Molecular Characterization of Bacterial Phylogenetic and Functional Groups at Terrebonne Bay along the Coastline of the Gulf of Mexico

Abstract

The detection and quantification of bacterial phylogenetic and functional groups as well as community diversity at the site of the Deepwater Horizon oil spill in Terrebonne Bay along the Gulf of Mexico were carried out using nucleic acid staining, Fluorescence in situ Hybridization (FISH) and 16S rRNA gene cloning and sequencing approaches. Results from the 16S rRNA gene clone library analysis revealed high occurrences of bacterial members belonging to the Cyanobacteria (28%), β- Proteobacteria (21%), Bacteroidetes (17%), Actinobacteria (12%) and the α- Proteobacteria (10%). Particularly, bacterial members identified within the clone library as belonging to the β- Proteobacteria subclass were mostly hydrocarbon degraders, including Methylibium petroleiphilum, Burkholderia cepacia, Hydrogenophaga taeniospiralis and Methylobacillus flagellates. Simultaneous analyses of both planktonic and benthic bacterial communities by FISH revealed the numerical dominance of members of the type I Methanotrophic Bacteria (MB) over the type II populations. The results from the study clearly reveal a shift in the bacterial community structure and composition in response to the tragic methane and crude oil discharges from the Deepwater Horizon rig along the Gulf of Mexico.