Distinct microcolony morphologies promote flow-dependent bacterial colonization

Fluid flows can impact bacterial behaviors in unexpected ways ( 1 – 3 ). The high shear rate in heart valves should reduce colonization, but in endocarditis, valves are often counter-intuitively colonized by Staphylococcus aureus and Enterococcus faecalis ( 4, 5 ). Here we discover bacteria-specific mechanisms for preferential surface colonization in higher shear rate environments. This behavior enables bacteria that are outcompeted in low flow to dominate in high flow. Flow-dependent colonization by S. aureus and E. faecalis are mediated by distinct mechanisms that depend on each species’ microcolony morphologies: transport of a dispersal signaling molecule for clustered S. aureus and mechanical forces for linear chains of E. faecalis . These results suggest that microcolony morphologies have previously unappreciated costs and benefits in different environments, like those introduced by flow. One-Sentence Summary Bacterial surface colonization in high fluid flow depends upon the species’ clustered or chained microcolony morphologies.