Desulfonatronum thiodismutans sp. nov., a novel alkaliphilic, sulfate-reducing bacterium capable of lithoautotrophic growth

Abstract

A novel alkaliphilic, sulfate-reducing bacterium, strain MLF1 T , was isolated from sediments of soda Mono Lake, California. Gram-negative vibrio-shaped cells were observed, which were 0?6-0?761?2-2?7 mm in size, motile by a single polar flagellum and occurred singly, in pairs or as short spirilla. Growth was observed at 15-48 6C (optimum, 37 6C), >1-7 % NaCl, w/v (optimum, 3 %) and pH 8?0-10?0 (optimum, 9?5). The novel isolate is strictly alkaliphilic, requires a high concentration of carbonate in the growth medium and is obligately anaerobic and catalasenegative. As electron donors, strain MLF1 T uses hydrogen, formate and ethanol. Sulfate, sulfite and thiosulfate (but not sulfur or nitrate) can be used as electron acceptors. The novel isolate is a lithoheterotroph and a facultative lithoautotroph that is able to grow on hydrogen without an organic source of carbon. Strain MLF1 T is resistant to kanamycin and gentamicin, but sensitive to chloramphenicol and tetracycline. The DNA G+C content is 63?0 mol% (HPLC). DNA-DNA hybridization with the most closely related species, Desulfonatronum lacustre Z-7951 T , exhibited 51 % homology. Also, the genome size (1?6610 9 Da) and T m value of the genomic DNA (71±2 6C) for strain MLF1 T were significantly different from the genome size (2?1610 9 Da) and T m value (63±2 6C) for Desulfonatronum lacustre Z-7951 T . On the basis of physiological and molecular properties, the isolate was considered to be a novel species of the genus Desulfonatronum, for which the name Desulfonatronum thiodismutans sp. nov. is proposed (the type strain is MLF1 T

Ecology, Diversity, and Evolution of Magnetotactic Bacteria

“…This rationale has been used successfully, however, as several alkaliphilic strains of MTB, including ML-1, ZZ-1, and AV-1, were isolated in culture after their phylogeny was determined in an environmental study. These strains were found to be phylogenetically very closely related to the known nonmagnetotactic dissimilatory sulfate-reducing bacterium Desulfonatronum thiodismutans strain MLF-1 (46). By slightly modifying the growth medium for the latter organism, the magnetotactic strains ML-1, ZZ-1, and AV-1 (28) were grown and isolated in axenic culture.…”

“…Recently, three strains of obligately alkaliphilic, obligately anaerobic, sulfate-reducing MTB belonging to the Deltaproteobacteria with optimal growth pHs of 9.0 to 9.5 were isolated and grown in axenic culture (28). All strains biomineralize bullet-shaped crystals of magnetite, are closely related to each other, and appear to be strains of Desulfonatronum thiodismutans, a known alkaliphilic sulfate-reducing bacterium that does not biomineralize magnetosomes (46), based on the very high sequence identities of their 16S rRNA genes (28) (Fig. 7A).…”

“…Magnetotactic sulfate-reducing bacteria seem to require a higher concentration of iron for magnetite biomineralization than other non-sulfate-reducing MTB (e.g., Magnetospirillum species) (ϳ20 M) and a low sulfide concentration, if sulfide is used as the reducing agent in the growth medium to prevent scavenging of iron from the medium. Thus, the systematic use of high concentrations of sulfide (e.g., 0.4 g/liter Na 2 S · 9H 2 O [46]), as a commonly used reducing agent in growth medium for sulfate-reducing bacteria (169), might preclude the formation of magnetite by magnetotactic sulfate reducers. A specific example is whether Desulfonatronum thiodismutans, isolated from Mono Lake, where one of the alkaliphilic MTB was also isolated, was magnetotactic when originally isolated.…”

Dethiobacter alkaliphilus gen. nov. sp. nov., and Desulfurivibrio alkaliphilus gen. nov. sp. nov.: two novel representatives of reductive sulfur cycle from soda lakes

“…Until now, two culturable groups of low salt-tolerant alkaliphilic SRB belonging to the Deltaproteobacteria (order Desulfovibrionales) have been found in soda lakes. Both utilize acetate only as a carbon, but not energy source, and both can use H 2 as an electron donor (Zhilina et al 1997Pikuta et al 1998Pikuta et al , 2003. Culture-independent study of the SRB populations in soda lakes so far have been limited to two studies.…”

Desulfovibrio alkalitolerans sp. nov., a novel alkalitolerant, sulphate-reducing bacterium isolated from district heating water

“…Although SRB thrive in a broad range of environments, only a few species, representing the genera Desulfonatronovibrio and Desulfonatronum, are obligately alkaliphilic. Some of these bacteria are able to grow at pH values >10 and not below pH 7?0 (Zhilina et al, 1997(Zhilina et al, , 2005Pikuta et al, 1998Pikuta et al, , 2003. In addition, a moderately alkaliphilic species with a growth range between pH 8?0 and 9?2 is known within the genus Desulfotomaculum (Pikuta et al, 2000).…”