Molecular characterization of bacterial communities associated with sediments in the Laurentian Great Lakes

The Laurentian Great Lakes freshwater ecosystem comprises a series of interconnected lakes exhibiting wide spatial differences in hydrogeochemistry, productivity, and allochthonous inputs of nutrients and xenobiotics. Bacterial communities associated with offshore sediments in this ecosystem have been rarely studied. We evaluated bacterial communities associated with sediments from 10 locations in four of the five Great Lakes (Lakes Superior, Michigan, Huron, and Ontario) by generating16S rRNA pyrosequence libraries. Pyrosequencing analysis revealed the presence of 26 bacterial phyla and proteobacterial classes among Great Lakes sediment samples. Actinobacteria, Acidobacteria, Betaproteobacteria, and Gammaproteobacteria were the most abundant groups of bacteria. Redundancy analysis was used to examine the role of sediment properties, including depth and chemical composition, in shaping bacterial community structure. One sample from Lake Huron was distinctly different from all other samples. Phylogenetic analysis revealed that the sample contained greater abundances of groups of bacteria associated with polluted environments. This study constitutes the most extensive examination of bacteria associated with Laurentian Great Lakes sediments and sheds useful insight into the microbial ecology of the Great Lakes.