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 72259(T) and YIM 72238(T), 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 72259(T) and YIM 72238(T) are closely related to Tepidimonas ignava SPS-1037(T) (97.0 and 97.5%, respectively), Tepidimonas taiwanensis I1-1(T) (96.5 and 97.3%), while sharing 98.0% sequence similarity with each other. The DNA-DNA relatedness values of strains YIM 72238(T) with T. ignava SPS-1037(T) and T. taiwanensis I1-1(T) were determined to be 25.2 +/- 1.2 and 24.6 +/- 3.1%, respectively, while the two strains (YIM 72259(T) and YIM 72238(T)) 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 72259(T) and YIM 72238(T) were determined to be 71.6 and 68.9 mol%, respectively. The major fatty acids in both strains were identified as (> 10%) C-16:0, C-17:0 and summed feature 8, while the strain YIM 72238(T) contained a moderately high amount of summed feature 3 as well. The polar lipid profiles for strains YIM 72259(T) and YIM 72238(T) 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 72259(T) (= NBRC 112410(T) = CGMCC 1.15971(T)) and Tepidimonas alkaliphilus sp. nov. [type strain YIM 72238(T) (= KCTC 52717(T) = CCTCC AB 2017168(T))] are proposed.