Abstract

A novel thermotolerant bacterial strain was isolated from a hot spring in a Tibetan geothermal field. Phylogenetic analysis of the 16S rRNA gene sequence of the novel strain showed that it belongs to a distinct lineage far from any known taxa. The new isolate shared the highest pairwise sequence identity withPhreatobacter cathodiphilusS-12T(92.8 % similarity) according to the 16S rRNA gene sequences. Cells were Gram-stain-negative, aerobic, rod-shaped and formed white round colonies. The strain grew at the ranges of 28–45 °C (optimum, 37 °C), pH 5.0–7.0 (optimum, pH 6.0) and 0–2 % NaCl. The strain was positive for catalase and oxidase. The major respiratory quinone was ubiquinone Q-10. Polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine. The major fatty acids were summed feature 8 (C18 : 1ω7cand/or C18 : 1ω6c). The DNA G+C content was 68.3 mol%. Based on these distinguishing properties, this strain is proposed to represent a new species of a new genusRhabdaerophilum calidifontisgen. nov., sp. nov., within a new familyRhabdaerophilaceaefam. nov. The type strain of the type species ofRhabdaerophilum calidifontisis SYSU G02060T(=KCTC 72351T=CGMCC 1.17070T).