Bacterial triterpenoids of the hopane series from the methanotrophic bacteria Methylocaldum spp.: phylogenetic implications and first evidence for anunsaturated aminobacteriopanepolyol

The hopanoid content of the two methanotrophic bacteria Methylocaldum szege diense and Methylocaldum tepidum was investigated. 35-Aminobacteriohopane-3 0R,31R,32R,33S,34S-pentol and its 3 beta-methyl homologue were present in b oth strains. In M. tepidum, they were accompanied by 35-aminobacteriohopane -31R,32R,33S,34S-tetrol and its 3 beta-methyl homologue. The side chain str ucture was identical to those previously reported from two other obligate m ethanotrophs, Methylococcus capsulatus and Methylomonas methanica. The two Methylocaldum species shared with the Methylococcus species the presence of 3 beta-methylhopanoid as well as of a hopanoid releasing adiantol upon H5I O6/NaBH4 treatment. A rare feature was in addition found in M. szegediense. The saturated hopanoids were accompanied by an unsaturated aminobacterioho panepentol with a Delta(11) double bond. Comparison of the hopanoid fingerp rints was in accordance with the close phylogenetic relationship of Methylo coccus and Methylocaldum. The major difference was the absence of sterols i n Methylocaldum which were always detected in the Methylococcus species. (C ) 2000 Federation of European Microbiological Societies. Published by Elsev ier Science B.V. All rights reserved.