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 , , , 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 C_16 : 0, C_{16 : 1ω7c}, C_18 : 0 and C_{18 : 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.