Colony-morphology screening uncovers a role for thePseudomonas aeruginosanitrogen-related phosphotransferase system in biofilm formation

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Pseudomonas aeruginosais an opportunistic human pathogen whose survival is aided by forming communities known as biofilms, in which cells are encased in a self-produced matrix. We devised a mutant screen based on colony morphology to identify additional genes with previously unappreciated roles in biofilm formation. Our screen, which identified most known biofilm-related genes, also uncoveredPA14_16550andPA14_69700, deletions of which abrogated and augmented biofilm formation respectively. We also identifiedptsP, which encodes enzyme I of the nitrogen-regulated phosphotransferase (PTSNtr) system, as being important for cyclic-di-GMP production and for biofilm formation. Further experiments showed that biofilm formation is hindered in the absence of phosphotransfer through the PTSNtr, but only in the presence of enzyme II (PtsN), the putative regulatory module of the PTSNtr. These results implicate unphosphorylated PtsN as a negative regulator of biofilm formation and establish one of the first known roles of the PTSNtr inP. aeruginosa.

By using colony morphology as a screen for genes involved in matrix production byPseudomonasaeruginosa, we identified several genes with previously unappreciated roles in biofilm formation. These included the gene for the phosphotransferase protein PtsP, allowing us to deduce that robust biofilm formation requires phosphate flow through the nitrogen-regulated phosphotransferase system.

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