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The composition and macroscopic structure of the floating oxygenic phototrophic communities from Kulunda steppe soda lakes (Petukhovskoe sodovoe, Tanatara VI, and Gorchiny 3) was described based on the data of the 2011 and 2012 expeditions (Winogradsky Institute of Microbiology). The algo-bacterial community with a green alga Ctenocladus circinnatus as an edificator was the typical one. Filamentous Geitlerinema sp. and Nodosilinea sp. were the dominant cyanobacteria. Apart from C. circinnatus, the algological component of the community contained unicellular green algae Dunaliella viridis and cf. Chlorella minutissima, as well as diatoms (Anomeoneis sphaerophora, Brchysira brebissonii, Brachysira zellensis, Mastogloia pusilla var. subcapitata, Nitzschia amphibia, Nitzschia communis, and Nitzschia sp.1). The latter have not been previously identified in the lakes under study. In all lakes, a considerable increase in salinity was found to result in changes in the composition and macroscopic structure of algo-bacterial communities.

Although thermokarst alas lakes of Central Yakutia are of great climatic and economic importance, there is currently virtually no information on microbial communities and microbial processes in these lakes. This paper characterizes the hydrochemical features and presents a primary analysis of the diversity of planktonic microbial communities in three alas lakes of Central Yakutia—Tyungulyu, Taby, and Kharyyalakh. It was shown that in terms of the water physicochemical composition, the studied lakes were quite typical for this region; they had increased alkalinity and trophicity, but differed from each other in microbiological indicators. Chemoheterotrophic prokaryotes predominated in the studied planktonic communities, but a significant proportion of the 16S rRNA gene sequences were most similar to uncultured microorganisms whose functional potential is still unknown. [ABSTRACT FROM AUTHOR]

The diurnal dynamics of methane content in the near-bottom phototrophic biomass of the shallow soda lake Bitter 1 (Gorchina 1) with a salinity of 30 g/L during the study period was investigated. The community was dominated by filamentous cyanobacteria, although no layered mat was formed. The maximum value of methane content up to 202.4 nmol CH4/cm3 was revealed in the morning hours, which significantly exceeded the night values (28.9–42.8 nmol CH4/cm3). Comparison of data on the content of methane with the relative abundance of cyanobacteria, methanogenic archaea, and methanotrophic bacteria during the twenty-four hours indicated that active processes of the methane cycle in soda lakes occurred not only in the sediments, but also in the near-bottom cyanobacterial communities. Methane content in the biomass of such a community is the result of a balance between the processes of its release by methanogens, consumption by methanotrophic bacteria, and natural degassing. It is assumed that the morning peak of methane content is associated with the release of hydrogen by diazotrophic cyanobacteria, which stimulates the development and activity of hydrogenotrophic methanogens of the genus Methanocalculus. [ABSTRACT FROM AUTHOR]

Soda lakes are relic ecosystems inhabited by unique microorganisms, which are doubly extremophilic: both haloalkaliphilic and natronophilic. Two morphologically and physiologically similar monocultures of filamentous anoxygenic phototrophic bacteria (FAPB) were isolated from the water samples and biofilms on plants of the coastal zones of the steppe soda lakes Tanatar 6 and Gorchina 1 (Kulunda, Altai krai) during the season of their desalination. In their natural environments, FAPB coexisted with anoxygenic purple sulfur bacteria of the genera Chromatium,Thiocapsa, Ectothiorhodospira, and Thiorhodospira, as well as with oxygenic phototrophs (alkaliphilic cyanobacteria, euglenophytes, and diatoms). FAPB formed filaments surrounded by thin sheaths; their cells contained antenna structures (chlorosomes). Apart from small amounts of bacteriochlorophyll (BChl) a in the reaction center, both isolates contained also antenna BChl c and BChl d. Alpha- and beta-carotenes and their derivatives were also detected. FAPB grew well in the medium containing Na2S ∙ 9H2O (500 mg/L) at total mineralization of 15−30 g/L and pH 8−9.5. Identification of both cultures based on amino acid composition of the PufLM complex revealed that they belonged to the phylum Chloroflexi and were almost 100% identical both to each other and to the halo-alkaliphilic isolate "Candidatus Viridilinea mediisalina" Kir15-3F revealed previously in the Kiran soda lake (Eastern Siberia, Russia). It may be concluded that "Cand. Viridilinea mediisalina" is a typical component of Siberian soda lakes with moderate salinity. [ABSTRACT FROM AUTHOR]