Deciphering the role of mechanical cues during bacterial adhesion and biofilm formation

Bacteria adhere to surfaces where they form macrocolonies called biofilms. This biofouling is a problem both in industry and healthcare. However, the cues that regulate the switch from an individual motile lifestyle to a collective sessile one are still poorly understood. In particular, we are interested in the role of mechanical cues during bacterial adhesion and early biofilm development. I will illustrate the importance of environmental forces for the biofilm-formers Pseudomonas aeruginosa and Escherichia Coli, with a few experimental studies:

- We investigated the effect of hydrodynamics on bacterial adhesion to model abiotic surfaces in microfluidic channels. We discovered a counter-intuitive strengthened adhesion as shear stress increases over a large range of values [1]. Using reflection interference contrast microscopy, and simultaneously imaging fluorescent reporters to visualize the phenotypic transition to a sessile lifestyle, we show that bacteria attach by one pole, and we are able to decipher the dynamics of early biofilm formation.

- Next, I will present recent results obtained by adapting traction force microscopy (TFM) to the study of bacterial microcolonies. We have monitored bacterial growth on soft hydrogels seeded with fluorescent microspheres to measure substrate deformation, and calculated the stress field under microcolonies. Interestingly, we show that adhesion properties of individual cells influences microcolony morphogenesis, thus regulating cell-environment interactions.

If time allows, I will present recent efforts in the lab aimed at visualizing and quantifying bacteria-surface interactions for individual cells.

[1] Lecuyer S, Rusconi R, Shen Y, Vlamakis H, Forsyth A, Kolter R and Stone HA, Biophys. J. (100) 341-50, 2011.

[2] Duvernoy MC, Mora T, Ardré M, Croquette V, Bensimon D, Quilliet C, Ghigo JM, Balland M, Beloin C, Lecuyer S and Desprat N, submitted.