A conserved genetic basis for commensal-host specificity through live imaging of colonization dynamics

Animals throughout the metazoa selectively acquire specific symbiotic gut
bacteria from their environment that aid host fitness. Current models of
colonization suggest these bacteria use weakly specific receptors to stick
to host tissues and that colonization results when they stick in a region
of the host gut that overlaps with their nutritional niche. An alternative
model is that unique receptor-ligand binding interactions provide
specificity for target niches. Here we use live imaging of individual
symbiotic bacterial cells colonizing the gut of living Drosophila
melanogaster to show that Lactiplantibacillus plantarum specifically
recognizes a distinct physical niche in the host gut. We find that
recognition is controlled by a colonization island that is widely
conserved in commensals and pathogens from the Lactobacillales to the
Clostridia. Our findings indicate a genetic mechanism of host specificity
that is broadly conserved.