Distinct functions for diguanylate cyclases in regulating Pseudomonas aeruginosa PA14 surface-associated behaviors

Biofilm formation is a complex process culminating in a multicellular microbial structure encased in an extracellular matrix. In order for planktonic cells to initiate and proceed through biofilm formation, they must appropriately regulate a number of cellular structures and behaviors including the flagellum and flagellar function, pili and twitching motility, and EPS production.;Studies of biofilm formation in Pseudomonas aeruginosa PA14 have revealed that cyclic-di-GMP (c-di-GMP) is an important intracellular signal impacting this process. We identified two genes, sadC and roeA, both predicted to function in c-di-GMP synthesis, and characterized their contributions to regulation of biofilm formation and other surface associated behaviors.;SadC is an inner-membrane localized diguanylate cyclase (DGC). Deleting the sadC gene results in a biofilm deficient strain. A DeltasadC mutant was also found to be hyper-motile in regards to swarming motility, a type of flagellar motility observed on semi-solid surfaces. Deleting the sadC gene also results in a small defect in production of the Pel polysaccharide, a critical component of the biofilm matrix.;RoeA was also found to participate in regulation of surface-associated behaviors, most notably biofilm formation and production of the exopolysaccharide (EPS) matrix. A DeltaroeA mutant has a defect in biofilm formation and fails to synthesize the Pel EPS. The DeltaroeA mutant also consistently swarms slightly better than the WT strain. Like SadC, the RoeA protein is also a functional DGC that localizes to the inner membrane.