2008-12-01

    Diatoms are unicellular photosynthetic algae with enormous diversity of patterns in their silica structures at the nano- to micronscale. In this study, we present results, which support the hypothesis that silica nanoparticles are released into the diatom culture medium. The formation of an opalescent film by the self-assembly of silica nanoparticles produced in the growth medium of diatoms. This film was formed on the filter paper from the culture medium of a Coscinodiscus sp. culture. A numbers of diatoms with partially opened valves were observed on the film surface under light microscopy and SEM, which indicates that cell contents inside of diatoms had been released into the culture solution. AFM images of produced opalescent films show ordered arrays of silica nanoparticles with different diameters depending on the colors observed by light microscopy. The film forming silica nanoparticles are either released by the diatoms during reproduction or after cell death. This approach provides an environmentally friendly means for fabricating silica nanoparticles, decorative coatings and novel optical materials.

  18. The Effects of Bryophyte Morphology on Epiphytic Diatom Distribution in the Great Smoky Mountains National Park

    Science.gov (United States)

    Knapp, J. M.; Lowe, R. L.

    2005-05-01

    Diatoms and aquatic bryophytes have specific habitat requirements and are easily accessible in the field, making them ideal taxa for assessing water quality and environmental change. Although they both inhabit the same substrates within streams, there is a dearth of information regarding the relationship between these two indicator organisms. With this study, we examined the relationship between bryophytes and their epiphytic diatom communities from streams in the Great Smoky Mountains National Park. We hypothesized that bryophyte morphologies with more crevices between leaves would provide algae with a more protected micro-environment, resulting in a higher density of diatoms on these taxa compared to bryophytes with greatly exposed leaves. In addition, we also expect that bryophytes rich in crevices will have a high relative abundance of non-rheophilic taxa. Diatom community structure on bryophytes was determined using light microscopy. Using scanning electron microscopy, bryophytes were examined to compare the distribution and density of diatoms on the abnate and adnate surfaces of leaves. Preliminary results indicate that diatom density is not correlated with bryophyte species.

  19. Multiple Routes to Smart Nanostructured Materials from Diatom Microalgae: A Chemical Perspective.

    Science.gov (United States)

    Ragni, Roberta; Cicco, Stefania R; Vona, Danilo; Farinola, Gianluca M

    2017-11-27

    Diatoms are unicellular photosynthetic microalgae, ubiquitously diffused in both marine and freshwater environments, which exist worldwide with more than 100 000 species, each with different morphologies and dimensions, but typically ranging from 10 to 200 µm. A special feature of diatoms is their production of siliceous micro- to nanoporous cell walls, the frustules, whose hierarchical organization of silica layers produces extraordinarily intricate pore patterns. Due to the high surface area, mechanical resistance, unique optical features, and biocompatibility, a number of applications of diatom frustules have been investigated in photonics, sensing, optoelectronics, biomedicine, and energy conversion and storage. Current progress in diatom-based nanotechnology relies primarily on the availability of various strategies to isolate frustules, retaining their morphological features, and modify their chemical composition for applications that are not restricted to those of the bare biosilica produced by diatoms. Chemical or biological methods that decorate, integrate, convert, or mimic diatoms' biosilica shells while preserving their structural features represent powerful tools in developing scalable, low-cost routes to a wide variety of nanostructured smart materials. Here, the different approaches to chemical modification as the basis for the description of applications relating to the different materials thus obtained are presented. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Marennine, Promising Blue Pigments from a Widespread Haslea Diatom Species Complex

    Directory of Open Access Journals (Sweden)

    Romain Gastineau

    2014-05-01

    Full Text Available In diatoms, the main photosynthetic pigments are chlorophylls a and c, fucoxanthin, diadinoxanthin and diatoxanthin. The marine pennate diatom Haslea ostrearia has long been known for producing, in addition to these generic pigments, a water-soluble blue pigment, marennine. This pigment, responsible for the greening of oysters in western France, presents different biological activities: allelopathic, antioxidant, antibacterial, antiviral, and growth-inhibiting. A method to extract and purify marennine has been developed, but its chemical structure could hitherto not be resolved. For decades, H. ostrearia was the only organism known to produce marennine, and can be found worldwide. Our knowledge about H. ostrearia-like diatom biodiversity has recently been extended with the discovery of several new species of blue diatoms, the recently described H. karadagensis, H. silbo sp. inedit. and H. provincialis sp. inedit. These blue diatoms produce different marennine-like pigments, which belong to the same chemical family and present similar biological activities. Aside from being a potential source of natural blue pigments, H. ostrearia-like diatoms thus present a commercial potential for aquaculture, cosmetics, food and health industries.

  1. Diatoms on the carapace of common snapping turtles: Luticola spp. dominate despite spatial variation in assemblages.

    Science.gov (United States)

    Wu, Shelly C; Bergey, Elizabeth A

    2017-01-01

    Filamentous algae are often visible on the carapaces of freshwater turtles and these algae are dominated by a few species with varying geographic distributions. Compared to filamentous algae, little is known about the much more speciose microalgae on turtles. Our objectives were to compare the diatom flora on a single turtle species (the common snapping turtle, Chelydra serpentina) across part of its range to examine spatial patterns and determine whether specific diatom taxa were consistently associated with turtles (as occurs in the filamentous alga Basicladia spp.). Using preserved turtle specimens from museums, we systematically sampled diatoms on the carapaces of 25 snapping turtles across five states. The diverse diatom assemblages formed two groups-the southern Oklahoma group and the northern Illinois/Wisconsin/New York group, with Arkansas not differing from either group. Of the six diatom species found in all five states, four species are widespread, whereas Luticola cf. goeppertiana and L. cf. mutica are undescribed species, known only from turtles in our study. L. cf. goeppertiana comprised 83% of the diatom abundance on Oklahoma turtles and was relatively more abundant on southern turtles (Oklahoma and Arkansas) than on northern turtles (where mean abundance/state was > 10%). L. cf. mutica was the most abundant species (40%) on New York turtles. Some Luticola species are apparently turtle associates and results support a pattern of spatial variation in Luticola species, similar to that in Basicladia. Using museum specimens is an efficient and effective method to study the distribution of micro-epibionts.

  2. Quantifying the Cenozoic marine diatom deposition history: links to the C and Si cycles

    Science.gov (United States)

    Renaudie, Johan

    2016-11-01

    Marine planktonic diatoms are, today, among the world's main primary producers as well as the main organic carbon exporter to the deep sea despite the fact that they were a very minor component of the plankton at the beginning of the Cenozoic. They are also the main silica exporter to the deep sea, thus balancing global chemical weathering. This study reviews their global Cenozoic depositional pattern in order to understand the modality and the context of their rise to dominance, but also to understand how diatom evolution affected the Cenozoic functioning of the ocean's biological pump. After two short-lived major abundance peaks near the Eocene-Oligocene boundary and in the late Oligocene, diatom abundance in sediments shifted in the middle Miocene to globally higher values which have largely persisted to the modern day. These quantitative findings provide support for the hypothesis according to which diatoms, through their ecological role in the ocean's biological carbon pump, have contributed to the Cenozoic changes in atmospheric carbon dioxide pressure and consequently to changes in the global climate state. Additionally, correlations between diatom abundance peaks and shifts in seawater strontium and osmium isotopic composition hint at a strong control of the silicate weathering on diatom deposition.

  3. Marennine, promising blue pigments from a widespread Haslea diatom species complex.

    Science.gov (United States)

    Gastineau, Romain; Turcotte, François; Pouvreau, Jean-Bernard; Morançais, Michèle; Fleurence, Joël; Windarto, Eko; Prasetiya, Fiddy Semba; Arsad, Sulastri; Jaouen, Pascal; Babin, Mathieu; Coiffard, Laurence; Couteau, Céline; Bardeau, Jean-François; Jacquette, Boris; Leignel, Vincent; Hardivillier, Yann; Marcotte, Isabelle; Bourgougnon, Nathalie; Tremblay, Réjean; Deschênes, Jean-Sébastien; Badawy, Hope; Pasetto, Pamela; Davidovich, Nikolai; Hansen, Gert; Dittmer, Jens; Mouget, Jean-Luc

    2014-05-28

    In diatoms, the main photosynthetic pigments are chlorophylls a and c, fucoxanthin, diadinoxanthin and diatoxanthin. The marine pennate diatom Haslea ostrearia has long been known for producing, in addition to these generic pigments, a water-soluble blue pigment, marennine. This pigment, responsible for the greening of oysters in western France, presents different biological activities: allelopathic, antioxidant, antibacterial, antiviral, and growth-inhibiting. A method to extract and purify marennine has been developed, but its chemical structure could hitherto not be resolved. For decades, H. ostrearia was the only organism known to produce marennine, and can be found worldwide. Our knowledge about H. ostrearia-like diatom biodiversity has recently been extended with the discovery of several new species of blue diatoms, the recently described H. karadagensis, H. silbo sp. inedit. and H. provincialis sp. inedit. These blue diatoms produce different marennine-like pigments, which belong to the same chemical family and present similar biological activities. Aside from being a potential source of natural blue pigments, H. ostrearia-like diatoms thus present a commercial potential for aquaculture, cosmetics, food and health industries.

  4. Update of the Diatom EST Database: a new tool for digital transcriptomics

    Science.gov (United States)

    Maheswari, Uma; Mock, Thomas; Armbrust, E. Virginia; Bowler, Chris

    2009-01-01

    The Diatom Expressed Sequence Tag (EST) Database was constructed to provide integral access to ESTs from these ecologically and evolutionarily interesting microalgae. It has now been updated with 130 000 Phaeodactylum tricornutum ESTs from 16 cDNA libraries and 77 000 Thalassiosira pseudonana ESTs from seven libraries, derived from cells grown in different nutrient and stress regimes. The updated relational database incorporates results from statistical analyses such as log-likelihood ratios and hierarchical clustering, which help to identify differentially expressed genes under different conditions, and allow similarities in gene expression in different libraries to be investigated in a functional context. The database also incorporates links to the recently sequenced genomes of P. tricornutum and T. pseudonana, enabling an easy cross-talk between the expression pattern of diatom orthologs and the genome browsers. These improvements will facilitate exploration of diatom responses to conditions of ecological relevance and will aid gene function identification of diatom-specific genes and in silico gene prediction in this largely unexplored class of eukaryotes. The updated Diatom EST Database is available at http://www.biologie.ens.fr/diatomics/EST3. PMID:19029140

  5. Marennine, Promising Blue Pigments from a Widespread Haslea Diatom Species Complex

    Science.gov (United States)

    Gastineau, Romain; Turcotte, François; Pouvreau, Jean-Bernard; Morançais, Michèle; Fleurence, Joël; Windarto, Eko; Semba Prasetiya, Fiddy; Arsad, Sulastri; Jaouen, Pascal; Babin, Mathieu; Coiffard, Laurence; Couteau, Céline; Bardeau, Jean-François; Jacquette, Boris; Leignel, Vincent; Hardivillier, Yann; Marcotte, Isabelle; Bourgougnon, Nathalie; Tremblay, Réjean; Deschênes, Jean-Sébastien; Badawy, Hope; Pasetto, Pamela; Davidovich, Nikolai; Hansen, Gert; Dittmer, Jens; Mouget, Jean-Luc

    2014-01-01

    In diatoms, the main photosynthetic pigments are chlorophylls a and c, fucoxanthin, diadinoxanthin and diatoxanthin. The marine pennate diatom Haslea ostrearia has long been known for producing, in addition to these generic pigments, a water-soluble blue pigment, marennine. This pigment, responsible for the greening of oysters in western France, presents different biological activities: allelopathic, antioxidant, antibacterial, antiviral, and growth-inhibiting. A method to extract and purify marennine has been developed, but its chemical structure could hitherto not be resolved. For decades, H. ostrearia was the only organism known to produce marennine, and can be found worldwide. Our knowledge about H. ostrearia-like diatom biodiversity has recently been extended with the discovery of several new species of blue diatoms, the recently described H. karadagensis, H. silbo sp. inedit. and H. provincialis sp. inedit. These blue diatoms produce different marennine-like pigments, which belong to the same chemical family and present similar biological activities. Aside from being a potential source of natural blue pigments, H. ostrearia-like diatoms thus present a commercial potential for aquaculture, cosmetics, food and health industries. PMID:24879542

  6. Early perturbation in mitochondria redox homeostasis in response to environmental stress predicts cell fate in diatoms

    Science.gov (United States)

    van Creveld, Shiri Graff; Rosenwasser, Shilo; Schatz, Daniella; Koren, Ilan; Vardi, Assaf

    2015-01-01

    Diatoms are ubiquitous marine photosynthetic eukaryotes that are responsible for about 20% of global photosynthesis. Nevertheless, little is known about the redox-based mechanisms that mediate diatom sensing and acclimation to environmental stress. Here we used a redox-sensitive green fluorescent protein sensor targeted to various subcellular organelles in the marine diatom Phaeodactylum tricornutum, to map the spatial and temporal oxidation patterns in response to environmental stresses. Specific organelle oxidation patterns were found in response to various stress conditions such as oxidative stress, nutrient limitation and exposure to diatom-derived infochemicals. We found a strong correlation between the mitochondrial glutathione (GSH) redox potential (EGSH) and subsequent induction of cell death in response to the diatom-derived unsaturated aldehyde 2E,4E/Z-decadienal (DD), and a volatile halocarbon (BrCN) that mediate trophic-level interactions in marine diatoms. Induction of cell death in response to DD was mediated by oxidation of mitochondrial EGSH and was reversible by application of GSH only within a narrow time frame. We found that cell fate can be accurately predicted by a distinct life-death threshold of mitochondrial EGSH (−335 mV). We propose that compartmentalized redox-based signaling can integrate the input of diverse environmental cues and will determine cell fate decisions as part of algal acclimation to stress conditions. PMID:25083933

  7. Interactions between benthic copepods, bacteria and diatoms promote nitrogen retention in intertidal marine sediments.

    Directory of Open Access Journals (Sweden)

    Willem Stock

    Full Text Available The present study aims at evaluating the impact of diatoms and copepods on microbial processes mediating nitrate removal in fine-grained intertidal sediments. More specifically, we studied the interactions between copepods, diatoms and bacteria in relation to their effects on nitrate reduction and denitrification. Microcosms containing defaunated marine sediments were subjected to different treatments: an excess of nitrate, copepods, diatoms (Navicula sp., a combination of copepods and diatoms, and spent medium from copepods. The microcosms were incubated for seven and a half days, after which nutrient concentrations and denitrification potential were measured. Ammonium concentrations were highest in the treatments with copepods or their spent medium, whilst denitrification potential was lowest in these treatments, suggesting that copepods enhance dissimilatory nitrate reduction to ammonium over denitrification. We hypothesize that this is an indirect effect, by providing extra carbon for the bacterial community through the copepods' excretion products, thus changing the C/N ratio in favour of dissimilatory nitrate reduction. Diatoms alone had no effect on the nitrogen fluxes, but they did enhance the effect of copepods, possibly by influencing the quantity and quality of the copepods' excretion products. Our results show that small-scale biological interactions between bacteria, copepods and diatoms can have an important impact on denitrification and hence sediment nitrogen fluxes.

  8. Hidden diversity in diatoms of Kenyan Lake Naivasha: a genetic approach detects temporal variation.

    Science.gov (United States)

    Stoof-Leichsenring, Kathleen R; Epp, Laura S; Trauth, Martin H; Tiedemann, Ralph

    2012-04-01

    This study provides insights into the morphological and genetic diversity in diatoms occurring in core sediments from tropical lakes in Kenya. We developed a genetic survey technique specific for diatoms utilizing a short region (76-67 bp) of the ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL) gene as genetic barcode. Our analyses (i) validated the use of rbcL as a barcoding marker for diatoms, applied to sediment samples, (ii) showed a significant correlation between the results obtained by morphological and molecular data and (iii) indicated temporal variation in diatom assemblages on the inter- and intra-specific level. Diatom assemblages from a short core from Lake Naivasha show a drastic shift over the last 200 years, as littoral species (e.g. Navicula) are replaced by more planktonic ones (e.g. Aulacoseira). Within that same period, we detected periodic changes in the respective frequencies of distinct haplotype groups of Navicula, which coincide with wet and dry periods of Lake Naivasha between 1820 and 1938 AD. Our genetic analyses on historical lake sediments revealed inter- and intra-specific variation in diatoms, which is partially hidden behind single morphotypes. The occurrence of particular genetic lineages is probably correlated with environmental factors. © 2012 Blackwell Publishing Ltd.

  9. Interactions between Benthic Copepods, Bacteria and Diatoms Promote Nitrogen Retention in Intertidal Marine Sediments

    Science.gov (United States)

    Stock, Willem; Heylen, Kim; Sabbe, Koen; Willems, Anne; De Troch, Marleen

    2014-01-01

    The present study aims at evaluating the impact of diatoms and copepods on microbial processes mediating nitrate removal in fine-grained intertidal sediments. More specifically, we studied the interactions between copepods, diatoms and bacteria in relation to their effects on nitrate reduction and denitrification. Microcosms containing defaunated marine sediments were subjected to different treatments: an excess of nitrate, copepods, diatoms (Navicula sp.), a combination of copepods and diatoms, and spent medium from copepods. The microcosms were incubated for seven and a half days, after which nutrient concentrations and denitrification potential were measured. Ammonium concentrations were highest in the treatments with copepods or their spent medium, whilst denitrification potential was lowest in these treatments, suggesting that copepods enhance dissimilatory nitrate reduction to ammonium over denitrification. We hypothesize that this is an indirect effect, by providing extra carbon for the bacterial community through the copepods' excretion products, thus changing the C/N ratio in favour of dissimilatory nitrate reduction. Diatoms alone had no effect on the nitrogen fluxes, but they did enhance the effect of copepods, possibly by influencing the quantity and quality of the copepods' excretion products. Our results show that small-scale biological interactions between bacteria, copepods and diatoms can have an important impact on denitrification and hence sediment nitrogen fluxes. PMID:25360602

  10. Unusual diatom layers in upper pleistocene sediments from the northern Weddell Sea

    Science.gov (United States)

    Jordan, R. W.; Priddle, J.; Pudsey, C. J.; Barker, P. F.; Whitehouse, M. J.

    1991-07-01

    A sediment core from Jane Basin, northern Weddell Sea, contains distinct bands, up to 3 cm thick, of well preserved diatom frustules, contrasting with the generally poor preservation of adjacent material. Most notably, the fragile diatom genus Corethron is abundant in the layers and found as whole valves, while in the remainder of the core is rare and valves are broken and corroded. Extrapolation from contemporary data on phytoplankton production and standing crop suggests that the silicon content of the diatom ooze layers is very much greater than could be expected from a single year's phytoplankton production sedimenting from a corresponding area of the water column. Assuming direct, quantitative sedimentation, it would have taken decades to centuries to accumulate 3 cm of diatom ooze. The preservation of these layer indicates that unusual conditions prevailed, so that diatom valves settled through the water column more-or-less unaltered and remained preserved in this state in the sediment. Mass sedimentation of a diatom bloom followed by rapid burial seems the most likely combination of circumstances that could have caused this. It is unlikely that this would have occurred consistently over a long period. Horizontal concentration must have taken place, and this is most likely to have been associated with a physical feature of the water column such as an eddy or "chimney", which entrained phytoplankton biomass from a wide area of the surface mixed layer and caused it to sediment to a smaller area of the seabed.

  11. Multipurpose Compound

    Science.gov (United States)

    1983-01-01

    Specially formulated derivatives of an unusual basic compound known as Alcide may be the answer to effective treatment and prevention of the disease bovine mastitis, a bacterial inflammation of a cow's mammary gland that results in loss of milk production and in extreme cases, death. Manufactured by Alcide Corporation the Alcide compound has killed all tested bacteria, virus and fungi, shortly after contact, with minimal toxic effects on humans or animals. Alcide Corporation credits the existence of the mastitis treatment/prevention products to assistance provided the company by NERAC, Inc.

  12. Analysis of organo-silica interactions during valve formation in synchronously growing cells of the diatom Navicula pelliculosa.

    Science.gov (United States)

    Heredia, Alejandro; van der Strate, Han J; Delgadillo, Ivonne; Basiuk, Vladimir A; Vrieling, Engel G

    2008-03-03

    Biologically formed silica is produced at ambient conditions under the control of molecular and physicochemical processes that are apparently integrated in biosilica morphogenesis, but the mechanisms are not yet fully understood. With the recent identification of small polypeptides and proteins that are encapsulated inside the biosilica and functional in silica polymerization in vitro, it is of importance to determine whether interactions between inorganic silica species and these organic compounds occur in vivo. A time-resolved analysis of valve formation in synchronously growing cells of the diatom species Navicula pelliculosa enabled us to characterize the relevant chemical bonds by attenuated total reflectance Fourier-transformed infrared (ATR-FTIR) spectroscopy. Typically, inorganic bonds of Si-O-Si (bands at 1058, 843 cm(-1)), Si-OH (3689 cm(-1)), and P=O (1239 cm(-1)) and organic bonds of proteinaceous matter (with the amide I and II bands at 1642 and 1543 cm(-1), respectively) were positively identified during one cycle of valve formation. The observed variations in FTIR band intensity and location represented specific interactions between organic and inorganic molecules during the major silicification event, during which stretching of the Si-O bonds was predominantly noticed. The experimentally obtained frequencies (nu) of the major bonds corresponded to those that were obtained by MM+ and PM3 FTIR simulations for organo-silica interactions based on biomolecules that are proposed to be involved in biosilica formation. The results indicated that hydrogen bonds originated from interactions, albeit weak, between organic phosphate or amine groups to the inorganic hydroxyl groups or oxygen atoms from the silicic acid and/or silica. The existence of covalent P-O-Si bonds and electrostatic interactions could not be excluded. These interactions clearly suggest that biomolecules actively contribute to the silica polymerization process during valve formation in N

  13. Mesoionic Compounds

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 11; Issue 10. Mesoionic Compounds - An Unconventional Class of Aromatic Heterocycles. Bharati V Badami. General Article Volume 11 Issue 10 October 2006 pp 40-48. Fulltext. Click here to view fulltext PDF. Permanent link:

  14. Mesoionic Compounds

    Indian Academy of Sciences (India)

    Sydnone, the representative mesoionic compound has been extensively studied because of its unusual structure, chemi- cal properties and synthetic utility. Sydnone is used as a versatile synthon in heterocyclic synthesis. This article gives a brief account of the comparative studies of the structural features of mesoionic ...

  15. Long range intermolecular forces in triatomic systems: connecting the atom-diatom and atom-atom-atom representations

    OpenAIRE

    Cvitas, Marko T.; Soldan, Pavel; Hutson, Jeremy M.

    2005-01-01

    The long-range forces that act between three atoms are analysed in both atom-diatom and atom-atom-atom representations. Expressions for atom-diatom dispersion coefficients are obtained in terms of 3-body nonadditive coefficients. The anisotropy of atom-diatom C_6 dispersion coefficients arises primarily from nonadditive triple-dipole and quadruple-dipole forces, while pairwise-additive forces and nonadditive triple-dipole and dipole-dipole-quadrupole forces contribute significantly to atom-di...

  16. Studies of light responses and the development of a transformation system for the benthic diatom Seminavis robusta

    OpenAIRE

    Kirupamurthy, Darshan

    2014-01-01

    Diatoms are a divergent group of organisms with a complex evolutionary background, and belong to the Heterokonta group phylogenetically. Diatoms have gone through several endosymbiotic processes with both green algae and red algae, and have acquired a complex genome. Some of the genes and protein found in diatoms are similar to those found in plants and green algae, while others show similarities to animals (metazoa), yeast, bacteria and other unicellular microorganisms. This genomic diversit...

  17. Kinetic approach to condensation: Diatomic gases with dipolar molecules

    Science.gov (United States)

    Benilov, E. S.; Benilov, M. S.

    2017-10-01

    We derive a kinetic equation for rarefied diatomic gases whose molecules have a permanent dipole moment. Estimating typical parameters of such gases, we show that quantum effects cannot be neglected when describing the rotation of molecules, which we thus approximate by quantum rotators. The intermolecular potential is assumed to involve an unspecified short-range repulsive component and a long-range dipole-dipole Coulomb interaction. In the kinetic equation derived, the former and the latter give rise, respectively, to the collision integral and a self-consistent electric field generated collectively by the dipoles (as in the Vlasov model of plasma). It turns out that the characteristic period of the molecules' rotation is much shorter than the time scale of the collective electric force and the latter is much shorter than the time scale of the collision integral, which allows us to average the kinetic equation over rotation. In the averaged model, collisions and interaction with the collective field affect only those rotational levels of the molecules that satisfy certain conditions of synchronism. It is then shown that the derived model does not describe condensation; i.e., permanent dipoles of molecules cannot exert the level of intermolecular attraction necessary for condensation. It is argued that an adequate model of condensation must include the temporary dipoles that molecules induce on each other during interaction, and that this model must be quantum, not classical.

  18. Development of techniques for cooling and trapping polar diatomic molecules

    Science.gov (United States)

    Glenn, David R.

    The study of ultracold dipolar molecules is an important emerging frontier in atomic physics. This thesis discusses the development of techniques for cooling diatomic molecules, focussing specifically on the idea of using a microwave frequency quasi-optical dipole trap for evaporative cooling. A prototype for such a trap has been designed, constructed, and tested. In order to load the microwave trap, a helium buffer gas cooled molecular beam source has been developed and characterized - in a variety of flow regimes, ranging from the effusive (thermal mean velocity, moderate flux), to the deeply hydrodynamic (large forward velocity, high-flux, high collimation). We explain the development of this source in detail. In particular, we describe recent work towards demonstrating direct laser cooling of a hydrodynamic SrF molecular beam. We have identified a set of quasi-closed transitions which should enable more than 104 photon scattering events, sufficient to decelerate a hydrodynamic beam to the Doppler limit. We present experimental results demonstrating optical deflection of a SrF beam by radiative force using this scheme, in which each molecule scatters on the order of 150 photons, limited by its interaction time with the lasers.

  19. Heat conduction in diatomic chains with correlated disorder

    Energy Technology Data Exchange (ETDEWEB)

    Savin, Alexander V., E-mail: asavin@center.chph.ras.ru [Semenov Institute of Chemical Physics, Russian Academy of Sciences, 4 Kosygin str., 119991 Moscow (Russian Federation); Zolotarevskiy, Vadim; Gendelman, Oleg V. [Faculty of Mechanical Engineering, Technion – Israel Institute of Technology, Haifa 32000 (Israel)

    2017-01-23

    The paper considers heat transport in diatomic one-dimensional lattices, containing equal amounts of particles with different masses. Ordering of the particles in the chain is governed by single correlation parameter – the probability for two neighboring particles to have the same mass. As this parameter grows from zero to unity, the structure of the chain varies from regular staggering chain to completely random configuration, and then – to very long clusters of particles with equal masses. Therefore, this correlation parameter allows a control of typical cluster size in the chain. In order to explore different regimes of the heat transport, two interatomic potentials are considered. The first one is an infinite potential wall, corresponding to instantaneous elastic collisions between the neighboring particles. In homogeneous chains such interaction leads to an anomalous heat transport. The other one is classical Lennard–Jones interatomic potential, which leads to a normal heat transport. The simulations demonstrate that the correlated disorder of the particle arrangement does not change the convergence properties of the heat conduction coefficient, but essentially modifies its value. For the collision potential, one observes essential growth of the coefficient for fixed chain length as the limit of large homogeneous clusters is approached. The thermal transport in these models remains superdiffusive. In the Lennard–Jones chain the effect of correlation appears to be not monotonous in the limit of low temperatures. This behavior stems from the competition between formation of long clusters mentioned above, and Anderson localization close to the staggering ordered state.

  20. Quantum entanglement and the dissociation process of diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Esquivel, Rodolfo O; Molina-Espiritu, Moyocoyani [Departamento de Quimica, Universidad Autonoma Metropolitana, 09340-Mexico DF (Mexico); Flores-Gallegos, Nelson [Unidad Profesional Interdisciplinaria de IngenierIa, Campus Guanajuato del Instituto Politecnico Nacional, 36275-Guanajuato (Mexico); Plastino, A R; Angulo, Juan Carlos; Dehesa, Jesus S [Instituto Carlos I de Fisica Teorica y Computacional, and Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, 18071-Granada (Spain); Antolin, Juan, E-mail: esquivel@xanum.uam.mx, E-mail: arplastino@ugr.es [Departamento de Fisica Aplicada, EUITIZ, Universidad de Zaragoza, 50018-Zaragoza (Spain)

    2011-09-14

    In this work, we investigate quantum entanglement-related aspects of the dissociation process of some selected, representative homo- and heteronuclear diatomic molecules. This study is based upon high-quality ab initio calculations of the (correlated) molecular wavefunctions involved in the dissociation processes. The values of the electronic entanglement characterizing the system in the limit cases corresponding to (i) the united-atom representation and (ii) the asymptotic region when atoms dissociate are discussed in detail. It is also shown that the behaviour of the electronic entanglement as a function of the reaction coordinate R exhibits remarkable correspondences with the phenomenological description of the physically meaningful regimes comprising the processes under study. In particular, the extrema of the total energies and the electronic entanglement are shown to be associated with the main physical changes experienced by the molecular spatial electronic density, such as charge depletion and accumulation or bond cleavage regions. These structural changes are characterized by several selected descriptors of the density, such as the Laplacian of the electronic molecular distributions (LAP), the molecular electrostatic potential (MEP) and the atomic electric potentials fitted to the MEP.

  1. One-dimensional flows of an imperfect diatomic gas

    Science.gov (United States)

    1959-01-01

    With the assumptions that Berthelot's equation of state accounts for molecular size and intermolecular force effects, and that changes in the vibrational heat capacities are given by a Planck term, expressions are developed for analyzing one-dimensional flows of a diatomic gas. The special cases of flow through normal and oblique shocks in free air at sea level are investigated. It is found that up to a Mach number 10 pressure ratio across a normal shock differs by less than 6 percent from its ideal gas value; whereas at Mach numbers above 4 the temperature rise is considerable below and hence the density rise is well above that predicted assuming ideal gas behavior. It is further shown that only the caloric imperfection in air has an appreciable effect on the pressures developed in the shock process considered. The effects of gaseous imperfections on oblique shock-flows are studied from the standpoint of their influence on the life and pressure drag of a flat plate operating at Mach numbers of 10 and 20. The influence is found to be small. (author)

  2. Oil from the tropical marine benthic-diatom Navicula sp.

    Science.gov (United States)

    Nurachman, Zeily; Brataningtyas, Dewi Susan; Hartati; Panggabean, Lily Maria Goretty

    2012-11-01

    The potential of the tropical marine benthic-diatom Navicula sp. for biodiesel feedstock was investigated. Growth profiles were analyzed by changing nutrient compositions in three different media (Walne, plain seawater, and modified seawater) and irradiance intensities. Navicula sp. cells showed significant growth in Walne and modified seawater medium but not in plain seawater medium. The microalgae grew well in a pH range of 7.8-8.4, and the cells were very sensitive to the intensity of direct sunlight exposure. The average cell concentration obtained from the cultures in plain seawater, Walne, and modified seawater media at the beginning of the stationary phase was 0.70, 2.17, and 2.54 g/L, respectively. Electron spray ionization-ion trap-mass spectrometry showed that the triacylglycerols of the algae oil were identified as POP (palmitic-oleic-palmitic), POO (palmitic-oleic-oleic), and OOLn (oleic-oleic-linoleic). The oil productivity of Navicula sp. cultivated in Walne and modified seawater media was 90 and 124 μL L(-1) culture d(-1). The Navicula sp. biodiesel exhibited a kinematic viscosity of 1.299 mm(2)/s, density of 0.8347 g/mL, and internal energy of 0.90 kJ/mL.

  3. Shared Epizoic Taxa and Differences in Diatom Community Structure Between Green Turtles (Chelonia mydas) from Distant Habitats.

    Science.gov (United States)

    Majewska, Roksana; de Vijver, Bart Van; Nasrolahi, Ali; Ehsanpour, Maryam; Afkhami, Majid; Bolaños, Federico; Iamunno, Franco; Santoro, Mario; De Stefano, Mario

    2017-11-01

    The first reports of diatoms growing on marine mammals date back to the early 1900s. However, only recently has direct evidence been provided for similar associations between diatoms and sea turtles. We present a comparison of diatom communities inhabiting carapaces of green turtles Chelonia mydas sampled at two remote sites located within the Indian (Iran) and Atlantic (Costa Rica) Ocean basins. Diatom observations and counts were carried out using scanning electron microscopy. Techniques involving critical point drying enabled observations of diatoms and other microepibionts still attached to sea turtle carapace and revealed specific aspects of the epizoic community structure. Species-poor, well-developed diatom communities were found on all examined sea turtles. Significant differences between the two host sea turtle populations were observed in terms of diatom abundance and their community structure (including growth form structure). A total of 12 and 22 diatom taxa were found from sea turtles in Iran and Costa Rica, respectively, and eight of these species belonging to Amphora, Chelonicola, Cocconeis, Navicula, Nitzschia and Poulinea genera were observed in samples from both locations. Potential mechanisms of diatom dispersal and the influence of the external environment, sea turtle behaviour, its life stage, and foraging and breeding habitats, as well as epibiotic bacterial flora on epizoic communities, are discussed.

  4. Molecular Tools for the Selective Detection of Nine Diatom Species Biomarkers of Various Water Quality Levels

    Directory of Open Access Journals (Sweden)

    Lucia Cimarelli

    2015-05-01

    Full Text Available Our understanding of the composition of diatom communities and their response to environmental changes is currently limited by laborious taxonomic identification procedures. Advances in molecular technologies are expected to contribute more efficient, robust and sensitive tools for the detection of these ecologically relevant microorganisms. There is a need to explore and test phylogenetic markers as an alternative to the use of rRNA genes, whose limited sequence divergence does not allow the accurate discrimination of diatoms at the species level. In this work, nine diatom species belonging to eight genera, isolated from epylithic environmental samples collected in central Italy, were chosen to implement a panel of diatoms covering the full range of ecological status of freshwaters. The procedure described in this work relies on the PCR amplification of specific regions in two conserved diatom genes, elongation factor 1-a (eEF1-a and silicic acid transporter (SIT, as a first step to narrow down the complexity of the targets, followed by microarray hybridization experiments. Oligonucleotide probes with the potential to discriminate closely related species were designed taking into account the genetic polymorphisms found in target genes. These probes were tested, refined and validated on a small-scale prototype DNA chip. Overall, we obtained 17 highly specific probes targeting eEF1-a and SIT, along with 19 probes having lower discriminatory power recognizing at the same time two or three species. This basic array was validated in a laboratory setting and is ready for tests with crude environmental samples eventually to be scaled-up to include a larger panel of diatoms. Its possible use for the simultaneous detection of diatoms selected from the classes of water quality identified by the European Water Framework Directive is discussed.

  5. Effect of hydrological variability on diatom distribution in Poyang Lake, China

    Science.gov (United States)

    Qian, Kuimei; Liu, Xia; Chen, Yuwei

    2017-01-01

    Poyang Lake is the largest freshwater lake in China, and it has a seasonal flooding cycle that significantly changes the water level every year. The aim of this paper was to explain how these hydrological changes influence diatom populations in Poyang Lake. The yearly hydrological cycle can be divided into 4 phases: low water-level phase, increasing water-level phase, high water-level phase and decreasing water-level phase. Variations in the abundance of planktonic diatoms were studied using quarterly monitoring data collected from January 2009 to October 2013. Generally, diatoms were dominant in Poyang Lake and accounted for more than 50% of the total phytoplankton biomass except in July 2009 (26%) and January 2012 (35%). Aulacoseira granulata and Surirella robusta were the predominant species in all four phases, and they accounted for 25.02% to 56.89% and 5.07% to 14.78% of the total phytoplankton biomass, respectively. A redundancy analysis (RDA) showed that changes in physico-chemical parameter were related to the water level, and changes in diatom biomass were related to nitrite levels and pH. These results indicate that changes in environmental parameters related to both seasonal variations and water-level fluctuations caused variations in diatom biomass and community composition in Poyang Lake. Furthermore, extreme hydrological events can have different influences on the diatom community composition in the main channel and lentic regions. This research provides data on the diatom variations in Poyang Lake and will be useful for establishing biological indicators of environmental change and protecting Poyang Lake in the future.

  6. Molecular tools for the selective detection of nine diatom species biomarkers of various water quality levels.

    Science.gov (United States)

    Cimarelli, Lucia; Singh, Kumar Saurabh; Mai, Nguyen Thi Nhu; Dhar, Bidhan Chandra; Brandi, Anna; Brandi, Letizia; Spurio, Roberto

    2015-05-22

    Our understanding of the composition of diatom communities and their response to environmental changes is currently limited by laborious taxonomic identification procedures. Advances in molecular technologies are expected to contribute more efficient, robust and sensitive tools for the detection of these ecologically relevant microorganisms. There is a need to explore and test phylogenetic markers as an alternative to the use of rRNA genes, whose limited sequence divergence does not allow the accurate discrimination of diatoms at the species level. In this work, nine diatom species belonging to eight genera, isolated from epylithic environmental samples collected in central Italy, were chosen to implement a panel of diatoms covering the full range of ecological status of freshwaters. The procedure described in this work relies on the PCR amplification of specific regions in two conserved diatom genes, elongation factor 1-a (eEF1-a) and silicic acid transporter (SIT), as a first step to narrow down the complexity of the targets, followed by microarray hybridization experiments. Oligonucleotide probes with the potential to discriminate closely related species were designed taking into account the genetic polymorphisms found in target genes. These probes were tested, refined and validated on a small-scale prototype DNA chip. Overall, we obtained 17 highly specific probes targeting eEF1-a and SIT, along with 19 probes having lower discriminatory power recognizing at the same time two or three species. This basic array was validated in a laboratory setting and is ready for tests with crude environmental samples eventually to be scaled-up to include a larger panel of diatoms. Its possible use for the simultaneous detection of diatoms selected from the classes of water quality identified by the European Water Framework Directive is discussed.

  7. Insights into global diatom distribution and diversity in the world’s ocean

    KAUST Repository

    Malviya, Shruti

    2016-03-01

    Diatoms (Bacillariophyta) constitute one of the most diverse and ecologically important groups of phytoplankton. They are considered to be particularly important in nutrient-rich coastal ecosystems and at high latitudes, but considerably less so in the oligotrophic open ocean. The Tara Oceans circumnavigation collected samples from a wide range of oceanic regions using a standardized sampling procedure. Here, a total of ∼12 million diatom V9-18S ribosomal DNA (rDNA) ribotypes, derived from 293 sizefractionated plankton communities collected at 46 sampling sites across the global ocean euphotic zone, have been analyzed to explore diatom global diversity and community composition. We provide a new estimate of diversity of marine planktonic diatoms at 4,748 operational taxonomic units (OTUs). Based on the total assigned ribotypes, Chaetoceros was the most abundant and diverse genus, followed by Fragilariopsis, Thalassiosira, and Corethron. We found only a few cosmopolitan ribotypes displaying an even distribution across stations and high abundance, many of which could not be assigned with confidence to any known genus. Three distinct communities from South Pacific, Mediterranean, and Southern Ocean waters were identified that share a substantial percentage of ribotypes within them. Sudden drops in diversity were observed at Cape Agulhas, which separates the Indian and Atlantic Oceans, and across the Drake Passage between the Atlantic and Southern Oceans, indicating the importance of these ocean circulation choke points in constraining diatom distribution and diversity. We also observed high diatom diversity in the open ocean, suggesting that diatoms may be more relevant in these oceanic systems than generally considered.

  8. Diatoms in drowning cases in forensic veterinary context: a preliminary study.

    Science.gov (United States)

    Fucci, Nadia; Campobasso, Carlo P; Mastrogiuseppe, L; Puccinelli, C; Marcheggiani, S; Mancini, L; Marino, L; Pascali, V L

    2017-11-01

    In this preliminary study, a digestive method used in forensic context to extract diatoms has been applied in organs taken from ten wildlife animals belonging three species of mammals (a deer, a roe and five otters) and one species of birds (two magpies). Only four carcasses were recovered from aquatic environments (bath trough for animals, bathtub irrigation, river) and only in three cases out of ten that the cause of death was ruled out as drowning. In seven cases, the death was due to other causes: gunshot injuries for one otter, blunt trauma for a magpie, and traumatic injuries followed by motor vehicle collision in other four otters and a roe. Post-mortem examination was performed in all carcasses. The diatom test protocol was performed according to the Italian guidelines for analysis of benthic diatoms for ecological status assessment of inland waters. Five grams of lung, liver, and kidney was taken from all the animal carcasses. In some cases, additional tissue samples were also available among which brain, heart, spleen, and bone marrow. In all four cases found in water, the drowning medium was also available. Hydrogen peroxide (H 2 O 2 ) digestion was performed, and identification of 21 genera of diatoms was obtained. The method proved to be suitable for the identification of diatoms in the organs of the animals drowned supporting the final diagnosis of drowning. Only in otters, all died for causes other than drowning, diatoms did not prove to be suitable for the diagnosis of drowning since their presence in the internal organs was mainly related to their main diet based on fishmeal. The authors believe that this first trial is very promising, and the results suggest that diatom test can be easily applied in forensic veterinary context.

  9. Compound odontoma

    Directory of Open Access Journals (Sweden)

    Monica Yadav

    2012-01-01

    Full Text Available Odontomas have been extensively reported in the dental literature, and the term refers to tumors of odontogenic origin. Though the exact etiology is still unknown, the postulated causes include: local trauma, infection, inheritance and genetic mutation. The majority of the lesions are asymptomatic; however, may be accompanied with pain and swelling as secondary complaints in some cases. Here, we report a case of a compound odontome in a 14 year old patient.

  10. Effect of vertical mixing on short-term mycosporine-like amino acid synthesis in the Antarctic diatom, Thalasiossira sp.

    Directory of Open Access Journals (Sweden)

    Marcelo Pablo Hernando

    2011-12-01

    Full Text Available One of the adaptations whereby phytoplankton can alleviate damage induced by ultraviolet radiation (280-400 nm is the synthesis of mycosporine-like amino acids (MAAs. The synthesis of MAAs was studied after exposure of the Antarctic diatom Thalassiosira sp. isolated from Potter Cove (South Shetland Is., Antarctica to 2 treatments with a solar simulator: surface (Sfix and vertical mixing (Mix irradiance conditions. Light exposure was simulated in daily cycles with maximum irradiance at noon. Only 2 MAAs, Porphyra-334 (82-85% and Shinorine (15-18%, were identified. The concentration of the two compounds increased during experimental light exposure (50-55% and declined in the dark (10-15%. During the light period the synthesis rate of MAAs per unit of chlorophyll a was higher in the Sfix treatment (µ=0.17 h-1 than in the Mix treatment (µ=0.05 h-1. In spite of the higher MAA levels, low cell numbers were observed in the Sfix treatment, suggesting that the algae synthesized photoprotective compounds at the expense of growth. Our results document overlapping effects of both daily light cycles and vertical mixing affecting the synthesis of MAAs. This, and the high thermal dissipation of the ultraviolet B radiation energy (280-320 nm absorbed by these substances, suggest a rapid photoadaptive response of Thalasiossira sp. upon exposure to elevated irradiance in a stratified water column, as well as the complementary role of vertical mixing in photo-protection.

  11. Physiological and molecular analysis of carbon source supplementation and pH stress-induced lipid accumulation in the marine diatom Phaeodactylum tricornutum.

    Science.gov (United States)

    Mus, Florence; Toussaint, Jean-Paul; Cooksey, Keith E; Fields, Matthew W; Gerlach, Robin; Peyton, Brent M; Carlson, Ross P

    2013-04-01

    A detailed physiological and molecular analysis of lipid accumulation under a suite of conditions including nitrogen limitation, alkaline pH stress, bicarbonate supplementation, and organic acid supplementation was performed on the marine diatom Phaeodactylum tricornutum. For all tested conditions, nitrogen limitation was a prerequisite for lipid accumulation and the other culturing strategies only enhanced accumulation highlighting the importance of compounded stresses on lipid metabolism. Volumetric lipid levels varied depending on condition; the observed rankings from highest to lowest were for inorganic carbon addition (15 mM bicarbonate), organic acid addition (15 carbon mM acetate), and alkaline pH stress (pH 9.0). For all lipid-accumulating cultures except acetate supplementation, a common series of physiological steps were observed. Upon extracellular nitrogen exhaustion, culture growth continued for approximately 1.5 cell doublings with decreases in specific protein and photosynthetic pigment content. As nitrogen limitation arrested cell growth, carbohydrate content decreased with a corresponding increase in lipid content. Addition of the organic carbon source acetate appeared to activate alternative metabolic pathways for lipid accumulation. Molecular level data on more than 50 central metabolism transcripts were measured using real-time PCR. Analysis of transcripts suggested the central metabolism pathways associated with bicarbonate transport, carbonic anhydrases, and C4 carbon fixations were important for lipid accumulation. Transcriptomic data also suggested that repurposing of phospholipids may play a role in lipid accumulation. This study provides a detailed physiological and molecular-level foundation for improved understanding of diatom nutrient cycling and contributes to a metabolic blueprint for controlling lipid accumulation in diatoms.

  12. A multicompartment approach--diatoms, macrophytes, benthic macroinvertebrates and fish--to assess the impact of toxic industrial releases on a small French river.

    Directory of Open Access Journals (Sweden)

    Manon Lainé

    Full Text Available The River Luzou flows through a sandy substrate in the South West of France. According to the results of two assessment surveys, the Water Agency appraised that this river may not achieve the good ecological status by 2015 as required by the Water Framework Directive (2000/60/EC. This ecosystem is impacted by industrial effluents (organic matter, metals and aromatic compounds. In order to assess and characterize the impact, this study aimed to combine a set of taxonomic and non-taxonomic metrics for diatoms, macrophytes, macroinvertebrates and fish along the up- to downstream gradient of the river. Diversity metrics, biological indices, biological and ecological traits were determined for the four biological quality elements (BQE. Various quantitative metrics (biomass estimates were also calculated for diatom communities. The results were compared to physicochemical analysis. Biological measurements were more informative than physicochemical analysis, in the context of the study. Biological responses indicated both the contamination of water and its intensity. Diversity metrics and biological indices strongly decreased with pollution for all BQE but diatoms. Convergent trait selection with pollution was observed among BQE: reproduction, colonization strategies, or trophic regime were clearly modified at impaired sites. Taxon size and relation to the substrate diverged among biological compartments. Multiple anthropogenic pollution calls for alternate assessment methods of rivers' health. Our study exemplifies the fact that, in the case of complex contaminations, biological indicators can be more informative for environmental risk, than a wide screening of contaminants by chemical analysis alone. The combination of diverse biological compartments provided a refined diagnostic about the nature (general mode of action and intensity of the contamination.

  13. Diatoms confirm coseismic uplift and subsidence along the eastern Alaska-Aleutian megathrust

    Science.gov (United States)

    Dura, T.; Briggs, R. W.; Engelhart, S. E.; Nelson, A. R.; Horton, B.

    2013-12-01

    The Alaska-Aleutian subduction zone is the source of a series of Mw 8-9.2 20th century ruptures, including the second largest historical earthquake ever recorded in 1964. Paleoseismic studies, employing coastal stratigraphic sequences, have been successfully applied at sites within the 1964 rupture zone, but geologic records are unstudied west of the 1964 rupture. Understanding the behavior of the megathrust is important because a tsunamigenic rupture could damage the west coast of the United States. Investigations in the tidal marshes of Sitkinak Island, off the southwest coast of Kodiak Island, have uncovered stratigraphic evidence of five apparent coseismic land-level changes. Radiocarbon, 210Pb, and 137Cs dating indicate this record may include the 1964 and 1788 earthquakes and some predecessors. Here, we present new paleoecological evidence that independently confirms the inference that at least four of the abrupt lithologic changes in the stratigraphy of Sitkinak Island record coseismic land-level changes. Sudden and lasting changes in fossil diatom assemblages spanning tidal lithologic contacts reveal both coseismic subsidence (mud over peat) and coseismic uplift (peat over mud) during the last 1000 years. Across the contact that may mark the 1964 earthquake, a shift from a brackish, low-marsh diatom assemblage dominated by Diploneis interrupta and Navicula cincta to a tidal flat assemblage containing Actinocyclus normanii and Synedra tabulata indicates a sudden rise in relative sea-level, which we infer to record coseismic subsidence. In contrast, diatoms show evidence of coseismic uplift across the probable 1788 contact. An abrupt transition from a fully marine assemblage containing coastal planktonic and tychoplanktonic taxa to a freshwater marsh assemblage dominated by the salt-intolerant benthic diatom Eunotia fallax is consistent with a sudden and lasting relative sea-level fall. Abrupt changes in lithology across a contact dated about ~575 cal yr

  14. Quantifying the impact of freshwater diatom productivity on silicon isotopes and silicon fluxes: Lake Myvatn, Iceland

    Science.gov (United States)

    Opfergelt, S.; Eiriksdottir, E. S.; Burton, K. W.; Einarsson, A.; Siebert, C.; Gislason, S. R.; Halliday, A. N.

    2011-05-01

    Diatom productivity in the oceans plays a crucial role in the carbon cycle, but is strongly dependent upon the continental silicon supply. However, the relative influence of weathering and biological processes on continental Si fluxes remains poorly constrained. This study aims to quantify the impact of terrestrial diatom productivity on Si fluxes to the ocean. Lake Myvatn in North Iceland is one of the most productive lakes in the Northern Hemisphere, with nutrient-rich waters almost uniquely sourced by groundwater. The primary production is mainly controlled by diatom growth but also by cyanobacteria, and the lake output is via a single river, thereby providing a relatively simple natural laboratory to quantify the impact of diatom growth on the chemistry and Si budget of lake waters. Silicon stable isotopes (δ 30Si) provide a tracer of this biocycling, and have been measured in groundwater inputs to the lake, and in time-series monitoring of waters at the lake outlet. The δ 30Si values at the outlet range from + 0.70 ± 0.08 to + 1.42 ± 0.06‰, which is significantly heavier than the groundwater input (average cold and hot springs: + 0.50 ± 0.17‰, 2SD) and consistent with the preferential uptake of light Si isotopes by diatoms. The δ 30Si value at the outlet increases by up to 0.9‰ in spring and autumn relative to the Si isotope composition of the inflow. These seasonal diatom blooms can be modeled by an open system of Si uptake and affect Si fluxes at the outlet of the lake by up to 79%, or 53% integrated over the year. In the summer a shift to lighter δ 30Si values is correlated with a higher pH, which results in dissolution of diatoms releasing light Si isotopes. From mass balance, this seasonal diatom dissolution affects Si fluxes by up to 33%, but is limited to 3.7% integrated over the year. These results clearly illustrate that biological activity can have a significant impact on both isotope composition and elemental abundance of continental

  15. Experimental toxicity and bioaccumulation of cadmium in freshwater periphytic diatoms in relation with biofilm maturity

    Energy Technology Data Exchange (ETDEWEB)

    Duong, Thi Thuy, E-mail: duongthuy0712@yahoo.com [Institute of Environmental Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi (Viet Nam); Morin, Soizic, E-mail: soizic.morin@cemagref.fr [Cemagref, UR REBX, 50 avenue de Verdun, F-33612 Cestas Cedex (France); Coste, Michel [Cemagref, UR REBX, 50 avenue de Verdun, F-33612 Cestas Cedex (France); Herlory, Olivier; Feurtet-Mazel, Agnes; Boudou, Alain [Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France)

    2010-01-01

    A study was undertaken to examine cadmium accumulation in freshwater biofilm, its effects on biofilm development and on diatom community structure in laboratory experimental conditions. A suspension of a biofilm originated from the Riou-Mort River (South West France) was inoculated into three experimental units containing clean glass substrates under laboratory conditions. Settling and already developed biofilms were exposed to a Cd concentration of 100 {mu}g L{sup -1}. Metal accumulation (total and intracellular metal content) in biofilms, dry weight and ash-free dry mass, diatom cell density and diatom community composition were analyzed. Both total and intracellular Cd accumulated by the biofilm throughout the experiment increased with duration of metal exposure. Biofilms in the course of maturation were showed higher Cd content and less effective development than settled biofilms. However diatom communities in younger biofilms exposed to Cd increased their tolerance to Cd by a highly significant development of Nitzschia palea. In contrast, Cd exposure had different effect in installed biofilm and taxonomic composition. These results indicate that mature biofilm may limit Cd accumulation into its architecture and protect diatom communities from the effects of metals.

  16. Inland diatoms from the McMurdo Dry Valleys and James Ross Island, Antarctica

    Science.gov (United States)

    Esposito, R.M.M.; Spaulding, S.A.; McKnight, Diane M.; Van De Vijver, B.; Kopalova, K.; Lubinski, D.; Hall, B.; Whittaker, T.

    2008-01-01

    Diatom taxa present in the inland streams and lakes of the McMurdo Dry Valleys and James Ross Island, Antarctica, are presented in this paper. A total of nine taxa are illustrated, with descriptions of four new species (Luticola austroatlantica sp. nov., Luticola dolia sp. nov., Luticola laeta sp. nov., Muelleria supra sp. nov.). In the perennially ice-covered lakes of the McMurdo Dry Valleys, diatoms are confined to benthic mats within the photic zone. In streams, diatoms are attached to benthic surfaces and within the microbial mat matrix. One species, L. austroatlantica, is found on James Ross Island, of the southern Atlantic archipelago, and the McMurdo Dry Valleys. The McMurdo Dry Valley populations are at the lower range of the size spectrum for the species. Streams flow for 6-10 weeks during the austral summer, when temperatures and solar radiation allow glacial ice to melt. The diatom flora of the region is characterized by species assemblages favored under harsh conditions, with naviculoid taxa as the dominant group and several major diatom groups conspicuously absent. ?? 2008 NRC.

  17. An ecological and floristic study of the diatoms in Babolrud river

    Directory of Open Access Journals (Sweden)

    Naser Jafari

    2014-03-01

    Full Text Available Epilithic diatoms are a division of Bacillariophyceae which live on stone and hard surfaces. This study was aimed to investigate the population dynamics of diatoms in Babolrud river. Samples were collected from 5 stations from May 2012 through September 2012 in a monthly interval. Temperature, pH, NO3-, PO4- and (EC were measured for each sampling. Samples were prepared using Patrick and Reimer procedure. 72 taxa were identified, among which 33 taxa (46% were cosmopolitan or widely distributed. The genera with the highest species were Navicula (12, Nitzschia (9, Achnanthes (9, Cymbella (8 and Gomphonema (6. The decrease in diatoms diversity from upstream toward downstream can be regarded as an indicator of increasing water pollution. Trends in distribution of diatom species in the sampling sites were explained by variations in environmental parameters such as conductivity, pH, temperature, nitrate and phosphate. In highly contaminated sites of the Babolrud River, species such as Gomphonema olivaceum, Navicula pupula, Nitzschia flexa and Pinnularia major were observed, while individuals of Achnanthes clevei, Achnanthes deflexa, Cymbella affinis and Fragilaria virescens were found in sampling sites with relatively less environmental perturbation. We concluded that diatoms can be used as quantitative indicators of environmental conditions in lotic systems.

  18. Metabolic Influence of Psychrophilic Diatoms on Travertines at the Huanglong Natural Scenic District of China

    Directory of Open Access Journals (Sweden)

    Shiyong Sun

    2014-12-01

    Full Text Available Diatoms are a highly diversified group of algae that are widely distributed in aquatic ecosystems, and various species have different nutrient and temperature requirements for optimal growth. Here, we describe unusual psychrophilic diatoms of Cymbella in a travertine deposition environment in southwestern China in winter season. Travertine surfaces are colonized by these psychrophilic diatoms, which form biofilms of extracellular polysaccharide substances (EPS with active metabolic activities in extremely cold conditions. The travertine in Huanglong, is a typical single crystalline calcite with anisotropic lattice distortions of unit cell parameters along axes of a and c, and this structure is suggestive of some level of metabolic mediation on mineralization. Near-edge X-ray absorption fine structure spectroscopy (NEXAFS results further confirmed the occurrence of biogenic distortion of the crystal lattice of travertine calcite. Overall, our results imply that the metabolic influence of psychrophilic diatoms may be particularly important for promoting formation and dissolution of travertine in extremely cold environments of Huanglong. The EPS of psychrophilic diatoms will protect travertine from HCO3− etching and provide template for forming travertine when water re-flowing, in warm season.

  19. Low-Molecular-Weight Metabolites from Diatoms: Structures, Biological Roles and Biosynthesis

    Directory of Open Access Journals (Sweden)

    Valentin Stonik

    2015-06-01

    Full Text Available Diatoms are abundant and important biological components of the marine environment that biosynthesize diverse natural products. These microalgae are rich in various lipids, carotenoids, sterols and isoprenoids, some of them containing toxins and other metabolites. Several groups of diatom natural products have attracted great interest due to their potential practical application as energy sources (biofuel, valuable food constituents, and prospective materials for nanotechnology. In addition, hydrocarbons, which are used in climate reconstruction, polyamines which participate in biomineralization, new apoptotic agents against tumor cells, attractants and deterrents that regulate the biochemical communications between marine species in seawaters have also been isolated from diatoms. However, chemical studies on these microalgae are complicated by difficulties, connected with obtaining their biomass, and the influence of nutrients and contaminators in their environment as well as by seasonal and climatic factors on the biosynthesis of the corresponding natural products. Overall, the number of chemically studied diatoms is lower than that of other algae, but further studies, particularly those connected with improvements in the isolation and structure elucidation technique as well as the genomics of diatoms, promise both to increase the number of studied species with isolated biologically active natural products and to provide a clearer perception of their biosynthesis.

  20. Marine diatoms change their gene expression profile when exposed to microscale turbulence under nutrient replete conditions.

    Science.gov (United States)

    Amato, Alberto; Dell'Aquila, Gianluca; Musacchia, Francesco; Annunziata, Rossella; Ugarte, Ari; Maillet, Nicolas; Carbone, Alessandra; Ribera d'Alcalà, Maurizio; Sanges, Remo; Iudicone, Daniele; Ferrante, Maria I

    2017-06-19

    Diatoms are a fundamental microalgal phylum that thrives in turbulent environments. Despite several experimental and numerical studies, if and how diatoms may profit from turbulence is still an open question. One of the leading arguments is that turbulence favours nutrient uptake. Morphological features, such as the absence of flagella, the presence of a rigid exoskeleton and the micrometre size would support the possible passive but beneficial role of turbulence on diatoms. We demonstrate that in fact diatoms actively respond to turbulence in non-limiting nutrient conditions. TURBOGEN, a prototypic instrument to generate natural levels of microscale turbulence, was used to expose diatoms to the mechanical stimulus. Differential expression analyses, coupled with microscopy inspections, enabled us to study the morphological and transcriptional response of Chaetoceros decipiens to turbulence. Our target species responds to turbulence by activating energy storage pathways like fatty acid biosynthesis and by modifying its cell chain spectrum. Two other ecologically important species were examined and the occurrence of a morphological response was confirmed. These results challenge the view of phytoplankton as unsophisticated passive organisms.

  1. Diversity of Benthic Diatoms and Water Quality of the Ping River, Northern Thailand

    Directory of Open Access Journals (Sweden)

    Pongpan Leelahakriengkrai

    2010-01-01

    Full Text Available A study on the diversity of benthic diatoms and water quality of the Ping River, Northern Thailand were carried out from December 2004-December 2005. Samples were collected from 15 sites covering the whole river. The water quality was based on specific physical and chemical factors indicated the water in the Ping River was moderately clean and classified in the mesotrophic status, except in the upstream area which was clean to moderate and of the oligo-mesotrophic status. Changing in water quality depended on the environmental status surrounding the sampling sites and seasonal changes. Two orders, forty genera and one hundred and twenty eight species of benthic diatoms were found and classified into the Division Bacillariophyta. Most of them (97% were pennate diatoms in the Order Bacillariales. The remaining 3% were centric diatoms in the Order Biddulphiales. The relationship between water quality and dominant benthic diatoms in each sampling site and season were determined. It was found that Nitzschia palea (Kützing W. smith, Nitzschia sp. 2 and Synedra ulna var. aequalis (Kützing Hustedt were indicator species for moderate water quality whilst Cymbella turgidula Grunow, Gomphonema lagenula Kützing and Navicula symmetrica Patrick were indicator species of clean to moderate water quality.

  2. The effect of Fucus vesiculosus on the grazing of harpacticoid copepods on diatom biofilms

    Science.gov (United States)

    De Troch, M.; Chepurnov, V. A.; Vincx, M.; Ólafsson, E.

    2008-10-01

    The effect of Fucus vesiculosus on the functional traits of three harpacticoid copepod species ( Tigriopus brevicornis, Paramphiascella fulvofasciata and Microarthridion littorale) was studied. These copepods are likely to be important grazers on biofilms consisting mainly of diatoms. Several microcosms were created using diatom cultures ( Navicula phyllepta and Seminavis robusta) and vegetative thalli of Fucus, with the biofilm associated, collected from the field. The diatoms were enriched in the stable carbon 13C to facilitate tracing in the harpacticoids. The biofilm on the Fucus was labeled through impregnation of the Fucus leaves in 13C enriched seawater. In all treatments a measurable uptake of diatoms was found for the three copepod species. All copepods showed a low uptake of labeled material when only Fucus thalli were available. The grazing on the benthic diatoms was negatively affected by the presence of the Fucus thalli in the case of P. fulvofasciata. One species, T. brevicornis, grazed efficiently both on sedimentary and epiphytic biofilms. We hereby proved experimentally that benthic harpacticoid copepods are able to switch their food uptake under different habitat/food circumstances. This variety of food uptake is an illustration of the so-called 'niche complementarity effect' that lies at the basis of diverse communities.

  3. Early Middle Eocene Palaeoenvironments and Biostratigraphy of the Lomonosov Ridge: A Diatom and Chrysophyte Perspective

    Science.gov (United States)

    Stickley, C.; Koc, N.; Jordan, R.; Suto, I.

    2006-12-01

    The Arctic Coring Expedition (ACEX), Integrated Ocean Drilling Program Leg 302 recovered sediment cores from the Lomonosov Ridge to >400 meters below seafloor (mbsf). Dark grey mud-bearing organic-rich laminated biosiliceous ooze, between ~200-300 mbsf in Holes M0002A and M0004A, are Middle Eocene in age and contain shallow water marine diatoms in good preservation with abundances on the order of 106-107 valves/gram. The highest levels of biogenic silica, and the best siliceous microfossil preservation, occur below 220 mbsf, corresponding to Lithostratigraphic Unit 2. The diatoms occur in conjunction with variable abundances of other marine to brackish siliceous microfossils (ebridians, silicoflagellates and endoskeletal dinoflagellates) as well as diverse assemblages of freshwater chrysophyte cysts and marine and terrestrial palynomorphs. There are clear and frequent changes in dominance between the main siliceous microfossil groups, reflecting of an extraordinary depositional environment where both shallow marine and freshwater influences prevailed. We quantify these changes for the diatoms and chrysophytes. While the cyclical nature of these inferred salinity changes is under investigation, we report here on the broad scale variation in biosiliceous components through the Middle Eocene focusing in particular on the diatom and chrysophyte changes. Our initial results highlight the potential for an integrated regional diatom biostratigraphy for the Middle Eocene of the Arctic and Barents Sea, and indicate basin-wide palaeo-environmental fluctuations on long and short timescales. This poster outlines the various lines of work we are currently exploring in more detail.

  4. Pulsed gas lasers based on electric transitions of diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Kaslin, V.M.; Petrash, G.G.

    1975-01-01

    A detailed experimental study was carried out on the most important laser systems based on electron-oscillatory-rotational transitions of diatomic molecules. A study was made of the following transitions: in the N/sub 2/ molecule the C/sup 3/P/sub u/-B/sup 3/P/sub g/ (second positive band system) and the B/sup 3/P/sub g/-A/sup 3/..sigma../sub u//sup +/ (first positive band system) transitions; in the CO molecule the transition B/sup 1/..sigma../sup +/-A/sup 1/P (band system of Angstrom); in the H/sub 2/ molecule the transition 2sE/sup 1/..sigma../sub g//sup +/-2psigmab/sup 1/..sigma../sub u//sup +/. It is shown that in all these systems a single mechanism is responsible for the inverse population. It is based on excitation of the working levels by direct electron shock from the ground state of the molecules. The distribution of excitation and amplification among the bands is determined by the Frank-Cordon principle. The energy and temporal characteristics of light generation in tubes of equal diameter is unambiguously defined by the parameter E/N, where E is the tension of the electric field in the discharge tube, and N is the density of the working gas. It was found that cooling the active substance in these lasers leads to a sharp increase of the amplification coefficient. This feature made it possible to obtain record radiation output in most of these lasers, to observe modes of high emission in the lasers, to observe a variation of intensities in the molecular spectra, and to realize more than 180 new lines of light generation.

  5. Heterotrophic nutrition of the marine pennate diatom Navicula pavillardi Hustedt.

    Science.gov (United States)

    Lewin, J; Hellebust, J A

    1975-09-01

    Navicula pavillardi Hustedt, a marine, littoral, pennate diatom, can grow in the dark on glutamate or on the complex organic supplements tryptone or yeast extract. Growth on glutamate in the dark took place without an initial lag phase, whereas growth on tryptone began only after a 2-day lag phase that could be abolished by the simultaneous presence of glucose. Lactate inhibited growth in the dark on glutamate, but not photoautotrophic growth. Relatively low concentrations of glutamine inhibited photoautotrophic growth. The observed doubling time for heterotrophic growth on glutamate or tryptone was about 70 h, compared with a doubling time of 24 h under optimal photoautotrophic conditions. Glucose did not decrease the doubling time in the dark on tryptone. The assimilation efficiency for glutamate was 41%. The estimated necessary uptake rate for glutamate to account for the observed heterotrophic doubling time on glutamate was close to those measured with isotope techniques. The kinetic parameters for glutamate uptake, which followed Michelis-Menten kinetics, were Ks = 0.018 mM, and Vmax = 7.0 X 10(-10) mumol per cell per minute. Although several amino acids served as sole nitrogen sources for photoautotrophic growth and were demonstrated by the use of isotope techniques to enter the cells, they could not be used as substrates for growth in the dark. Glucose was not taken up to a significant extent except by cells grown in the presence of tryptone. Lactate was taken up only by dark-grown cells. Results of preliminary studies on the metabolic fate of several uniformly labeled amino acids are presented.

  6. Thick-shelled, grazer-protected diatoms decouple ocean carbon and silicon cycles in the iron-limited Antarctic Circumpolar Current

    Digital Repository Service at National Institute of Oceanography (India)

    Assmy, P.; Smetacek, V.; Montresor, M.; Klaas, C.; Henjes, J.; Strass, V.H.; Arrieta, J.M.; Bathmann, U.; Berg, G.M.; Breitbarth, E.; Cisewski, B.; Friedrichs, L.; Fuchs, N.; Herndl, G.J.; Jansen, S.; Kragefsky, S.; Latasa, M.; Peeken, I.; Rottgers, R.; Scharek, R.; Schuller, S.E.; Steigenberger, S.; Webb, A.; Wolf-Gladrow, D.

    Diatoms of the iron-replete continental margins and North Atlantic are key exporters of organic carbon. In contrast, diatoms of the iron-limited Antarctic Circumpolar Current sequester silicon, but comparatively little carbon, in the underlying deep...

  7. Magnesium compounds

    Science.gov (United States)

    Kramer, D.A.

    2007-01-01

    Seawater and natural brines accounted for about 52 percent of U.S. magnesium compounds production in 2006. Dead-burned magnesia was produced by Martin Marietta Magnesia Specialties from well brines in Michigan. Caustic-calcined magnesia was recovered from sea-water by Premier Chemicals in Florida; from well brines in Michigan by Martin Marietta and Rohm and Haas; and from magnesite in Nevada by Premier Chemicals. Intrepid Potash-Wendover and Great Salt Lake Minerals recovered magnesium chloride brines from the Great Salt Lake in Utah. Magnesium hydroxide was produced from brucite by Applied Chemical Magnesias in Texas, from seawater by SPI Pharma in Delaware and Premier Chemicals in Florida, and by Martin Marietta and Rohm and Haas from their operations mentioned above. About 59 percent of the magnesium compounds consumed in the United States was used for refractories that are used mainly to line steelmaking furnaces. The remaining 41 percent was consumed in agricultural, chemical, construction, environmental and industrial applications.

  8. Tellurium rings as electron pair donors in cluster compounds and coordination polymers; Tellurringe als Elektronenpaardonoren in Clusterverbindungen und Koordinationspolymeren

    Energy Technology Data Exchange (ETDEWEB)

    Guenther, Anja

    2011-11-08

    In this dissertation novel and already known molecular tellurium rings are presented in cluster compounds and quasi-one-dimensional coordination polymers. The cyclic, homonuclear units are always stabilized by coordination to electron-rich transition metal atoms, with the coordinating tellurium atoms acting as two-electron donors. As a synthesis route, the solid-state reaction in quartz glass vials was used uniformly. In addition to structural determination, the focus was on the characterization of the resulting compounds. For this purpose, resistance measurements were carried out on selected compounds, the magnetic behavior and the thermal degradation reactions were investigated and accompanying quantum chemical calculations were carried out. [German] In dieser Dissertation werden neuartige sowie bereits bekannte molekulare Tellurringe in Clusterverbindungen und quasi-eindimensionalen Koordinationspolymeren vorgestellt. Die Stabilisierung der zyklischen, homonuklearen Einheiten erfolgt dabei stets durch die Koordination an elektronenreiche Uebergangsmetallatome, wobei die koordinierenden Telluratome gegenueber diesen als Zwei-Elektronendonoren fungieren. Als Syntheseroute wurde dabei einheitlich auf die Festkoerperreaktion in Quarzglasampullen zurueckgegriffen. Neben der Strukturaufklaerung stand die Charakterisierung der erhaltenden Verbindungen im Fokus der Arbeit. Dazu wurden an ausgewaehlten Verbindungen Widerstandsmessungen durchgefuehrt, das magnetische Verhalten sowie die thermischen Abbaureaktionen untersucht und begleitende quantenchemische Rechnungen durchgefuehrt.

  9. Biodegradation of triclosan in diatom Navicula sp.: Kinetics, transformation products, toxicity evaluation and the effects of pH and potassium permanganate.

    Science.gov (United States)

    Ding, Tengda; Lin, Kunde; Yang, Mengting; Bao, Lianjun; Li, Juying; Yang, Bo; Gan, Jay

    2018-02-15

    Triclosan (TCS) is one of the most widely used pharmaceutically active compounds and frequently detected in treated wastewater and the impacted aquatic environment. However, the fate and toxicity of TCS in aquatic organisms is poorly known, including in particular the potential for the formation of incomplete biological transformation products. In this study, TCS posed high toxic effects (e.g., growth inhibition and damage of photosynthesis) to typical freshwater diatom Navicula sp., with the 24h and 72h EC 50 values of 173.3 and 145.6μgL -1 , respectively. The bioaccumulation of TCS in diatom cells increased with the increasing exposure to TCS and showed to be time-dependent. The higher intracellular TCS lead to higher toxicity on Navicula sp. The intracellular TCS concentration and the growth inhibition of TCS in Navicula sp. at pH 7.5 was obviously higher than that at pH 8.3, which was likely due to the higher abundance of unionized TCS in the culture. KMnO 4 reduced both bioaccumulation and toxicity of TCS in Navicula sp., especially at pH 8.3. A total of seven products were detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS). These findings will provide a reference for the risk assessment of TCS in aquatic environment. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Isolation and Physiological Characterization of a Novel Algicidal Virus Infecting the Marine Diatom Skeletonema costatum

    Directory of Open Access Journals (Sweden)

    JinJoo Kim

    2015-06-01

    Full Text Available Diatoms are a major component of the biological community, serving as the principal primary producers in the food web and sustaining oxygen levels in aquatic environments. Among marine planktonic diatoms, the cosmopolitan Skeletonema costatum is one of the most abundant and widespread species in the world’s oceans. Here, we report the basic characteristics of a new diatom-infecting S. costatum virus (ScosV isolated from Jaran Bay, Korea, in June 2008. ScosV is a polyhedral virus (45–50 nm in diameter that propagates in the cytoplasm of host cells and causes lysis of S. costatum cultures. The infectivity of ScosV was determined to be strain- rather than species-specific, similar to other algal viruses. The burst size and latent period were roughly estimated at 90–250 infectious units/cell and <48 h, respectively.

  11. Biosilica from Living Diatoms: Investigations on Biocompatibility of Bare and Chemically Modified Thalassiosira weissflogii Silica Shells

    Directory of Open Access Journals (Sweden)

    Stefania Roberta Cicco

    2016-12-01

    Full Text Available In the past decade, mesoporous silica nanoparticles (MSNs with a large surface area and pore volume have attracted considerable attention for their application in drug delivery and biomedicine. Here we propose biosilica from diatoms as an alternative source of mesoporous materials in the field of multifunctional supports for cell growth: the biosilica surfaces were chemically modified by traditional silanization methods resulting in diatom silica microparticles functionalized with 3-mercaptopropyl-trimethoxysilane (MPTMS and 3-aminopropyl-triethoxysilane (APTES. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that the –SH or –NH2 were successfully grafted onto the biosilica surface. The relationship among the type of functional groups and the cell viability was established as well as the interaction of the cells with the nanoporosity of frustules. These results show that diatom microparticles are promising natural biomaterials suitable for cell growth, and that the surfaces, owing to the mercapto groups, exhibit good biocompatibility.

  12. Occurrence of phosphatidylsulfocholine, the sulfonium analog of phosphatidylcholine in some diatoms and algae.

    Science.gov (United States)

    Bisseret, P; Ito, S; Tremblay, P A; Volcani, B E; Dessort, D; Kates, M

    1984-12-06

    A survey of seven species of diatoms, one Euglena sp. and one dinoflagellate sp. for the presence of phosphatidylsulfocholine (PSC), the sulfonium analog of phosphatidylcholine (PC), was carried out using 1H-NMR spectroscopy and ammonia desorption chemical ionization mass spectrometry. PSC alone was found only in a non-photosynthetic diatom, Nitzschia alba. PSC, together with PC, was found in four of the diatoms (Nitzschia angularis, Cylindrotheca fusiformis, Phaeodactylum tricornutum and Navicula pelliculosa) in proportions of 6-24% of the total PC + PSC fraction, but little or no PSC (less than 2%) was detected in the remaining two (Cyclotella nana and Navicula incerta). Little or no PSC (less than 2%) was detected in a Euglena sp. by 1H-NMR but its presence was confirmed by 35S-labeling. The amount of PSC, if any, in the dinoflagellate (Amphidinium carterae) was below the level of detection by 1H-NMR.

  13. Role of Diatoms in the Spatial-Temporal Distribution of Intracellular Nitrate in Intertidal Sediment

    DEFF Research Database (Denmark)

    Stief, P.; Kamp, A.; de Beer, D.

    2013-01-01

    Intracellular nitrate storage allows microorganisms to survive fluctuating nutrient availability and anoxic conditions in aquatic ecosystems. Here we show that diatoms, ubiquitous and highly abundant microalgae, represent major cellular reservoirs of nitrate in an intertidal flat of the German...... Wadden Sea and are potentially involved in anaerobic nitrate respiration. Intracellular nitrate (ICNO3) was present year-round in the sediment and was spatially and temporally correlated with fucoxanthin, the marker photopigment of diatoms. Pyrosequencing of SSU rRNA genes of all domains of life...... in anaerobic nitrate respiration. Due to the widespread dominance of diatoms in microphytobenthos, the total nitrate pool in coastal marine sediments may generally be at least two times larger than derived from porewater measurements and partially be recycled to ammonium....

  14. Mussel- and Diatom-Inspired Micropattern Generation of Silica on a Solid Substrate

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jungkyu K. [Kyungpook National Univ., Daegu (Korea, Republic of); Kang, Sung Min [Pukyong National Univ., Busan (Korea, Republic of)

    2013-02-15

    Biosilicification in diatoms and sponges potentially promises physiological, mild reaction conditions for controlling silica structures at the nanometer scale. Since Sumper et al. had isolated catalytic peptides (i. e., silaffins) from diatoms, a number of polymers bearing tertiary amine or ammonium groups have been used as a counterpart of silaffins to biomimetically synthesize silica structures. We demonstrated a micropattern generation of silica on the solid substrate by a mussel- and diatom-inspired approach combined with a soft lithography. This method shows several advantages to apply for a wide range of materials without harsh reaction conditions. Moreover, it could allow us to give proper functionalities on silica layers via well-defined organosilane chemistry.

  15. Probing the evolutionary history of epigenetic mechanisms: what can we learn from marine diatoms

    Directory of Open Access Journals (Sweden)

    Achal Rastogi

    2015-07-01

    Full Text Available Recent progress made on epigenetic studies revealed the conservation of epigenetic features in deep diverse branching species including Stramenopiles, plants and animals. This suggests their fundamental role in shaping species genomes across different evolutionary time scales. Diatoms are a highly successful and diverse group of phytoplankton with a fossil record of about 190 million years ago. They are distantly related from other super-groups of Eukaryotes and have retained some of the epigenetic features found in mammals and plants suggesting their ancient origin. Phaeodactylum tricornutum and Thalassiosira pseudonana, pennate and centric diatoms, respectively, emerged as model species to address questions on the evolution of epigenetic phenomena such as what has been lost, retained or has evolved in contemporary species. In the present work, we will discuss how the study of non-model or emerging model organisms, such as diatoms, helps understand the evolutionary history of epigenetic mechanisms with a particular focus on DNA methylation and histone modifications.

  16. Implications for photonic applications of diatom growth and frustule nanostructure changes in response to different light wavelengths

    DEFF Research Database (Denmark)

    Su, Yanyan; Lundholm, Nina; Friis, Søren Michael Mørk

    2015-01-01

    Diatoms are unicellular algae enclosed in intricate bio - silicified walls with repetitive nanostructures in a size range which makes them potentially relevant for a broad spectrum of industrial applications. How to optimize the nano - scale structures of the frustule for utilization of diatoms...

  17. Relationship of fouling diatom number and chlorophyll-a value from Zuari estuary, Goa (west coast of India)

    Digital Repository Service at National Institute of Oceanography (India)

    Redekar, P.D.; Wagh, A.B.

    The diatom cell biomass is expressed in terms of diatom number and chlorophyll -a value on panel of glass slide. The Chlorophyll value in a water body is indicative of the productivity. The present study was conducted to find out the relationship...

  18. Molecular and Photosynthetic Responses to Prolonged Darkness and Subsequent Acclimation to Re-Illumination in the Diatom Phaeodactylum tricornutum

    DEFF Research Database (Denmark)

    Nymark, Marianne; Valle, Kristi Collier; Hancke, Kasper

    2013-01-01

    Photosynthetic diatoms that live suspended throughout the water column will constantly be swept up and down by vertical mixing. When returned to the photic zone after experiencing longer periods in darkness, mechanisms exist that enable the diatoms both to survive sudden light exposure and immedi...

  19. Environmental determinants of diatom assemblages along a North African wadi, the Kebir-East, North-East Algeria

    Directory of Open Access Journals (Sweden)

    Boudjéma SAMRAOUI

    2011-02-01

    Full Text Available A total of 322 benthic diatoms with the majority being cosmopolitan species was recorded during a survey of the catchment area of the Kebir-East wadi, northeast Algeria. The spatial distribution patterns of diatom communities in relation to environmental gradients were examined using Co-Inertia Analysis (CIA for ascertaining the interdependence between physico-chemical descriptors and diatom assemblages in 182 samples, collected over a period of 3 years, across 23 sampling stations. There was a significant covariance between the environmental data set and the benthic diatom data set with the CIA highlighting correlations between environmental factors and diatom species. A clear longitudinal gradient was a main driver of diatom communities with upstream sites characterized by high dissolved oxygen concentrations and downstream sites characterized by high organic load and nutrient enrichment of the water. A further factor influencing the shape of diatom assemblages was related to the conductivity, and the high values possibly reflected the close proximity of the sea to the downstream sites. An anthropogenic impact was also most evident in structuring diatom assemblages at sites close to Lake Oubeïra where agriculture was concentrated.

  20. Influence d'un traitement au chlore sur la croissance d'une diatomée : Phaeodactylum Tricornutum (BOHLIN)

    OpenAIRE

    Bardouil, Michele; Bocquene, Gilles; Le Dean, Loic

    1981-01-01

    Ces travaux complètent l'étude de l'influence de chocs thermiques sur la croissance de la diatomée Phaeodactylum tricornutum (BOHLIN). Ils concernent les effets d'un traitement au chlore sur le développement de cette diatomée.

  1. Biological responses of the marine diatom Chaetoceros socialis to changing environmental conditions: A laboratory experiment.

    Science.gov (United States)

    Li, Xuefeng; Roevros, Nathalie; Dehairs, Frank; Chou, Lei

    2017-01-01

    Diatoms constitute a major group of phytoplankton, accounting for ~20% of the world's primary production. It has been shown that iron (Fe) can be the limiting factor for phytoplankton growth, in particular, in the HNLC (High Nutrient Low Chlorophyll) regions. Iron plays thus an essential role in governing the marine primary productivity and the efficiency of biological carbon pump. Oceanic systems are undergoing continuous modifications at varying rates and magnitudes as a result of changing climate. The objective of our research is to evaluate how changing environmental conditions (dust deposition, ocean warming and acidification) can affect marine Fe biogeochemistry and diatom growth. Laboratory culture experiments using a marine diatom Chaetoceros socialis were conducted at two temperatures (13°C and 18°C) and under two pCO2 (carbon dioxide partial pressure) (400 μatm and 800 μatm) conditions. The present study clearly highlights the effect of ocean acidification on enhancing the release of Fe upon dust deposition. Our results also confirm that being a potential source of Fe, dust provides in addition a readily utilizable source of macronutrients such as dissolved phosphate (PO4) and silicate (DSi). However, elevated atmospheric CO2 concentrations may also have an adverse impact on diatom growth, causing a decrease in cell size and possible further changes in phytoplankton composition. Meanwhile, ocean warming may lead to the reduction of diatom production and cell size, inducing poleward shifts in the biogeographic distribution of diatoms. The changing climate has thus a significant implication for ocean phytoplankton growth, cell size and primary productivity, phytoplankton distribution and community composition, and carbon (C), nitrogen (N), phosphorus (P), silicon (Si) and Fe biogeochemical cycles in various ways.

  2. The ancestors of diatoms evolved a unique mitochondrial dehydrogenase to oxidize photorespiratory glycolate.

    Science.gov (United States)

    Schmitz, Jessica; Srikanth, Nishtala V; Hüdig, Meike; Poschmann, Gereon; Lercher, Martin J; Maurino, Veronica G

    2017-05-01

    Like other oxygenic photosynthetic organisms, diatoms produce glycolate, a toxic intermediate, as a consequence of the oxygenase activity of Rubisco. Diatoms can remove glycolate through excretion and through oxidation as part of the photorespiratory pathway. The diatom Phaeodactylum tricornutum encodes two proteins suggested to be involved in glycolate metabolism: PtGO1 and PtGO2. We found that these proteins differ substantially from the sequences of experimentally characterized proteins responsible for glycolate oxidation in other species, glycolate oxidase (GOX) and glycolate dehydrogenase. We show that PtGO1 and PtGO2 are the only sequences of P. tricornutum homologous to GOX. Our phylogenetic analyses indicate that the ancestors of diatoms acquired PtGO1 during the proposed first secondary endosymbiosis with a chlorophyte alga, which may have previously obtained this gene from proteobacteria. In contrast, PtGO2 is orthologous to an uncharacterized protein in Galdieria sulphuraria, consistent with its acquisition during the secondary endosymbiosis with a red alga that gave rise to the current plastid. The analysis of amino acid residues at conserved positions suggests that PtGO2, which localizes to peroxisomes, may use substrates other than glycolate, explaining the lack of GOX activity we observe in vitro. Instead, PtGO1, while only very distantly related to previously characterized GOX proteins, evolved glycolate-oxidizing activity, as demonstrated by in gel activity assays and mass spectrometry analysis. PtGO1 localizes to mitochondria, consistent with previous suggestions that photorespiration in diatoms proceeds in these organelles. We conclude that the ancestors of diatoms evolved a unique alternative to oxidize photorespiratory glycolate: a mitochondrial dehydrogenase homologous to GOX able to use electron acceptors other than O 2 .

  3. The influence of environmental, biotic and spatial factors on diatom metacommunity structure in Swedish headwater streams.

    Directory of Open Access Journals (Sweden)

    Emma Göthe

    Full Text Available Stream assemblages are structured by a combination of local (environmental filtering and biotic interactions and regional factors (e.g., dispersal related processes. The relative importance of environmental and spatial (i.e., regional factors structuring stream assemblages has been frequently assessed in previous large-scale studies, but biotic predictors (potentially reflecting local biotic interactions have rarely been included. Diatoms may be useful for studying the effect of trophic interactions on community structure since: (1 a majority of experimental studies shows significant grazing effects on diatom species composition, and (2 assemblages can be divided into guilds that have different susceptibility to grazing. We used a dataset from boreal headwater streams in south-central Sweden (covering a spatial extent of ∼14000 km(2, which included information about diatom taxonomic composition, abundance of invertebrate grazers (biotic factor, environmental (physicochemical and spatial factors (obtained through spatial eigenfunction analyses. We assessed the relative importance of environmental, biotic, and spatial factors structuring diatom assemblages, and performed separate analyses on different diatom guilds. Our results showed that the diatom assemblages were mainly structured by environmental factors. However, unique spatial and biological gradients, specific to different guilds and unrelated to each other, were also evident. We conclude that biological predictors, in combination with environmental and spatial variables, can reveal a more complete picture of the local vs. regional control of species assemblages in lotic environments. Biotic factors should therefore not be overlooked in applied research since they can capture additional local control and therefore increase accuracy and performance of predictive models. The inclusion of biotic predictors did, however, not significantly influence the unique fraction explained by spatial

  4. The Influence of Environmental, Biotic and Spatial Factors on Diatom Metacommunity Structure in Swedish Headwater Streams

    Science.gov (United States)

    Göthe, Emma; Angeler, David G.; Gottschalk, Steffi; Löfgren, Stefan; Sandin, Leonard

    2013-01-01

    Stream assemblages are structured by a combination of local (environmental filtering and biotic interactions) and regional factors (e.g., dispersal related processes). The relative importance of environmental and spatial (i.e., regional) factors structuring stream assemblages has been frequently assessed in previous large-scale studies, but biotic predictors (potentially reflecting local biotic interactions) have rarely been included. Diatoms may be useful for studying the effect of trophic interactions on community structure since: (1) a majority of experimental studies shows significant grazing effects on diatom species composition, and (2) assemblages can be divided into guilds that have different susceptibility to grazing. We used a dataset from boreal headwater streams in south-central Sweden (covering a spatial extent of ∼14000 km2), which included information about diatom taxonomic composition, abundance of invertebrate grazers (biotic factor), environmental (physicochemical) and spatial factors (obtained through spatial eigenfunction analyses). We assessed the relative importance of environmental, biotic, and spatial factors structuring diatom assemblages, and performed separate analyses on different diatom guilds. Our results showed that the diatom assemblages were mainly structured by environmental factors. However, unique spatial and biological gradients, specific to different guilds and unrelated to each other, were also evident. We conclude that biological predictors, in combination with environmental and spatial variables, can reveal a more complete picture of the local vs. regional control of species assemblages in lotic environments. Biotic factors should therefore not be overlooked in applied research since they can capture additional local control and therefore increase accuracy and performance of predictive models. The inclusion of biotic predictors did, however, not significantly influence the unique fraction explained by spatial factors

  5. Biological responses of the marine diatom Chaetoceros socialis to changing environmental conditions: A laboratory experiment.

    Directory of Open Access Journals (Sweden)

    Xuefeng Li

    Full Text Available Diatoms constitute a major group of phytoplankton, accounting for ~20% of the world's primary production. It has been shown that iron (Fe can be the limiting factor for phytoplankton growth, in particular, in the HNLC (High Nutrient Low Chlorophyll regions. Iron plays thus an essential role in governing the marine primary productivity and the efficiency of biological carbon pump. Oceanic systems are undergoing continuous modifications at varying rates and magnitudes as a result of changing climate. The objective of our research is to evaluate how changing environmental conditions (dust deposition, ocean warming and acidification can affect marine Fe biogeochemistry and diatom growth. Laboratory culture experiments using a marine diatom Chaetoceros socialis were conducted at two temperatures (13°C and 18°C and under two pCO2 (carbon dioxide partial pressure (400 μatm and 800 μatm conditions. The present study clearly highlights the effect of ocean acidification on enhancing the release of Fe upon dust deposition. Our results also confirm that being a potential source of Fe, dust provides in addition a readily utilizable source of macronutrients such as dissolved phosphate (PO4 and silicate (DSi. However, elevated atmospheric CO2 concentrations may also have an adverse impact on diatom growth, causing a decrease in cell size and possible further changes in phytoplankton composition. Meanwhile, ocean warming may lead to the reduction of diatom production and cell size, inducing poleward shifts in the biogeographic distribution of diatoms. The changing climate has thus a significant implication for ocean phytoplankton growth, cell size and primary productivity, phytoplankton distribution and community composition, and carbon (C, nitrogen (N, phosphorus (P, silicon (Si and Fe biogeochemical cycles in various ways.

  6. Metatranscriptomes reveal functional variation in diatom communities from the Antarctic Peninsula

    KAUST Repository

    Pearson, Gareth A

    2015-04-14

    Functional genomics of diatom-dominated communities fromthe Antarctic Peninsula was studied using comparative metatranscriptomics. Samples obtained from diatom-rich communities in the Bransfield Strait, the western Weddell Sea and sea ice in the Bellingshausen Sea/Wilkins Ice Shelf yielded more than 500K pyrosequencing reads that were combined to produce a global metatranscriptome assembly. Multi-gene phylogenies recovered three distinct communities, and diatom-assigned contigs further indicated little read-sharing between communities, validating an assembly-based annotation and analysis approach. Although functional analysis recovered a core of abundant shared annotations that were expressed across the three diatom communities, over 40% of annotations (but accounting for <10% of sequences) were community-specific. The two pelagic communities differed in their expression of N-metabolism and acquisition genes, which was almost absent in post-bloom conditions in the Weddell Sea community, while enrichment of transporters for ammonia and urea in Bransfield Strait diatoms suggests a physiological stance towards acquisition of reduced N-sources. The depletion of carbohydrate and energy metabolism pathways in sea ice relative to pelagic communities, together with increased light energy dissipation (via LHCSR proteins), photorespiration, and NO3 - uptake and utilization all pointed to irradiance stress and/or inorganic carbon limitation within sea ice. Ice-binding proteins and cold-shock transcription factors were also enriched in sea ice diatoms. Surprisingly, the abundance of gene transcripts for the translational machinery tracked decreasing environmental temperature across only a 4 °C range, possibly reflecting constraints on translational efficiency and protein production in cold environments. © 2015 International Society for Microbial Ecology All rights reserved.

  7. Red and green algal origin of diatom membrane transporters: insights into environmental adaptation and cell evolution.

    Directory of Open Access Journals (Sweden)

    Cheong Xin Chan

    Full Text Available Membrane transporters (MTs facilitate the movement of molecules between cellular compartments. The evolutionary history of these key components of eukaryote genomes remains unclear. Many photosynthetic microbial eukaryotes (e.g., diatoms, haptophytes, and dinoflagellates appear to have undergone serial endosymbiosis and thereby recruited foreign genes through endosymbiotic/horizontal gene transfer (E/HGT. Here we used the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum as models to examine the evolutionary origin of MTs in this important group of marine primary producers. Using phylogenomics, we used 1,014 diatom MTs as query against a broadly sampled protein sequence database that includes novel genome data from the mesophilic red algae Porphyridium cruentum and Calliarthron tuberculosum, and the stramenopile Ectocarpus siliculosus. Our conservative approach resulted in 879 maximum likelihood trees of which 399 genes show a non-lineal history between diatoms and other eukaryotes and prokaryotes (at the bootstrap value ≥70%. Of the eukaryote-derived MTs, 172 (ca. 25% of 697 examined phylogenies have members of both red/green algae as sister groups, with 103 putatively arising from green algae, 19 from red algae, and 50 have an unresolved affiliation to red and/or green algae. We used topology tests to analyze the most convincing cases of non-lineal gene history in which red and/or green algae were nested within stramenopiles. This analysis showed that ca. 6% of all trees (our most conservative estimate support an algal origin of MTs in stramenopiles with the majority derived from green algae. Our findings demonstrate the complex evolutionary history of photosynthetic eukaryotes and indicate a reticulate origin of MT genes in diatoms. We postulate that the algal-derived MTs acquired via E/HGT provided diatoms and other related microbial eukaryotes the ability to persist under conditions of fluctuating ocean chemistry, likely

  8. Anaerobic Nitrogen Turnover by Sinking Diatom Aggregates at Varying Ambient Oxygen Levels

    Directory of Open Access Journals (Sweden)

    Peter eStief

    2016-02-01

    Full Text Available In the world’s oceans, even relatively low oxygen (O2 levels inhibit anaerobic nitrogen cycling by free-living microbes. Sinking organic aggregates, however, might provide oxygen-depleted microbial hotspots in otherwise oxygenated surface waters. Here we show that sinking diatom aggregates can host anaerobic nitrogen cycling at ambient O2 levels well above the hypoxic threshold. Aggregates were produced from the ubiquitous diatom Skeletonema marinoi and the natural microbial community of seawater. Microsensor profiling through the center of sinking aggregates revealed internal anoxia at ambient 40% air saturation (~100 µmol O2 L-1 and below. Accordingly, anaerobic nitrate turnover inside the aggregates was evident within this range of ambient O2 levels. In incubations with 15N-labeled nitrate, individual Skeletonema aggregates produced NO2- (up to 10.7 nmol N h-1 per aggregate, N2 (up to 7.1 nmol N h-1, NH4+ (up to 2.0 nmol N h-1, and N2O (up to 0.2 nmol N h-1. Intriguingly, nitrate stored inside the diatom cells served as an additional, internal nitrate source for N2 production, which may partially uncouple anaerobic nitrate turnover by diatom aggregates from direct ambient nitrate supply. Sinking diatom aggregates can contribute directly to fixed-nitrogen loss in low-oxygen environments in the ocean and vastly expand the ocean volume in which anaerobic nitrogen turnover is possible, despite relatively high ambient O2 levels. Depending on the extent of intracellular nitrate consumption during the sinking process, diatom aggregates may also be involved in the long-distance export of nitrate to the deep ocean.

  9. Feeding, growth, and survival of post-larval abalone Haliotis asinina on different benthic diatoms

    Directory of Open Access Journals (Sweden)

    Emmanuel C. Capinpin, Jr.

    2007-12-01

    Full Text Available The feeding behavior, digestive efficiency, growth, and survival of post-larval abalone Haliotis asininafed with 5 species of locally isolated benthic diatom strains (Navicula mollis, N. ramosissima, Stauroneissp., Pleurosigma sp., and Cocconeis sp. were examined in the laboratory. Two 15-day feeding trialsusing 1 mm post-larvae were conducted. No significant differences were observed in sizes of post-larvalabalone after 15 days in all diatom treatments (P>0.05. However, in both trials, Cocconeis sp. resulted inhigh survival rates (88.9±5.6% and 80.0±20.0% for Trials 1 and 2, respectively. Cocconeis sp. wasefficiently digested by post-larval abalone, with most of the cells being ruptured during ingestion and/orpassage through the gut. One diatom strain, Pleurosigma sp., resulted to a high survival but producedthe slowest growth rate (<10 ìm.d-1 SL. It was probably not ingested easily during the experiment due toits large size or mobility. For the other diatom strains, N. mollis and N. ramosissima, most cells passedthrough the gut with the cells left intact. Stauroneis sp. is highly digestible, but did not result to highsurvival, although the remaining live post-larval abalone fed on this diatom as well as on N. mollis grewfaster during the second week of both feeding trials. N. ramosissima resulted to poorest survival rate(<10% due to its poor digestibility. Only Cocconeis sp. showed a fairly high growth rate, digestionefficiency, and survival rate. N. mollis which gave a fairly high survival rate and Stauroneis may be addedtowards the later stages of post-larval rearing as well as other large diatoms. The digestion efficiency ofdiatom strains is considered an important factor determining its dietary value, but other factors may alsobe important such as volume contents, biochemical composition, and other physical characteristics.

  10. Hydrological variables play a remarkable role in temporal dynamics of daily sampled diatom community in a German lowland river

    Science.gov (United States)

    Sun, Xiuming; Wu, Naicheng; Faber, Claas; Fohrer, Nicola

    2017-04-01

    Temporal dynamics of diatom community with relation to abiotic factors is an important part of water quality monitoring and water resource management. However, the contribution of hydrological variables to temporal diatom variation has been rarely reported, especially at a short-interval sampling scale. Based on daily riverine diatom samples over a 1-year period (25 April 2013 - 30 April 2014) at the outlet of a German lowland river, we aimed to examine the temporal variation patterns of diatom community and to compare the relative importance between chemical and hydrological variables of affecting the temporal diatom community variation. Among the 339 samples, a total of 113 diatom taxa from 45 genera were identified. Sampling dates with similar species composition and structure were classified into five clusters by a Kohonen Self-Organizing Map (SOM) method within Matlab software. These five groups were distinct with respect to species composition, density, richness, and indicator species, as well as environmental variables. Redundancy analysis (RDA) and variance partitioning techniques were used to explain the relationships between environmental variables and diatom community dynamics. For the whole dataset, chemical and hydrological variables could jointly explain 50.17% of the diatom community variation including chemical variables with 36.45% and hydrological variables with 12.89%. The most important chemical variables were Phosphate-Phosphorus (PO4-P) and Silicon (Si) concentrations, while the most significant hydrological variable was antecedent precipitation index (API), indicating the importance of nutrient and hydrological factor in shaping diatom structure. In general, the relative importance of chemical and hydrological factors to diatom communities varied among seasons (or SOM clusters). Partial RDAs revealed that 3.60%, 11.96%, 7.10%, 10.4% and 7.11% of diatom variation can be explained by hydrological variables from cluster 1 to 5, while 52.71%, 47

  11. Magnesium compounds

    Science.gov (United States)

    Kramer, D.A.

    2012-01-01

    Seawater and natural brines accounted for about 57 percent of magnesium compounds produced in the United States in 2011. Dead-burned magnesia was produced by Martin Marietta Magnesia Specialties LLC from well brines in Michigan. Caustic-calcined magnesia was recovered from seawater by Premier Magnesia LLC in Florida, from well brines in Michigan by Martin Marietta and from magnesite in Nevada by Premier Magnesia. Intrepid Potash Wendover LLC and Great Salt Lake Minerals Corp. recovered magnesium chloride brines from the Great Salt Lake in Utah. Magnesium hydroxide was produced from seawater by SPI Pharma Inc. in Delaware and Premier Magnesia in Florida, and by Martin Marietta from its brine operation in Michigan.

  12. Bismaleimide compounds

    Science.gov (United States)

    Adams, Johnnie E.; Jamieson, Donald R.

    1986-01-14

    Bismaleimides of the formula ##STR1## wherein R.sub.1 and R.sub.2 each independently is H, C.sub.1-4 -alkyl, C.sub.1-4 -alkoxy, C1 or Br, or R.sub.1 and R.sub.2 together form a fused 6-membered hydrocarbon aromatic ring, with the proviso that R.sub.1 and R.sub.2 are not t-butyl or t-butoxy; X is O, S or Se; n is 1-3; and the alkylene bridging group, optionally, is substituted by 1-3 methyl groups or by fluorine, form polybismaleimide resins which have valuable physical properties. Uniquely, these compounds permit extended cure times, i.e., they remain fluid for a time sufficient to permit the formation of a homogeneous melt prior to curing.

  13. Morphological and transcriptomic evidence for ammonium induction of sexual reproduction in Thalassiosira pseudonana and other centric diatoms.

    Science.gov (United States)

    Moore, Eric R; Bullington, Briana S; Weisberg, Alexandra J; Jiang, Yuan; Chang, Jeff; Halsey, Kimberly H

    2017-01-01

    The reproductive strategy of diatoms includes asexual and sexual phases, but in many species, including the model centric diatom Thalassiosira pseudonana, sexual reproduction has never been observed. Furthermore, the environmental factors that trigger sexual reproduction in diatoms are not understood. Although genome sequences of a few diatoms are available, little is known about the molecular basis for sexual reproduction. Here we show that ammonium reliably induces the key sexual morphologies, including oogonia, auxospores, and spermatogonia, in two strains of T. pseudonana, T. weissflogii, and Cyclotella cryptica. RNA sequencing revealed 1,274 genes whose expression patterns changed when T. pseudonana was induced into sexual reproduction by ammonium. Some of the induced genes are linked to meiosis or encode flagellar structures of heterokont and cryptophyte algae. The identification of ammonium as an environmental trigger suggests an unexpected link between diatom bloom dynamics and strategies for enhancing population genetic diversity.

  14. Hundred years of genetic structure in a sediment revived diatom population

    DEFF Research Database (Denmark)

    Haernstroem, Karolina; Ellegaard, Marianne; Andersen, Thorbjørn Joest

    2011-01-01

    This paper presents research on the genetic structure and diversity of populations of a common marine protist and their changes over time. The bloom-forming diatom Skeletonema marinoi was used as a model organism. Strains were revived from anoxic discrete layers of a 210Pb-dated sediment core...... accumulated over more than 100 y, corresponding to >40,000 diatom mitotic generations. The sediment core was sampled from the highly eutrophic Mariager Fjord in Denmark. The genetic structure of S. marinoi was examined using microsatellite markers, enabling exploration of changes through time...

  15. Momentum and velocity autocorrelation functions of a diatomic molecule are not necessarily proportional to each other.

    Science.gov (United States)

    Moix, Jeremy M; Hernandez, Rigoberto; Pollak, Eli

    2008-01-17

    We present a computation of the classical momentum and velocity correlation functions of Br2 considered as an idealized molecular wire connecting dissipated lead atoms at each end of the dimer. It is demonstrated that coupling of the diatomic relative momentum to the leads may result in momenta that are not equal to the mass-weighted velocity. These differences show up in numerical simulations of both the average value and time correlations of the bond momentum and velocity. These observations are supported by analytical predictions for the average temperature of the diatomic. They imply that the "standard recipes" for modeling the system with a generalized Langevin equation are insufficient.

  16. Diatom-inferred history of one of the northernmost Greenland lakes

    DEFF Research Database (Denmark)

    Ludikova, Anna; Olsen, Jesper; Kjær, Kurt H.

    Arctic lakes are known among the most effective tools in reconstructing past climatic and environmental variability. In formerly (and presently) glaciated regions they also help reconstructing relative sea-level changes resulted from glacioisostatic rebound. In this study, the diatom stratigraphy......, as well as physical and geochemical proxies was used to reconstruct the Holocene history of one of the small lakes located in Peary Land, northernmost Greenland, to decipher the environmental changes of the past. The diatom record of Bliss Lake (83°35'14''N 28°21'12''W, 17 m a.s.l.) reveals three main...

  17. Discrete breathers at the interface between a diatomic and a monoatomic granular chain.

    Science.gov (United States)

    Hoogeboom, C; Theocharis, G; Kevrekidis, P G

    2010-12-01

    In the present work, we develop a systematic examination of the existence, stability, and dynamical properties of a discrete breather at the interface between a diatomic and a monoatomic granular chain. We remarkably find that such an "interface breather" is more robust than its bulk diatomic counterpart throughout the gap of the linear spectrum. The latter linear spectral gap needs to exist for the breather state to arise and the relevant spectral conditions are discussed. We illustrate the minimal excitation conditions under which such an interface breather can be "nucleated" and analyze its apparently weak interaction with regular highly nonlinear solitary waveforms.

  18. Distribution of Epilithic Diatoms in Estuaries of the Korean Peninsula in Relation to Environmental Variables

    Directory of Open Access Journals (Sweden)

    Ha-Kyung Kim

    2015-11-01

    Full Text Available This study explores the relationships between environmental factors and the distribution of epilithic diatoms in 161 estuaries of three coastal areas on the Korean peninsula. We investigated epilithic diatoms, water quality, and land use in the vicinities of the estuaries during the months of May 2012, 2013 and 2014, because Korea is relatively free from the influences of rainfall at that time of year. We recorded 327 diatom taxa from the study sites, and the assemblage was dominated by members of the Naviculaceae. Bacillariaceae accounted for the largest proportion of diatoms, and Nitzschia inconspicua (18% and N. frustulum (9.6% were the most dominant species. A cluster analysis based on epilithic diatom abundance suggested that the epilithic diatom communities of Korean estuaries can be classified into four large groups (G according to geography, as follows: Ia—the East Sea watershed, Ib—the eastern watershed of the South Sea, IIa—the West Sea watershed, and IIb—the western watershed of the South Sea. The former two groups, Ia and Ib, showed higher proportions of forest land cover and use, higher species occurrence, lower salinity, lower turbidity, and lower concentrations of nutrients than the latter two groups, while the latter groups, IIa and IIb, had higher proportions of agricultural land cover and use, higher electrical conductivity, higher turbidity, higher concentrations of nutrients, and lower species occurrence. The environmental factors underlying the distribution of epilithic diatoms, representative of each region, are as follows: dissolved oxygen and forest land cover and use for Reimeria sinuate and Rhoicosphenia abbreviate of the East Sea (ES, salinity and turbidity for Tabularia fasciculate of the West Sea (WS, and biochemical oxygen demand (BOD and nutrients for Cyclotella meneghiniana of the WS. On the other hand, the most influential environmental factors affecting the occurrence of indicator species showing the

  19. Anaerobic nitrogen turnover by sinking diatom aggregates at varying ambient oxygen levels

    DEFF Research Database (Denmark)

    Stief, Peter; Kamp, Anja; Thamdrup, Bo

    2016-01-01

    In the world’s oceans, even relatively low oxygen levels inhibit anaerobic nitrogen cycling by free-living microbes. Sinking organic aggregates, however, might provide oxygen-depleted microbial hotspots in otherwise oxygenated surface waters. Here, we show that sinking diatom aggregates can host...... nitrate supply. Sinking diatom aggregates can contribute directly to fixed-nitrogen loss in low-oxygen environments in the ocean and vastly expand the ocean volume in which anaerobic nitrogen turnover is possible, despite relatively high ambient oxygen levels. Depending on the extent of intracellular...

  20. Polymer networks produced by marine diatoms in the northern Adriatic sea.

    Science.gov (United States)

    Svetličić, Vesna; Zutić, Vera; Radić, Tea Mišić; Pletikapić, Galja; Zimmermann, Amela Hozić; Urbani, Ranieri

    2011-01-01

    Using high resolution molecular technique of atomic force microscopy, we address the extracellular polymer production of Adriatic diatom Cylindrotheca closterium analyzed at the single cell level and the supramolecular organization of gel phase isolated from the Northern Adriatic macroaggregates. Our results revealed that extracellular polysaccharides freshly produced by marine diatoms can self-assemble directly to form gel network characteristics of the macroscopic gel phase in the natural aquatorium. Based on the experiments performed with isolated polysaccharide fractions of C. closterium and of macroaggregates gel phase, we demonstrated that the polysaccharide self-assembly into gel network can proceed independent of any bacterial mediation or interaction with inorganic particles.

  1. Diatoms and Other Epibionts Associated with Olive Ridley (Lepidochelys olivacea Sea Turtles from the Pacific Coast of Costa Rica.

    Directory of Open Access Journals (Sweden)

    Roksana Majewska

    Full Text Available Although the sea turtles have long been familiar and even iconic to marine biologists, many aspects of their ecology remain unaddressed. The present study is the first of the epizoic diatom community covering the olive ridley turtle's (Lepidochelys olivacea carapace and the first describing diatoms living on sea turtles in general, with the primary objective of providing detailed information on turtle epibiotic associations. Samples of turtle carapace including the associated diatom biofilm and epizoic macro-fauna were collected from Ostional beach (9° 59´ 23.7´´ N 85° 41´ 52.6´´ W, Costa Rica, during the arribada event in October 2013. A complex diatom community was present in every sample. In total, 11 macro-faunal and 21 diatom taxa were recorded. Amongst diatoms, the most numerous were erect (Achnanthes spp., Tripterion spp. and motile (Haslea sp., Navicula spp., Nitzschia spp., Proschkinia sp. forms, followed by adnate Amphora spp., while the most common macro-faunal species was Stomatolepas elegans (Cirripedia. Diatom densities ranged from 8179 ± 750 to 27685 ± 4885 cells mm-2. Epizoic microalgae were either partly immersed or entirely encapsulated within an exopolymeric coat. The relatively low diatom species number, stable species composition and low inter-sample dissimilarities (14.4% on average may indicate a mutualistic relationship between the epibiont and the basibiont. Dispersal of sea turtle diatoms is probably highly restricted and similar studies will help to understand both diatom diversity, evolution and biogeography, and sea turtle ecology and foraging strategies.

  2. Diatoms and Other Epibionts Associated with Olive Ridley (Lepidochelys olivacea) Sea Turtles from the Pacific Coast of Costa Rica.

    Science.gov (United States)

    Majewska, Roksana; Santoro, Mario; Bolaños, Federico; Chaves, Gerardo; De Stefano, Mario

    2015-01-01

    Although the sea turtles have long been familiar and even iconic to marine biologists, many aspects of their ecology remain unaddressed. The present study is the first of the epizoic diatom community covering the olive ridley turtle's (Lepidochelys olivacea) carapace and the first describing diatoms living on sea turtles in general, with the primary objective of providing detailed information on turtle epibiotic associations. Samples of turtle carapace including the associated diatom biofilm and epizoic macro-fauna were collected from Ostional beach (9° 59´ 23.7´´ N 85° 41´ 52.6´´ W), Costa Rica, during the arribada event in October 2013. A complex diatom community was present in every sample. In total, 11 macro-faunal and 21 diatom taxa were recorded. Amongst diatoms, the most numerous were erect (Achnanthes spp., Tripterion spp.) and motile (Haslea sp., Navicula spp., Nitzschia spp., Proschkinia sp.) forms, followed by adnate Amphora spp., while the most common macro-faunal species was Stomatolepas elegans (Cirripedia). Diatom densities ranged from 8179 ± 750 to 27685 ± 4885 cells mm-2. Epizoic microalgae were either partly immersed or entirely encapsulated within an exopolymeric coat. The relatively low diatom species number, stable species composition and low inter-sample dissimilarities (14.4% on average) may indicate a mutualistic relationship between the epibiont and the basibiont. Dispersal of sea turtle diatoms is probably highly restricted and similar studies will help to understand both diatom diversity, evolution and biogeography, and sea turtle ecology and foraging strategies.

  3. Diatoms and Other Epibionts Associated with Olive Ridley (Lepidochelys olivacea) Sea Turtles from the Pacific Coast of Costa Rica

    Science.gov (United States)

    Majewska, Roksana; Santoro, Mario; Bolaños, Federico; Chaves, Gerardo; De Stefano, Mario

    2015-01-01

    Although the sea turtles have long been familiar and even iconic to marine biologists, many aspects of their ecology remain unaddressed. The present study is the first of the epizoic diatom community covering the olive ridley turtle’s (Lepidochelys olivacea) carapace and the first describing diatoms living on sea turtles in general, with the primary objective of providing detailed information on turtle epibiotic associations. Samples of turtle carapace including the associated diatom biofilm and epizoic macro-fauna were collected from Ostional beach (9° 59´ 23.7´´ N 85° 41´ 52.6´´ W), Costa Rica, during the arribada event in October 2013. A complex diatom community was present in every sample. In total, 11 macro-faunal and 21 diatom taxa were recorded. Amongst diatoms, the most numerous were erect (Achnanthes spp., Tripterion spp.) and motile (Haslea sp., Navicula spp., Nitzschia spp., Proschkinia sp.) forms, followed by adnate Amphora spp., while the most common macro-faunal species was Stomatolepas elegans (Cirripedia). Diatom densities ranged from 8179 ± 750 to 27685 ± 4885 cells mm-2. Epizoic microalgae were either partly immersed or entirely encapsulated within an exopolymeric coat. The relatively low diatom species number, stable species composition and low inter-sample dissimilarities (14.4% on average) may indicate a mutualistic relationship between the epibiont and the basibiont. Dispersal of sea turtle diatoms is probably highly restricted and similar studies will help to understand both diatom diversity, evolution and biogeography, and sea turtle ecology and foraging strategies. PMID:26083535

  4. The Reimer Diatom Herbarium: An important resource for teaching and research

    Science.gov (United States)

    Rushforth, S.J.; Edlund, M.B.; Spaulding, S.A.; Stoermer, E.F.

    2010-01-01

    The Reimer Diatom Herbarium (ILH) at Iowa Lakeside Laboratory (ILL), a field station of Iowa's state universities, contains 3,280 permanent diatom slides of collections made from prairie potholes, alkaline fens, acid bogs, eutrophic lakes, saline lakes, Pleistocene paleolakes, and Miocene fossil deposits near ILL. The herbarium has a focus on collections made within Dickinson County, a region with an important legacy of study by students and visiting researchers from the US, Canada, and international institutions. The herbarium is well documented by taxon and location catalogues. The taxon card catalogue contains over 2,800 records referencing 67 genera, and the location card catalogue references collection sites from 51 counties in 16 North American states. Curated slides include over 300 species identifications made, or verified, by C.W. Reimer. Most curated slides have diatom specimens identified to species, circled with a diamond objective marker, and indicated on the slide label Six holotypes are included in the herbarium and we present the first light micrograph images of these type specimens. We present documentation of the contents and current condition of the herbarium and report that it is now available to researchers for scientific study. Many of the sites represented in the Reimer Diatom Herbarium are the same locations visited each year by students and visiting researchers at ILL, resulting in an important resource for monitoring environmental change, resolving taxonomic issues, and understanding species distributions in unique habitats.

  5. Chemical and Biological Sensing Using Diatom Photonic Crystal Biosilica With In-Situ Growth Plasmonic Nanoparticles

    Science.gov (United States)

    Kong, Xianming; Squire, Kenny; Li, Erwen; LeDuff, Paul; Rorrer, Gregory L.; Tang, Suning; Chen, Bin; McKay, Christopher P; Navarro-Gonzalez, Rafael

    2017-01-01

    In this paper, we described a new type of bioenabled nano-plasmonic sensors based on diatom photonic crystal biosilica with in-situ growth silver nanoparticles and demonstrated label-free chemical and biological sensing based on surface-enhanced Raman scattering (SERs) from complex samples. Diatoms are photosynthetic marine micro-organisms that create their own skeletal shells of hydrated amorphous silica, called frustules, which possess photonic crystal-like hierarchical micro-& nanoscale periodic pores. Our research shows that such hybrid plasmonic-biosilica nanostructures formed by cost-effective and eco-friendly bottom-up processes can achieve ultra-high limit of detection for medical applications, food sensing, water/air quality monitoring and geological/space research. The enhanced sensitivity comes from the optical coupling of the guided-mode resonance of the diatom frustules and the localized surface plasmons of the silver nanoparticles. Additionally, the nanoporous, ultra-hydrophilic diatom biosilica with large surface-to-volume ratio can concentrate more analyte molecules to the surface of the SERS substrates, which can help to detect biomolecules that cannot be easily adsorbed by metallic nanoparticles. PMID:27959817

  6. Morphological adaptations to small size in the marine diatom Minidiscus comicus

    Directory of Open Access Journals (Sweden)

    David Jewson

    2016-09-01

    Full Text Available Minidiscus comicus is a marine centric diatom that has cells with diameters as small as 1.9 μm, which brings it close to the lower limit of diatom cell size and also near to the lower limit of photosynthetic eukaryote cells. One of the questions that this raises is whether the cycle of size decline and size restoration used by most diatoms to time their life cycle can operate in such small cells. In samples collected from the western Mediterranean during 2009, M. comicus cells were found with diameters ranging from 1.9 to 6.0 μm. The larger cells were initial cells after size restoration, and these still had the valves of their parent cells attached, making it possible to determine the diameter of the threshold below which size restoration could be induced (3.1 μm. During size decline, M. comicus cell shape changed from discoid to spherical. This adaptation helped to reduce and even halt the rate of cell volume decrease, allowing cells to continue to use diameter decline as a clocking mechanism. The results show how adaptable the diatom cell wall can be, in spite of its rigid appearance.

  7. Structural identification of the C-25 highly branched isoprenoid pentaene in the marine diatom Rhizosolenia setigera

    NARCIS (Netherlands)

    Damste, JSS; Rijpstra, WIC; Hopmans, EC; Peletier, H; Gieskes, WWC; Geenevasen, JAJ

    1999-01-01

    2,6,10, 14-tetramethyl-7-(3-methylpent-4-enyl)-pentadeca-2,5E,9E, 13-tetraene I possessing a C-25 highly branched isoprenoid skeleton has been isolated from the marine diatom Rhizosolenia setigera and identified by H-1 and C-13 NMR spectroscopy. (C) 1999 Elsevier Science Ltd. All rights reserved.

  8. Continuous gene flow contributes to low global species abundance and distribution of a marine model diatom

    KAUST Repository

    Rastogi, Achal

    2017-08-15

    Unlike terrestrial ecosystems where geographical isolation often leads to a restricted gene flow between species, genetic admixing in aquatic micro-eukaryotes is likely to be frequent. Diatoms inhabit marine ecosystems since the Mesozoic period and presently constitute one of the major primary producers in the world ocean. They are a highly diversified group of eukaryotic phytoplankton with estimates of up to 200,000 species. Since decades, Phaeodactylum tricornutum is used as a model diatom species to characterize the functional pathways, physiology and evolution of diatoms in general. In the current study, using whole genome sequencing of ten P. tricornutum strains, sampled at broad geospatial and temporal scales, we show a continuous dispersal and genetic admixing between geographically isolated strains. We also describe a very high level of heterozygosity and propose it to be a consequence of frequent ancestral admixture. Our finding that P. tricornutum sequences are plausibly detectable at low but broadly distributed levels in the world ocean further suggests that high admixing between geographically isolated strains may create a significant bottleneck, thus influencing their global abundance and distribution in nature. Finally, in an attempt to understand the functional implications of genetic diversity between different P. tricornutum ecotypes, we show the effects of domestication in inducing changes in the selection pressure on many genes and metabolic pathways. We propose these findings to have significant implications for understanding the genetic structure of diatom populations in nature and provide a framework to assess the genomic underpinnings of their ecological success.

  9. Assessment of water quality based on diatom indices in a small ...

    African Journals Online (AJOL)

    2016-04-02

    Apr 2, 2016 ... This will greatly improve water quality analysis based on diatom indices. ACKNOWLEDGEMENTS. We thank the two anonymous reviewers for their use- ful and insightful comments. This study was financially supported by the Water Research Commission, National. Research Foundation and the Rhodes ...

  10. Identification automatique des diatomées de la Merja fouarate : Une ...

    African Journals Online (AJOL)

    Conclusion and application of research : The special features of some potentially more complex species were resolved and the development of a computer program that automates the identification of diatoms, that of their specificity, is still difficult to solve and could therefore be generalized. But research continues and relies ...

  11. The application and testing of diatom-based indices of stream water ...

    African Journals Online (AJOL)

    The objective of this study was to test the applicability of foreign diatom-based water quality assessment indices to urban streams in Zimbabwe, with the view of stimulating research to develop improved approaches for assessing ecological integrity of lotic systems in the country. The study evaluated the relationship between ...

  12. Four new non-marine diatom taxa from the Subantactic and Antarctic Regions

    Czech Academy of Sciences Publication Activity Database

    Van de Vijver, B.; Sterken, M.; Vyverman, W.; Mataloni, G.; Nedbalová, L.; Kopalová, K.; Elster, Josef; Verleyen, E.; Sabbe, K.

    2010-01-01

    Roč. 25, č. 2 (2010), s. 431-443 ISSN 0269-249X R&D Projects: GA MŠk ME 945 Institutional research plan: CEZ:AV0Z60050516 Keywords : South Shetland islands * East Antarctica * diatom s Subject RIV: EF - Botanics Impact factor: 1.030, year: 2010

  13. Novel polyunsaturated n-alkenes in the marine diatom Rhizosolenia setigera

    NARCIS (Netherlands)

    Damste, JSS; Rijpstra, WIC; Hopmans, EC; Peletier, H; Gieskes, WWC; Geenevasen, JAJ

    Four previously unknown n-C-25 and n-C-27 heptaenes of the marine diatom Rhizosolenia setigera were isolated and identified using NMR spectroscopy. They possess six methylene interrupted (Z)-double bonds starting at C-3 and an additional terminal or n-2 Q-double bond. Structural and stable carbon

  14. Freshwater monsoon related inputs in the Japan Sea: a diatom record from IODP core U1427

    Science.gov (United States)

    Ventura, C. P. L.; Lopes, C.

    2016-12-01

    Monsoon rainfall is the life-blood of more than half the world's population. Extensive research is being conducted in order to refine projections regarding the impact of anthropogenic climate change on these systems. The East Asian monsoon (EAM) plays a significant role in large-scale climate variability. Due to its importance to global climate and world's population, there is an urgent need for greater understanding of this system, especially during past climate changes. The input of freshwater from the monsoon precipitation brings specific markers, such as freshwater diatoms and specific diatom ecological assemblages that are preserved in marine sediments. Freshwater diatoms are easily identifiable and have been used in the North Pacific to reconstruct environmental conditions (Lopes et al 2006) and flooding episodes (Lopes and Mix, 2009). Here we show preliminary results of freshwater diatoms records that are linked with river discharge due to increase land rainfall that can be derived from Monsoon rainfall. We extend our preliminary study to the past 400ky.

  15. Diatom communities from the sub-Antarctic Prince Edward Islands: diversity and distribution patterns

    NARCIS (Netherlands)

    Van de Vijver, B.; Gremmen, N.J.M.; Smith, V.

    2008-01-01

    During an extensive survey of the freshwater and moss-inhabiting diatoms of the Prince Edward Islands, a total of 214 taxa belonging to 60 genera were found. Three main communities can be found on the two islands. A large part of the samples was grouped into an aquatic group, bringing together all

  16. Are Diatoms “Green” Aluminosilicate Synthesis Microreactors for Future Catalyst Production?

    Directory of Open Access Journals (Sweden)

    Lydia Köhler

    2017-12-01

    Full Text Available Diatom biosilica may offer an interesting perspective in the search for sustainable solutions meeting the high demand for heterogeneous catalysts. Diatomaceous earth (diatomite, i.e., fossilized diatoms, is already used as adsorbent and carrier material. While diatomite is abundant and inexpensive, freshly harvested and cleaned diatom cell walls have other advantages, with respect to purity and uniformity. The present paper demonstrates an approach to modify diatoms both in vivo and in vitro to produce a porous aluminosilicate that is serving as a potential source for sustainable catalyst production. The obtained material was characterized at various processing stages with respect to morphology, elemental composition, surface area, and acidity. The cell walls appeared normal without morphological changes, while their aluminum content was raised from the molar ratio n(Al:n(Si 1:600 up to 1:50. A specific surface area of 55 m2/g was measured. The acidity of the material increased from 149 to 320 µmol NH3/g by ion exchange, as determined by NH3 TPD. Finally, the biosilica was examined by an acid catalyzed test reaction, the alkylation of benzene. While the cleaned cell walls did not catalyze the reaction at all, and the ion exchanged material was catalytically active. This demonstrates that modified biosilica does indeed has potential as a basis for future catalytically active materials.

  17. Automatic diatom identification using contour analysis by morphological curvature scale spaces

    NARCIS (Netherlands)

    Jalba, Andrei C.; Wilkinson, Michael H.F.; Roerdink, Jos B.T.M.; Bayer, Micha M.; Juggins, Stephen

    A method for automatic identification of diatoms (single-celled algae with silica shells) based on extraction of features on the contour of the cells by multi-scale mathematical morphology is presented. After extracting the contour of the cell, it is smoothed adaptively, encoded using Freeman chain

  18. Summer diatom blooms in the North Pacific subtropical gyre: 2008-2009.

    Directory of Open Access Journals (Sweden)

    Tracy A Villareal

    Full Text Available The summertime North Pacific subtropical gyre has widespread phytoplankton blooms between Hawaii and the subtropical front (∼30°N that appear as chlorophyll (chl increases in satellite ocean color data. Nitrogen-fixing diatom symbioses (diatom-diazotroph associations: DDAs often increase 10(2-10(3 fold in these blooms and contribute to elevated export flux. In 2008 and 2009, two cruises targeted satellite chlorophyll blooms to examine DDA species abundance, chlorophyll concentration, biogenic silica concentration, and hydrography. Generalized observations that DDA blooms occur when the mixed layer depth is 10 µm chl a fraction (∼40-90+% of total chl a. Integrated diatom abundance varied 10-fold over 10 µm size fraction, and increased up to 5-fold in the blooms. The two years differed in the magnitude of the surface chl a increase (2009>2008, the abundance of pennate diatoms within the bloom (2009>2008, and the substantially greater mixed layer depth in 2009. Only the 2009 bloom had sufficient chl a in the >10 µm fraction to produce the observed ocean color chl increase. Blooms had high spatial variability; ocean color images likely average over numerous small events over time and space scales that exceed the individual event scale. Summertime DDA export flux noted at the Hawaii time-series Sta. ALOHA is probably a generalized feature of the eastern N. Pacific north to the subtropical front.

  19. Photoelectron Spectroscopy and Electronic Structure of Heavy GroupIV-VI Diatomics

    Energy Technology Data Exchange (ETDEWEB)

    Wang, L.-S.; Niu, B.; Lee, Yuan T.; Shirley, D.A.; Balasubramanian, K.

    1989-09-01

    Vibrationally-resolved HeI (584{angstrom}) photoelectron spectra of the heavy group IV-VI diatomics SnSe, SnTe, PbSe, and PbTe were obtained with a new high temperature molecular beam source. Ionization potentials and spectroscopic constants are reported for all the ionic states observed. Relativistic complete active space MCSCF followed by multireference singles + doubles relativistic CI calculations which included up to 200,000 configurations were made on both the neutral diatomics and their positive ions. Ionization potentials and spectroscopic constants were calculated and were in good agreement with the experimentally-measured values. Relativistic CI potential energy curves were calculated for all the neutral ground states and the ionic states involved. Relativistic effects were shown to play an important role in these heavy diatomics. The {sup 2}{Sigma}{sub 1/2}{sup +} and {sup 2}{Pi}{sub 1/2} states for all four molecular ions showed avoided curve crossings, which resulted in pronounced shoulders in the {Omega} = 1/2 potential energy curves of PbTe{sup +}. Experimentally, autoionization transitions were also observed for the PbTe{sup +} spectrum. The importance of the relativistic effect and chemical bonding in the heavy diatomics are discussed.

  20. A water quality index for use with diatoms in the assessment of rivers

    African Journals Online (AJOL)

    driniev

    2004-10-04

    Oct 4, 2004 ... the Department of Tourism, Environmental and Economic Affairs. (DTEEA) initiated the ... but that it is hard to distinguish specific nutrients causing the effect. Nutrient kinetic ..... (1991) Reconstructing of past changes in salinity and climate using a diatom-based ... metropolitan area, Japan. Freshwater Biol.

  1. Production of extracellular polymeric substances (EPS) by benthic diatoms: the effect of irradiance and temperature

    NARCIS (Netherlands)

    Wolfstein, K.; Stal, L.J.

    2002-01-01

    An axenic culture of Cylindrotheca closterium and a natural community of benthic diatoms were used to study the effect of temperature and irradiance on the production of extracellular polymeric substances (EPS). In the culture, results depended on the growth stage of the algae and on whether

  2. Particulate Trace Element Cycling in a Diatom Bloom at Station ALOHA

    Science.gov (United States)

    Weisend, R.; Morton, P. L.; Landing, W. M.; Fitzsimmons, J. N.; Hayes, C. T.; Boyle, E. A.

    2014-12-01

    Phytoplankton in oligotrophic marine deserts depend on remote sources to supply trace nutrients. To examine these sources, marine particulate matter samples from the central North Pacific (Station ALOHA) were collected during the July-August 2012 HOE-DYLAN cruises and analyzed for a suite of trace (e.g., Fe, Mn) and major (e.g. Al, P) elements. Daily surface SPM samples were examined for evidence of atmospheric deposition and biological uptake, while five vertical profiles were examined for evidence of surface vertical export and subsurface horizontal transport from nearby sources (e.g., margin sediments, hydrothermal plumes). Maxima in surface particulate P (a biological tracer) corresponded with a diatom bloom, and surprisingly also coincided with maxima in particulate Al (typically a tracer for lithogenic inputs). The surface particulate Al distributions likely result from the adsorption of dissolved Al onto diatom silica frustules, not from atmospheric dust deposition. In addition, a subsurface maximum in particulate Al and P was observed four days later at 75m, possibly resulting from vertical export of the surface diatom bloom. The distributions of other bioactive trace elements (e.g. Cd, Co, Cu) will be presented in the context of the diatom bloom and other biological, chemical and physical features. A second, complementary poster is also being presented which examines the cycling of trace elements in lithogenic particles (Morton et al., "Trace Element Cycling in Lithogenic Particles at Station ALOHA").

  3. Grazer-induced chain lenght plasticity reduces grazing risk in a marine diatom

    DEFF Research Database (Denmark)

    Bergkvist, Johanna; Thor, Peter; Jakobsen, Hans Henrik

    2012-01-01

    that chain length plasticity is a means for S. marinoi to reduce copepod grazing. In contrast, chain length was not suppressed in cultures exposed to the microzooplankton grazer Gyrodinium dominans. Size-selective predation may have played a key role in the evolution of chain formation and chain length...... plasticity in diatoms...

  4. Spatial scale and the diversity of benthic cyanobacteria and diatoms in a salina

    DEFF Research Database (Denmark)

    Nübel, U.; Garcia-Pichel, F.; Kühl, Michael

    1999-01-01

    We characterized the richness of benthic cyanobacteria and diatoms in a salina system using traditional and molecular biological methods. After determining the different morphotypes and 16S rRNA genes present in various localities within this hypersaline system, an analysis of the increase...

  5. The relevance of diatoms for water quality assessment in South Africa

    African Journals Online (AJOL)

    The method is applicable across a wide range of aquatic ecosystem types, namely freshwater, brackish, and estuarine, and is inclusive of both lentic and lotic environments, wetlands and their associated damp, marginal and littoral zones. Details provided by diatom assemblages support palaeoecological investigations, ...

  6. Silicon deposition in diatoms : Control by the pH inside the silicon deposition vesicle

    NARCIS (Netherlands)

    Vrieling, EG; Gieskes, WWC; Beelen, TPM

    To test the hypothesis that silicification occurs under acid conditions in the silicon deposition vesicle (SDV), the acidity of the SDV of the pennate diatoms Navicula pelliculosa (Brebisson et Kutzing) Hilse, N. salinarum (Grunow) Hustedt, and Nitzschia sigma (Kutzing) Smith was determined during

  7. The application and testing of diatom-based indices of stream water ...

    African Journals Online (AJOL)

    2014-06-30

    Jun 30, 2014 ... for assessing the effects of environmental stressors, making ... cability to the new system has not been explicitly evaluated. However, there is ... that diatoms may potentially be useful in assessing ecological ... temperature of around 24.5°C, with a mean monthly maxi- ...... NIWA, Christchurch, New Zealand.

  8. An integrative analysis of post-translational histone modifications in the marine diatom Phaeodactylum tricornutum.

    Science.gov (United States)

    Veluchamy, Alaguraj; Rastogi, Achal; Lin, Xin; Lombard, Bérangère; Murik, Omer; Thomas, Yann; Dingli, Florent; Rivarola, Maximo; Ott, Sandra; Liu, Xinyue; Sun, Yezhou; Rabinowicz, Pablo D; McCarthy, James; Allen, Andrew E; Loew, Damarys; Bowler, Chris; Tirichine, Leïla

    2015-05-20

    Nucleosomes are the building blocks of chromatin where gene regulation takes place. Chromatin landscapes have been profiled for several species, providing insights into the fundamental mechanisms of chromatin-mediated transcriptional regulation of gene expression. However, knowledge is missing for several major and deep-branching eukaryotic groups, such as the Stramenopiles, which include the diatoms. Diatoms are highly diverse and ubiquitous species of phytoplankton that play a key role in global biogeochemical cycles. Dissecting chromatin-mediated regulation of genes in diatoms will help understand the ecological success of these organisms in contemporary oceans. Here, we use high resolution mass spectrometry to identify a full repertoire of post-translational modifications on histones of the marine diatom Phaeodactylum tricornutum, including eight novel modifications. We map five histone marks coupled with expression data and show that P. tricornutum displays both unique and broadly conserved chromatin features, reflecting the chimeric nature of its genome. Combinatorial analysis of histone marks and DNA methylation demonstrates the presence of an epigenetic code defining activating or repressive chromatin states. We further profile three specific histone marks under conditions of nitrate depletion and show that the histone code is dynamic and targets specific sets of genes. This study is the first genome-wide characterization of the histone code from a stramenopile and a marine phytoplankton. The work represents an important initial step for understanding the evolutionary history of chromatin and how epigenetic modifications affect gene expression in response to environmental cues in marine environments.

  9. Solution of the Schrodinger Equation for a Diatomic Oscillator Using Linear Algebra: An Undergraduate Computational Experiment

    Science.gov (United States)

    Gasyna, Zbigniew L.

    2008-01-01

    Computational experiment is proposed in which a linear algebra method is applied to the solution of the Schrodinger equation for a diatomic oscillator. Calculations of the vibration-rotation spectrum for the HCl molecule are presented and the results show excellent agreement with experimental data. (Contains 1 table and 1 figure.)

  10. Do diatoms in the Swiss Alps reflect the length of ice-cover?

    NARCIS (Netherlands)

    Lotter, A.F.; Bigler, C.

    2000-01-01

    ment core from Hagelseewli (2339 m asl, Swiss Alps) give information about the present-day seasonal cycle of diatom blooms, taphonomic processes in the lake basin and the lake’s history. Analyses of surficial sediments show that water depth and thus light and nutrient availability is the most

  11. Structural identification of the C25 highly branched isoprenoid pentaene in the marine diatom Rhizosolenia setigera

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Schouten, S.; Rijpstra, W.I.C.; Hopmans, E.C.; Peletier, H.; Gieskes, W.W.C.; Geenevasen, J.A.J.

    1999-01-01

    2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadeca-2,5E,9E,13-tetraene I possessing a C25 highly branched isoprenoid skeleton has been isolated from the marine diatom Rhizosolenia setigera and identified by 1H and 13C NMR spectroscopy.

  12. C25 highly branched isoprenoid (HBI) alkenes from the marine benthic diatom Pleurosigma strigosum

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Grossi, V.; Beker, B.; Geenevasen, J.A.J.; Schouten, S.; Raphel, D.; Fontaine, M.F.

    2004-01-01

    The hydrocarbon composition of the marine diatom Pleurosigma strigosum isolated from coastal Mediterranean sediments is described. A suite of five C25 highly branched isoprenoid (HBI) alkenes with 2 5 double bonds were detected together with n-C21:4 and n-C21:5 alkenes and squalene. The analysis by

  13. Assessing anthropogenic pressures on streams: A random forest approach based on benthic diatom communities.

    Science.gov (United States)

    Larras, Floriane; Coulaud, Romain; Gautreau, Edwige; Billoir, Elise; Rosebery, Juliette; Usseglio-Polatera, Philippe

    2017-05-15

    Benthic diatoms have been widely used to assess the ecological status of freshwater ecosystems, especially in the context of recent international water framework directive policies (e.g. the WFD). Despite diatom-based indices are known to respond fastly to water quality degradation, they are not designed to precisely identify the nature of pressures co-occurring in the environment. Based on large scale monitoring data, we aimed at building models able to estimate the risk of stream impairment by many types of anthropogenic pressures from taxonomy-based and trait-based characteristics of diatom assemblages. Random forest models were built to individually evaluate the impairment risk of diatom assemblages for six chemical and five hydromorphological or land-use related pressure categories. Eight models provided good impairment risk assessment (Area Under the Curve≥0.70). Under multi-pressure scenarios, models built for chemical pressures exhibited a better accuracy than hydromorphological or land-use related ones. Models were able to detect both ecological restoration and degradation, based on long-term surveys. These models have been implemented in a R user-friendly routine, to help stream managers to early identify degrading processes and prioritize management actions. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Oxygenic photosynthesis as driving process in exopolysaccharide production of benthic diatoms

    NARCIS (Netherlands)

    Staats, N.; Stal, L.J.; de Winder, B.; Mur, L.R.

    2000-01-01

    The secretion of exopolysaccharide in an axenic culture of the marine benthic diatom Cylindrotheca closterium was investigated. The central question of the experiments was if polysaccharide secretion was dependent on light and photosynthesis. Cells were incubated in the Light, in the dark, or in the

  15. Zoosporic parasites infecting marine diatoms — A black box that needs to be opened

    Science.gov (United States)

    Scholz, Bettina; Guillou, Laure; Marano, Agostina V.; Neuhauser, Sigrid; Sullivan, Brooke K.; Karsten, Ulf; Küpper, Frithjof C.; Gleason, Frank H.

    2016-01-01

    Living organisms in aquatic ecosystems are almost constantly confronted by pathogens. Nevertheless, very little is known about diseases of marine diatoms, the main primary producers of the oceans. Only a few examples of marine diatoms infected by zoosporic parasites are published, yet these studies suggest that diseases may have significant impacts on the ecology of individual diatom hosts and the composition of communities at both the producer and consumer trophic levels of food webs. Here we summarize available ecological and morphological data on chytrids, aphelids, stramenopiles (including oomycetes, labyrinthuloids, and hyphochytrids), parasitic dinoflagellates, cercozoans and phytomyxids, all of which are known zoosporic parasites of marine diatoms. Difficulties in identification of host and pathogen species and possible effects of environmental parameters on the prevalence of zoosporic parasites are discussed. Based on published data, we conclude that zoosporic parasites are much more abundant in marine ecosystems than the available literature reports, and that, at present, both the diversity and the prevalence of such pathogens are underestimated. PMID:28083074

  16. Aulacoseira coroniformis sp. nov., a new diatom (Bacillariophyta) species from Highland Hammock State Park, Florida

    NARCIS (Netherlands)

    Cremer, H.; Pearce, C.; Wagner-Cremer, F.

    2010-01-01

    Aulacoseira coroniformis sp. nov. is described from a short peat core recovered in Highlands Hammock State Park, Florida, U.S.A. The morphology of the new diatom species is documented by light and scanning electron micrographs and discussed in detail, including a comparison with related species in

  17. Oxidative stress responses in the marine antarctic diatom Chaetoceros brevis (Bacillariophyceae) during photoacclimation

    NARCIS (Netherlands)

    Janknegt, P.J.; van de Poll, W.H.; Visser, R.J.W.; Rijstenbil, J.W.; Buma, A.G.J.

    2008-01-01

    The enzyme superoxide dismutase (SOD) holds a key position in the microalgal antioxidant network. The present research focused on oxidative stress responses in the Antarctic diatom Chaetoceros brevis F. Schütt during transition to excess (including ultraviolet radiation [UVR]) and limiting

  18. Diatom Frustule-Bound δ13c Measurements and Reconstruction of Εp

    Science.gov (United States)

    Stoll, H. M.; Mejia Ramirez, L. M.; Mendez-Vicente, A.; Abrevaya, L.; Bolton, C. T.; Anderson, R. F.

    2014-12-01

    Diatom frustules contain embedded organic matter such as amino acids, which may offer a potential phase for measuring the carbon isotopic fractionation during marine photosynthesis (ɛp). We describe optimal sample preparation methods for cleaning external organic matter and separating frustules into various size classes while reducing significance of opal from radiolaria and silicoflagellates. Analysis of discrete separated fractions of diatom opal from each sediment sample is facilitated by our new method for analysis of very small sample sizes using NanoEA with cryotrapping of evolved CO2. We evaluate the fidelity with which frustule-bound organic matter captures the variation in ɛp by comparing δ13C of frustule-bound organic matter with that of total cellular carbon in diatoms grown in culture, and by comparing the δ13C of frustule-bound organic matter in core tops with that of δ13C of diatom-produced biomarkers in the overlying water column. In core-top transects, frustule-bound δ13C is consistent with strong growth rate control over fractionation during photosynthesis (ɛp). Finally, we evaluate the temporal trends in carbon isotopic fractionation during photosynthesis since the Late Miocene in samples from the Eastern Equatorial Pacific.

  19. Daily fluctuations of exopolymers in cultures of the benthic diatoms Cylindrotheca closterium and Nitzschia sp (Bacillariophyceae)

    NARCIS (Netherlands)

    de Brouwer, J.F.C.; Stal, L.J.

    2002-01-01

    Dynamics in the production of extracellular polymeric substances (EPS) were investigated for the benthic diatoms Cylindrotheca closterium (Ehrenberg) and Nitzschia sp. The effect of growth phase and light:dark conditions were examined using axenic cultures. Two EPS fractions were distinguished.

  20. Chytrid infections and diatom spring blooms: paradoxical effects of climate warming on fungal epidemics in lakes?

    NARCIS (Netherlands)

    Ibelings, B.W.; Gsell, A.S.; Mooij, W.M.; Van Donk, E.; van den Wyngaert, Silke; De Senerpont Domis, L.N.

    2011-01-01

    1. We describe the dynamics of host–parasite interactions over a period of more than 30 years between the freshwater diatom Asterionella formosa and two highly virulent chytrid parasites (Rhizophydium planktonicum and Zygorhizidium planktonicum) in Lake Maarsseveen, The Netherlands. This period is

  1. Compartmental Analysis Suggests Macropinocytosis at the Onset of Diatom Valve Formation

    NARCIS (Netherlands)

    Brasser, H. J.; van der Strate, H. J.; Gieskes, W. W. C.; Krijger, G. C.; Vrieling, E. G.; Wolterbeek, H. T.

    During valve formation of the siliceous frustules of diatoms, bulk uptake of silicic acid and its subsequent transport through the cell is required before it can be deposited in the silica deposition vesicle (SDV). It has been assumed that transport takes place via silicon transporters (SITs), but

  2. Compartmental Analysis Suggests Macropinocytosis at the Onset of Diatom Valve Formation

    NARCIS (Netherlands)

    Brasser, H.J.; Van der Strate, H.J.; Gieskes, W.W.C.; Krijger, G.C.; Vrieling, E.G.; Wolterbeek, H.T.

    2010-01-01

    During valve formation of the siliceous frustules of diatoms, bulk uptake of silicic acid and its subsequent transport through the cell is required before it can be deposited in the silica deposition vesicle (SDV). It has been assumed that transport takes place via silicon transporters (SITs), but

  3. Cyclotella paleo-ocellata, a new centric diatom (Bacillariophyta) from lake Kinneret (Israel)

    NARCIS (Netherlands)

    Vossel, Hannah; Reed, Jane M.; Houk, Václav; Cvetkoska, Aleksandra; Van De Vijver, Bart

    2015-01-01

    Large, subfossil populations of an unknown centric, planktonic diatom were observed in a lake sediment core from Lake Kinneret (Israel), which is here described as Cyclotella paleo–ocellata sp. nov. The new taxon, which belongs to the Cyclotella ocellata species complex, is described and separated

  4. Comparative investigation of damage induced by diatomic and monoatomic ion implantation in silicon

    NARCIS (Netherlands)

    Lohner, T.; Lohner, T.; Toth, L.; Toth, L.; Fried, M.; Fried, M.; Khanh, N.Q.; Yang, Gen Qing; Lu, Lin Chen; Zou, Shichang; Hanekamp, L.J.; Hanekamp, L.J.; van Silfhout, Arend; Gyulai, J.

    1994-01-01

    The damaging effect of mono- and diatomic phosphorus and arsenic ions implanted into silicon was investigated by spectroscopic ellipsometry (SE) and high-depth-resolution Rutherford backscattering and channeling techniques. A comparison was made between the two methods to check the capability of

  5. Diatom-driven recolonization of microbial mat-dominated siliciclastic tidal flat sediments.

    Science.gov (United States)

    Pan, Jerónimo; Cuadrado, Diana G; Bournod, Constanza N

    2017-10-01

    Modern microbial mats and biofilms play a paramount role in sediment biostabilization. When sporadic storms affect tidal flats of Bahía Blanca Estuary, the underlying siliciclastic sediment is exposed by physical disruption of the mat, and in a few weeks' lapse, a microbial community re-establishes. With the objective of studying colonization patterns and the ecological succession of microorganisms at the scale of these erosional structures, these were experimentally made and their biological recolonization followed for 8 weeks, with replication in winter and spring. Motile pennate diatoms led the initial colonization following two distinct patterns: a dominance by Cylindrotheca closterium in winter and by naviculoid and nitzschioid diatoms in spring. During the first 7 days, cell numbers increased 2- to 17-fold. Cell densities further increased exhibiting sigmoidal community growth, reaching 2.9-8.9 × 106 cells cm-3 maxima around day 30; centric diatoms maintained low densities throughout. In 56 days after removal of the original mat, filamentous cyanobacteria that dominate mature mats did not establish a significant biomass, leading to the rejection of the hypothesis that cyanobacteria would drive the colonization. The observed dominance of pennate diatoms is attributed to extrinsic factors determined by tidal flooding, and intrinsic ones, e.g. motility, nutrient affinity and high growth rate. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  6. Carbohydrade metabolism in suspended and attached cells of marine fouling diatom, Navicula sp.

    Digital Repository Service at National Institute of Oceanography (India)

    Bhosle, N.B.; Sawant, S.S.; Garg, A.; Wagh, A.B.

    A marine fouling diatom, @iNavicula@@ sp. was cultured in the laboratory under 12-hour light : 12-hour dark conditions. Cells in suspension and attached to the flask walls were analyzed for chlorophyll a, cell organic carbon, total cell carbohydrate...

  7. On the 3D reconstruction of diatom frustules : a novel method, applications, and limitations

    NARCIS (Netherlands)

    Mansilla, Catalina; Novais, Maria Helena; Faber, Enne; Martinez-Martinez, Diego; De Hosson, J. Th.

    Because of the importance of diatoms and the lack of information about their third dimension, a new method for the 3D reconstruction is explored, based on digital image correlation of several scanning electron microscope images. The accuracy of the method to reconstruct both centric and pennate

  8. Response of the Ubiquitous Pelagic Diatom Thalassiosira weissflogii to Darkness and Anoxia

    DEFF Research Database (Denmark)

    Kamp, Anja; Stief, Peter; Knappe, Jan

    2013-01-01

    Thalassiosira weissflogii, an abundant, nitrate-storing, bloom-forming diatom in the world's oceans, can use its intracellular nitrate pool for dissimilatory nitrate reduction to ammonium (DNRA) after sudden shifts to darkness and anoxia, most likely as a survival mechanism. T. weissflogii cells ...

  9. Epipelic diatoms in the estuaries of South Africa | Bate | Water SA

    African Journals Online (AJOL)

    Epipelic diatom flora was sampled around the South African coast between the Olifants Estuary, on the cool Atlantic Ocean northwest coast, and the St. Lucia Estuary, on the Indian Ocean northeast coast. Altogether, 333 taxa were identified with 14 being ubiquitous, as they were found in the cool temperate, warm temperate ...

  10. Isolation and characterization of extracellular polysaccharides from the epipelic diatoms Cylindrotheca closterium and Navicula salinarum

    NARCIS (Netherlands)

    Staats, N.; de Winder, B.; Stal, L.J.; Mur, L.R.

    1999-01-01

    The production and composition of extracellular polymeric substances (EPS) in axenic batch cultures of the benthic marine epipelic diatoms Navicula salinarum and Cylindrotheca closterium were investigated. EPS was secreted into the medium and the bulk was loosely associated with the cells. Neither

  11. Epilithic diatoms (Bacillariophyceae from running watersin NW Iberian Peninsula (Galicia, Spain

    Directory of Open Access Journals (Sweden)

    Manel Leira

    2017-12-01

    Full Text Available A catalog of Bacillariophyceae for the rivers of NW of Spain is made for the first time. It includes a re-examination of the taxa reported in previous publications, taxa cited during the last years of the rivers of the Galicia-Costa Hydrographic Demarcation, and a revision of the taxonomy, in line with the systematic and nomenclature changes, which have occurred mainly in recent years. The epilethic diatoms of the river basins of Galicia-Costa were sampled during the years 2005, 2006, and 2007, in May-June and September. The study was carried out in 41 localities distributed along 31 rivers, samples were taken in upstream and downstream sections. Diatom communities were compared in all upstream sections of these rivers draining from siliceous substrates. We identified 141 taxa of diatoms from the coast of Galicia. In this paper we present 15 new citations for Galicia, two for Spain and three for the Iberian Peninsula, in addition to a new species recently described. The dominant taxa are: Achnanthidium minutissimum, Achnanthes subhudsonis, Karayevia oblongella, Cocconeis placentula var. euglypta, Gomphonema rhombicum, and Navicula minima. Achnanthes subhudsonis was the most abundant species during the spring and summer months. The remaining species showed no relevant changes regardless of the time of year. The results indicate that the river diatoms of Galicia are an important component of the diversity of the ecosystem.

  12. Using quantitative PCR to determine the distribution of a semicryptic benthic diatom, Navicula phyllepta (Bacillariophyceae)

    NARCIS (Netherlands)

    Creach, V.; Ernst, A.; Sabbe, K.; Stal, L.J.; Vanelslander, B.; Vyverman, W.

    2006-01-01

    Evidence has accumulated during the last decade showing that many established diatom morpho-species actually consist of several semicryptic or truly cryptic species. As these species are difficult or even impossible to differentiate by microscopic analysis, there is virtually no information on how

  13. [First attempts to synchronize cell division in the diatom Navicula ostrearia (Gaillon) Bory in axenic culture].

    Science.gov (United States)

    Neuville, D; Daste, P

    1977-02-28

    The diatom Navicula ostrearia, grown under small quantities, was synchronized in diurnally intermittent illuminations of 16 hour light and 8 hour dark. Under these experimental conditions, the doubling of the population only occurs during the dark period and the fission time is about 6 hours.

  14. Toxicity, degradation and metabolic fate of ibuprofen on freshwater diatom Navicula sp.

    Science.gov (United States)

    Ding, Tengda; Yang, Mengting; Zhang, Junmin; Yang, Bo; Lin, Kunde; Li, Juying; Gan, Jay

    2017-05-15

    Ibuprofen (IBU) is one of the most widely used and frequently detected human pharmaceuticals in aquatic environment. However, the toxicity of IBU on diatom and its fate remain still unkown. In the present study, the toxicity of IBU on the diatom was evaluated by the algal growth rate, the chlorophyll-a and carotenoids contents. The degradation of IBU including in particular the potential for the formation of incomplete degradation products was also explored. Biochemical characteristics of Navicula sp. were significantly inhibited at IBU concentrations up to 50mgL -1 after 10days of exposure. The degradation of IBU was retarded by Navicula sp. at low concentration (1mgL -1 ), with t 1/2 being extended from 9.6±1.8 d to 12.0±1.5 d, indicating that Navicula sp. could prolong the exposure time of IBU. A total of 8 metabolites were identified by LC-MS/MS and the degradation pathway of IBU in Navicula sp. was proposed. Hydroxylation, acylation, demethylation, and glucuronidation contributed to IBU transformative reactions in diatom cells. These findings indicate that the presence of diatom Navicula sp. could hinder degradation of IBU, and IBU and/or its metabolites may pose high risks on aquatic ecosystem in natural waters. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. UV-B induces DNA damage and DNA synthesis delay in the marine diatom Cyclotella sp.

    NARCIS (Netherlands)

    Buma, A.G.J.; van Hannen, E.J; Veldhuis, M.J W; Gieskes, W.W C

    The effect of UV-B on the occurrence of DNA damage and consequences for the cell cycle were studied in the marine diatom Cyclotella sp. DNA damage was quantified by immunofluorescent detection of thymine dimers in nuclear DNA of single cells using flow cytometry. A total UV-B dose (biologically

  16. UV-B induces DNA damage and DNA synthesis delay in the marine diatom Cyclotella sp

    NARCIS (Netherlands)

    Buma, A.G.J.; Van Hannen, E.J.; Veldhuis, M.; Gieskes, W.W.C.

    1996-01-01

    The effect of UV-B on the occurrence of DNA damage and consequences for the cell cycle were studied in the marine diatom Cyclotella sp. DNA damage was quantified by immunofluorescent detection of thymine dimers in nuclear DNA of single cells using flow cytometry. A total UV-B dose (biologically

  17. Genome-Scale Model Reveals Metabolic Basis of Biomass Partitioning in a Model Diatom.

    Directory of Open Access Journals (Sweden)

    Jennifer Levering

    Full Text Available Diatoms are eukaryotic microalgae that contain genes from various sources, including bacteria and the secondary endosymbiotic host. Due to this unique combination of genes, diatoms are taxonomically and functionally distinct from other algae and vascular plants and confer novel metabolic capabilities. Based on the genome annotation, we performed a genome-scale metabolic network reconstruction for the marine diatom Phaeodactylum tricornutum. Due to their endosymbiotic origin, diatoms possess a complex chloroplast structure which complicates the prediction of subcellular protein localization. Based on previous work we implemented a pipeline that exploits a series of bioinformatics tools to predict protein localization. The manually curated reconstructed metabolic network iLB1027_lipid accounts for 1,027 genes associated with 4,456 reactions and 2,172 metabolites distributed across six compartments. To constrain the genome-scale model, we determined the organism specific biomass composition in terms of lipids, carbohydrates, and proteins using Fourier transform infrared spectrometry. Our simulations indicate the presence of a yet unknown glutamine-ornithine shunt that could be used to transfer reducing equivalents generated by photosynthesis to the mitochondria. The model reflects the known biochemical composition of P. tricornutum in defined culture conditions and enables metabolic engineering strategies to improve the use of P. tricornutum for biotechnological applications.

  18. Genome-Scale Model Reveals Metabolic Basis of Biomass Partitioning in a Model Diatom.

    Science.gov (United States)

    Levering, Jennifer; Broddrick, Jared; Dupont, Christopher L; Peers, Graham; Beeri, Karen; Mayers, Joshua; Gallina, Alessandra A; Allen, Andrew E; Palsson, Bernhard O; Zengler, Karsten

    2016-01-01

    Diatoms are eukaryotic microalgae that contain genes from various sources, including bacteria and the secondary endosymbiotic host. Due to this unique combination of genes, diatoms are taxonomically and functionally distinct from other algae and vascular plants and confer novel metabolic capabilities. Based on the genome annotation, we performed a genome-scale metabolic network reconstruction for the marine diatom Phaeodactylum tricornutum. Due to their endosymbiotic origin, diatoms possess a complex chloroplast structure which complicates the prediction of subcellular protein localization. Based on previous work we implemented a pipeline that exploits a series of bioinformatics tools to predict protein localization. The manually curated reconstructed metabolic network iLB1027_lipid accounts for 1,027 genes associated with 4,456 reactions and 2,172 metabolites distributed across six compartments. To constrain the genome-scale model, we determined the organism specific biomass composition in terms of lipids, carbohydrates, and proteins using Fourier transform infrared spectrometry. Our simulations indicate the presence of a yet unknown glutamine-ornithine shunt that could be used to transfer reducing equivalents generated by photosynthesis to the mitochondria. The model reflects the known biochemical composition of P. tricornutum in defined culture conditions and enables metabolic engineering strategies to improve the use of P. tricornutum for biotechnological applications.

  19. Recommended conventions for defining transition moments and intensity factors in diatomic molecular spectra

    NARCIS (Netherlands)

    Whiting, E.E.; Schadee, A.; Tatum, J.B.; Hougen, J.T.; Nicholls, R.W.

    Two recommendations are made that can eliminate persistent confusion in the study of diatomic spectroscopy by providing uniform and consistent definitions of the electronic transition moments and the rotational line intensity factors. First, it is recommended that the equation for the line strength

  20. Species-dependent silicon isotope fractionation in unialgal cultures of marine diatoms

    Science.gov (United States)

    Sutton, J. N.; Varela, D. E.; Brzezinski, M. A.; Beucher, C.

    2011-12-01

    Variations in the natural abundance of stable isotopes of silicon (expressed as δ30Si in %) are a key tool for studying the marine silicon (Si) cycle in modern and ancient oceans. In particular, this tool can be used to track relative differences in silicic acid drawdown in surface waters by siliceous microplankton. Diatoms are siliceous phytoplankton that dominate the cycling of Si in the oceans. They represent a major source of primary production and are important in the transfer of Si, nitrogen, phosphorus, and atmospheric carbon to the deep sea. Previous investigations of Si isotope fractionation in diatom cultures have ruled out the influence of temperature (12-22°C) and shown that Si fractionation was invariant in different species of temperate diatoms (De La Rocha et al. 1997). However, the application of this proxy for marine paleo-silicon reconstructions has typically only been used in polar regions, such as the Southern Ocean, where high primary production rates give rise to diatom-rich sediments. Here, we present results on the fractionation of Si isotopes by four species of polar diatoms grown in semi-continuous cultures (Chaetoceros brevis, Fragilariopsis kerguelensis, Porosira glacialis, and Thalassiosira antarctica). To compare with previous studies (De La Rocha et al, 1997), we also tested Si isotope fractionation by two species of temperate diatoms (Thalassiosira pseudonana and Thalassiosira weissflogii). The temperate species yielded Si isotope fractionation (Δ30Si) values of -0.81 % (±0.12, SD, n=11) for T. pseudonana and -1.03% (±0.09, SD, n=3) for T. weissflogii, that are identical to the previously reported fractionation of -1.1 % (±0.4, SD, n=6) (De La Rocha et al. 1997). Similarly, our data for polar species F. kerguelensis, P. glacialis and T. antarctica suggest a fractionation of -0.7 to -1.1 %. Interestingly, our preliminary results from Chaetoceros brevis cultures show a Si isotope fractionation value of about -2.61 % (±0.05, SD

  1. Observations and experiments on the population dynamics of epipelic diatoms from an estuarine mudflat

    Science.gov (United States)

    Admiraal, Wim; Peletier, Harry; Zomer, Hans

    1982-05-01

    The kinetics of diatom growth on a mudflat in the Ems-Dollard estuary were analysed from field observations and experiments carried out during a spring bloom. Low-density natural populations of epipelic diatoms showed an exponential increase in cell number with an apparent cell division rate of 0·3 day -1. Similar division rates were measured in natural populations, incubated on their sediment in the laboratory and in unialgal cultures of dominant diatom species grown on interstitial water. The vertical migration of diatom cells in 'dark' millimeters deep sediment layers apparently did not decrease the mean cell division rate in the populations. The diatom populations on the mudflat reached densities of 1-×10 6 cells cm -2; these densities are comparable to peak values of chlorophyll a concentrations of 100-400 mg m -1 of sediment, as reported for microphytobenthos in the literature. In dense natural populations and in dense unialgal cultures similar patterns were found in the accumulation of biomass (as chlorophyll a or cell numbers), in the limitation of productivity (as mg O 2 m -2 h -1) and in the decrease of cell division rate. The diffusion of inorganic carbon and oxygen between the diatom film and the overlying water limited the productivity of dense diatom populations to ca. 500 mg O 2 h -1 or less depending on the external concentrations of inorganic carbon and oxygen, and the flow rate of the water. Correspondingly, the rate of cell production in dense culture reached an upper level and this resulted in linear growth curves. The rate of this linear growth was affected also by the length of the daily light period. At the highest densities of cultures and natural populations the population growth drops to zero, suggesting a per day balanced budget of carbon-limited photosynthesis and respiratory or excretory losses. Self-shading had no effect on the division rate in dense cultures. The supply of nutrients (as P, N or Si) was not a critical factor to the

  2. Identification of Odontella aurita by rbcL gene sequence - a high antibacterial potential centric marine diatom.

    Science.gov (United States)

    Hemalatha, Annadurai; Mohammed Esa, Syed Abdul Rahman; Suresh, Murugan; Thajuddin, Nooruddin; Anantharaman, Perumal

    2017-09-01

    The antibacterial potential of centric marine diatoms has been compared against the clinical pathogens and identified the potential diatom by rbcL gene sequencing. Totally, five diatoms namely Odontella aurita, Thalassiosira subtilis, Chaetoceros curvisetus, Skeletonema costatum and Coscinodiscus centralis were isolated from Cuddalore coastal waters. The diatoms were morphologically identified and isolated using micro capillary-pipette and serial dilution method. The isolated diatoms were cultured in Guillard's f/2 medium to get biomass for the antibacterial study. The dried biomass of the cultured diatoms was individually extracted with methanol, ethanol and hexane. All the obtained extracts were tested against Staphylococcus haemolyticus, Proteus vulgarius and Vibrio alginolyticus. The crude ethanol extract of O. aurita was exhibited highest zone of inhibition against all the test pathogens. The MIC of O. aurita was recorded as 50 μg/ml against both Staphylococcus haemolyticus and Proteus vulgarius whilst 75 μg/ml against Vibrio alginolyticus. This study indicates that O. aurita possesses antibacterial activities but the release of antibiotics depends on physical or chemical rupture of algal cells and extractive solvents. Based on the maximum antibacterial activity, O. aurita was further identified by rbcL gene sequencing. The rbcL gene could be an identical region for the species level identification of diatoms.

  3. Diatom Stratigraphy of FA-1 Core, Qarun Lake, Records of Holocene Environmental and Climatic Change in Faiyum Oasis, Egypt

    Directory of Open Access Journals (Sweden)

    Zalat Abdelfattah A.

    2017-06-01

    Full Text Available This study evaluates changes in the environmental and climatic conditions in the Faiyum Oasis during the Holocene based on diatom analyses of the sediment FA-1 core from the southern seashore of the Qarun Lake. The studied FA-1 core was 26 m long and covered the time span ca. 9.000 cal. yrs BP. Diatom taxa were abundant and moderately to well-preserved throughout the core sediments. Planktonic taxa were most abundant than the benthic and epiphytic forms, which were very rare and sparsely distributed. The most dominant planktonic genera were Aulacoseira and Stephanodiscus followed by frequently distribution of Cyclostephanos and Cyclotella species. The stratigraphic distribution patterns of the recorded diatoms through the Holocene sediments explained five ecological diatom groups. These groups represent distinctive environmental conditions, which were mainly related to climatic changes through the early and middle Holocene, in addition to anthropogenic activity during the late Holocene. Comparison of diatom assemblages in the studied sediment core suggests that considerable changes occurred in water level as well as salinity. There were several high stands of the freshwater lake level during humid, warmer-wet climatic phases marked by dominance of planktonic, oligohalobous and alkaliphilous diatoms alternated with lowering of the lake level and slight increases in salinity and alkalinity during warm arid conditions evident by prevalence of brackish water diatoms.

  4. [Comparative analysis between diatom nitric acid digestion method and plankton 16S rDNA PCR method].

    Science.gov (United States)

    Han, Jun-ge; Wang, Cheng-bao; Li, Xing-biao; Fan, Yan-yan; Feng, Xiang-ping

    2013-10-01

    To compare and explore the application value of diatom nitric acid digestion method and plankton 16S rDNA PCR method for drowning identification. Forty drowning cases from 2010 to 2011 were collected from Department of Forensic Medicine of Wenzhou Medical University. Samples including lung, kidney, liver and field water from each case were tested with diatom nitric acid digestion method and plankton 16S rDNA PCR method, respectively. The Diatom nitric acid digestion method and plankton 16S rDNA PCR method required 20 g and 2 g of each organ, and 15 mL and 1.5 mL of field water, respectively. The inspection time and detection rate were compared between the two methods. Diatom nitric acid digestion method mainly detected two species of diatoms, Centriae and Pennatae, while plankton 16S rDNA PCR method amplified a length of 162 bp band. The average inspection time of each case of the Diatom nitric acid digestion method was (95.30 +/- 2.78) min less than (325.33 +/- 14.18) min of plankton 16S rDNA PCR method (P plankton 16S rDNA PCR method was both 80%, higher than 40% and 30% of diatom nitric acid digestion method (P plankton 16S rDNA PCR method has practice values with such advantages as less quantity of samples, huge information and high specificity.

  5. Settlement and cell division of diatom Navicula can be influenced by light of various qualities and intensities.

    Science.gov (United States)

    Cao, Shan; Wang, Jiadao; Chen, Darong

    2013-11-01

    Diatom settlement and cell division is important in two major aspects. Firstly, biofouling is a costly problem in the shipping industry that necessitates the effective inhibition of diatom settlement and proliferation. Secondly, biological coatings on the basis of ordered and densely packed cell lawns of diatom are useful for nano- and biotechnology. This study demonstrated that the settlement and cell division of the marine unicellular diatom Navicula sp. can be influenced by light-emitting diodes of various light qualities and intensities. Except for blue light, the settlement of diatoms was reduced by weak (approx. 0.14-6 µE m(-2) s(-1)) green, yellow or red light. When the irradiance intensity, however, was higher than 8-9 µE m(-2) s(-1), the settlement was stimulated. This phenomenon could be explained by the hypothesis of spatial interference between a chloroplast and a holdfast-like structure. Densely packed lawn of diatoms with uniform distribution can be fabricated for nanotechnologies, using blue light that stimulates diatom cell division. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Hausa verbal compounds

    NARCIS (Netherlands)

    McIntyre, Joseph Anthony

    2006-01-01

    Verbal compounds abound in Hausa (a Chadic language). A very broad definition of Hausa verbal compounds (henceforth: VC) is “a compound with a verb”. Four types of verbal compound are analysed: V[erb]+X compounds, PAC+V compounds (a PAC is a pronoun complex indicating TAM), VCs with a ma prefix

  7. Spectroscopic Studies of Diatomic Transition Metal Oxides and Fluorides.

    Science.gov (United States)

    McCord, John Edward

    Wavelength selected fluorescence excitation spectroscopy (WSFES) techniques and ligand field theory (LFT) calculations have been applied to the following transition metal diatomics: CeO, UO, LaF, YF, ScF, HfO, TiO, and ZrO. All of the rotational spectra recorded for these molecules were at a resolution of 0.03 cm^{-1}, and, with few exceptions, Omega assignments for electronic states were unambiguously determined from observations of the first lines in at least two rotational branches. Accurate term energies and rotational constants are reported. Thirty one electronic transitions of CeO were recorded, and all of the sixteen states that correlate with rm Ce^{2+}(4f6s)O^ {2-} were characterized. The results are in good accord with a ligand field theory model of the low-lying states. New assignments were established for four previously observed transitions, and spectra for three new excited states were analyzed. LFT calculations have been used in an attempt to provide configurational assignments for the excited states (including those from previous studies). Twenty two states are tentatively assigned to the rm Ce^{2+}(4f6p)O ^{2-} configuration. Twelve others are tentatively assigned to rm Ce^ {2+}(4f5d)O^{2-}.. Rotation-electronic interactions between states of the 4f6s configuration of CeO, mediated by the operator {-}B(R)( J^+ cdot J_sp{a}{-}+ J^-cdot J_sp{a} {+}), have been calculated. Second-order perturbation theory was used to account for the effect of heterogeneous interactions on the rotation constants within a single configuration. Thirty-three electronic transitions of UO were analyzed, and nine low-lying electronic states that correlated with either rm U^{2+}(5f ^37s)O^{2-} or rm U^{2+}(5f^27s^2)O ^{2-} were characterized. Ligand field theory calculations were also used in an attempt to provide configurational assignments for the excited states of UO and ThO. Experimentally derived values for Delta B_sp{0} {0}(nl/n^' l^') parameters were used to predict

  8. Nitrogen deposition effects on diatom communities in lakes from three National Parks in Washington State

    Science.gov (United States)

    Sheibley, Richard W.; Enache, Mihaela; Swarzenski, Peter W.; Moran, Patrick W.; Foreman, James R.

    2014-01-01

    The goal of this study was to document if lakes in National Parks in Washington have exceeded critical levels of nitrogen (N) deposition, as observed in other Western States. We measured atmospheric N deposition, lake water quality, and sediment diatoms at our study lakes. Water chemistry showed that our study lakes were ultra-oligotrophic with ammonia and nitrate concentrations often at or below detection limits with low specific conductance (−1 year−1 and were variable both within and across the parks. Diatom assemblages in a single sediment core from Hoh Lake (Olympic National Park) displayed a shift to increased relative abundances of Asterionella formosa and Fragilaria tenera beginning in the 1969–1975 timeframe, whereas these species were not found at the remaining (nine) sites. These diatom species are known to be indicative of N enrichment and were used to determine an empirical critical load of N deposition, or threshold level, where changes in diatom communities were observed at Hoh Lake. However, N deposition at the remaining nine lakes does not seem to exceed a critical load at this time. At Milk Lake, also in Olympic National Park, there was some evidence that climate change might be altering diatom communities, but more research is needed to confirm this. We used modeled precipitation for Hoh Lake and annual inorganic N concentrations from a nearby National Atmospheric Deposition Program station, to calculate elevation-corrected N deposition for 1980–2009 at Hoh Lake. An exponential fit to this data was hindcasted to the 1969–1975 time period, and we estimate a critical load of 1.0 to 1.2 kg N ha−1 year−1 for wet deposition for this lake.

  9. Mediterranean river biomonitoring in Central Italy: Diatom biodiversity and characterization of communities

    Directory of Open Access Journals (Sweden)

    Valentina Della Bella

    2016-10-01

    Full Text Available In compliance with the European and Italian regulations, the Environmental Protection Agency of Umbria Region (ARPA Umbria defined specific river monitoring programs and networks based on river type definition, human pressures and risk analysis. The Umbria Region lies in Central Italy and it can be split into three hydro-ecoregions belonging to the Mediterranean area. Data on diatom community composition were collected in five different Mediterranean macrotypes (M1-M5 throughout the diatom-based river monitoring network that is composed by 52 sampling stations in 36 watercourses. The main aim of this study was to characterise and to analyse diatom diversity across the different regional river macrotypes. Specifically, we investigated if: i there were differences in species diversity (species richness and Shannon Index among macrotypes; ii there was difference in three water quality indexes (ICMi, IPS, and TI among sites; and iii there was a relationship between the observed ICMi, IPS and TI value and the diatom diversity. Two-hundred diatom species and varieties were identified, and the number of species per sampling station ranged from a minimum of 10 to a maximum of 38 species. The most frequent and abundant species were Amphora pediculus, Achnanthidium minutissimum, Navicula cryptotenella, Nitzschia dissipata, and each macrotype showed some peculiar species. The ecological status evaluation based on Intercalibration Common Metric Index (ICMi classified 69% of the water bodies in high or good class. Significant differences in diversity and ICMi value among stream macrotypes were found, with M4 (small and medium mountain and M5 (small, lowland, temporary typologies showing the lowest species richness, and with M5 showing the lowest Shannon Index. Conversely, M2 (small and medium lowland and M5 showed the highest ICMi value. Lastly, significant correlations between Shannon Index and the ICMi, IPS and TI indexes were found.

  10. A fast Na+/Ca2+-based action potential in a marine diatom.

    Directory of Open Access Journals (Sweden)

    Alison R Taylor

    Full Text Available BACKGROUND: Electrical impulses in animals play essential roles in co-ordinating an array of physiological functions including movement, secretion, environmental sensing and development. Underpinning many of these electrical signals is a fast Na+-based action potential that has been fully characterised only in cells associated with the neuromuscular systems of multicellular animals. Such rapid action potentials are thought to have evolved with the first metazoans, with cnidarians being the earliest representatives. The present study demonstrates that a unicellular protist, the marine diatom Odontella sinensis, can also generate a fast Na+/Ca2+ based action potential that has remarkably similar biophysical and pharmacological properties to invertebrates and vertebrate cardiac and skeletal muscle cells. METHODOLOGY/PRINCIPAL FINDINGS: The kinetic, ionic and pharmacological properties of the rapid diatom action potential were examined using single electrode current and voltage clamp techniques. Overall, the characteristics of the fast diatom currents most closely resemble those of vertebrate and invertebrate muscle Na+/Ca2+ currents. CONCLUSIONS/SIGNIFICANCE: This is the first demonstration of voltage-activated Na+ channels and the capacity to generate fast Na+-based action potentials in a unicellular photosynthetic organism. The biophysical and pharmacological characteristics together with the presence of a voltage activated Na+/Ca2+ channel homologue in the recently sequenced genome of the diatom Thalassiosira pseudonana, provides direct evidence supporting the hypothesis that this rapid signalling mechanism arose in ancestral unicellular eukaryotes and has been retained in at least two phylogenetically distant lineages of eukaryotes; opisthokonts and the stramenopiles. The functional role of the fast animal-like action potential in diatoms remains to be elucidated but is likely involved in rapid environmental sensing of these widespread and

  11. Using bioassays and species sensitivity distributions to assess herbicide toxicity towards benthic diatoms.

    Directory of Open Access Journals (Sweden)

    Floriane Larras

    Full Text Available Although benthic diatoms are widely used in ecological studies of aquatic systems, there is still a dearth of data concerning species sensitivities towards several contaminants. Within the same community, different species may respond differently depending on their physiological and ecological characteristics. This lack of knowledge makes specific appropriate risk assessment impossible. To find out whether species sensitivity distribution (SSD could be used to estimate the risk of herbicide toxicity for diatoms, we need to know whether their sensitivity depends on their physiological and ecological characteristics. We carried out single-species bioassays on 11 diatom species exposed to 8 herbicides. Dose-responses relationships were used to extrapolate the Effective Concentration 5 (EC(5 and the Effective Concentration 50 (EC(50 for each exposure. These data were used to fit a SSD curve for each herbicide, and to determine the Hazardous concentration 5 (HC(5 and 50 (HC(50. Our results revealed a high level of variability of the sensitivity in the set of species tested. For photosystem-II inhibitor (PSII herbicides, diatoms species displayed a typical grouping of sensitivity levels consistent with their trophic mode and their ecological guild. N-heterotroph and "motile" guild species were more tolerant of PSII inhibitors, while N-autotroph and "low profile" guild species were more sensitive. Comprehensive SSD curves were obtained for 5 herbicides, but not for sulfonylurea herbicides or for dimetachlor, which had toxicity levels that were below the range of concentration tested. The SSD curves provided the following ranking of toxicity: diuron> terbutryn> isoproturon> atrazine> metolachlor. The HC that affected 5% of the species revealed that, even at the usual environmental concentrations of herbicides, diatom assemblages could be affected, especially by isoproturon, terbutryn, and diuron.

  12. Using bioassays and species sensitivity distributions to assess herbicide toxicity towards benthic diatoms.

    Science.gov (United States)

    Larras, Floriane; Bouchez, Agnès; Rimet, Frédéric; Montuelle, Bernard

    2012-01-01

    Although benthic diatoms are widely used in ecological studies of aquatic systems, there is still a dearth of data concerning species sensitivities towards several contaminants. Within the same community, different species may respond differently depending on their physiological and ecological characteristics. This lack of knowledge makes specific appropriate risk assessment impossible. To find out whether species sensitivity distribution (SSD) could be used to estimate the risk of herbicide toxicity for diatoms, we need to know whether their sensitivity depends on their physiological and ecological characteristics. We carried out single-species bioassays on 11 diatom species exposed to 8 herbicides. Dose-responses relationships were used to extrapolate the Effective Concentration 5 (EC(5)) and the Effective Concentration 50 (EC(50)) for each exposure. These data were used to fit a SSD curve for each herbicide, and to determine the Hazardous concentration 5 (HC(5)) and 50 (HC(50)). Our results revealed a high level of variability of the sensitivity in the set of species tested. For photosystem-II inhibitor (PSII) herbicides, diatoms species displayed a typical grouping of sensitivity levels consistent with their trophic mode and their ecological guild. N-heterotroph and "motile" guild species were more tolerant of PSII inhibitors, while N-autotroph and "low profile" guild species were more sensitive. Comprehensive SSD curves were obtained for 5 herbicides, but not for sulfonylurea herbicides or for dimetachlor, which had toxicity levels that were below the range of concentration tested. The SSD curves provided the following ranking of toxicity: diuron> terbutryn> isoproturon> atrazine> metolachlor. The HC that affected 5% of the species revealed that, even at the usual environmental concentrations of herbicides, diatom assemblages could be affected, especially by isoproturon, terbutryn, and diuron.

  13. Effect of chlorination on the development of marine biofilms dominated by diatoms.

    Science.gov (United States)

    Patil, Jagadish S; Jagadeesan, V

    2011-03-01

    This study addressed the antifouling efficiency of commercially available chlorine at different concentrations (0.5%, 1%, and 2%) and exposure times (0.5 min, 1 min, 5 min, and 15 min). The rapid and non-destructive FIRe (fluorescence induction and relaxation) technique was used to evaluate the effects of the biocide on diatom dominated biofilms. The efficiency of chlorine in removing diatoms from the developed biofilms increased with an increase in concentration and exposure time. The fluorescence measurements revealed low F(v)/F(m) and high σ(PSII) values for chlorine-treated Navicula and Amphora biofilms indicating that chlorination was efficient in damaging the photosystem-II reaction centers. Chlorination also caused mortality of diatom cells by damaging the cell body. In natural biofilms, the biocidal effect of chlorine was species specific; species of Amphiphrora, Navicula, Cylindrotheca, and Coscinodiscus showed an increase in the density of the population, but species of Pleurosigma, Amphora, and Thalassionema did not increase in density after chlorine treatment. It was also demonstrated that diatoms can colonize, grow and photosynthesize on chlorine-treated surfaces. Under pulse chlorination (treatment every 6 h), irrespective of chlorine concentration, the development of biofouling decreased with an increase in exposure time. Differences between exposure times of 1 to 15 min were not significant. Additionally, transmission levels of the control (non-chlorine-treated) fouled coupons reduced significantly (∼20%) compared to the chlorine-treated fouled coupons (<2%). These results suggest that chlorine can be used as a biocide to control the development of diatom biofilms.

  14. Plastid proteomics for elucidating iron limited remodeling of plastid physiology in diatoms

    Science.gov (United States)

    Gomes, K. M.; Nunn, B. L.; Jenkins, B. D.

    2016-02-01

    Diatoms are important primary producers in the world's oceans and their growth is constrained in large regions by low iron availability. This low iron-induced limitation of primary production is due to the requirement for iron in components of essential metabolic pathways including key chloroplast functions such as photosynthesis and nitrate assimilation. Diatoms can bloom and accumulate high biomass during introduction of iron into low iron waters, indicating adaptations allowing for their survival in iron-limited waters and rapid growth when iron becomes more abundant. Prior studies have shown that under iron limited stress, diatoms alter plastid-specific processes including components of electron transport, size of light harvesting capacity and chlorophyll content, suggesting plastid-specific protein regulation. Due to their complex evolutionary history, resulting from a secondary endosymbiosis, knowledge regarding the complement of plastid localized proteins remains limited in comparison to other model photosynthetic organisms. While in-silico prediction of diatom protein localization provides putative candidates for plastid-localization, these analyses can be limited as most plastid prediction models were developed using plants, primary endosymbionts. In order to characterize proteins enriched in diatom chloroplast and to understand how the plastid proteome is remodeled in response to iron limitation, we used mass spectrometry based proteomics to compare plastid- enriched protein fractions from Thalassiosira pseudonana, grown in iron replete and limited conditions. These analyses show that iron stress alters regulation of major metabolic pathways in the plastid including the Calvin cycle and fatty acid synthesis. These components provide promising targets to further characterize the plastid specific response to iron limitation.

  15. Picocyanobacteria Dominance in Deep Biomass Layers: Relation to Diatom Presence and Episodic Events.

    Science.gov (United States)

    Aguilar, C.; Cuhel, R. L.

    2016-02-01

    In Offshore Marine and Large Lake Waters, most of the biomass and the productivity of phytoplankton occur below surface observation capabilities. Sub-mixed layer phytoplankton populations develop, increase, persist, and decay in relation to physical structure such as pycnocline density gradients interacting with progressively changing light fields. Basin-scale meteorological events and persistence of major invasive species have also left marks on biogeochemical cycling and ecosystem function in Lake Michigan. Among the former are precipitation and turbulence alterations brought on by unusual winter ice cover and a century-scale flood during 2008. Dampened seasonal silicate cycling indicated a basin-wide reduction of diatom production following mussel establishment. Communities in Lake Michigan shifted from diatom and big cell-dominated to small cell picocyanobacteria-dominated phytoplankton. Picocyanobacteria were beneficiaries of profound oligotrophication of the ecosystem starting in 2003. Photosynthetic parameters of pre-2003 Deep Biomass populations dominated by diatoms were systematically different from the cyanobacterial epoch following quagga mussel establishment and increase in depth of 1% incident light to 50-60m. Deep cyanobacterial production has now often been on the same scale as overlying waters. Photophysiology changes in a smooth depth gradient in this clear water as opposed to previous abrupt transition to shade adaptation. Among these many physicochemical permutations, community structure has consistently been a tradeoff between diatoms and picocyanobacteria. Opposing fluctuations of biomass favor one or the other on seasonal time frames of sequential years, with a complete system reset between each (winter mixing). For the Great Flood example, diatom surface blooms increased light extinction and drove the deep biomass maximum up - as populations settled into the pycnocline they had already outcompeted the picocyanobacteria. The opposite was true

  16. Physical processes affecting availability of dissolved silicate for diatom production in the Arabian Sea

    Science.gov (United States)

    Young, David K.; Kindle, John C.

    1994-11-01

    A passive tracer to represent dissolved silicate concentrations, with biologically realistic uptake kinetics, is successfully incorporated into a three-dimensional, eddy-resolving, ocean circulation model of the Indian Ocean. Hypotheses are tested to evaluate physical processes which potentially affect the availability of silicate for diatom production in the Arabian Sea. An alternative mechanism is offered to the idea that open ocean upwelling is primarily responsible for the high, vertical nutrient flux and consequent large-scale phytoplankton bloom in the northwestern Arabian Sea during the southwest monsoon. Model results show that dissolved silicate in surface waters available for uptake by diatoms is primarily influenced by the intensity of nearshore upwelling from southwest monsoonal wind forcing and by the offshore advective transport of surface waters. The upwelling, which in the model occurs within 200±50 km of the coast, appears to be a result of a combination of coastal upwelling, Ekman pumping, and divergence of the coastal flow as it turns offshore. Localized intensifications of silicate concentrations appear to be hydrodynamically driven and geographically correlated to coastal topographic features. The absence of diatoms in sediments of the eastern Arabian Basin is consistent with modeled distributional patterns of dissolved silicate resulting from limited westward advection of upwelled coastal waters from the western continental margin of India and rapid uptake of available silicate by diatoms. Concentrations of modeled silicate become sufficiently low to become unavailable for diatom production in the eastern Arabian Sea, a region between 61°E and 70°E at 8°N on the south, with the east and west boundaries converging on the north at ˜67°E, 20°N.

  17. The transferability of diatoms to clothing and the methods appropriate for their collection and analysis in forensic geoscience.

    Science.gov (United States)

    Scott, Kirstie R; Morgan, Ruth M; Jones, Vivienne J; Cameron, Nigel G

    2014-08-01

    Forensic geoscience is concerned with the analysis of geological materials in order to compare and exclude environmental samples from a common source, or to identify an unknown provenance in a criminal investigation. Diatom analysis is currently an underused technique within the forensic geoscience approach, which has the potential to provide an independent ecological assessment of trace evidence. This study presents empirical data to provide a preliminary evidence base in order to be able to understand the nature of diatom transfers to items of clothing, and the collection of transferred diatom trace evidence from a range of environments under experimental conditions. Three diatom extraction methods were tested on clothing that had been in contact with soil and water sites: rinsing in water (RW), rinsing in ethanol (RE), and submersion in H2O2 solution (H). Scanning electron microscopy (S.E.M.) analysis was undertaken in order to examine the degree of diatom retention on treated clothing samples. The total diatom yield and species richness data was recorded from each experimental sample in order to compare the efficacy of each method in collecting a representative sample for analysis. Similarity was explored using correspondence analysis. The results highlight the efficiency of H2O2 submersion in consistently extracting high diatom counts with representative species from clothing exposed to both aquatic and terrestrial sites. This is corroborated by S.E.M. analysis. This paper provides an important empirical evidence base for both establishing that diatoms do indeed transfer to clothing under forensic conditions in a range of environments, and in identifying that H2O2 extraction is the most efficient technique for the optimal collection of comparative samples. There is therefore potentially great value in collecting and analysing diatom components of geoforensic samples in order to aid in forensic investigation. Copyright © 2014 The Authors. Published by Elsevier

  18. Diatoms of the jukskei-crocodile river system (transvaal, republic of South Africa): a preliminary check list

    CSIR Research Space (South Africa)

    Schoeman, FR

    1982-01-01

    Full Text Available ALEEM, A. A. and HUSTEDT, F., 1951. Einige neue Diatomeen von der S?dkuste Englands. Bot. Notiser 1951: 13?20. Diatoms of the Jukskei?Crocodile rivers 307 ALLANSON, B. R., 1961. Investigations into the ecology of polluted inland waters... unterschiedlich starker Abwasserbelastung. Arch. Hydro biol. Suppl 56: 184?219. Diatoms of the Jukskei?Crocodile rivers 309 LANGE-BERTALOT, H., 1979b. Pollution tolerance of diatoms as a criterion for water quality estimation. Nova Hedwigia Suppl. 64: 285...

  19. Carbon content and C:N ratio of transparent exopolymeric particles (TEP) produced by bubbling exudates of diatoms

    DEFF Research Database (Denmark)

    Mari, Xavier

    1999-01-01

    The carbon content of transparent exopolymeric particles (TEP) was measured in the laboratory in particles produced by bubbling exudates of the diatom Thalassiosira weissflogii, grown under nitrogen non-limited conditions (N:P = 7). The carbon content of these particles (TEP-C) appears to vary...... for dissolved organic carbon in coastal seas. The carbon to nitrogen ratio of TEP was measured from particles formed by bubbling exudates of the diatoms T. weissflogii, Skeletonema costatum, Chaetoceros neogracile and C. affinis. Each of these diatom species was grown under various N:P ratios, from N...

  20. Diatom diversity and response in metal-polluted river environment: preliminary reports from Gromolo Torrent (Liguria, Italy)

    Science.gov (United States)

    Capello, Marco; Tolotti, Raffaella; Bernabè, Dimitri; Carbone, Cristina; Consani, Sirio; Vagge, Greta; Cutroneo, Laura

    2016-04-01

    Mineral content and physico-chemical properties of the freshwaters are the main factors affecting both algal assemblages and distributions, while presence of dissolved silicon, low water conductivity, and rocky-mountain habitats host benthic diatom assemblages of high species richness. It is shown that diatoms are sensible to the freshwater acidification (used as pH indicators in acid waters), environmental and climate changes, river organic load, and heavy metal water pollution. For this characteristic, diatoms are among the major biological markers for a variety of environmental and stratigraphic applications. In particular, qualitative and quantitative analyses (assemblage analyses) together with biotic indices as well as morphological and ultrastructure parameterisation provide tools for detailed environmental control and paleo-environmental reconstructions. Severe environmental problems are typically caused by "abandoned mine" and are consequences of the cessation of the mining activity with a lack in infrastructure maintenance. The mine waters which flow into the Gromolo Torrent are almost acidic (pH varying from 2.4 to 5) and enriched in heavy metals and SO42-. This pollution is caused by Acid Mine Drainage (AMD) processes that interest the Libiola mining area, known as a typical example of active AMD processes. The aim of this work is: 1) to characterise the local benthic diatom assemblages along the acidic mine effluents that discharge from Libiola mine, the entire Gromolo torrent course, and in the marine area off the torrent mouth; 2) to identify the main diatom biomarker taxa; 3) to highlight striking situations of equilibrium-disequilibrium in the algal communities, and 4) to point out types and frequency of some teratologies affecting specific diatom taxa as a response to environmental stressors (such as metal-metalloid enrichment). A total of 17 diatom samples was collected and examined, including some marine samples. Diatoms were collected in the