Natranaerobaculum magadiense gen. nov., sp. nov., an anaerobic, alkalithermophilic bacterium from soda lake sediment.

An obligately alkaliphilic, anaerobic, thermo- and halotolerant, spore-forming bacterium was isolated from sediments of soda lake Magadi (Kenya) and designated strain Z-1001(T). Cells of strain Z-1001(T) were straight, Gram-positive rods, slowly motile. Strain Z-1001(T) was found to be an obligate anaerobe. It grew within a pH range from 7.5 to 10.7 with an optimum at 9.25-9.5 (at 40 °C), a temperature range from 20 to 57 °C with an optimum at 45-50 °C, and a NaCl concentration range from 0 to 1.55 M with an optimum at 1.2-1.4 M. Peptides, such as meat and yeast extracts, peptone and tryptone, were fermented by Z-1001(T). Carbohydrates did not support growth. With yeast extract as an electron donor, strain Z-1001(T) reduced S(2)O(3)(2-), NO(-)(3), AsO(3-)(4), Fe(III) citrate and anthraquinone-2,6-disulfonate (AQDS) as electron acceptors. The isolate was able to grow oligotrophically with a very small amount of yeast extract: 0.03 g l(-1). The main fatty acids were C16 : 0, C16 : 1ω7c, C18 : 0 and C18 : 1ω9. The DNA G+C content of the isolate was 35.6 mol%. 16S rRNA gene sequence analysis showed that strain Z-1001(T) is a member of family Natranaerobiaceae, clustering with the type strain of Natranaerobius thermophilus (95.8-96.0 % sequence similarity). On the basis of physiological and phylogenetic data it is proposed that strain Z-1001(T) ( = DSM 24923(T) = VKM B-2666(T)) represents a novel genus and species, Natranaerobaculum magadiense gen. nov., sp. nov.

Fuchsiella alkaliacetigena gen. nov., sp. nov., an alkaliphilic, lithoautotrophic homoacetogen from a soda lake.

The first alkaliphilic obligately anaerobic hydrogenotrophic homoacetogenic bacterium, strain Z-7100(T), was isolated from sediments of the soda-depositing soda lake Tanatar III (Altay, Russia). Cells were thin, flexible rods, motile, Gram-negative and spore-forming. The organism was an obligate alkaliphile, growing at pH 8.5 to 10.5, with optimum growth at pH 8.8-9.3, and it grew in soda brines containing 1.9-4.7 M total Na(+) (optimum at 2.8-3.3 M). It exhibited an obligate dependence upon sodium carbonate but not upon chloride ions with an NaCl range for growth of 0-14% (w/v) and an optimum at 7.0-8.5% (w/v). The isolate was mesophilic and grew at temperatures from 25 to 45 °C, with an optimum at 40 °C. An H(2)+CO(2) mixture, ethanol, pyruvate and lactate were utilized with the formation of acetate as the sole metabolic product. Carbohydrates and amino acids did not support growth. The isolate had a respiratory type of metabolism, reducing NO3(-), SeO(4)(2-) or anthraquinone-2,6-disulfonate (as electron acceptors with ethanol as an electron donor). It was able to grow chemolithotrophically on H(2)+CO(2) in medium supplemented with a vitamin solution only. The major cellular fatty acids were the saturated fatty acids anteiso-C(15), C(14:0) and C(16:0) and the aldehydes C(16), C(14) and anteiso-C(15). The DNA G+C content of the isolate was 32.0 mol%. 16S rRNA gene sequence analysis showed that strain Z-7100(T) is a member of the order Halanaerobiales and represents a new branch within the family Halobacteroidaceae, clustering with the type strain of Selenihalanaerobacter shriftii (92.9% gene sequence similarity). On the basis of its physiological characteristics and phylogenetic position, the isolate is considered to represent a novel species in a new genus within the family Halobacteroidaceae. The name Fuchsiella alkaliacetigena gen. nov., sp. nov. is proposed. The type strain of the type species is Z-7100(T) (=DSM 24880(T)=VKM B-2667(T)).

Desulfonatronum cooperativum sp. nov., a novel hydrogenotrophic, alkaliphilic, sulfate-reducing bacterium, from a syntrophic culture growing on acetate.

A novel alkaliphilic, sulfate-reducing bacterium was isolated from a syntrophic acetate-decomposing community enriched from samples of the soda lake Khadin, Tuva, Russia; the isolate was designated strain Z-7999(T). Cells of strain Z-7999(T) were vibrioid, Gram-negative, 0.4-0.5 x 1.0-2.5 microm and motile by means of a polar flagellum. The temperature range for growth was 15-40 degrees C, with an optimum of 35-38 degrees C. The pH range for growth was 6.7-10.3, with an optimum of pH 8.0-9.0. The NaCl concentration range for growth was 1-80 g l(-1). The novel isolate was obligately anaerobic, was alkaliphilic with a broad pH range and had an obligate requirement for carbonate ions in the growth medium. In the presence of sulfate as electron acceptor, it grew with hydrogen, formate and lactate. It was not able to ferment sugars, organic acids, amino acids or peptides. During growth on formate, strain Z-7999(T) reduced sulfite and thiosulfate to sulfide. It was able to grow lithoheterotrophically with sulfate and formate when acetate was added as a carbon source for biosynthesis of biomass. The G + C content of the genomic DNA of strain Z-7999(T) was 56.5 mol%. Results of comparative 16S rRNA gene sequence analyses revealed that strain Z-7999(T) was part of the delta-Proteobacteria and clustered with other members of the genus Desulfonatronum (similarity values of 95.2 and 95.3 % to Desulfonatronum lacustre and Desulfonatronum thiodismutans, respectively). DNA-DNA hybridization with D. lacustre was 37 %. On the basis of physiological and phylogenetic data, it is proposed that strain Z-7999(T) (= DSM 16749(T) = VKM B-2329(T)) should be placed in the genus Desulfonatronum as a representative of a novel species, Desulfonatronum cooperativum sp. nov.

Anaerobic, alkaliphilic, saccharolytic bacterium Alkalibacter saccharofermentans gen. nov., sp. nov. from a soda lake in the Transbaikal region of Russia.

Three strains of new obligately anaerobic alkaliphilic bacteria have been isolated as a saccharolytic component from the cellulolytic community of alkaline Lake Nizhnee Beloe (Transbaikal region, Russia), a lake with low salt concentration. DNA analysis of these strains showed an interspecies level of DNA similarity of 96-100%. Strain Z-79820 was selected for further investigations. Cells were Gram-positive, asporogenous, nonmotile short rods with pointed ends. The strain was a true alkaliphile: growth occurred from pH 7.2 to 10.2 with the optimum at pH 9.0. Strain Z-79820 was halotolerant and could grow in medium with up to 10% (w/v) NaCl, with the optimum between 0 and 4% NaCl. The new isolate obligately depended on Na+ ions in the form of carbonates or chlorides. Total Na+ content needed for optimal growth was 0.46 M Na+, with a wide range from 0.023-0.9 M Na+ at which growth also occurred. The isolate was a mesophile and grew at temperatures from 6 to 50 degrees C (slow growth at 6 and 15 degrees C) with an optimum at 35 degrees C. The organotrophic organism fermented ribose, xylose, glucose, mannose, fructose, sucrose, mannitol, and peptone. The products of glucose fermentation were acetate, ethanol, formate, H2, and CO2. Yeast extract was required for some anabolic needs. The DNA G+C content of the type strain Z-79820 was 42.1 mol%. The new bacterium fell into the 16S rRNA gene cluster XV of the Gram-positive bacteria with low G+C content, where it formed an individual branch. Based on its growth characteristics and genotype traits, we propose the new genus and species named Alkalibacter saccharofermentans with the type strain Z-79820 (=DSM14828), Uniqem-218 (Institute Microbiology, RAS; http://inmi.da.ru).