Journal of Water and Health Vol 5 No 3 pp 395–406 © IWA Publishing 2007 doi:10.2166/wh.2007.035

Identification of culturable stream water bacteria from urban, agricultural, and forested watersheds using 16S rRNA gene sequencing

Kenneth T. Belt, Christina Hohn, Aiah Gbakima and James A. Higgins

Bacteria present in water samples taken on a weekly basis, from June 2004 through June 2005, from three streams, were cultured on Coliscan^® Easygel^® agar plates. Colonies representative of a variety of colors and morphologies were subjected to amplification and sequencing of a 1000–1100 nt portion of the 16S rRNA gene. A total of 528 colonies were sequenced; these categorized into 26 genera and 78 species. Of 175 dark blue/purple colonies presumed to be E. coli, sequence analysis indicated that 45 (25%) were actually other genera. For the urban stream Gwynns Falls Gwynns Run, E. coli was the most common genus/species encountered, followed by Klebsiella and Aeromonas. For Pond Branch, a stream located in a forested watershed, it was Serratia, followed by Yersinia and Aeromonas. For McDonogh (MCDN), a stream associated with Zea mays (corn) row crop agriculture, E. coli was the most frequently isolated genus/species, followed by Aeromonas and Enterobacter. ERIC-PCR genotyping of isolates from the most prevalent genera/species, indicated a high degree of diversity within-stream for E. coli and K. pneumoniae. Conversely, genotyping of Y. enterocolitica isolates indicated that some were shared between different streams.

Keywords: 16S rRNA; bacterial identification; freshwater bacteria; stream flora

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