Heterogeneity of bacterial communities within the zebra mussel ( Dreissena polymorpha) in the Laurentian Great Lakes Basin

Abstract

We analyzed and compared the structure of bacterial communities associated with zebra mussel mantle cavity fluid, gills, and gut samples collected from Lake Loon, an inland lake in Michigan's Lower Peninsula (U.S.A.) using partial 16S rRNA gene sequencing. A total of 713 cloned 16S ribosomal gene sequences were checked for similarity to existing 16S sequences in two public databases: the Ribosomal Database Project and BLAST. Based on a 98% sequence similarity threshold, a total of 355 phylotypes belonging to 12 bacterial phyla and the phylum Bacillariophyta (diatoms) were identified in zebra mussel samples. A dominance of sequences belonging to the class γ-proteobacteria was observed in the mantle cavity clone libraries ( P < 0.0001). Significant sample-specific sequence associations ( P < 0.001) included members of the orders Pseudomonadales and Vibrionales in mantle cavity fluid and gut clone libraries, members of both the phylum Actinobacteria and the class δ-proteobacteria in gill clone libraries, and the Cyanobacteria/Bacillariophyta group in gut clone libraries. Furthermore, our results suggest that the zebra mussel may serve as a reservoir for facultative and opportunistic pathogenic bacteria, e.g., Clostridium spp., Flavobacterium spp. and Mycobacterium spp., for many aquatic and terrestrial animals. This work constitutes the first account of the heterogeneity of bacterial communities associated with multiple compartments within the zebra mussel. The information gained in this study significantly contributes to what is known regarding the microbial ecology of the zebra mussel and its role in disease ecology and food-web shifts in the Great Lakes ecosystem.