Methylobacterium ajmalii sp. nov., isolated 1 from the International Space Station

Gram-negative, rod-shaped, catalase positive, oxidase positive, motile bacteria, designated as IF7SW-B2T, IIF1SW-B5, and IIF4SW-B5, were isolated from different locations across two consecutive flights, from the International Space Station (ISS). The sequence similarity of all ISS strains was <99.4% for 16S rRNA and <97.3% for gyrB genes with the closest being Methylobacterium indicum SE2.11T. Furthermore, the multi-locus sequence analysis placed the three ISS strains in the same clade of M. indicum. The average nucleotide identity (ANI) values of three ISS strains were <93% and digital DNA-DNA hybridization (dDDH) were <46.4% with any validly described Methylobacterium species. Based on the ANI and dDDH analyses, the ISS strains were considered as novel species belonging to the genus Methylobacterium. The three ISS strains showed 100% ANI similarity and dDDH values with each other, indicating that these three ISS strains, isolated during various flights and locations, belong to the same species. The ISS strains were found to grow optimally at temperature between 25°C to 30°C, pH 6.0 to 8.0, and NaCl 0 to 1%. Phenotypically, the ISS strains resemble M. aquaticum and M. terrae since they assimilate similar sugars as sole carbon substrate when compared to other Methylobacterium species. Fatty acid analysis showed that the major fatty acid produced by the ISS strains are C18:1- ω7c and C18:1- ω6c. The predominant quinone was ubiquinone 10 and the major polar lipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol and an unidentified lipid. Therefore, based on genomic, phylogenetic, biochemical, and fatty acid analyses, strains IF7SW-B2T, IIF1SW-B5, and IIF4SW-B5, are assigned to a novel species within the genus Methylobacterium, and the name Methylobacterium ajmalii sp. nov., is proposed. The type strain is IF7SW-B2T.