Methylobacillus caricis sp. nov., an obligate methylotroph isolated from roots of sedge (Carex sp.)

Abstract

A new obligately methylotrophic bacterium, strain OV^T, was isolated from roots of sedge (Carex sp.). The isolate was represented by aerobic gram-negative motile, non-spore-forming rods, which divided by binary fission. Optimal growth occurred at 22−29°C and pH 7.5−8.5 in the presence of 0.5−2% NaCl; growth was inhibited by 3.5% NaCl. Strain OV^T utilized methanol as the only carbon and energy source. The organism used the KDPG variant of the ribulose monophosphate pathway (RuMP) of С₁ metabolism. Ammonium was assimilated by reductive amination of α-ketoglutarate. The major cellular fatty acids were C_16:0 (45.5%), C_16:1ω7c (40.7%), and C_17cyc (8.0%). The major ubiquinone was Q₈. The dominant phospholipids were phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol. The DNA G + C content of strain OV^T was 51.4 mol % (T_m). While the 16S rRNA gene sequence of strain OV^T exhibited high similarity to those of Methylobacillus species: M. gramineus Lap^T (99.6%) and M. glycogenes TK 0113^T (98.7%), the DNA-DNA hybridization level between strain OV^T and M. gramineus Lap^T was only 52%. Based on the data obtained, strain OV^T was assigned to the new species Methylobacillus caricis sp. nov. (=VKM B-3158^T = JCM 32031^T).