Microbial community structure by fatty acid analysis during polycyclic aromatic hydrocarbon degradation in river sediment augmented with Pleurotus ostreatus

Abstract

This research was conducted to determine changes in the microbial community in contaminated sediment during fungal remediation of polycyclic aromatic hydrocarbon (PAH) contaminated Mahoning River sediment. The fungus used for remediation was Pleurotus ostreatus, white rot fungi which is capable of degrading a wide range of organic contaminants including PAHs. Microbial community structure was determined using fatty acid profiles from microbial lipids extracted directly from the sediment. Contaminated sediment was collected from Lowellville, OH and was incubated at 25 ̕C. There were 4 treatments (1 liter of contaminated river sediment) done in duplicate runs as follows: 1) untreated sediment, 2) sediment amended with sawdust, 3) sediment amended with sawdust and augmented with Pleurotus ostreatus and, 4) sediment amended with sawdust, augmented with Pleurotus ostreatus and amended with extra nitrogen after 21 days. At day 0, 21, and 42, lipids were extracted from each treatment (in triplicate). Microbial fatty acids were purified from the lipid extract, methylated and analyzed by GC-MS. The sediment microbial community structure showed great heterogeneity shown as high variability within triplicate samples and as differences between duplicate treatments. Groups of anaerobic bacteria (sulfate reducers and methanogens) persisted throughout the treatments, even though they were exposed to oxygen during mixing and from the surface during the incubation. The abundance of gram negative bacteria, a group of bacteria associated with PAH degradation, showed highest relative abundance on day 42. Even though the microbial structure changed, the microbial biomass (measured as lipid phosphate) remained consistent between triplicate samples and duplicate runs, and changed little during the incubation.