Regulation of Motility and Phenazine Pigment Production by FliA Is Cyclic-di-GMP Dependent in Pseudomonas aeruginosa PAO1

Abstract

The transcription factor FliA, also called sigma 28, is a major regulator of bacterial flagellar biosynthesis genes. Growing evidence suggest that in addition to motility, FliA is involved in controlling numerous bacterial behaviors, even though the underlying regulatory mechanism remains unclear. By using a transcriptional fusion to gfp that responds to cyclic (c)-di-GMP, this study revealed a higher c-di-GMP concentration in the fliA deletion mutant of Pseudomonas aeruginosa than in its wild-type strain PAO1. A comparative analysis of transcriptome profiles of P. aeruginosa PAO1 and its fliA deletion mutant revealed an altered expression of several c-di-GMP-modulating enzyme-encoding genes in the fliA deletion mutant. Moreover, the downregulation of PA4367 (bifA), a Glu-Ala-Leu motif-containing phosphodiesterase, in the fliA deletion mutant was confirmed using the β-glucuronidase reporter gene assay. FliA also altered pyocyanin and pyorubin production by modulating the c-di-GMP concentration. Complementing the fliA mutant strain with bifA restored the motility defect and pigment overproduction of the fliA mutant. Our results indicate that in addition to regulating flagellar gene transcription, FliA can modulate the c-di-GMP concentration to regulate the swarming motility and phenazine pigment production in P. aeruginosa.

Expression of the phosphodiesterase BifA facilitating swimming motility is partly controlled by FliA inPseudomonas putidaKT2440

“…In line with a recent study in P. aeruginosa PAO1 revealed that FliA modulates the C‐di‐GMP concentration via bifA to regulate motility (Lo et al., ), we also found that FliA acted as a negative regulator to modulate the c‐di‐GMP level via controlling the transcription of bifA to facilitate motility in P. putida KT2440. Together with the former finding in E. coli (Claret et al., ), it seems that modulation of the c‐di‐GMP level by controlling expression of PDE coding genes is a conservative function of FliA and its homologs.…”

“…A recent study in P. aeruginosa PAO1 revealed that the FliA gene modulates the c‐di‐GMP concentration via bifA to regulate motility and phenazine pigment production (Lo et al., ), and suggested that this regulation may be indirect due to the lack of a canonical FliA promoter sequence in the promoter region of bifA . We also tried to compare the upstream regions of bifA in P. putida KT2440 with those in P. aeruginosa PAO1, but no significant similarity was found between the two sequences, and no σ 28 consensus sequence was found in the bifA promoter region of the PAO1 strain (sequences of the two promoter were shown in Data S1).…”

“…A recent study in P. aeruginosa PAO1 revealed that the FliA gene modulates the c-di-GMP concentration via bifA to regulate motility and phenazine pigment production (Lo et al, 2016), and suggested that this regulation may be indirect due to the lack of a canonical FliA promoter sequence in the promoter region of bifA.…”

The Diguanylate Cyclase HsbD Intersects with the HptB Regulatory Cascade to Control Pseudomonas aeruginosa Biofilm and Motility

“…The switch of interaction between either one of these partners depends on the phosphorylation status of HsbA: FlgM when HsbA is dephosphorylated or HsbR if HsbA is phosphorylated. In this model, dephosphorylated HsbA would promote FliA(σ 28 )-dependent transcription of class IV flagellar genes, hence swimming and swarming motilities [51–53]. Phosphorylated HsbA would instead repress swarming motility and intersect with the Gac/Rsm cascade for the control of biofilm formation [17, 20].…”

Involvement of three FliA‐family sigma factors in the sporangium formation, spore dormancy and sporangium dehiscence in Actinoplanes missouriensis

“…In E. coli , FliA modulates the intracellular concentration of cyclic dimeric GMP (c‐di‐GMP) (Claret et al, ). Furthermore, FliA in P. aeruginosa is a global transcriptional regulator controlling multiple gene networks for adherence to and invasion of mammalian cells, interbacterial competition and phenazine pigment production (Lo et al, , ). The comprehensive regulon of FliA was identified in E. coli using chromatin immunoprecipitation followed by the next‐generation sequencing and RNA sequencing (RNA‐Seq) techniques, indicating that the sigma factor directly regulates at least 14 transcriptional units under the tested conditions (Fitzgerald, Bonocora, & Wade, ).…”