Filamentous Anoxygenic Phototrophic Bacteria in Microbial Communities of the Kulunda Steppe Soda Lakes (Altai Krai, Russ
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RIMENTAL ARTICLES
Filamentous Anoxygenic Phototrophic Bacteria in Microbial Communities of the Kulunda Steppe Soda Lakes (Altai Krai, Russia) V. M. Gorlenkoa, *, I. A. Bryantsevaa, O. S. Samylinaa, A. A. Ashikhminb, M. A. Sinetovac, N. A. Kostrikina a, and V. V. Kozyaevaa aResearch
Center of Biotechnology, Russian Academy of Sciences, Moscow, 119071 Russia Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, 142290 Russia c Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow, 127276 Russia *e-mail: [email protected]
b
Received April 25, 2020; revised May 20, 2020; accepted May 26, 2020
Abstract—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. Keywords: soda lake phototrophic communities, haloalkaliphiles, anoxygenic filamentous phototrophic bacteria, cyanobacteria DOI: 10.1134/S0026261720060053
Being extreme habitats, soda lakes have been and remain a focus of researchers’ attention due to specific features of haloalkaliphilic microorganisms, a doubly extremophilic microbial group, as well as to the hypothesis that soda lake microbial communities are a relic analog of the early Proterozoic terrestrial biota (Zavarzin, 1993). Until recently, our knowledge of ecology and biodiversity of members of the phylum Chloroflexi (Chloroflexota) was based on the data on the thermophilic Chloroflexus species: Chloroflexus aurantiacus, Cfl. aggregans, Cfl. islandicus, and Rhoseiflexus castenholzii, which have been isolated and studied in pure cultures
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