期刊
GEOBIOLOGY
卷 7, 期 3, 页码 308-323出版社
WILEY
DOI: 10.1111/j.1472-4669.2009.00198.x
关键词
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资金
- MIT Earth System Initiative Exploration Fund Award
- Gary Comer Abrupt Climate Change Foundation
- US National Science Foundation [NSF-ESH-0639640]
- European Community [MOIF-CT-2004-509865]
- MARUM
- Alexander von Humboldt Foundation
- Bad Godesberg, Germany
- Deutsche Forschungsgemeinschaft [Hi 616/4-2]
- Hanse Wissenschaftskolleg
- NASA Astrobiology Institute
- Directorate For Geosciences
- Division Of Earth Sciences [0823503] Funding Source: National Science Foundation
Modern microbial mats are widely recognized as useful analogs for the study of biogeochemical processes relevant to paleoenvironmental reconstruction in the Precambrian. We combined microscopic observations and investigations of biomarker composition to investigate community structure and function in the upper layers of a thick phototrophic microbial mat system from a hypersaline lake on Kiritimati (Christmas Island) in the Northern Line Islands, Republic of Kiribati. In particular, an exploratory incubation experiment with C-13-labeled bicarbonate was conducted to pinpoint biomarkers from organisms actively fixing carbon. A high relative abundance of the cyanobacterial taxa Aphanocapsa and Aphanothece was revealed by microscopic observation, and cyanobacterial fatty acids and hydrocarbons showed C-13-uptake in the labeling experiment. Microscopic observations also revealed purple sulfur bacteria (PSB) in the deeper layers. A cyclic C-19:0 fatty acid and farnesol were attributed to this group that was also actively fixing carbon. Background isotopic values indicate Calvin-Benson cycle-based autotrophy for cycC(19:0) and farnesol-producing PSBs. Biomarkers from sulfate-reducing bacteria (SRB) in the top layer of the mat and their C-13-uptake patterns indicated a close coupling between SRBs and cyanobacteria. Archaeol, possibly from methanogens, was detected in all layers and was especially abundant near the surface where it contained substantial amounts of C-13-label. Intact glycosidic tetraether lipids detected in the deepest layer indicated other archaea. Large amounts of ornithine and betaine bearing intact polar lipids could be an indicator of a phosphate-limited ecosystem, where organisms that are able to substitute these for phospholipids may have a competitive advantage.
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