Residents and transients

The scientists who study these communities are microbial ecologists, and like ecologists of the macro world, they like to think about the interactions between different organisms. But this research is still new, and this way of thinking is only just starting to make it into the world of clinical microbiology, which is still focused on defeating the bad microbes. “We noticed there is kind of a division between the clinical human skin microbiology research and this more recent emergence of microbial ecology,” says Roo Vandegrift, an ecologist who co-authored the recent paper, “There wasn’t very much crosstalk between those segments of the scientific literature.”

Even the language the two groups use is different. Microbial ecologists tend to divide microbes into how they behave in communities: are they residents or are they transient? Clinical microbiologist divide them up based on whether they’re harmful: commensal or pathogenic? You could say the two sets of vocabulary roughly map onto one another. Resident microbes tend to be commensal (the bacteria are harmless to you but they’re benefitting from living on you) and the transients are the pathogens that make you sick when they appear.

–Sarah Zhang, What Is the Right Way to Wash Your Hands?