Tracking microbes within communities

Background/Question/Methods: The majority of human body sites inhabited by bacteria are exposed to external sources of bacteria on a daily basis, providing numerous opportunities for bacterial transmission. Amongst the potential factors impacting human-associated microbial diversity, the interpersonal spread of bacteria has gained little attention, despite its most obvious importance for disease transmission and the spread of resistant or bioengineered organisms. We take advantage of advances in profiling microbial communities using their 16S sequences to determine what factors shape the transmission of microbes. We surveyed individuals from several isolated villages in the Fiji Islands where bacterial transmission is known to be high. Instead of focusing solely on demographic factors, diet and health factors, we acquired information on potential transmission pathways including social interactions, geospatial distances and behaviors that promote or prevent bacterial spread. We then analyzed the microbial composition present within the guts of study participants, as this is a body site of high, daily exposure to bacteria. Results/Conclusions: Our results point to village association as the single, largest factor in discriminating between microbiomes, suggesting that local exposure may play an important role in shaping microbial communities. This is the first evidence of a local biogeographic pattern present within among human-associated microbial communities.