Expression of the Pho regulon negatively regulates biofilm formation by Pseudomonas aureofaciens PA147-2

Monds, RD Silby, MW Mahanty, HK

Rd. Monds et al., Expression of the Pho regulon negatively regulates biofilm formation by Pseudomonas aureofaciens PA147-2, MOL MICROB, 42(2), 2001, pp. 415-426

39

INGLESE

Article

Microbiology

MOLECULAR MICROBIOLOGY

0950-382X → ACNP

42

2

2001

415 - 426

ISI

0950-382X(200110)42:2<415:EOTPRN>2.0.ZU;2-R

We report the isolation of insertional mutations to the pstC and pstA genes of the phosphate-specific transport (pst) operon that results in loss of b iofilm formation by Pseudomonas aureofaciens PA147-2. Consistent with the k nown roles of the Pst system in Escherichia coli and Pseudomonas aeruginosa , both P. aureofaciens pst mutants were demonstrated to have defects in ino rganic phosphate (P-i) transport and repression of Pho regulon expression. Subsequently, biofilm formation by the wild type was shown to require a thr eshold concentration of extracellular P-i. The two-component regulatory pai r PhoR/PhoB is responsible for upregulation of Pho regulon expression in re sponse to P-i-limiting environments. By generating phoR mutants that were u nable to express the Pho regulon, we were able to restore biofilm formation by A aureofaciens in P-i-limiting conditions. This result suggests that ge ne(s) within the Pho regulon act to regulate biofilm formation negatively i n low-P-i environments, and that phoR mutations uncouple PA147-2 from such regulatory constraints. Furthermore, the inability of psi mutants to repres s Pho regulon expression accounts for their inability to form biofilms in n on-limiting P-i environments. Preliminary evidence suggests that the st sys tem is also required for antifungal activity by PA147-2. During phenotypic analysis of pst mutants, we also uncovered novelties in relation to P-i ass imilation and Pho regulon control in P. aureofaciens.