Isachenkonia alkalipeptolytica gen. nov. sp. nov., a new anaerobic, alkaliphilic proteolytic bacterium capable of reducing Fe(III) and sulfur.

An obligately alkaliphilic, anaerobic, proteolytic bacterium was isolated from a sample of Tanatar III soda lake sediment (Altai region, Russia) and designated as strain Z-1701T. Cells of strain Z-1701T were short, straight, motile Gram-stain-positive rods. Growth of Z-1701T obligately depended on the presence of sodium carbonate. Strain Z-1701T could utilize various peptides mixtures, such as beef and yeast extracts, peptone, soytone, trypticase and tryptone, as well as such proteins as albumin, gelatin and sodium caseinate. It was able to grow oligotrophically with 0.02 g l-1 yeast extract as the sole energy and carbon source. Carbohydrates did not support the growth of strain Z-1701T. The main products released during the growth of strain Z-1701T on tryptone were formate, acetate and ammonium. Strain Z-1701T was able to reduce ferrihydrite, Fe(III)-EDTA, anthraquinone-2,6-disulfonate and elemental sulfur, using proteinaceous substrates as electron donors. In all cases the presence of the electron acceptor in the medium stimulated growth. The main cellular fatty acids were iso-C15 : 0, iso-C15 : 0 aldehyde, iso-C15 : 1 ω6, C16 : 0, iso-C17 : 0 aldehyde, C16 : 0 aldehyde and C14 : 0. The DNA G+C content of the isolate was 43.9 mol%. Phylogenetic analysis based on the concatenated alignment of 120 protein-marker sequences revealed that strain Z-1701T falls into a cluster with the genus Tindallia, family Clostridiaceae. 16S rRNA gene sequence identity between strain Z-1701T and Tindallia species were 88.3-89.75 %. On the basis of its phenotypic characteristics and phylogenetic position, the novel isolate is considered to be a representative of a novel genus and species for which the name Isachenkonia alkalipeptolytica gen. nov., sp. nov. is proposed, with Z-1701T (=JCM 32929Т=DSM 109060Т=VKM B-3261Т) as its type strain.

Syntrophic growth of alkaliphilic anaerobes controlled by ferric and ferrous minerals transformation coupled to acetogenesis.

Redox-active iron minerals can act as energy sources or electron-transferring mediators in microbial syntrophic associations, being important means of interspecies metabolic cooperation in sedimentary environments. Alkaline conditions alter the thermodynamic stability of iron minerals, influencing their availability for interspecies syntrophic interactions. We have modeled anaerobic alkaliphilic microbial associations in ethanol-oxidizing co-culture of an obligate syntroph Candidatus "Contubernalis alkalaceticum" and a facultative lithotroph Geoalkalibacter ferrihydriticus, which is capable of dissimilatory Fe(III) reduction and homoacetogenic oxidation of Fe(II) with CO2. The co-cultures were cultivated with thermodynamically metastable ferric-containing ferrihydrite, or ferrous-containing siderite, or without minerals. Mössbauer spectral analysis revealed the transformation of both minerals to the stable magnetite. In the presence of ferrihydrite, G. ferrihydriticus firstly reduced Fe(III) with ethanol and then switched to syntrophic homoacetogenesis, providing the growth of obligate syntroph on ethanol. The ability of G. ferrihydriticus to accept hydrogen from its syntrophic partner and produce extra acetate from carbonate during ethanol oxidation was confirmed by co-culture growth without minerals. In the presence of siderite, G. ferrihydriticus performed homoacetogenesis using two electron donors simultaneously- siderite and hydrogen. Pieces of evidence for direct and indirect hydrogen-mediated electron exchange between partner organisms were obtained. Relative abundancies of partner organisms and the rate of acetate production by their co-cultures were strongly determined by thermodynamic benefits, which G. ferrihydriticus got from redox transformations of iron minerals. Even the minor growth of G. ferrihydriticus sustained the growth of the syntroph. Accordingly, microbe-to-mineral interactions could represent underestimated drivers of syntrophic interactions in alkaline sedimentary environments.

Fuchsiella ferrireducens sp. nov., a novel haloalkaliphilic, lithoautotrophic homoacetogen capable of iron reduction, and emendation of the description of the genus Fuchsiella.

Two strains of haloalkaliphilic homoacetogenic bacteria capable of iron reduction, Z-7101T and Z-7102, were isolated from soda lake Tanatar III (Altai, Russia). Cells of both strains were flexible, motile, Gram-negative, spore-forming rods. The strains were mesophilic and obligately alkaliphilic: the pH range for growth was 8.5-10.2 (pHopt 9.8). Growth depended on carbonate and chloride ions. The strains were able to grow chemolithoautotrophically on H2+CO2, producing acetate as the only metabolic product. In medium with carbonates as the only potential electron acceptor, the following substrates were utilized for chemo-organotrophic growth: pyruvate, lactate, ethanol, 1-propanol, ethylene glycol and 1-butanol. Strain Z-7101T was able to reduce nitrate, selenate, thiosulfate and anthraquinone 2,6-disulfonate with ethanol as an electron donor. It was also able to reduce synthesized ferrihydrite to siderite with molecular hydrogen or organic compounds, including acetate and formate, as electron donors. It was able to reduce S0 with acetate or formate as electron donors. The DNA G+C content of strain Z-7101T was 34.6 mol%. 16S rRNA gene sequence analysis showed that strains Z-7101T and Z-7102 were members of the order Halanaerobiales and family Halobacteroidaceae, clustering with Fuchsiella alkaliacetigena Z-7100T (98.9-98.4% similarity). DNA-DNA hybridization was 63.0% between strain Z-7101T and F. alkaliacetigena Z-7100T. Based on morphological and physiological differences from F. alkaliacetigena Z-7100T and the results of phylogenetic analysis and DNA-DNA hybridization, it is proposed to assign strains Z-7101T and Z-7102 ( = DSM 26052 = VKM B-2790) to the novel species Fuchsiellaferrireducens sp. nov. The type strain is strain Z-7101T ( = DSM 26031T = VKM B-2766T).

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)).

Alkaliflexus imshenetskii gen. nov. sp. nov., a new alkaliphilic gliding carbohydrate-fermenting bacterium with propionate formation from a soda lake.

Anaerobic saccharolytic bacteria thriving at high pH values were studied in a cellulose-degrading enrichment culture originating from the alkaline lake, Verkhneye Beloye (Central Asia). In situ hybridization of the enrichment culture with 16S rRNA-targeted probes revealed that abundant, long, thin, rod-shaped cells were related to Cytophaga. Bacteria of this type were isolated with cellobiose and five isolates were characterized. Isolates were thin, flexible, gliding rods. They formed a spherical cyst-like structure at one cell end during the late growth phase. The pH range for growth was 7.5-10.2, with an optimum around pH 8.5. Cultures produced a pinkish pigment tentatively identified as a carotenoid. Isolates did not degrade cellulose, indicating that they utilized soluble products formed by so far uncultured hydrolytic cellulose degraders. Besides cellobiose, the isolates utilized other carbohydrates, including xylose, maltose, xylan, starch, and pectin. The main organic fermentation products were propionate, acetate, and succinate. Oxygen, which was not used as electron acceptor, impaired growth. A representative isolate, strain Z-7010, with Marinilabilia salmonicolor as the closest relative, is described as a new genus and species, Alkaliflexus imshenetskii. This is the first cultivated alkaliphilic anaerobic member of the Cytophaga/ Flavobacterium/ Bacteroides phylum.