title: Extragenic suppressor mutations that restore twitching motility to fimL mutants of Pseudomonas aeruginosa are associated with elevated intracellular cyclic AMP levels.
abstract: Cyclic AMP (cAMP) is a signaling molecule that is involved in the regulation of multiple virulence systems of the opportunistic pathogen Pseudomonas aeruginosa. The intracellular concentration of cAMP in P. aeruginosa cells is tightly controlled at the levels of cAMP synthesis and degradation through regulation of the activity and/or expression of the adenylate cyclases CyaA and CyaB or the cAMP phosphodiesterase CpdA. Interestingly, mutants of fimL, which usually demonstrate defective twitching motility, frequently revert to a wild-type twitching-motility phenotype presumably via the acquisition of an extragenic suppressor mutation(s). In this study, we have characterized five independent fimL twitching-motility revertants and have determined that all have increased intracellular cAMP levels compared with the parent fimL mutant. Whole-genome sequencing revealed that only one of these fimL revertants has acquired a loss-of-function mutation in cpdA that accounts for the elevated levels of intracellular cAMP. As mutation of cpdA did not account for the restoration of twitching motility observed in the other four fimL revertants, these observations suggest that there is at least another, as yet unidentified, site of extragenic suppressor mutation that can cause phenotypic reversion in fimL mutants and modulation of intracellular cAMP levels of P. aeruginosa.
authors.affiliation: The ithree institute, University of Technology Sydney, Sydney, New South Wales, 2007, Australia.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Nolan
authors.forename: Scott A
authors.initials: SA
authors.lastname: Beatson
authors.forename: Larry
authors.initials: L
authors.lastname: Croft
authors.forename: Peter M
authors.initials: PM
authors.lastname: Jones
authors.forename: Anthony M
authors.initials: AM
authors.lastname: George
authors.forename: John S
authors.initials: JS
authors.lastname: Mattick
authors.forename: Lynne
authors.initials: L
authors.lastname: Turnbull
authors.forename: Cynthia B
authors.initials: CB
authors.lastname: Whitchurch
mesh_terms: D000595:Amino Acid Sequence; D000242:Cyclic AMP / Q000502:physiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D036781:Fimbriae Proteins / Q000235:genetics / Q000502:physiology*; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000502:physiology*; D016680:Genome, Bacterial; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013489:Suppression, Genetic
chemical_list: D004269:DNA, Bacterial; D036781:Fimbriae Proteins; D000242:Cyclic AMP