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Stratified communities of active Archaea in deep marine subsurface sediments.

ABSTRACT: Archaeal 16S rRNA was extracted from samples of deep marine subsurface sediments from Peru Margin site 1227, Ocean Drilling Program leg 201. The amounts of archaeal 16S rRNA in each extract were quantified by serial dilution and reverse transcription (RT)-PCR. The results indicated a 1,000-fold variation in rRNA content with depth in the sediment, with the highest concentrations found near the sediment surface and in the sulfate-methane transition zone (SMTZ). The phylogenetic composition of the active archaeal population revealed by cloning and sequencing of RT-PCR products changed with depth. Several phylotypes affiliated with marine benthic group B (MBGB) dominated clone libraries from the upper part of the SMTZ and were detected only in this layer. Members of the miscellaneous crenarchaeotal group (MCG) dominated clone libraries from the other layers. These results demonstrate that archaeal communities change in activity and community composition over short distances in geochemically distinct zones of deep subseafloor sediments and that these changes are traceable in the rRNA pool. It was shown for the first time that members of both the MCG and MBGB Archaea are more active in the SMTZ than in layers above and below. This indicates that they benefit either directly or indirectly from the anaerobic oxidation of methane. They also appear to be ecophysiologically flexible, as they have been retrieved from a wide range of marine sediments of various geochemical properties.

SUBMITTER: Sorensen KB

PROVIDER: S-EPMC1489303 | biostudies-literature | 2006 Jul

REPOSITORIES: biostudies-literature

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Stratified communities of active Archaea in deep marine subsurface sediments.

Sørensen Ketil B KB Teske Andreas A

Applied and environmental microbiology 20060701 7

Archaeal 16S rRNA was extracted from samples of deep marine subsurface sediments from Peru Margin site 1227, Ocean Drilling Program leg 201. The amounts of archaeal 16S rRNA in each extract were quantified by serial dilution and reverse transcription (RT)-PCR. The results indicated a 1,000-fold variation in rRNA content with depth in the sediment, with the highest concentrations found near the sediment surface and in the sulfate-methane transition zone (SMTZ). The phylogenetic composition of the ...[more]

PMID: 16820449

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Project description:Chemoautotrophy has been little studied in typical coastal marine sediments, but may be an important component of carbon recycling as intense anaerobic mineralization processes in these sediments lead to accumulation of high amounts of reduced compounds, such as sulfides and ammonium. We studied chemoautotrophy by measuring dark-fixation of 13C-bicarbonate into phospholipid derived fatty acid (PLFA) biomarkers at two coastal sediment sites with contrasting sulfur chemistry in the Eastern Scheldt estuary, The Netherlands. At one site where free sulfide accumulated in the pore water right to the top of the sediment, PLFA labeling was restricted to compounds typically found in sulfur and ammonium oxidizing bacteria. At the other site, with no detectable free sulfide in the pore water, a very different PLFA labeling pattern was found with high amounts of label in branched i- and a-PLFA besides the typical compounds for sulfur and ammonium oxidizing bacteria. This suggests that other types of chemoautotrophic bacteria were also active, most likely Deltaproteobacteria related to sulfate reducers. Maximum rates of chemoautotrophy were detected in first 1 to 2 centimeters of both sediments and chemosynthetic biomass production was high ranging from 3 to 36 mmol C m(-2) d(-1). Average dark carbon fixation to sediment oxygen uptake ratios were 0.22±0.07 mol C (mol O2)(-1), which is in the range of the maximum growth yields reported for sulfur oxidizing bacteria indicating highly efficient growth. Chemoautotrophic biomass production was similar to carbon mineralization rates in the top of the free sulfide site, suggesting that chemoautotrophic bacteria could play a crucial role in the microbial food web and labeling in eukaryotic poly-unsaturated PLFA was indeed detectable. Our study shows that dark carbon fixation by chemoautotrophic bacteria is a major process in the carbon cycle of coastal sediments, and should therefore receive more attention in future studies on sediment biogeochemistry and microbial ecology.

Dataset Information

Stratified communities of active Archaea in deep marine subsurface sediments.

Publications

Stratified communities of active Archaea in deep marine subsurface sediments.

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