Journal
MICROBIAL ECOLOGY
Volume 70, Issue 2, Pages 459-472Publisher
SPRINGER
DOI: 10.1007/s00248-015-0598-3
Keywords
Microbial mats; Lipid biomarkers; Stable isotopes; Sulfate-reducing bacteria; Cyanobacteria
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Funding
- Australian Research Council
- WA Organic and Isotope Geochemistry Centre
- Curtin University
- CSIRO
- University of New South Wales
- Agouron Institute
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Modern microbial mats from Shark Bay present some structural similarities with ancient stromatolites; thus, the functionality of microbial communities and processes of diagenetic preservation of modern mats may provide an insight into ancient microbial assemblages and preservation. In this study, the vertical distribution of microbial communities was investigated in a well-laminated smooth mat from Shark Bay. Biolipid and compound-specific isotopic analyses were performed to investigate the distribution of microbial communities in four distinct layers of the mat. Biomarkers indicative of cyanobacteria were more abundant in the uppermost oxic layer. Diatom markers (e.g. C-25 HBI alkene, C-20:4 omega 6 and C-20:5 omega 3 polar lipid fatty acids (PLFAs)) were also detected in high abundance in the uppermost layer, but also in the deepest layer under conditions of permanent darkness and anoxia, where they probably used NO3 (-) for respiration. CycC(19:0), an abundant PLFA of purple sulfur bacteria (PSB), was detected in all layers and presented the most C-13-depleted values of all PLFAs, consistent with photoautotrophic PSB. Sulfur-bound aliphatic and aromatic biomarkers were detected in all layers, highlighting the occurrence of early sulfurisation which may be an important mechanism in the sedimentary preservation of functional biolipids in living and, thus, also ancient mats.
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