2005 BES Annual Meeting Presentation and Poster Abstracts
16S rRNA -based diversity of culturable stream water bacteria: urban, agricultural and forested land use
Kenneth T Belt, Christina Hohn, Aiah Gbakima, and James A Higgins
Abstract: Weekly stream samples (from agricultural, urban and forested catchments) were cultured from June/04- May/05 to examine bacterial taxonomic/genetic diversity and to assess E. coli enumeration methods. Bacterial colonies from agar plates were subjected to DNA extraction and amplification and sequencing of a 1000-1100 nt portion of the 16S rRNA gene. For the year 528 colonies were categorized into 26 genera and 78 species (similarity scores of > 0.99, Ribosomal Database II project). Of 175 putative Escherichia coli colonies (from agar plates), 45 (25%) were actually Citrobacter, Buttiauxella, Shigella, Enterobacter, Klebsiella and Pseudomonas. For the polluted inner city stream (Gwynns Run), these false positives were greater during warm months (55%) than at other times of the year (14%) and E. coli was the most common genus encountered on the plates, followed by Klebsiella and Aeromonas. For Pond Branch, a suburban forested catchment, it was Serratia, followed by Yersinia and Aeromonas. McDonogh, a catchment with forested/row crop land use, was similar to the urban site in that E. coli was the most frequently isolated genus, followed by Aeromonas and Enterobacter. ERIC- PCR genotyping of isolates of selected bacterial species indicated that genetic diversity was high within-stream for E. coli (agricultural stream) and for K. pneumoniae (urban stream). Genotypes of some isolates of Y. enterocolitica were similar between streams. Pantoea agglomerans showed appreciable levels of clustering only within land use types (the agric. & urban streams). A number of potentially pathogenic species were found. Not surprisingly, Salmonella typhimurium, several Shigella species (S. Flexneri, S. boydii, S. sonnei) and Y. enterocolitica, occurred in Gwynns Run but Y. enterocolitica and S. typhimurium were also found in the forested catchment.