ABSTRACT
The microbiology of caves is an important topic for better understanding subsurface biosphere diversity. The diversity and taxonomic composition of bacterial communities associated with cave walls of the Oylat Cave was studied first time by molecular cloning based on Sanger/pyrosequencing approach. Results showed an average of 1,822 operational taxonomic units per sample. Clones analyzed from Oylat Cave were found to belong to 10 common phyla within the domain Bacteria. Proteobacteria dominated the phyla, followed by Actinobacteria, Acidobacteria and Nitrospirae. Shannon diversity index was between to 3.76 and 5.35. The robust analysis conducted for this study demonstrated high bacterial diversity on cave rock wall surfaces.
Subject(s)
Bacteria/genetics , Bacteria/isolation & purification , Caves/microbiology , Nucleic Acid Amplification Techniques/methods , Bacteria/classification , Genetic Variation , Microscopy, Electron, Scanning , Phylogeny , RNA, Bacterial/genetics , RNA, Ribosomal, 16S/genetics , TurkeyABSTRACT
Gas seeps emanating from Yanartas (Chimera), Turkey, have been documented for thousands of years. Active serpentinization produces hydrogen and a range of carbon gases that may provide fuel for life. Here we report a newly discovered, ephemeral fluid seep emanating from a small gas vent at Yanartas. Fluids and biofilms were sampled at the source and points downstream. We describe site conditions, and provide microbiological data in the form of enrichment cultures, Scanning electron microscopy (SEM), carbon and nitrogen isotopic composition of solids, and PCR screens of nitrogen cycle genes. Source fluids are pH 11.95, with a Ca:Mg of ~200, and sediments under the ignited gas seep measure 60°C. Collectively, these data suggest the fluid is the product of active serpentinization at depth. Source sediments are primarily calcite and alteration products (chlorite and montmorillonite). Downstream, biofilms are mixed with montmorillonite. SEM shows biofilms distributed homogeneously with carbonates. Organic carbon accounts for 60% of the total carbon at the source, decreasing downstream to <15% as inorganic carbon precipitates. δ(13)C ratios of the organic carbon fraction of solids are depleted (-25 to -28) relative to the carbonates (-11 to -20). We conclude that heterotrophic processes are dominant throughout the surface ecosystem, and carbon fixation may be key down channel. δ(15)N ratios ~3, and absence of nifH in extracted DNA suggest that nitrogen fixation is not occurring in sediments. However, the presence of narG and nirS at most locations and in enrichments indicates genomic potential for nitrate and nitrite reduction. This small seep with shallow run-off is likely ephemeral, but abundant preserved microterracettes in the outflow and the surrounding area suggest it has been present for some time. This site and others like it present an opportunity for investigations of preserved deep biosphere signatures, and subsurface-surface interactions.
