Halonatronomonas betaini gen. nov., sp. nov., a haloalkaliphilic isolate from soda lake capable of betaine degradation and proposal of Halarsenatibacteraceae fam. nov. and Halothermotrichaceae fam. nov. within the order Halanaerobiales.

A search for the organisms responsible for anaerobic betaine degradation in soda lakes resulted in isolation of a novel bacterial strain, designated Z-7014. The cells were Gram-stain-negative, non-endospore-forming rods. Growth occurred at 8-52 °C (optimum 40-45 °C), pH 7.1-10.1 (optimum pH 8.1-8.8) and 1.0-3.5 M Na (optimum 1.8 M), i.e. it can be regarded as a haloalkaliphile. The strain utilized a limited range of substrates, mostly peptonaceous but not amino acids, and was able to degrade betaine. Growth on betaine occurred only in the presence of peptonaceous substances which could not be replaced by vitamins. The G + C content of the genomic DNA of strain Z-7014 was 36.1 mol%. The major cellular fatty acids (>5% of the total) were C DMA, C DMA, Cω8, C, C DMA, C DMA, Cω9, and C. Phylogenetic analysis of the 16S rRNA gene sequence revealed that strain Z-7014 formed a distinct evolutionary lineage in the order Halanaerobiales with the highest similarity to Halarsenitibacter silvermanii SLAS-1 (83.6%), Halothermothrix orenii H168 (85.6%), and Halocella cellulosilytica DSM 7362 (85.6%). AAI and POCP values between strain Z-7014 and type strains of the order Halanaerobiales were 51.7-57.8%, and 33.8-58.3%, respectively. Based on polyphasic results including phylogenomic data, the novel strain could be distinguished from other genera, which suggests that strain Z-7014 represents a novel species of a new genus, for which the name Halonatronomonas betaini gen. nov., sp. nov. is proposed. The type strain is Z-7014 (=KCTC 25237 = VKM B-3506). On the basis of phylogenomic data, it is also proposed to evolve two novel families Halarsenitibacteraceae fam. nov. and Halothermotrichaceae fam. nov. within the current order Halanaerobiales.