A moderately thermophilic and heterotrophic bacterial strain, LAT, was isolated from microbial mats sampled at a hot spring in Nakabusa, Nagano, Japan. The cells of strain LAT were aerobic, Gram-stain-negative, non-sporulating, non-motile and rod-shaped (2.0-4.1 µm long). The formation of dense cell aggregates in liquid medium was a unique characteristic of the strain. Strain LAT grew optimally at 50°C and at pH 7.5. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the nearest neighbour of strain LAT was Schleiferia thermophila JCM 30197T with 94.1 % sequence similarity. The draft genome sequence of strain LAT (2 671 880 bp) showed 18.0 % digital DNA-DNA hybridization, 70.9 % average nucleotide identity and 72.1 % average amino acid identity (AAI) values in comparison with the genome sequence of S. thermophila JCM 30197T (2 606 763 bp); the 16S rRNA gene sequence similarity and AAI values are lower than the cutoffs used for assignment to a separate genus. On the basis of phenotypic features, major cellular fatty acid composition, genome sequencing and phylogenetic position, a novel genus and species are proposed for strain LAT, to be named Thermaurantimonas aggregans (= JCM 31826T=DSM 106522T).
Keywords: Thermaurantimonas; Thermaurantimonas aggregans; dense cell aggregates; heterotroph; hot spring; moderatory thermophilic.