Biofilms as Refuge against Predation

Bacterial growth and survival in the environment as well as in association with human hosts are constrained by the action of phagocytic eukaryotic cells. Phagocytic predation on bacteria by host immune cells shares a number of cellular mechanisms with free-living protozoa. In and outside the human host, bacteria growing in biofilms appear to be less vulnerable to phagocytic predators than planktonic cells. Widespread resistance against predators is mediated by the interplay of biofilm-specific traits such as substratum adherence, exopolymer production, cellular cooperation, inhibitor secretion, and phenotypic variation. Selective predation is suggested to promote bacterial life in the biofilm niche and to govern structure-function relationships. There is increasing evidence that some of the pathogenicity traits may have their origin specifically in successful antipredator adaptations. Parallel selective pressures in and outside the human host may result in cross-adaptations of bacterial pathogens.