Methylobacterium currus sp. nov., isolated from a car air conditioning system

Abstract

A novel bacterial strain, designated PR1016A^T, was isolated from a car air conditioning system. This rod-shaped strain showed catalase and oxidase activities, was aerobic and methylotrophic, and had a reddish pink colour. The genomic DNA G+C content of strain PR1016A^T was 70.2 mol%, as determined by genome sequencing. Phylogenetic analysis based on 16S rRNA gene sequence similarity showed that strain PR1016A^T was most closely related to Methylobacterium aquaticum GR16^T (98.86 %), M. variabile GR3^T (98.43 %), M. platani PMB 02^T (98.36 %) and M. tarhaniae N4211^T (98.14 %). The average nucleotide identity and digital DNA-DNA hybridization values between strain PR1016A^T and M. aquaticum GR16^T, M. platani PMB02^T and M. variabile GR3^T were 88.61, 88.14 and 87.88 %, and 36.4, 35.8 and 34.7 %, respectively. Numerous insertion sequences are present in the genome of strain PR1016A^T, which has a larger genome than the four Methylobacterium species described above. Cells grew at 18-42 °C (optimum, 30 °C), at pH 4.0-9.0 (optimum, pH 7.0) and in the presence of 0-1.0 % (w/v) NaCl (optimum, 0 %). The major respiratory quinone was Q10. Fatty acid methyl ester analysis revealed that summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) was the predominant cellular fatty acid in strain PR1016A^T. Two-dimensional TLC indicated that the major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine. The genotypic and phenotypic characteristics indicate that strain PR1016A^T represents a novel species of the genus Methylobacterium, for which the name Methylobacterium currus sp. nov. is proposed. The type strain is PR1016A^T (=KACC 19662^T=JCM 32670^T).

Keywords: Alphaproteobacteria; Methylobacterium; taxonomy.