Bacterial hopanoids from pink-pigmented facultative methylotrophs (PPFMs) and from green plant surfaces

Abstract

Six strains of pink-pigmented facultatively methylotrophic bacteria (PPFMs) isolated from phylloplane surfaces of different plants were analysed for the presence of triterpenoids of the hopane series. All of the cultures produced hopanoids in abundant quantities and contained the same compounds as the type strain of Methylobacterium organophilum: diplopterol, 2β-methyldiplopterol, bacteriohopanetetrol, a tetrol glycoside and two tetrol ethers. The presence of a guanidinium group on the carbapseudopentose moiety of one of these ethers and/or of 2β-methyldiplopterol seems to be restricted to the genus Methylobacterium. Small amounts of bacteriohopanepolyols were detected in three of seven plants studied. Since no bacterial C35 hopanoids have been reported in eukaryotes, we believe they are probably derived from eubacterial epibionts present on the phylloplane surfaces, the most numerous of which are Methylobacterium spp.