We show that is a vibroid-shaped gram-negative bacterium found in coastal
We show that is a vibroid-shaped gram-negative bacterium found in coastal and brackish oceans, and is the causative agent of the diarrheal disease cholera (see Fig. colours. The scale … The model organism reversibly attach to surfaces in a vertical orientation9 and move along random trajectories with type IV pili (TFP) driven walking motility in the early stages of biofilm formation.13 These cells can progress to an irreversibly attached state where the cell axis is oriented parallel to the surface. Such horizontal cells can move by TFP-driven crawling or twitching motility, which has much more directional persistence. Recent AS 602801 work has shown that PAO1 cells interact with a network of Psl polysaccharides secreted onto the surface that allows them to self-organise in a manner reminiscent of rich-get-richer economies, ultimately producing in the formation of microcolonies. 14 also use TFP to engage nonnutritive, abiotic surfaces. Despite having three different types of TFP, mannose-sensitive hemagglutinin (MSHA) pili, virulence-associated toxin co-regulated pili (TCP), and chitin-regulated pili (ChiRP), do not appear to have a twitching surface motility mode9,15 and it is usually unclear how they form microcolonies. Although lack a twitching mode, it is usually known that MSHA pili and flagella play important functions in biofilm development; MSHA pili (use their polar flagellum and MSHA pili synergistically to scan a surface mechanically before irreversible attachment and micro-colony formation. Flagellum rotation causes the cell body to AS 602801 counter-rotate along its major axis, which in theory allows MSHA appendages to have periodic mechanical contact with the surface for surface skimming cells. AS 602801 We apply cell-tracking algorithms to high-speed movies of taken at 5 ms resolution to reconstruct the motility history of every cell that comes within 1 m of the surface in a 160 m x 120 m field of view, and observe two distinct near-surface motility modes: roaming motility, which is usually characterised by long persistence length trajectories, and orbiting motility, which is usually characterised by near-circular trajectories with well-defined radii. In both motility modes cells move in an oblique direction that deviates strongly from the major cell axis and have strong nutations along the trajectory. These motility behaviours are ablated in and mutants. We develop a hydrodynamic model to show that the bifurcation into these two surface motility phenotypes is usually a consequence of the highly nonlinear dependence of trajectory shape on frictional causes between MSHA pili and the surface: cells naturally loiter over regions that interact more strongly with MSHA pili, due to orbiting motility. This simple theoretical description agrees amazingly well with the observed trajectories, including the distribution of velocities, and the direction of motion comparative to the major axis of the cells. Oddly enough, cells that eventually attach exhibit a distribution of intermittent pauses during the preceding orbiting motility. Both the frequency and duration of these pauses are strongly suppressed when cells are incubated with a non-metabolisable mannose derivative to saturate MSHA pili binding. Moreover, the sites of irreversible attachment correlate with the positions of eventual microcolonies, which indicates that purely TFP driven motility plays a minor role in determining positions of microcolonies, unlike the case for and monotrichous have been observed to swim in clockwise circular patterns near surfaces.15,18,20,24,26 Hydrodynamic models show that a torque on the cell body is induced by viscous drag forces felt by the flagellum as it sweeps past a surface; this surface-induced torque deflects the swimming direction of cells into curved clockwise paths.20 are among the fastest bacterial swimmers. They are equipped with a Na+ motor that enables them to swim at speeds up to 100 m h?1.27 We record bright-field movies using a high-speed camera and use cell tracking algorithms28 (on glass at different occasions after inoculation. The trajectories of the centroids of all WT cells tracked in this period are shown in Fig. 1a. Tracking all cells in the field of view reveals many cells that appear AS 602801 to travel in tight orbital paths. A large number of mobile bacteria visit the surface, but relatively few attach irreversibly during this initial period. A binary image of the stationary cells taken during the same period and location is usually shown Fig. 1b. To extract the orbital motion evident in the WT ensemble (see Fig. 1a), we limit our search to mobile cells, defined as cells that travel a minimum distance of at least one cell length, that are visible for at least 1 s, and have a mean-squared displacement (MSD) slope 1 (is usually the number of points in the track, is usually the position vector of the point AS 602801 on the trajectory, and is usually the centre of Rabbit Polyclonal to NCAPG mass of all points. For a perfect circle of radius, = 255, 149, and 352). We search for S-shaped trajectories among the roaming cells, which is usually a signature.