Calidifontimicrobium sediminis gen. nov., sp. nov., a new member of the family Comamonadaceae.

Two Gram-stain-negative and facultative anaerobic bacteria, designated strains SYSU G00088 and YIM 73032, were isolated from sediment samples collected from hot springs in Tibet, China. Based on the analyses of the 16S rRNA gene sequences, the two isolates were observed to be a member of the family Comamonadaceae, sharing highest pairwise sequence identity with type strains of Piscinibacter defluvii SH-1 (97.8  and 97.7 %, respectively). They were able to grow in the temperature range of 37-50 °C, pH 5.0-9.0 and in the presence of up to 0.5 % (w/v) NaCl. Both strains were positive for catalase and oxidase reactions. Cells of the novel isolates were short-rods and motile by means of a polar flagellum. The chemotaxonomic features of the two strains include ubiquinone 8 as the respiratory isoprenologue, diphosphatidylglycerol, phosphatidylethanolamine and phoshatidylglycerol as the known polar lipids, and C16 : 0 and C17 : 0cyclo as major fatty acids. The genomic DNA of strains SYSU G00088 and YIM 73032 had G+C contents of 71.8 and 71.9%, respectively. Based on the analyses of the phylogenetic, chemotaxonomic, morphological and genomic data, the two isolates are considered to represent a novel species of a new genus, for which the name Calidifontimicrobium sediminis gen. nov., sp. nov. is proposed. The type strain of Calidifontimicrobium sediminis is SYSU G00088 (=KCTC 52671=CGMCC 1.13597).