Microbial community assessment in oil-impacted salt marsh sediment microcosms by traditional and nucleic acid-based indices

The effect of oil amendment in salt marsh sediment microcosms was examined by most probable number (MPN), DNA-hybridization with domain-specific oligonucleotide probes and whole community 16S rDNA-hybridizations. Gas chromatography (GC/MS) analysis of oil residues in sediments from microcosms after 3 months of operation showed that the quantity of petroleum hydrocarbons was lower in microcosms amended with oil compared to microcosms amended with oil + plant detritus. Bacterial numbers (total-MPN) increased in all experimental microcosms (amended with plant detritus, oil, and oil + plant detritus). In comparison to the intact sediment, the proportions of oil-degrading bacteria increased > 100-fold in the oil amended microcosm and > 10-fold in the plant detritus and the oil + plant detritus amended microcosms. DNA-hybridizations with Bacteria, Archaea and Eukarya oligonucleotide probes indicated few changes in the petroleum contaminated sediment community profile. In contrast, rDNA-hybridizations indicated that the bacterial community profile of the oil-impacted sediments, after 1 month of exposure, was significantly different from the control sediment. (C) 2001 Elsevier Science B.V. All rights reserved.