Phospholipid fatty acids of a marine sedimentary microbial community in a laboratory microcosm: Responses to petroleum hydrocarbon contamination

Laboratory microcosm experiments were performed to evaluate petroleum hydrocarbon biodegradation and phospholipid fatty acid (PLFA) composition in either non-contaminated (NC) or contaminated (C) sedimentary microcosms with a crude oil. An analytical procedure was developed to extract both hydrocarbons and PLFAs from the same culture. PLFAs were analyzed over time during an aerobic microcosm experiment (0-21 days) to obtain a better understanding of the structural changes in bacterial sedimentary communities. We observed an increase in both hydrocarbon degraders and heterotrophic bacteria as reflected in PLFA concentrations. Inferred total biomass ranged from 4 to 11.3 × 109 and 22.1 to 199.2 × 109 bacterial cells kg−1 dry sediment for NC and C sediments, respectively. Total biomass was greater in C than NC sediment, increasing by about twice, 3×, 13× and 50× for 0, 2, 7 and 21 days, respectively. These modifications coincided with removal of petroleum hydrocarbons that reached 35% of total hydrocarbon and 64% of total n-alkanes after 21 days. Microbial community structure changes over time in the C and NC microcosms were shown with principal components analysis and a study of some characteristic PLFAs as biomarkers. Some modifications occurred after several days of petroleum exposure, but crude oil addition did not produce an obvious increase in the biomass of petroleum degraders.