Restroom Microbiome Succession Study

The indoor environment is the dominant ecosystem for the majority of industrialized humanity and is unlike any biome previously experienced by our species. Bacteria commonly associated with our bodies dominate the Built Environment (BE). Using a unique ecosystem model - a public restroom - we show that surface-associated microbial communities follow a predictable ecological succession, from a community dominated by fecal microbiota to one dominated by skin and ‘outdoor’ microbiota. We analyzed microbial communities following decontamination of floors, toilet seats, and soap dispensers in 4 public restrooms hourly, daily, and weekly. Only toilet seat communities showed differentiation based on gender, with Lactobacillus dominating female seats and Roseburia and Blautia more prevalent on male seats. On floors, a late successional community developed quickly, and showed remarkably stability over weeks to months. Despite late-successional dominance by skin- and outdoor-associated microbiota, the core microbiome was composed almost exclusively of human gut bacteria, suggesting that a relatively homogenous pool of abundant fecal microbes is continuously dispersed to all floor surfaces. OTU abundances were not significantly correlated with measured physical parameters. Together, these data indicate that human-associated microbes dominate restroom surfaces and follow neutral community assembly. We suggest that BE surface environments are microbial ‘deserts’, where resources are scarce and persistence depends upon dormancy or continuous dispersal, and we show that overzealous cleaning regimes in public restrooms lead to a transient dominance of human fecal microbiota, while normal soap and water cleaning results in a stable community dominated by skin-associated microbes.