Detection of a microbial consortium, including type II methanotrophs, by use of phospholipid fatty acids in an aerobic halogenated hydrocarbon-degrading soil column enriched with natural gas

The phospholipid ester-linked normal and lipopolysaccharide layer hydroxy fatty acids from microbes in a natural gas (85% methane)-stimulated soil column capable of degrading halogenated hydrocarbons were analyzed in detail by capillary column GC-MS. Microbial biomass, calculated from phospholipid fatty acid (PLFA) concentrations to be 5.6 × 10⁹ bacteria/g (dry weight), was greater in the hydrocarbon-degrading column than in either an azide-inhibited soil column or an untreated surface soil. Microbial community structure information, using GC-MS analysis of derivatized monounsaturated PLFA, indicated that the major component (16 to 28%) of the PLFA in the hydrocarbon-degrading column was the PLFA 18:1δ10c. This novel PLFA has been reported as a major component in type II methanotrophs. The high relative proportions of C₁₈ components relative to C₁₆ fatty acids indicated that type II rather than type I methanotrophs were the most abundant microbial flora present in the active soil column. Fatty acids from other bacterial groups and microeukaryotes also were detected in the hydrocarbon-degrading soil column. Differences between the relative proportions of these metabolic groups of microorganisms were quantified and compared among the three soils analyzed. Based on these differences, the potential exists to use these methods to monitor shifts in microbial biomass and community structure in aquifers where indigenous bacteria are stimulated to biotransform pollutant compounds.