Bacteria walk before they crawl: surface motility prior to biofilm formation

RLM 11.204
Jacinta Conrad
Chemical and Biomolecular Engineering, University of Houston
Bacteria walk before they crawl: surface motility prior to biofilm formation
Bacterial biofilms are structured multicellular communities responsible for lethal infections and catastrophic implant failure in the human body as well as industrial and marine biofouling. Knowing how free-swimming bacteria adapt their motility mechanisms near a surface is crucial for understanding the transition from the planktonic to the biofilm phenotype. Here, we identify single-bacterium surface motility mechanisms by tracking every cell in a library of microscopy movies, and show how these mechanisms influence life cycle events and biofilm morphology.  We extract the motility histories of individual surface-associated P. aeruginosa cells by translating video microscopy movies into searchable databases of bacterial behavior using automated tracking algorithms, and identify fundamental appendage-specific mechanisms for P. aeruginosa surface motility. Type IV pili mediate two surface motility mechanisms: horizontally-oriented ‘crawling,’ by which the bacterium moves lengthwise with high directional persistence, and vertically-oriented ‘walking’, by which the bacterium moves with low directional persistence and high instantaneous velocity, allowing it to rapidly explore microenvironments. The flagellum mediates two additional motility mechanisms: near-surface swimming and surface- anchored ‘spinning,’ which often precedes detachment from a surface. Synergistic interactions between these different motility mechanisms influence cell attachment, division, and detachment and hence affect biofilm morphology.