Citation:

Korajkic, A., W. Parfrey, B. McMinn, N. Ashbolt, Y. Vazquez Baeza, W. Van Teuren, W. Walters, R. Knight, AND O. Shanks. Sewage Decomposition in Ambient Water: Influence of Solarradiation and Biotic Interactions on Microorganism Communities and Bacteroidales Real-Time Quantitative PCR Measurements - poster/abstract. Presented at 17th International Symposium on Health-Related Water Microbiology, Florianopolis, BRAZIL, September 15 - 20, 2013.

Impact/Purpose:

To inform the public.

Description:

AIMS: Sewage and ambient water both consist of a highly complex array of bacteria and eukaryotic microbes. When these communities are mixed, solar radiation and biotic interactions (predation and competition) can influence pathogen decay based on experiments targeting indicator microorganisms. However, very little is known about the microbial community structure of each of these sources and how it shifts due to mixing and subsequent decomposition of the sewage contaminant. METHODS: We compared the relative contribution of sunlight exposure and the presence of natural river microbiota on decay of sewage and ambient upper Mississippi River microbial communities using Illumina sequencing of 16S and 18S hypervariable regions and qPCR for human-associated and fecal Bacteroidales. Mixtures of primary treated sewage and river water were placed in dialysis bags and incubated in situ under ambient conditions for seven days using a submersible mesocosm. Treatments included: 1) exposure to sunlight and river microbiota, 2) exposure to sunlight in sterilized river water, 3) no sunlight exposure in the presence of river microbiota, and 4) no exposure to either variable. RESULTS: For Illumina 16S and 18S sequence data, diversity estimates were greater in sewage compared to ambient river water. A highly significant difference was observed between treatment groups for bacteria and eukaryotes (p < 0.05). An analysis of similarity indicated that biotic interactions account for the majority of variation between treatments in both bacteria (R = 0.50; 0 > 0.001) and eukaryotes (R = 0.91; p = 0.001) compared to solar radiation. A comparison of 16S sequence data and Bacteroidales qPCR target concentration estimates indicated a strong correlation between these two DNA-based methods (HF183 R2=0.91; GenBac3 R2=0.85). qPCR data was also a good predictor of overall bacterial community change over time (HF183 rho=0.814 p=.001; GenBac3 rho=0.804 p=.001). CONCLUSIONS: These findings suggest that both biotic interactions and solar radiation can be critical factors in the decomposition of sewage fecal bacteria in freshwater habitats. Dramatic shifts in community composition are associated with specific eukaryotes (Parabodo spp., Tetrahymena spp., and others) as well as several bacterial families. Finally, human-associated (HF183) and general Bacteroidales (GenBac3) qPCR measurements can be good predictors of sewage bacterial community decomposition.

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