Distinct microcolony morphologies promote flow-dependent bacterial colonization

Fluid flows can impact bacterial behaviors in unexpected ways ( [1][1] – [3][2] ). 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][3], [5][4] ). 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. ### Competing Interest Statement The authors have declared no competing interest. [1]: #ref-1 [2]: #ref-3 [3]: #ref-4 [4]: #ref-5