Methylopila carotae sp. nov., a facultative methylotroph, isolated from a root of Daucus carota L.

An aerobic facultatively methylotrophic bacterium, designated strain Das4.1, was isolated from a root of Daucus carota L. The cells of this strain were observed to be Gram-stain negative, asporogenous, non-motile short rods multiplying by binary fission. Strain Das4.1 can utilise methanol, methylamine and a variety of polycarbon compounds as carbon and energy sources. C-compounds were found to be assimilated via the isocitrate lyase-negative variant of the serine pathway. On medium with 0.5% methanol, growth of strain Das4.1 was observed at pH 5.5-9.0 (optimum, pH 6.0-7.0) and 18-37 °C (optimum, 24-29 °C) and in the presence of 0-2% (w/v) NaCl (optimum, 0.05%). Cells are catalase and oxidase positive and synthesise indole from L-tryptophan. The major fatty acids of methanol-grown cells were identified as C, C and 11-methyl-C. The predominant phospholipids were found to be phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine and phosphatidylmonomethylethanolamine. The major respiratory quinone was identified as Q-10. The DNA G + C content of strain Das4.1 was determined to be 67.3 mol% (T). Phylogenetic analysis based on 16S rRNA gene sequence comparison revealed that strain Das4.1 belongs to the genus Methylopila and shows high sequence similarity to Methylopila oligotropha 2395A (98.4%) and Methylopila capsulata IM1 (98.0%). However, the DNA-DNA relatedness of strain Das4.1 with M. oligotropha 2395A was only 22 ± 3%. Based on genotypic, chemotaxonomic and physiological characterisation, the isolate can be classified as a novel species of the genus Methylopila, for which the name Methylopila carotae sp. nov. is proposed. The type strain is Das4.1 (= VKM B-3244 = CCUG 72399).