title: Cyclic di-GMP-mediated repression of swarming motility by Pseudomonas aeruginosa PA14 requires the MotAB stator.
abstract: The second messenger cyclic diguanylate (c-di-GMP) plays a critical role in the regulation of motility. In Pseudomonas aeruginosa PA14, c-di-GMP inversely controls biofilm formation and surface swarming motility, with high levels of this dinucleotide signal stimulating biofilm formation and repressing swarming. P. aeruginosa encodes two stator complexes, MotAB and MotCD, that participate in the function of its single polar flagellum. Here we show that the repression of swarming motility requires a functional MotAB stator complex. Mutating the motAB genes restores swarming motility to a strain with artificially elevated levels of c-di-GMP as well as stimulates swarming in the wild-type strain, while overexpression of MotA from a plasmid represses swarming motility. Using point mutations in MotA and the FliG rotor protein of the motor supports the conclusion that MotA-FliG interactions are critical for c-di-GMP-mediated swarming inhibition. Finally, we show that high c-di-GMP levels affect the localization of a green fluorescent protein (GFP)-MotD fusion, indicating a mechanism whereby this second messenger has an impact on MotCD function. We propose that when c-di-GMP level is high, the MotAB stator can displace MotCD from the motor, thereby affecting motor function. Our data suggest a newly identified means of c-di-GMP-mediated control of surface motility, perhaps conserved among Pseudomonas, Xanthomonas, and other organisms that encode two stator systems.
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Kuchma
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford, United Kingdom.
authors.forename: N J
authors.initials: NJ
authors.lastname: Delalez
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Filkins
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: E A
authors.initials: EA
authors.lastname: Snavely
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford, United Kingdom.
authors.forename: J P
authors.initials: JP
authors.lastname: Armitage
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA georgeo@dartmouth.edu.
authors.forename: G A
authors.initials: GA
authors.lastname: O'Toole
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism; D017353:Gene Deletion; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D008124:Locomotion; D017354:Point Mutation; D011550:Pseudomonas aeruginosa / Q000378:metabolism / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; C063010:MotA protein, Bacteria; C064779:MotB protein, Bacteria; C062025:bis(3',5')-cyclic diguanylic acid; D006152:Cyclic GMP