RESUMO
Bacterial mats formed by a colorless sulfur bacterium Thioploca sp. in the area of the Posolski Bank cold methane seep (southern Baikal) were -studied using electron microscopy and phylogenetic analysis. Morphologically the bacteria were identified as Thioploca ingrica.- Confocal microscopy of DAPI-stained samples revealed numerous rod-shaped, filamentous, and spiral microorganisms in the sheaths, as well as in- side and between the trichomes. Transmission electron microscopy revealed nonvacuolated bacteria and small cells-without cell envelopes within the sheath. Bacteria with pronounced intracytoplasmic membranes characteristic; of type I methanotrophs were observed at the outer side of the sheath. Based on analysis of the 16S rRNA gene sequences, the following phyla were idenified in the sheath community: Bacteroidetes, Nitro- spira, Chloroflexi, Planctomycetes, Verrucomicrobia,'y-, and 6-Proteobacteria, Euryarchaeota, Crenarchaeota, and Thaumarchaeota, as well as anammox bacteria. A hypothetical scheme of matter flows in the Lake Baikal bacterial mats was proposed based on the data on metabolism of the cultured homologues.
Assuntos
Água Subterrânea/microbiologia , Lagos/microbiologia , Consórcios Microbianos/fisiologia , RNA Ribossômico 16S/genética , Thiotrichaceae/genética , Bacteroidetes/classificação , Bacteroidetes/genética , Bacteroidetes/isolamento & purificação , Chloroflexi/classificação , Chloroflexi/genética , Chloroflexi/isolamento & purificação , Crenarchaeota/classificação , Crenarchaeota/genética , Crenarchaeota/isolamento & purificação , Ecossistema , Euryarchaeota/classificação , Euryarchaeota/genética , Euryarchaeota/isolamento & purificação , Metano/química , Metano/metabolismo , Filogenia , Planctomycetales/classificação , Planctomycetales/genética , Planctomycetales/isolamento & purificação , Proteobactérias/classificação , Proteobactérias/genética , Proteobactérias/isolamento & purificação , Sibéria , Thiotrichaceae/classificação , Thiotrichaceae/isolamento & purificação , Thiotrichaceae/ultraestrutura , Verrucomicrobia/classificação , Verrucomicrobia/genética , Verrucomicrobia/isolamento & purificaçãoAssuntos
DNA Bacteriano/classificação , Bactérias Gram-Negativas/classificação , Bactérias Gram-Positivas/classificação , Consórcios Microbianos/genética , RNA Ribossômico 16S/classificação , Microbiologia do Solo , Aerobiose , Biodiversidade , Temperatura Baixa , DNA Bacteriano/genética , DNA Bacteriano/isolamento & purificação , Bactérias Gram-Negativas/genética , Bactérias Gram-Negativas/isolamento & purificação , Bactérias Gram-Positivas/genética , Bactérias Gram-Positivas/isolamento & purificação , Paleontologia , Filogenia , RNA Ribossômico 16S/genética , RNA Ribossômico 16S/isolamento & purificação , Análise de Sequência de DNARESUMO
A colorless sulfur bacterium of the genus Thioploca, which forms bacterial mats, was studied in the region of underwater thermal vents (Frolikha Bay, northern Baikal). The organism occurs under microaerobic conditions in top sediment layers, and its biomass can amount to 65 mg of wet weight per 1 kg of silt. Individual filaments of the bacterium penetrate the anaerobic zone to the depth of 19 cm. Thioploca is distributed in a mosaic pattern over the bottom of the bay. Thioploca mats are typically found near vents that discharge low-temperature underground water. In the form of separate filaments, this bacterium is more widely distributed in the top sediment layer, particularly in sediments with a more active sulfate reduction. The bacteria from the deep-water and coastal areas of the bay have different morphology. Cells of Thioploca are able to accumulate nitrate, and the coefficient of nitrate accumulation in wet bacterial mass in relation to the near-bottom water is 1.3 x 10(4), suggesting a similarity of metabolism with seawater species. A more lightweight isotopic composition of nitrogen in cell mass as compared to that of representatives of zoobenthos also indicates an active metabolism of nitrogen, apparently, in the process of nitrogen respiration. Comparison of the composition of stable isotopes of carbon in the biomass of representatives of different trophic levels, including Thioploca, found at a depth of 105 m indicates its planktonic origin, whereas, in the deeper bay region, the biomass of Thioploca incorporates more of the light carbon originating from biogenic methane.
