The Impact of Household Biocides and Antibiotics on Aquatic Microbial Community Composition

Triclosan (TCS) is antimicrobial agent that is used in a lot of consumer products, including toothpaste, liquid and bar soap, and cosmetics. TCS has been found in many lakes and rivers in the United States. However, The Food and Drug Administration (FDA) banned TCS recently and it will no longer be used in household products. Despite the recent ban, TCS is known to persist in the environment and may have long-term impacts. We conducted an experiment on using fresh water from three locations Houghton, Green Bay and the Huron Mountains. Our goals in the study is to assess the impact of TCS on environmental microbial communities and compare the response to an antibiotic, and to estimate the impact of human activity on the environment. We set up microcosms from each location. One microcosm had 2 ppm TCS, another 6 ppm TCS and a third with 2 ppm Tetracycline. An additional set of microcosms had no added chemicals and were used as a control. We filtered our water samples from 0 hour and 24 hours then 7 days and once a week until 50 days. From these samples, we measured the microbial community change using next-generation sequencing of the 16S rRNA. Our results indicate there is a significant difference between the two Triclosan treatments concentrations. Also, there is a significant difference between the biocide and antibiotic treatments. Finally, there is a large change in the microbial community in regions with different population sizes; the bigger the population the less change. For example, there is large change in the microbial community composition in response to TCS addition in Huron Mountains. In Houghton, there is also a change in the community composition, but not as big of a change as in the Huron Mountains. Finally, there is very little change in the microbial community in response to TCS in Green Bay. These findings combine to suggest that TCS can have a strong impact on the microbes in aquatic settings and that this response appears to vary based on population size