Multicellular signalling and growth of Pseudomonas aeruginosa.

The main reason for Pseudomonas aeruginosa persistence within the lungs of chronically infected cystic fibrosis patients seems to be that the bacteria reside within biofilm structures which protect them from diverse adverse environmental conditions, antibiotic treatment, and from the host immune response. Thereby, it may be of great significance that the human defence systems do not face single bacteria but multicellular communities in which the high level of diversity of both phenotypes and genotypes provides insurance for bacterial survival. Indeed, in the last decade, the orthodox view of bacterial populations as being a homogeneous collection of sibling cells has been abandoned, and there is accumulating evidence of bacterial interactiveness within biofilm structures, which is supported by the identification of signalling molecules that mediate cooperative traits and a coordinated behaviour. A detailed understanding of the molecular mechanisms that contribute to multicellular development in bacterial biofilms will be pivotal for the identification of novel targets as the basis for the development of new alternative treatment strategies directed against chronic persistent biofilm infections.