Biofilm Formation in Pseudomonas aeruginosa : Fimbrial cup Gene Clusters Are Controlled by the Transcriptional Regulator MvaT

Abstract

Pseudomonas aeruginosa is an opportunistic bacterial pathogen which poses a major threat to long-termhospitalized patients and individuals with cystic fibrosis. The capacity of P. aeruginosa to form biofilms is an important requirement for chronic colonization of human tissues and for persistence in implanted medical devices. Various stages of biofilm formation by this organism are mediated by extracellular appendages, such as type IV pili and flagella. Recently, we identified three P. aeruginosa gene clusters that were termed cup (chaperone-usher pathway) based on their sequence relatedness to the chaperone-usher fimbrial assembly pathway in other bacteria. The cupA gene cluster, but not the cupB or cupC cluster, is required for biofilm formation on abiotic surfaces. In this study, we identified a gene (mvaT) encoding a negative regulator of cupA expression. Such regulatory control was confirmed by several approaches, including lacZ transcriptional fusions, Northern blotting, and transcriptional profiling using DNA microarrays. MvaT also represses the expression of the cupB and cupC genes, although the extent of the regulatory effect is not as pronounced as with cupA. Consistent with this finding, mvaT mutants exhibit enhanced biofilm formation. Although the P. aeruginosa genome contains a highly homologous gene, mvaU, the repression of cupA genes is MvaT specific. Thus, MvaT appears to be an important regulatory component within a complex network that controls biofilm formation and maturation in P. aeruginosa.

Influence of the regulatory protein RsmA on cellular functions in Pseudomonas aeruginosa PAO1, as revealed by transcriptome analysis

“…Another candidate target of direct RsmA control is the regulatory protein MvaT. Recently, MvaT has been shown to be a negative regulator of the transcription of cupA genes and, to a lesser extent, of cupB and cupC expression (Vallet et al, 2004). Expression of cupA2 and cupC3 was decreased in the rsmA mutant compared to PAO1 wild-type.…”

Sticky Situations: Key Components That Control Bacterial Surface Attachment

“…In addition to controlling the adhesiveness of P. aeruginosa upon surface contact, WspR is also linked to regulation of the chaperone usher pathway (cup) genes that encode putative fimbrial adhesins. These genes have been demonstrated to be required for biofilm formation in P. aeruginosa (158,159) and to be inversely controlled by the EAL-containing PvrR response regulator (106). Mutations in a gene called wspF, part of the Wsp chemosensory signal-transduction operon, have been shown to result in cell aggregation and altered colony morphology, a phenotype which correlated with increased cellular levels of c-di-GMP and increased biofilm formation.…”

Global Regulatory Pathways and Cross-talk ControlPseudomonas aeruginosaEnvironmental Lifestyle and Virulence Phenotype

“…Multiple cup gene clusters are present in various strains of Pseudomonas, and in the PAO1 genome three (cupA, cupB, and cupC) have been identified (Vallet, 2001). A cupA gene cluster mutant is defective in attachment to solid surfaces (Vallet, 2004).…”

“…Mutation of the mvaT gene results in premature and elevated expression of quorumregulated genes, demonstrating that MvaT is involved in controlling the magnitude and timing of QS-dependent gene expression (Diggle, 2002). MvaT is a member of the histone-like nucleoid structuring (H-NS) protein family, involved in transcriptional silencing (Vallet, 2004). MvaT and its homolog MvaU bind specific sequences in AT-rich DNA and oligomerize to form extended protein-DNA complexes that prevent transcription (Castang, 2008).…”