Desulfonatronum zhilinae sp. nov., a novel haloalkaliphilic sulfate-reducing bacterium from soda Lake Alginskoe, Trans-Baikal Region, Russia.

A novel haloalkaliphilic sulfate-reducing bacterium, designated Al915-01(T), was isolated from benthic sediments of the Lake Alginskoe, a soda lake located in the Trans-Baikal Region, Russia. Cells of the strain were Gram-stain negative, motile, non-spore-forming vibrion (0.4-0.5 × 1.2-2.3 µm). Strain Al915-01(T) grew in the pH range from 8.0 to 10.5 (optimum pH 9.0) and required NaCl for growth (5-100 g l(-1) NaCl, optimum 40 g l(-1)). The bacterium grew at 10-40 °C (optimally at 36 °C) and used lactate, formate and pyruvate as electron donors in the presence of sulfate. It was able to reduce sulfate, sulfite, thiosulfate and nitrate with lactate as an electron donor. The isolate was able to grow lithoheterotrophically with sulfate and molecular hydrogen if acetate was added as a carbon source. The predominant fatty acids were anteisoC15:0, isoC17:1, C18:1ω7 and C16:1ω7. The G+C content in the DNA was 58.3 ± 1 mol %. Analysis of the 16S rRNA gene sequence showed that the new bacterium belongs to the genus Desulfonatronum. The closest relatives were Desulfonatronum buryatense Ki5(T) (99.9 % similarity) and Desulfonatronum lacustre Z-7951(T) (99.2 % similarity). On the basis of the genotypic, phenotypic and phylogenetic characteristics, the isolate is proposed as a representative of a novel species Desulfonatronum zhilinae with the type strain Al915-01(T) (=VKM B-2744(T) = DSM 26338(T)).

High abundances of aerobic anoxygenic phototrophs in saline steppe lakes.

We studied the distribution of anoxygenic phototrophs in 23 steppe lakes in the Transbaikal region (Russia), in Uzbekistan (Central Asia) and in the Crimean peninsula (Ukraine). The lakes varied in their mineral content and composition (salinities from 0.2 to 300 g L(-1) ). The Transbaikal lakes were alkaline (pH>9), with high amounts of soda. The Uzbek and Crimean lakes were more pH neutral, frequently with high amounts of sulfates. The presence of anoxygenic phototrophs was registered by infrared epifluorescence microscopy, infrared fluorometry and pigment analyses. In mostly shallow, fully oxic lakes, the anoxygenic phototrophs represented 7-65% of the total prokaryotes, with the maxima observed in Transbaikal soda lakes Gorbunka (32%), Khilganta (65%), Zanday (58%) and Zun-Kholvo (46%). Some of the lakes contained over 1 µg bacteriochlorophyll L(-1) . In contrast, only small amounts of anoxygenic phototrophs were present in highly mineralized lakes (>100 g total salts L(-1) ); Borzinskoe, Tsagan-Nur (Transbaikal), Staroe (Crimea) and in the residual part of the south-west Aral Sea (Uzbekistan). The oxic environment and the specific diurnal changes of bacteriochlorophyll concentration observed suggest that the phototrophic community was mostly composed of aerobic anoxygenic phototrophs. The high abundances and bacteriochlorophyll concentrations point to an important role of aerobic anoxygenic phototrophs in the habitats studied.