The Structure of the Anoxygenic Phototrophic Bacterial Community and Features of Green Sulfur Bacteria in the Meromictic Lake Bol’shiye Khruslomeny (Oleniy Island, Kandalaksha Bay of the White Sea, Murmansk Region, Russia)

In March 2019, hydrochemical and microbiological studies of the meromictic Lake Bol’shiye Khruslomeny, artificially separated from the main marine basin of the White Sea, were carried out. It was shown that the hydrochemical parameters of the lake water in March 2019 and in March 2017 were almost the same, which confirms the meromictic status of the reservoir. In the work, a method for separating bacteriochlorophylls of green sulfur bacteria (GSB) from the absorption spectra of lake water, previously developed on GSB monocultures, was used for the first time. According to the calculation, the proportion of BChl e of brown-colored GSB at the peak of community development reached a third of the total BChl (d + e) content. It was shown that even a small content of brown-colored sulfur bacteria that stably survive in lake water can significantly mask the green pigment of green-colored sulfur bacteria. In the chemocline zone community, Chlorobium phaeovibrioides dominated among anoxygenic phototrophic bacteria (APB) (97.9–99.8% of the total APB community). Thiocapsa rosea, Thiocystis gelatinosa, and Thiohalocapsa halophila were also found. Microscopic examination of brown-stained isolates of Chlorobium phaeovibrioides showed a high diversity of cell morphotypes and cell aggregates (curled filaments, twisted spirals, short chains), characteristic of bacteria of the species Chlorobium phaeovibrioides (DSM 265) (formerly Chlorobium vibriforme sbsp. thiosulfatophilum DSM 265).

arctic ecosystems, White Sea, stratified water bodies, meromictic lakes, green sulfur bacteria, Chlorobium phaeovibrioides, Thiocapsa, Thiocystis gelatinosa, bacteriochlorophylls d and e, total concentration of chlorosomal bacteriochlorophylls, fluorescent separation of pigments