A novel anaerobic, thermophilic bacterium (strain A05 MBT) was isolated from Daginsky thermal springs (Sakhalin, Russia) on 2-methoxybenzoate as a substrate. Cells of the strain were motile long rods, 3.0-5.0 µm in length and 0.5-0.6 µm in diameter. The temperature range for growth was 47-68 °C, with an optimum at 60 °C. The pH range for growth was 4.5-8.0, with an optimum at pH 5.5-6.0. Strain A05 MBT did not require NaCl for growth. The strain utilized methoxylated aromatic compounds (2-methoxybenzoate and 3,4-dimethoxybenzoate), a number of carbohydrates (glucose, fructose, mannose, trehalose, xylose, sucrose, galactose, ribose, maltose, raffinose, lactose, cellobiose and dextrin) and proteinaceous substrates (yeast extract, beef extract, peptone and tryptone). The end products of glucose fermentation were acetate, ethanol and CO2. The DNA G+C content of strain A05 MBT was 40.2 mol% (whole-genome analysis). 16S rRNA gene sequence analysis revealed that strain A05MBT belongs to the order Thermoanaerobacterales (phylum Firmicutes). The closest relative of strain A05 MBT was Caloribacterium cisternae (94.3 % 16S rRNA gene sequence similarity). Based on the phenotypic, genotypic and phylogenetic characteristics of the isolate, strain A05 MBT is considered to represent a novel species of a new genus, for which the name Calorimonas adulescens gen. nov., sp. nov. is proposed. The type strain of Calorimonas adulescens is A05 MBT (=KCTC 15839T=VKM B-3388T).
Keywords: Thermoanaerobacterales; anaerobe; hot spring; methoxylated aromatic compounds; thermophile.