Sex rather than wastewater associated stresses determines intestinal bacterial communities in the insectivorous bat, neoromicia nana.
Mehl, Calvin Carl.
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Wastewater treatment works (WWTWs) receive influent from domestic, agricultural and industrial sources, producing a cocktail of toxicants at these sites. WWTWs are unable to remove all the toxicants or bacterial and viral pathogens in the wastewater before it is released into surrounding ecosystems. Large amounts of nutrients in the wastewater supports abundant populations of chironomid midges (Diptera), that transfer these toxicants to their predators, such as Neoromicia nana (Vespertilionidae), resulting in numerous biochemical and metabolic effects. However, little is known if foraging at WWTWs affects the intestinal bacteria of bats. This study compared intestinal bacteria communities that play essential roles in nutrient absorption and immunity in their hosts between N. nana populations at WWTWs and reference sites. I hypothesised that bacterial communities of N. nana should differ between individuals foraging at WWTWs and reference sites. Next generation sequencing was used to identify intestinal bacteria of bats at two reference sites (Buffelsdrift and Inkunzi) and two WWTWs (Verulam and Umbilo). Differences in intestinal bacterial loads (at each taxonomic level) and host attributes (sex, body condition, locality) of individuals were quantified using the Gower distance measure. Hierarchical cluster analysis was used to identify the factors that determine the similarity between individuals. As predicted, bats at WWTW sites showed greater intestinal bacteria diversity than those at reference sites. This is likely due to exposure to the high diversity of bacteria within wastewater. Further, differences in certain bacterial taxa, such as the family Chitinophagaceae, may be due to differences in diet between WWTWs and reference site bats. Statistical analyses revealed that sex, and site to a lesser degree, were the best predictors of similarity in intestinal bacteria communities among N. nana bats. Because bacterial diversity did not correlate with body condition, sex-specific factors (such as sex hormones) may be the greatest drivers of these differences. Further, site specific factors such as toxicant and ectoparasite exposure likely had some influence on the difference observed between reference and WWTWs bats. Dysbiosis of intestinal bacterium communities, because of wastewater exposure, may have significant sex-biased impacts on host metabolism and immune functioning.