Very similar strains of Halococcus salifodinae are found in geographically separated permo-triassic salt deposits.
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The authors have previously isolated a novel extremely halophilic archaeon, Halococcus salifodinae Blp, from Austrian rock salt deposited about 250 million years ago. In this study they compared strain Blp with two other halococci isolated independently from geographically distant salt deposits of similar age, and with two recent isolates (N1 and H2) from the same site as strain Blp. Strain BG2/2 was from a salt mine in Germany and strain Br3 from a halite deposit in England; both resembled Hc. salifodinae Blp in cellular and colonial morphology. Strains Blp, BG2/2 and Br3 had identical 16S rRNA sequences, very similar whole-cell protein patterns, which were different from those of other halococci, similar G+C contents and identical sequences in a 108-base insertion in their 5S rRNA gene. Other similarities included composition and relative abundances of polar lipids, antibiotic susceptibility, enzymic activities and Fourier-transform infrared spectra. Strains N1 and H2 showed similar morphology, whole-cell protein patterns and biochemical characteristics as strains Blp, Br3 and BG2/2. Their partial 16S rRNA sequences (682 and 641 bases, respectively) were indistinguishable from those of strains Blp, Br3 and BG2/2. Therefore strains N1 and H2 can be considered as reisolates of Hc. salifodinae which were obtained 8 years after the first samples were taken from that mine. The results presented suggest that viable halophilic archaea, which belong to the same species, occur in widely separated evaporite locations of similar geological age, and support the notion that these halophilic isolates from subterranean salt deposits may be the remnants of populations which inhabited ancient hypersaline seas. (+info)
Influences of dietary uptake and reactive sulfides on metal bioavailability from aquatic sediments.
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Understanding how animals are exposed to the large repository of metal pollutants in aquatic sediments is complicated and is important in regulatory decisions. Experiments with four types of invertebrates showed that feeding behavior and dietary uptake control bioaccumulation of cadmium, silver, nickel, and zinc. Metal concentrations in animal tissue correlated with metal concentrations extracted from sediments, but not with metal in porewater, across a range of reactive sulfide concentrations, from 0.5 to 30 micromoles per gram. These results contradict the notion that metal bioavailability in sediments is controlled by geochemical equilibration of metals between porewater and reactive sulfides, a proposed basis for regulatory criteria for metals. (+info)
Dissimilatory metal reduction by the facultative anaerobe Pantoea agglomerans SP1.
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Anaerobic enrichments with acetate as the electron donor and Fe(III) as the terminal electron acceptor were obtained from sediments of Salt Pond, a coastal marine basin near Woods Hole, Mass. A pure culture of a facultatively anaerobic Fe(III) reducer was isolated, and 16S rRNA analysis demonstrated that this organism was most closely related to Pantoea (formerly Enterobacter) agglomerans, a member of the family Enterobacteriaceae within the gamma subdivision of the Proteobacteria. This organism, designated strain SP1, can grow by coupling the oxidation of acetate or H(2) to the reduction of a variety of electron acceptors, including Fe(III), Mn(IV), Cr(VI), and the humic substance analog 2,6-anthraquinone disulfonate, but not sulfate. To our knowledge, this is the first mesophilic facultative anaerobe reported to couple acetate oxidation to dissimilatory metal reduction. (+info)
Application of neural computing methods for interpreting phospholipid fatty acid profiles of natural microbial communities.
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The microbial community compositions of surface and subsurface marine sediments and sediments lining burrows of marine polychaetes and hemichordates from the North Inlet estuary (near Georgetown, S.C. ) were analyzed by comparing ester-linked phospholipid fatty acid (PLFA) profiles with a back-propagating neural network (NN). The NNs were trained to relate PLFA inputs to sediment type outputs (e.g., surface, subsurface, and burrow lining) and worm species (e.g., Notomastus lobatus, Balanoglossus aurantiacus, and Branchyoasychus americana). Sensitivity analysis was used to determine which of the 60 PLFAs significantly contributed to training the NN. The NN architecture was optimized by changing the number of hidden neurons and calculating the cross-validation error between predicted and actual outputs of training and test data. The optimal NN architecture was found to be four hidden neurons with 60-input neurons representing the 60 PLFAs, and four output neurons coding for both sediment types and worm species. Comparison of cross-validation results using NNs and linear discriminant analysis (LDA) revealed that NNs had significantly fewer incorrect classifications (2.7%) than LDA (8.4%). For the NN cross-validation, both sediment type and worm species had 3 incorrect classifications out of 112. For the LDA cross-validation, sediment type and worm species had 7 and 12 incorrect classifications out of 112, respectively. Sensitivity analysis of the trained NNs revealed that 17 fatty acids explained 50% of variability in the data set. These PLFAs were highly different among sediments and burrow types, indicating significant differences in the microbiota. (+info)
Increase in bacterial community diversity in subsurface aquifers receiving livestock wastewater input.
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Despite intensive studies of microbial-community diversity, the questions of which kinds of microbial populations are associated with changes in community diversity have not yet been fully solved by molecular approaches. In this study, to investigate the impact of livestock wastewater on changes in the bacterial communities in groundwater, bacterial communities in subsurface aquifers were analyzed by characterizing their 16S rDNA sequences. The similarity coefficients of restriction fragment length polymorphism (RFLP) patterns of the cloned 16S ribosomal DNAs showed that the bacterial communities in livestock wastewater samples were more closely related to those in contaminated aquifer samples. In addition, calculations of community diversity clearly showed that bacterial communities in the livestock wastewater and the contaminated aquifer were much more diverse than those in the uncontaminated aquifer. Thus, the increase in bacterial-community diversity in the contaminated aquifer was assumed to be due to the infiltration of livestock wastewater, containing high concentrations of diverse microbial flora, into the aquifer. Phylogenetic analysis of the sequences from a subset of the RFLP patterns showed that the Cytophaga-Flexibacter-Bacteroides and low-G+C gram-positive groups originating from livestock wastewater were responsible for the change in the bacterial community in groundwater. This was evidenced by the occurrence of rumen-related sequences not only in the livestock wastewater samples but also in the contaminated-groundwater samples. Rumen-related sequences, therefore, can be used as indicator sequences for fecal contamination of groundwater, particularly from livestock. (+info)
Biomarker evidence for widespread anaerobic methane oxidation in Mediterranean sediments by a consortium of methanogenic archaea and bacteria. The Medinaut Shipboard Scientific Party.
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Although abundant geochemical data indicate that anaerobic methane oxidation occurs in marine sediments, the linkage to specific microorganisms remains unclear. In order to examine processes of methane consumption and oxidation, sediment samples from mud volcanoes at two distinct sites on the Mediterranean Ridge were collected via the submersible Nautile. Geochemical data strongly indicate that methane is oxidized under anaerobic conditions, and compound-specific carbon isotope analyses indicate that this reaction is facilitated by a consortium of archaea and bacteria. Specifically, these methane-rich sediments contain high abundances of methanogen-specific biomarkers that are significantly depleted in (13)C (delta(13)C values are as low as -95 per thousand). Biomarkers inferred to derive from sulfate-reducing bacteria and other heterotrophic bacteria are similarly depleted. Consistent with previous work, such depletion can be explained by consumption of (13)C-depleted methane by methanogens operating in reverse and as part a consortium of organisms in which sulfate serves as the terminal electron acceptor. Moreover, our results indicate that this process is widespread in Mediterranean mud volcanoes and in some localized settings is the predominant microbiological process. (+info)
Internal structure and early thermal evolution of Mars from Mars Global Surveyor topography and gravity.
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Topography and gravity measured by the Mars Global Surveyor have enabled determination of the global crust and upper mantle structure of Mars. The planet displays two distinct crustal zones that do not correlate globally with the geologic dichotomy: a region of crust that thins progressively from south to north and encompasses much of the southern highlands and Tharsis province and a region of approximately uniform crustal thickness that includes the northern lowlands and Arabia Terra. The strength of the lithosphere beneath the ancient southern highlands suggests that the northern hemisphere was a locus of high heat flow early in martian history. The thickness of the elastic lithosphere increases with time of loading in the northern plains and Tharsis. The northern lowlands contain structures interpreted as large buried channels that are consistent with northward transport of water and sediment to the lowlands before the end of northern hemisphere resurfacing. (+info)
An archaeal iron-oxidizing extreme acidophile important in acid mine drainage.
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A new species of Archaea grows at pH approximately 0.5 and approximately 40 degrees C in slime streamers and attached to pyrite surfaces at a sulfide ore body, Iron Mountain, California. This iron-oxidizing Archaeon is capable of growth at pH 0. This species represents a dominant prokaryote in the environment studied (slimes and sediments) and constituted up to 85% of the microbial community when solution concentrations were high (conductivity of 100 to 160 millisiemens per centimeter). The presence of this and other closely related Thermoplasmales suggests that these acidophiles are important contributors to acid mine drainage and may substantially impact iron and sulfur cycles. (+info)