Escherichia coli is used to indicate fecal contamination in freshwater systems and is an indicator of the potential presence of human pathogens. However, naturalized E. coli strains that persist and grow in the environment confound the use of this bacterium as a fecal indicator. Here we examined the spatial and temporal distribution of E. coli in water and sediments of the Seven Mile Creek (SMC), a constructed, ephemeral watershed. E. coli concentrations showed variation by site and date, likely due to changes in temperature and rainfall. Horizontal fluorophore enhanced rep-PCR (HFERP) DNA fingerprint analyses indicated that E. coli populations were very diverse and consisted of transient and naturalized strains, which were especially prevalent in sediment. E. coli fingerprints from water and sediment collected in the same year clustered together with significant overlap, indicating exchange of strains between matrices. Isolates obtained during periods of flow, but not during non-flow conditions, clustered together regardless of sample site, indicating that transport between sites occurred. Naturalized E. coli strains were found in the SMC and strains become geographically isolated and distinct during non-flow conditions. Isolates collected during late spring to fall clustered together at each site, suggesting that temperature and growth of naturalized strains are likely factors affecting population dynamics. Results of this study show that newly introduced and naturalized E. coli strains are present in the SMC. Results of this study highlight an important concern for resource managers using this species for water quality monitoring.
Bibliographical noteFunding Information:
This study was supported, in part, by Clean Water Legacy Act funds , obtained via a grant from the Minnesota Department of Agriculture (to MJS and SM). The authors wish to thank John Ferguson for his assistance with statistical analyses, HFERP DNA fingerprints, and figures, and Asbah Hadi for help with samples. We also thank Scott Kudelka, and the field crew at Minnesota State University -Mankato for sample collection and for providing raw E. coli count data, Jack Bovee and the Brown Nicollet Cottonwood Water Quality Board for project organization, and Scott McLean (MPCA) for the collection of physical data from the SMC.
© 2015 Elsevier B.V.
- DNA fingerprinting
- Escherichia coli
- Naturalized population
- Water quality