Fatty acid and isoprenoid quinone composition in the classification of Bacteroides melaninogenicus and related taxa.

Abstract

The fatty acid and isoprenoid quinone composition of 37 Bacteroides strains was examined. In a single strain of Bacteroides melaninogenicus subsp. levii neither menaquinones nor ubiquinones was detected. Menaquinones were the only isoprenoid quinones found in the remaining 36 Bacteroides strains examined. Unsaturated menaquinones with six isoprene units were the main components isolated from B. ochraceus. The menaquinone components of B. asaccharolyticus strains enable them to be divided into two subgroups containing menaquinones with nine and ten isoprene units respectively. Bacteroides vulgatus strains contained menaquinones with ten isoprene units as the major component, whereas B. fragilis, B. thetaiotaomicron and B. melaninogenicus subsp. melaninogenicus were characterized by comparable amounts of menaquinones with 10 and 11 isoprene units. Unsaturated menaquinones with 11 isoprene units were found in B. melaninogenicus subsp. intermedius and with 11 and 12 isoprene units in rumen strains of B. ruminicola subsp. brevis and B. ruminicola subsp. ruminicola. By contrast, oral strains of B. ruminicola subsp. brevis were characterized by major amounts of menaquinones with 12 and 13 isoprene units. Strains at present designated B. oralis, however, were heterogeneous with respect to menaquinone composition.The non‐hydroxylated fatty acids of all the Bacteroides strains examined consisted predominantly of straight‐chain, anteiso‐ and iso‐methyl branched‐chain acids. Monounsaturated fatty acids were found in only small amounts. The major fatty acid in B. ochraceus and B. asaccharolyticus strains was 13‐methyltetradecanoic acid (iso C15) whereas 12‐methyl‐tetradecanoic acid (anteiso C15) predominated in B. melaninogenicus subsp. melaninogenicus. B. melaninogenicus subsp. intermedius. B. melaninogenicus subsp. levii, B. oralis and oral isolates of B. ruminicola subsp, brevis. The rumen strains of B. ruminicola subsp. brevis and B. ruminicola subsp. ruminicola were characterized by major amounts of anteiso C15 and pentadecanoic (C15:0) fatty acids.The accumulated lipid data correlate well with the major trends in Bacteroides taxonomy and appear to be of value in the classification of this group.