Understanding the impact of human activities on microbial populations is important for public safety. Interactions between humans and their environment can affect the size and diversity of both their internal and external microbiomes. Currently, most of the research has focused on indoor microbiomes. Few studies have looked at the effect of human activities on exterior communities, and none have focused specifically on the effect of mass human traffic on urban microbial communities.
The purpose of this study was to determine if one type of human traffic, a marathon foot race, causes a change in microbial communities. Sponges, composed of cellulose, were used as a method of sampling the running surface (pavement or wood). DNA was extracted from samples and the bacteria specific 16S rRNA gene was sequenced using the Illumina MiSeq platform. 16S rRNA gene sequences were used to analyze the pre- and post-marathon sampling of the park’s path (early in the race route) and boardwalk’s (end of the race route) microbiome.
Hypothesis: Exposure to bacteria carried into the park and boardwalk by heavy foot traffic during a half-marathon race will alter the park’s microbiome communities.
Despite previous studies which suggest that bacterial diversity grows as the number of individuals in the environment increases, we found no relationship between foot traffic and biodiversity in the microbiomes we investigated. We hypothesized that the number of runners, their diversity, and the diversity of microbes they picked up outside the park and boardwalk would all combine to contribute to an increase in the number and diversity of microbial communities in these two locations, but they did not. Extensive taxonomic diversity was found, however, with the most common bacterial genera being those associated with the oral cavity and skin. Overall, pre-marathon and post-marathon microbiomes harbored similar phyla and the same relative abundance, suggesting no change in microbial taxa before and after unusually heavy foot traffic.