Growth characteristics of Heterosigma akashiwo virus and its possible use as a microbiological agent for red tide control.
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The growth characteristics of Heterosigma akashiwo virus clone 01 (HaV01) were examined by performing a one-step growth experiment. The virus had a latent period of 30 to 33 h and a burst size of 7.7 x 10(2) lysis-causing units in an infected cell. Transmission electron microscopy showed that the virus particles formed on the peripheries of viroplasms, as observed in a natural H. akashiwo cell. Inoculation of HaV01 into a mixed algal culture containing four phytoplankton species, H. akashiwo H93616, Chattonella antiqua (a member of the family Raphidophyceae), Heterocapsa triquetra (a member of the family Dinophyceae), and Ditylum brightwellii (a member of the family Bacillariophyceae), resulted in selective growth inhibition of H. akashiwo. Inoculation of HaV01 and H. akashiwo H93616 into a natural seawater sample produced similar results. However, a natural H. akashiwo red tide sample did not exhibit any conspicuous sensitivity to HaV01, presumably because of the great diversity of the host species with respect to virus infection. The growth characteristics of the lytic virus infecting the noxious harmful algal bloom-causing alga were considered, and the possibility of using this virus as a microbiological agent against H. akashiwo red tides is discussed. (+info)
Evolutionary patterns from mass originations and mass extinctions.
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The Fossil Record 2 database gives a stratigraphic range of most known animal and plant families. We have used it to plot the number of families extant through time and argue for an exponential fit, rather than a logistic one, on the basis of power spectra of the residuals from the exponential. The times of origins and extinctions, when plotted for all families of marine and terrestrial organisms over the last 600 Myr, reveal different origination and extinction peaks. This suggests that patterns of biological evolution are driven by its own internal dynamics as well as responding to upsets from external causes. Spectral analysis shows that the residuals from the exponential model of the marine system are more consistent with 1/f noise suggesting that self-organized criticality phenomena may be involved. (+info)
Mechanism of inhibition of a poxvirus topoisomerase by the marine natural product sansalvamide A.
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At present no antiviral agents are available for treatment of infection by the pathogenic poxvirus molluscum contagiosum virus (MCV). Here we report the identification and characterization of an inhibitor active against the virus-encoded type-1 topoisomerase, an enzyme likely to be required for MCV replication. We screened a library of marine extracts and natural products from microorganisms using MCV topoisomerase assays in vitro. The cyclic depsipeptide sansalvamide A was found to inhibit topoisomerase-catalyzed DNA relaxation. Sansalvamide A was inactive against two other DNA-modifying enzymes tested as a counterscreen. Assays of discrete steps in the topoisomerase reaction cycle revealed that sansalvamide A inhibited DNA binding and thereby covalent complex formation, but not resealing of a DNA nick in a preformed covalent complex. Sansalvamide A also inhibits DNA binding by the isolated catalytic domain, thereby specifying the part of the protein sensitive to sansalvamide A. These data specify the mechanism by which sansalvamide A inhibits MCV topoisomerase. Cyclic depsipeptides related to sansalvamide A represent a potentially promising chemical family for development of anti-MCV agents. (+info)
Low-molecular-weight sulfonates, a major substrate for sulfate reducers in marine microbial mats.
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Several low-molecular-weight sulfonates were added to microbial mat slurries to investigate their effects on sulfate reduction. Instantaneous production of sulfide occurred after taurine and cysteate were added to all of the microbial mats tested. The rates of production in the presence of taurine and cysteate were 35 and 24 microM HS(-) h(-1) in a stromatolite mat, 38 and 36 microM HS(-) h(-1) in a salt pond mat, and 27 and 18 microM HS(-) h(-1) in a salt marsh mat, respectively. The traditionally used substrates lactate and acetate stimulated the rate of sulfide production 3 to 10 times more than taurine and cysteate stimulated the rate of sulfide production in all mats, but when ethanol, glycolate, and glutamate were added to stromatolite mat slurries, the resulting increases were similar to the increases observed with taurine and cysteate. Isethionate, sulfosuccinate, and sulfobenzoate were tested only with the stromatolite mat slurry, and these compounds had much smaller effects on sulfide production. Addition of molybdate resulted in a greater inhibitory effect on acetate and lactate utilization than on sulfonate use, suggesting that different metabolic pathways were involved. In all of the mats tested taurine and cysteate were present in the pore water at nanomolar to micromolar concentrations. An enrichment culture from the stromatolite mat was obtained on cysteate in a medium lacking sulfate and incubated anaerobically. The rate of cysteate consumption by this enrichment culture was 1.6 pmol cell(-1) h(-1). Compared to the results of slurry studies, this rate suggests that organisms with properties similar to the properties of this enrichment culture are a major constituent of the sulfidogenic population. In addition, taurine was consumed at some of highest dilutions obtained from most-probable-number enrichment cultures obtained from stromatolite samples. Based on our comparison of the sulfide production rates found in various mats, low-molecular-weight sulfonates are important sources of C and S in these ecosystems. (+info)
An octaene fatty acid, 4,7,10,13,16,19,22,25-octacosaoctaenoic acid (28:8n-3), found in marine oils.
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We report structure determination of an octaene fatty acid, 4,7,10, 13,16,19,22,25-octacosaoctaenoic acid (28:8n-3). The molecular weight and double bond locations were determined using acetonitrile chemical ionization mass spectrometry (MS) and MS/MS and were confirmed by MS of hydrogenated and deuterogenated 28:8 and by argentation thin-layer chromatography. 28:8n-3 was 1.2 +/- 0.1%, in oil derived from the heterotrophic dinoflagellate Crypthecodinium cohnii and a commercial polyunsaturated fatty acid concentrate derived from fish oils (0.16 +/- 0.01%), both components of human dietary supplements. It was not found in whole bovine retina, cultured Y79 human retinoblastoma cells, or neonate baboon cerebral cortex. The long chain polyunsaturates present in the C. cohnii oil suggest a possible route for 28:8n-3 biosynthesis similar to that for biosynthesis of 22:6n-3. (+info)
Genetic diversity of archaea in deep-sea hydrothermal vent environments.
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Molecular phylogenetic analysis of naturally occurring archaeal communities in deep-sea hydrothermal vent environments was carried out by PCR-mediated small subunit rRNA gene (SSU rDNA) sequencing. As determined through partial sequencing of rDNA clones amplified with archaea-specific primers, the archaeal populations in deep-sea hydrothermal vent environments showed a great genetic diversity, and most members of these populations appeared to be uncultivated and unidentified organisms. In the phylogenetic analysis, a number of rDNA sequences obtained from deep-sea hydrothermal vents were placed in deep lineages of the crenarchaeotic phylum prior to the divergence of cultivated thermophilic members of the crenarchaeota or between thermophilic members of the euryarchaeota and members of the methanogen-halophile clade. Whole cell in situ hybridization analysis suggested that some microorganisms of novel phylotypes predicted by molecular phylogenetic analysis were likely present in deep-sea hydrothermal vent environments. These findings expand our view of the genetic diversity of archaea in deep-sea hydrothermal vent environments and of the phylogenetic organization of archaea. (+info)
Roots as a site of hydrogen sulfide uptake in the hydrocarbon seep vestimentiferan Lamellibrachia sp.
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Vestimentiferan tubeworms have no mouth or gut, and the majority of their nutritional requirements are provided by endosymbiotic bacteria that utilize hydrogen sulfide oxidation to fix CO(2) into organic molecules. It has been assumed that all vestimentiferans obtain the sulfide, O(2) and CO(2) needed by the bacteria across the plume (gill) surface, but some live in locations where very little sulfide is available in the sea water surrounding the plume. We propose that at least some of these vestimentiferans can grow a posterior extension of their body and tube down into the sea-floor sediment, and that they can use this extension, which we call the 'root', to take up sulfide directly from the interstitial water. In this study of the vestimentiferan Lamellibrachia sp., found at hydrocarbon seeps in the Gulf of Mexico at depths of approximately 700 m, we measured seawater and interstitial sulfide concentrations in the hydrocarbon seep habitat, determined the structural characteristics of the root tube using transmission electron microscopy, characterized the biochemical composition of the tube wall, and measured the sulfide permeability of the root tube. We found that, while the sulfide concentration is less than 1 (micro)mol l(-)(1) in the sea water surrounding the gills, it can be over 1.5 mmol l(-)(1) at a depth of 10-25 cm in sediment beneath tubeworm bushes. The root tube is composed primarily of giant (&bgr;)-chitin crystallites (12-30 % of total mass) embedded in a protein matrix (50 % of total mass). Root tubes have a mean diameter of 1.4 mm, a mean wall thickness of 70 (micro)m and can be over 20 cm long. The tubeworm itself typically extends its body to the distal tip of the root tube. The root tube wall was quite permeable to sulfide, having a permeability coefficient at 20 degrees C of 0. 41x10(-)(3 )cm s(-)(1), with root tube being 2.5 times more permeable to sulfide than trunk tube of the same diameter. The characteristics of the root suggest that it reaches down to the higher sulfide levels present in the deeper sediment and that it functions to increase the surface area available for sulfide uptake in a manner analogous to a respiratory organ. (+info)
Diversity and heterogeneity of epibiotic bacterial communities on the marine nematode Eubostrichus dianae.
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The diversity of a microbial community covering the surface of a marine nematode was analyzed by performing a 16S ribosomal DNA (rDNA) restriction cutting and sequencing analysis. In two clone libraries constructed by using individual nematodes, 54 and 85 restriction patterns were identified, and only 13 of these patterns were common to both libraries. Sequence analysis indicated that the common patterns belonged to four groups related to sequences of cytophagas, sulfate-reducing bacteria, members of the gamma subclass of the class Proteobacteria, and caulobacters. At least two groups appeared to be permanent members of the community as they were also detected in a 16S rDNA library constructed 3 years previously by using 100 pooled nematode specimens. A surprising outcome was that very dominant filamentous bacteria were apparently not represented in the clone libraries, as quantitative probing showed that none of the common operational taxonomic unit groups displayed the expected overwhelming dominance. Nevertheless, our analysis revealed both an unexpectedly high level of bacterial diversity and heterogeneity in samples representing presumably very similar microenvironments. (+info)