Mechanosensing of shear by Pseudomonas aeruginosa leads to increased levels of the cyclic-di-GMP signal initiating biofilm development

Biofilms are communities of sessile microbes that are phenotypically distinct from their genetically identical, free-swimming counterparts. Biofilms initiate when bacteria attach to a solid surface. Attachment triggers intracellular signaling to change gene expression from the planktonic to the biofilm phenotype. For Pseudomonas aeruginosa, it has long been known that intracellular levels of the signal cyclic-di-GMP increase upon surface adhesion and that this is required to begin biofilm development. However, what cue is sensed to notify bacteria that they are attached to the surface has not been known. Here, we show that mechanical shear acts as a cue for surface adhesion and activates cyclic-di-GMP signaling. The magnitude of the shear force, and thereby the corresponding activation of cyclic-di-GMP signaling, can be adjusted both by varying the strength of the adhesion that binds bacteria to the surface and by varying the rate of fluid flow over surface-bound bacteria. We show that the envelope protein PilY1 and functional type IV pili are required mechanosensory elements. An analytic model that accounts for the feedback between mechanosensors, cyclic-di-GMP signaling, and production of adhesive polysaccharides describes our data well

Single-Cell Control of Initial Spatial Structure in Biofilm Development Using Laser Trapping

Biofilms are sessile communities of microbes that are spatially structured by an embedding matrix. Biofilm infections are notoriously intractable. This arises, in part, from changes in the bacterial phenotype that result from spatial structure. Understanding these interactions requires methods to control the spatial structure of biofilms. We present a method for growing biofilms from initiating cells whose positions are controlled with single-cell precision using laser trapping. The native growth, motility, and surface adhesion of positioned microbes are preserved, as we show for model organisms <i>Pseudomonas aeruginosa</i> and <i>Staphylococcus aureus</i>. We demonstrate that laser-trapping and placing bacteria on surfaces can reveal the effects of spatial structure on bacterial growth in early biofilm development

Single-Cell Control of Initial Spatial Structure in Biofilm Development Using Laser Trapping

Biofilms are sessile communities of microbes that are spatially structured by an embedding matrix. Biofilm infections are notoriously intractable. This arises, in part, from changes in the bacterial phenotype that result from spatial structure. Understanding these interactions requires methods to control the spatial structure of biofilms. We present a method for growing biofilms from initiating cells whose positions are controlled with single-cell precision using laser trapping. The native growth, motility, and surface adhesion of positioned microbes are preserved, as we show for model organisms Pseudomonas aeruginosa and Staphylococcus aureus. We demonstrate that laser-trapping and placing bacteria on surfaces can reveal the effects of spatial structure on bacterial growth in early biofilm development