Novel aerobic methylotrophic isolates from the soda lakes of the southern Transbaikal region

Twenty-one bacterial associations isolated from the soda lakes of the south ern Transbaikal region were found to be able to actively grow at pH 9-10 on methanol as the source of carbon and energy. Two alkali-tolerant facultati vely methylotrophic strains, Bur 3 and Bur 5, were obtained in pure culture s. Both strains represent gram-negative, nonmotile, bean-shaped, encapsulat ed cells that reproduce by binary fission. The strains are able to grow at temperatures ranging from 6 to 42 degreesC, with an optimum growth temperat ure of 25-29 degreesC (strain Bur 3) and 35-37 degreesC (strain Bur 5) and at pH between 6.5 and 9.5, with an optimum pH value of 8.0-8.5. At pH 9.0, strain Bur 3 exhibits an increased content of phosphatidylglycerol and a de creased content of phasphatidylethanolamine. Strains Bur 3 and Bur 5 are si milar in the G+C content of their DNAs (66.2 and 65.5 mol %, respectively) and in the type of the dominant ubiquinone (Q(10)) Unlike Bur 5, strain Bur 3 is able to grow autotrophically in an atmosphere of CO2 + O-2 + H-2. The strains oxidize, by the respective dehydrogenases, methanol to CO2, which is assimilated by the ribulose bisphosphate pathway. Ammonium ions are assi milated in the glutamate cycle and by the reductive amination of a-ketoglut arate. The Strains are highly homologous to each other (92%) and are much l ess homologous (at a level of 28-35%) to representatives of the genus Anzcy lobacter A. aquaticus ATCC 25396(T) and A. vacuolatum DSM 1277. Based on th e results obtained, both strains are assigned to a new species, Ancylobacte r natronum sp. nov.