Bacterial signalling mechanisms: Checking out the neighbourhood

In much the same way that people check out the neighbourhood and ask their friends for advice before they decide to move to a new house, bacteria perceive, integrate and respond to various different environmental and social cues during the processes of surface colonization and biofilm formation. These integrated signalling responses determine whether bacteria adopt a free-living individualist lifestyle associated with motility and elevated virulence, or whether they form a complex multicellular community known as a biofilm. Biofilms consist of large surface-attached multicellular structures, where the individual bacteria are encased in a matrix of proteins, exopolysaccharides and extracellular DNA strands. Within the biofilm, discrete bacterial subpopulations fulfil distinct phenotypic roles. These include support cells, persister cells that can resist high concentrations of antibiotics, and swarmer cells that burst from the surfaces of mature biofilms and colonies into new environments. As the majority of chronic hospital-acquired and implant-associated infections are biofilm-based, understanding the signalling networks that underpin bacterial biofilm formation is of vital importance.