Key two‐component regulatory systems that control biofilm formation in Pseudomonas aeruginosa

Abstract

SummaryBiofilm formation in P. aeruginosa is a highly regulated process that proceeds through a number of distinct stages. This development is controlled by a wide range of factors, of which two-component systems (TCSs) play a key role. In this review, we focus on some of the TCSs that regulate the switch from a motile to a sessile bacterial lifestyle, either via the production of extracellular appendages or by the production of exopolysaccharides. Extracellular appendages, such as flagella, type IV pili and Cup fimbriae are often involved in the initial attachment of bacteria to a surface. In P. aeruginosa, many of these surface structures are regulated by TCSs, and some systems regulate more than one type of appendage. Furthermore, the production of exopolysaccharides, such as Pel and Psl, is required for P. aeruginosa biofilm formation. The regulation of Pel and Psl is posttranscriptionally repressed by RsmA, the activity of which is controlled by a complex regulatory system involving several sensor kinases and accessory components. Furthermore, the Rsm system is a major control system that inversely regulates factors involved in motility and acute infection on one hand, and factors involved in biofilm formation and chronic infection on the other hand. Finally, a series of TCSs has recently been discovered that regulates biofilm development in a stage-specific manner. Taken together, these complex regulatory networks allow the bacterium to respond appropriately to diverse environmental stimuli, and increased knowledge of their mechanisms and signals could be of great importance in the design of novel antibacterial strategies.

Genetic and phenotypic analysis of the GacS/GacA system in the moderate halophile Halomonas anticariensis

“…Importantly, biofilm formation was reduced in the H. anticariensis Gac mutants compared with the wild-type, which provides evidence that these two traits are correlated in this bacterium as they are in other micro-organisms. Lately, it has been reported that in Pseudomonas aeruginosa extracellular polymeric substances play a distinct key role during biofilm formation (Yang et al, 2011) and this development is controlled by TCSs among other elements such us QS, c-di-GMP and sigma factors (Mikkelsen et al, 2011). Since biofilm formation is a complex process controlled by multiple factors, the TCS might indirectly affect it by contributing to the regulation of some key genes, all of which requires further study.…”

Sticky Situations: Key Components That Control Bacterial Surface Attachment

“…Considering that the multicomponent Csr and Gac/Rsm systems inversely control attachment (and polysaccharide production and adhesiveness) and virulence, it has been suggested that they act as a genetic switch that reciprocally regulates free-swimming and surface-attached lifestyles as well as acute and chronic infections (6,107,135). Unfortunately, the signals perceived by the Gac/Rsm system or SagS are not known.…”

Division of Labor in Biofilms: the Ecology of Cell Differentiation

“…aeruginosa is an opportunistic pathogen with a broad host range and, like B. subtilis and M. xanthus, a common inhabitant of the soil (176). Biofilm formation in P. aeruginosa is typically studied in flow chambers.…”

“…To understand their development, many studies have examined biofilms composed of two different strains (176,(178)(179)(180)(181)(182)(183)(184). Like in the case of M. xanthus, multiple predefined mutants were mixed to examine how these mixtures affect microcolony development.…”