title: PilB localization correlates with the direction of twitching motility in the cyanobacterium Synechocystis sp. PCC 6803.
abstract: Twitching motility depends on the adhesion of type IV pili (T4P) to a substrate, with cell movement driven by extension and retraction of the pili. The mechanism of twitching motility, and the events that lead to a reversal of direction, are best understood in rod-shaped bacteria such as Myxococcus xanthus. In M. xanthus, the direction of movement depends on the unipolar localization of the pilus extension and retraction motors PilB and PilT to opposite cell poles. Reversal of direction results from relocalization of PilB and PilT. Some cyanobacteria utilize twitching motility for phototaxis. Here, we examine twitching motility in the cyanobacterium Synechocystis sp. PCC 6803, which has a spherical cell shape without obvious polarity. We use a motile Synechocystis sp. PCC 6803 strain expressing a functional GFP-tagged PilB1 protein to show that PilB1 tends to localize in 'crescents' adjacent to a specific region of the cytoplasmic membrane. Crescents are more prevalent under the low-light conditions that favour phototactic motility, and the direction of motility strongly correlates with the orientation of the crescent. We conclude that the direction of twitching motility in Synechocystis sp. PCC 6803 is controlled by the localization of the T4P apparatus, as it is in M. xanthus. The PilB1 crescents in the spherical cells of Synechocystis can be regarded as being equivalent to the leading pole in the rod-shaped cells.
authors.affiliation: Molecular Genetics, Institute of Biology III, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Nils
authors.initials: N
authors.lastname: Schuergers
authors.affiliation: Department of Life Sciences, Imperial College London, London SW7 2AZ, UK.|School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK.
authors.forename: Dennis J
authors.initials: DJ
authors.lastname: Nürnberg
authors.affiliation: Molecular Genetics, Institute of Biology III, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wallner
authors.affiliation: Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg, 79104 Freiburg, Germany.|School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK.
authors.forename: Conrad W
authors.initials: CW
authors.lastname: Mullineaux
authors.affiliation: Molecular Genetics, Institute of Biology III, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Annegret
authors.initials: A
authors.lastname: Wilde
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002633:Chemotaxis; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D011993:Recombinant Fusion Proteins; D046939:Synechocystis / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D011993:Recombinant Fusion Proteins; D010088:Oxidoreductases; C068255:pilB protein, Bacteria