Bacteria often show very strong biogeography—some bacteria are abundant in specific locations while absent from others—leading to major questions when applying microbiology to therapeutics or probiotics: how did the bacteria get into the wrong place? How do we add the right bacteria into the right place when the biogeography has gotten 'out of whack'?
source https://phys.org/news/2020-12-closer-genomes-microbial-human-mouth.html