N-209. Phylogenetic Diversity and Membership Patterns of Fecal and Environmental Bacteroidales Populations

R. Lamendella1, D. B. Oerther1, J. W. Santo Domingo2;
1Univ. of Cincinnati, Cincinnati, OH, 2US EPA, Cincinnati, OH.

Members of the Bacteroidales order have recently been targets of microbial source tracking assays. While several studies have documented that some populations exhibit preferential host-distribution, given the vast diversity of this bacterial group, it is still necessary to resolve the level of specificity of Bacteroidales populations via comprehensive molecular surveys. In this study, we further evaluated the Bacteroidales population structure within feces and environmental samples impacted by fecal pollution using 16S rRNA gene sequence analyses. Approximately, 4,100 clones derived from 21 different hosts and 12 environmental samples were analyzed using phylogenetic analyses and diversity and membership tools (i.e., Distance-Based OTU and Richness; Shared Operational Taxonomic Unit and Similarity). Phylogentic analysis of the sequences indicated that a majority of the clones were related to non-cultured representatives of Bacteroides and Prevotella genera. Nearly two-thirds of the sequences belong to cosmopolitan populations as they were present in multiple hosts including humans, horses, dogs, cats, and pigs. In contrast, we identified clusters of Prevotella-like sequences derived exclusively from swine feces from Ohio, Oregon, and Japan. These populations were also present in water contaminated with swine feces, implying the presence of geographically stable populations endemic to the swine-gut. Furthermore, analyses of membership patterns indicated that nearly half of the Bacteroidales pig fecal populations were also present in Bacteroidales environmental clone libraries developed with swine polluted samples. These data suggest that the latter populations are promising targets for detecting swine-specific fecal pollution in environmental waters. Altogether, the results from this study confirm the occurrence and identity of swine-specific Bacteroidales populations also found in waters impacted by swine fecal pollution. This information is critical to the design of comprehensive assays for accurately quantifying contributions of fecal pollution from different hosts.