Bacterial triterpenoids of the hopane series from the methanotrophic bacteriaMethylocaldumspp.: phylogenetic implications and first evidence for an unsaturated aminobacteriohopanepolyol

Abstract

The hopanoid content of the two methanotrophic bacteria Methylocaldum szegediense and Methylocaldum tepidum was investigated. 35-Aminobacteriohopane-30R,31R,32R,33S, 34S-pentol and its 3beta-methyl homologue were present in both strains. In M. tepidum, they were accompanied by 35-aminobacteriohopane-31R,32R,33S, 34S-tetrol and its 3beta-methyl homologue. The side chain structure was identical to those previously reported from two other obligate methanotrophs, Methylococcus capsulatus and Methylomonas methanica. The two Methylocaldum species shared with the Methylococcus species the presence of 3beta-methylhopanoid as well as of a hopanoid releasing adiantol upon H(5)IO(6)/NaBH(4) treatment. A rare feature was in addition found in M. szegediense. The saturated hopanoids were accompanied by an unsaturated aminobacteriohopanepentol with a Delta(11) double bond. Comparison of the hopanoid fingerprints was in accordance with the close phylogenetic relationship of Methylococcus and Methylocaldum. The major difference was the absence of sterols in Methylocaldum which were always detected in the Methylococcus species.

The Bacteriohopanepolyol Inventory of Novel Aerobic Methane Oxidising Bacteria Reveals New Biomarker Signatures of Aerobic Methanotrophy in Marine Systems

“…[42,46,52], psychrotolerant isolate CEL 1923 [42], and Methylocaldum tepidum [22]. However, a species in the same genus ( Methylomarinovum sp.…”

“…Type II methanotrophs, members of the Alphaproteobacteria , are associated with terrestrial settings ([8], and references therein), whereas Type I methanotrophs members of the Gammaproteobacteria are widespread in aquatic systems, although they are also found in terrestrial systems. Both Type I and Type II methanotrophs are known to synthesise bacteriohopanepolyol (BHP) lipids [22]. BHPs are precursors to hopanes, which are the most ubiquitous lipids in the geological record [23,24].…”

“…Aminopentol and its methylated and unsaturated homologues (i.e., I 3Me , ΔI ) have been found almost exclusively in Type I aerobic methanotrophs [22,44–46]. Moreover, aminopentol ( I ) has been found in a wide range of environments, which indicates potential as a biomarker for AMO (Table 1).…”

“…Representatives from only a small number of Type I methanotroph genera have been tested for BHP production (e.g., [22,36,46,52,53]. Many more recently described genera, including novel genera from marine and other (hyper)saline environments, have yet to be explored (e.g., [54–56]).…”

Diastereoselective Synthesis of Aminobacteriohopanetetrol, a Biomarker for Methanotrophic Bacteria: Confirmation of the Absolute Configuration

“…Amongst these bacteriohopanepolyols, the aminobacteriohopanepolyols are special since they have been detected in all methanotrophic bacteria, which use methane as the sole carbon and energy source [5] [7]. Interestingly, compounds 1 -4 ( Fig.…”