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Effect of Sunlight on the Divergence of Community Structure of Fecal Bacteria in Cowpats Collected from Three Different Farms
Citation:
Wong, Kelvin, T. Shaw, A. Oladeinde, AND M. Molina. Effect of Sunlight on the Divergence of Community Structure of Fecal Bacteria in Cowpats Collected from Three Different Farms. Presented at 2014 Water Microbiology Conference: Microbial Contaminants from Watershed to Human Exposure, Durham, NC, May 05 - 09, 2014.
Impact/Purpose:
Presented at the 2014 Water Microbiology Conference: Microbial Contaminants from Watershed to Human Exposure.
Description:
Fecal pollution of environmental waters is a major concern for the general public because exposure to fecal-associated pathogens can have severe impacts on human health. In the last few years, numerous metagenomic studies applied next generation sequencing to understand the shift in microbial communities due to wastewater and sewage sludge treatment, antibiotic intake and nanoparticles exposure. However, the influence of sunlight, moisture and oxygen level on fecal bacterial diversity has rarely been investigated using metagenomic methods even though these stressors are some of the most important factors influencing the survival of bacteria in natural environments. In this study, we monitored bacterial community changes in cattle feces for 57 days after excretion (day 0, 2, 4, 8 15, 22, 29, 43, 57) by sequencing the 16s variable region 4, using Illumnia MiSeq. A total of 8 cattle feces from 2 different commercial farms (4 from each farm) were studied; half of the samples were directly exposed to sunlight (unshaded) and half were shaded. RESults indicated that the relative abundance (RA) profiles at the class level in both shaded and unshaded samples at day 0 were similar, with Clostridia (~50%), Sphingobacteria (~10%), and Bacteroidia (~22%) being the most abundant bacteria. In the shaded samples, Gammaproteobacteria, Betaproteobacteria, Alphaproteobacteria, and Actinobacteria became the most dominant bacteria by day 57 and the diversity profiles between all shaded samples were very similar. However, for unshaded samples, the diversity profiles of samples collected from one farm diverge differently than the other, and by day 57 two farms had a significantly different community profile especially the RA of Bacilli, Actinobacteria and Alphaproteobacteria. Since the moisture content was relatively similar in all unshaded samples, and each sample was exposed to the same intensity of UV radiation, we speculate that the main reason causing different community profiles the unshaded cowpats after 57 days was the breakdown of fecal materials to different organic compositions by UV radiation. Future studies should investigate the effect of UV radiation on nutrient and organic matter (OM) composition in fecal material from different origins and identify the relationship between profiles of nutrient/OM and bacterial community. Overall, this study indicated that freshly excreted feces from different locations can have similar community profile but their profiles can become distinctly different after UV radiation and gaining.
