44 research outputs found
Correlating microbial community profiles with geochemical data in highly stratified sediments from the Arctic Mid-Ocean Ridge
Microbial communities and their associated metabolic activity in
marine sediments have a profound impact on global biogeochemical
cycles. Their composition and structure are attributed to geochemical
and physical factors, but finding direct correlations has remained a
challenge. Here we show a significant statistical relationship between
variation in geochemical composition and prokaryotic community
structure within deep-sea sediments. We obtained comprehensive
geochemical data from two gravity cores near the hydrothermal
vent field Loki’s Castle at the Arctic Mid-Ocean Ridge, in the Norwegian-
Greenland Sea. Geochemical properties in the rift valley
sediments exhibited strong centimeter-scale stratigraphic variability.
Microbial populations were profiled by pyrosequencing from
15 sediment horizons (59,364 16S rRNA gene tags), quantitatively
assessed by qPCR, and phylogenetically analyzed. Although the
same taxa were generally present in all samples, their relative
abundances varied substantially among horizons and fluctuated
between Bacteria- and Archaea-dominated communities. By independently
summarizing covariance structures of the relative
abundance data and geochemical data, using principal components
analysis, we found a significant correlation between changes in
geochemical composition and changes in community structure.
Differences in organic carbon and mineralogy shaped the relative
abundance of microbial taxa. We used correlations to build hypotheses
about energy metabolisms, particularly of the Deep Sea Archaeal
Group, specific Deltaproteobacteria, and sediment lineages
of potentially anaerobic Marine Group I Archaea. We demonstrate
that total prokaryotic community structure can be directly correlated
to geochemistry within these sediments, thus enhancing our
understanding of biogeochemical cycling and our ability to predict
metabolisms of uncultured microbes in deep-sea sediments
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Investigation of microorganisms and DNA from subsuface thermal water and rock from the east flank of Juan de Fuca Ridge
During Leg 168 of the Ocean Drilling Program, basalts were recovered by drilling and subsurface water was collected with a water sampling tool at Hole 1026B on the east flank of Juan de Fuca Ridge. Microorganisms were found in both types of samples. The microorganisms in the basalt appear to have been in situ, but the origin of microorganisms in the water is not certain. Particles filtered from the formation water collected with the water sampling tool indicate that there were several potential sources of contamination including the drill string, sea water, and the water sampling tool. The number of microorganisms in the formation water (including those introduced through contamination) was probably less than 1000 per mL, and this low number of cells did not permit us to identify them. Improvements in sampling may provide suitable samples for identification and culturing of microbes from subseafloor aquifers
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Microbial activity in the alteration of glass from pillow lavas from hole 896a
Within the altered parts of the glass rim of pillow lavas of Hole 896A, at depths at least 432 m below seafloor (237 m below the top of volcanic basement), microbes have been identified. This is indicated by the size and shapes of alteration textures and verified by the presence of DNA and extreme accumulation of K₂O. This demonstrates the existence of a volcanic subterranean biosphere. The microbially processed parts of the glass show wide scatter with respect to all major elements, which may be attributed to active cells. Compared to the host basaltic glass, CaO and Na₂O are invariably depleted, as are SiO₂ and MgO generally. A1₂O₃, FeO(t), and TiO₂ show either depletion or enrichment, K₂O is invariably enriched, and P₂O₅ may be enriched. Microbes living on, and causing dissolution of, basaltic glass may accommodate elements released from it within the cells, and thus function as individual element reservoirs. Microbes may also produce precipitates or water-soluble compounds. Hence, the microbial alteration of basaltic glass, which comprises a substantial volume of the volcanic component of the oceanic crust and an enormous surface area, may have a significant bearing on the mechanism for chemical exchange between oceanic crust and ocean water
Energy Landscapes in Hydrothermal Chimneys Shape Distributions of Primary Producers
Hydrothermal systems are excellent natural laboratories for the study of how chemical energy landscapes shape microbial communities. Yet, only a few attempts have been made to quantify relationships between energy availability and microbial community structure in these systems. Here, we have investigated how microbial communities and chemical energy availabilities vary along cross-sections of two hydrothermal chimneys from the Soria Moria Vent Field and the Bruse Vent Field. Both vent fields are located on the Arctic Mid-Ocean Ridge, north of the Jan Mayen Island and the investigated chimneys were venting fluids with markedly different H2S:CH4 ratios. Energy landscapes were inferred from a stepwise in silico mixing of hydrothermal fluids (HFs) with seawater, where Gibbs energies of relevant redox-reactions were calculated at each step. These calculations formed the basis for simulations of relative abundances of primary producers in microbial communities. The simulations were compared with an analysis of 24 samples from chimney wall transects by sequencing of 16S rRNA gene amplicons using 454 sequencing. Patterns in relative abundances of sulfide oxidizing Epsilonproteobacteria and methane oxidizing Methylococcales and ANME-1, were consistent with simulations. However, even though H2 was present in HFs from both chimneys, the observed abundances of putative hydrogen oxidizing anaerobic sulfate reducers (Archaeoglobales) and methanogens (Methanococcales) in the inner parts of the Soria Moria Chimney were considerably higher than predicted by simulations. This indicates biogenic production of H2 in the chimney wall by fermentation, and suggests that biological activity inside the chimneys may modulate energy landscapes significantly. Our results are consistent with the notion that energy landscapes largely shape the distribution of primary producers in hydrothermal systems. Our study demonstrates how a combination of modeling and field observations can be useful in deciphering connections between chemical energy landscapes and metabolic networks within microbial communities