Phenazines and Bacterial Biofilms

Most bacteria in the environment exist in biofilms—structured, surface-attached multicellular communities that are enmeshed in a self-produced polysaccharide matrix. Biofilms allow bacteria to participate is social interactions, survive under harsh conditions and successfully resist antimicrobials, invasion by competitors, predation, and destruction by components of the immune system. Fluorescent Pseudomonas spp. are prolific biofilm formers and some members of the genus have become model organisms for the study of biofilm biology. Several economically important groups of pseudomonads produce phenazines, pigmented, redox-active metabolites that have long been recognized for their broad-spectrum antibiotic activity. The current chapter focuses on the emerging close link between phenazine production and biofilm formation in Pseudomonas spp., and on the important role of phenazines in biofilms associated with human infectious diseases and highly competitive environmental niches such as soil and the plant rhizosphere