Phototrophic Communities of Algo-Bacterial Mats of the Unique Relict Salt Pool Manych-Gudilo

Lake Manych-Gudilo is a relict lake formed 2–3 million years ago at the site of the ancient strait connecting the Black and Caspian seas. During the dry season, total water salinity exceeds 50 g/L, with the levels of sulfate and magnesium in the brine higher than in the ocean water. The coastline has numerous bays and separating shallow basins. The article reports the results of investigation of microbial biodiversity in the algo-bacterial mat in a shallow basin with salinity varying from 40 to 70 g/L, which is associated with Lake Manych-Gudilo. The studied mat had the properties of a sulfuret, a community with an intense sulfur turnover. Microalgae of the genus Cladophora and filamentous cyanobacteria were the main producers of organic matter in the benthic community. Among the anoxygenic phototrophic bacteria isolated in pure cultures, halophilic purple sulfur bacteria Ectothiorhodospira marina and Lamprobacter modestohalophilus and green sulfur bacteria Prosthecochloris sp. predominated. Nonsulfur purple bacteria Rhodovulum adriatica, also present in the community, were able to use sulfide for photosynthesis. All identified species were typical of microbial mats of saline and hypersaline basins with elevated levels of sulfate and bivalent cations. The algo-bacterial mat was reconstructed in the laboratory at 80 g/L salinity using a Winogradsky column. Microbial diversity of the experimental mat was studied by sequencing the 16S rRNA gene fragments. The data obtained improved our understanding of bacterial species diversity in microbial mats adapted to extreme hypersaline conditions.

Relict lake Manych-Gudilo, hypersaline ecosystems, algal-bacterial mats, anoxygenic phototrophic bacteria, sulfur cycle bacteria