Tepidimonas sediminis sp. nov. and Tepidimonas alkaliphilus sp. nov., two novel moderately thermophilic species isolated from a hot spring.

The taxonomic positions of two moderately thermophilic bacteria, strains YIM 72259T and YIM 72238T, isolated from a hot spring sediment sample were determined using polyphasic taxonomic approaches. Pairwise comparison of the 16S rRNA gene sequences showed that strains YIM 72259T and YIM 72238T are closely related to Tepidimonas ignava SPS-1037T (97.0 and 97.5%, respectively), Tepidimonas taiwanensis I1-1T (96.5 and 97.3%), while sharing 98.0% sequence similarity with each other. The DNA-DNA relatedness values of strains YIM 72238T with T. ignava SPS-1037T and T. taiwanensis I1-1T were determined to be 25.2 ± 1.2 and 24.6 ± 3.1%, respectively, while the two strains (YIM 72259T and YIM 72238T) had a relatedness value of 38.3 ± 4.4% between themselves. The two strains were aerobic, Gram-stain negative, motile by means of a polar flagellum and formed non-pigmented colonies. The DNA G+C contents of strains YIM 72259T and YIM 72238T were determined to be 71.6 and 68.9 mol%, respectively. The major fatty acids in both strains were identified as (> 10%) C16:0, C17:0 and summed feature 8, while the strain YIM 72238T contained a moderately high amount of summed feature 3 as well. The polar lipid profiles for strains YIM 72259T and YIM 72238T consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, an unidentified aminolipid and several unidentified phospholipids. Besides the morphological and chemotaxonomic characteristics, phylogenetic analyses of the 16S rRNA gene sequences and the biochemical characteristics indicated that the two strains represented two novel members of the genus Tepidimonas, for which the name Tepidimonas sediminis sp. nov. [type strain YIM 72259T (= NBRC 112410T = CGMCC 1.15971T) and Tepidimonas alkaliphilus sp. nov. [type strain YIM 72238T (= KCTC 52717T = CCTCC AB 2017168T)] are proposed.