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Changes in bacterial and eukaryotic communities during sewage decomposition in Mississippi River water
Citation:
Korajkic, A., L. Parfrey, B. McMinn, Y. Baeza, W. VanTeuren, R. Knight, AND O. Shanks. Changes in bacterial and eukaryotic communities during sewage decomposition in Mississippi River water. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 69:30-39, (2015).
Impact/Purpose:
To inform the public.
Description:
Microbial decay processes are one of the mechanisms whereby sewage contamination is reduced in the environment. This decomposition process involves a highly complex array of bacterial and eukaryotic communities from both sewage and ambient waters. However, relatively little is known about how these communities change due to mixing and subsequent decomposition of the sewage contaminant. We investigated decay of sewage in upper Mississippi River water using Illumina sequencing of 16S and 18S rRNA gene hypervariable regions and qPCR for human-associated and fecal Bacteroidales indicators. Mixtures of primary treated sewage and river water were placed in dialysis bags and incubated in situ under ambient conditions for seven days. We assessed changes in microbial community composition under two treatments in a replicated factorial design: sunlight exposure and biotic interaction with native river microbiota. Initial diversity was higher in sewage compared to river water for bacteria, but the reverse was observed for eukaryotic microbes. Both treatments significantly shifted community composition for eukaryotes and bacteria (P < 0.05). Data indicated that biotic interactions, rather than exposure to sunlight, accounted for the majority of variation between treatments for both 16S (R = 0.50; P > 0.001) and 18S (R = 0.91; P = 0.001) communities. A comparison of 16S sequence data and fecal indicator qPCR measurements indicated a strong correlation between these two DNA-based methods (R2: 0.85 - 0.91) and qPCR data was also a good predictor of overall bacterial community change over time (rho: 0.804-0.814, P = 0.001). These findings suggest that biotic interactions can be critical factors in the decomposition of sewage in freshwater habitats and support the use of Bacteroidales genetic markers as indicators of fecal pollution.
