Quorum vs. diffusion sensing: a quantitative analysis of the relevance of absorbing or reflecting boundaries. Issue 2 (19th February 2014) - Trovato, Antonio
Abstract The consequences of the boundary conditions (signal reflecting vs. signal adsorbing) on bacterial intercellular communication were addressed by a combined physics and microbiology approach. A predictive biophysical model was devised that considered system size, diffusion from given points, signal molecule decay and boundary properties. The theoretical predictions were tested with two experimental agarose‐gel‐based set‐ups for reflecting or absorbing boundaries. N‐acyl homoserine lactone (AHL) concentration profiles were measured using the Agrobacterium tumefaciens NTL4 bioassay and found to agree with model predictions. The half‐life of AHL was estimated to be 7 days. The absorbing vs. reflecting nature of the boundaries drastically changed AHL concentration profiles. The effect of a single nonreflecting boundary side was equivalent to a 100‐fold lower cell concentration. Results suggest that the kinetics of signal accumulation vs. signal removal and their threshold‐mediated phenotypic consequences are directly linked to the properties of biofilm boundaries, stressing the relevance of the diffusion sensing component in bacterial communication.