Dataset Information

On torque and tumbling in swimming Escherichia coli.

ABSTRACT: Bacteria swim by rotating long thin helical filaments, each driven at its base by a reversible rotary motor. When the motors of peritrichous cells turn counterclockwise (CCW), their filaments form bundles that drive the cells forward. We imaged fluorescently labeled cells of Escherichia coli with a high-speed charge-coupled-device camera (500 frames/s) and measured swimming speeds, rotation rates of cell bodies, and rotation rates of flagellar bundles. Using cells stuck to glass, we studied individual filaments, stopping their rotation by exposing the cells to high-intensity light. From these measurements we calculated approximate values for bundle torque and thrust and body torque and drag, and we estimated the filament stiffness. For both immobilized and swimming cells, the motor torque, as estimated using resistive force theory, was significantly lower than the motor torque reported previously. Also, a bundle of several flagella produced little more torque than a single flagellum produced. Motors driving individual filaments frequently changed directions of rotation. Usually, but not always, this led to a change in the handedness of the filament, which went through a sequence of polymorphic transformations, from normal to semicoiled to curly 1 and then, when the motor again spun CCW, back to normal. Motor reversals were necessary, although not always sufficient, to cause changes in filament chirality. Polymorphic transformations among helices having the same handedness occurred without changes in the sign of the applied torque.

SUBMITTER: Darnton NC

PROVIDER: S-EPMC1855780 | biostudies-literature | 2007 Mar

REPOSITORIES: biostudies-literature

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On torque and tumbling in swimming Escherichia coli.

Darnton Nicholas C NC Turner Linda L Rojevsky Svetlana S Berg Howard C HC

Journal of bacteriology 20061222 5

Bacteria swim by rotating long thin helical filaments, each driven at its base by a reversible rotary motor. When the motors of peritrichous cells turn counterclockwise (CCW), their filaments form bundles that drive the cells forward. We imaged fluorescently labeled cells of Escherichia coli with a high-speed charge-coupled-device camera (500 frames/s) and measured swimming speeds, rotation rates of cell bodies, and rotation rates of flagellar bundles. Using cells stuck to glass, we studied indi ...[more]

PMID: 17189361

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Project description:Bacterial swimming in flow near surfaces is critical to the spread of infection and device colonization. Understanding how material properties affect flagella- and motility-dependent bacteria-surface interactions is a first step in designing new medical devices that mitigate the risk of infection. We report that, on biomaterial coatings such as polyethylene glycol (PEG) hydrogels and end-tethered layers that prevent adhesive bacteria accumulation, the coating mechanics and hydration control the near-surface travel and dynamic surface contact of E. coli cells in gentle shear flow (order 10 s-1). Along relatively stiff (order 1 MPa) PEG hydrogels or end-tethered layers of PEG chains of similar polymer correlation length, run-and-tumble E. coli travel nanometrically close to the coating's surface in the flow direction in distinguishable runs or "engagements" that persist for several seconds, after which cells leave the interface. The duration of these engagements was greater along stiff hydrogels and end-tethered layers compared with softer, more-hydrated hydrogels. Swimming cells that left stiff hydrogels or end-tethered layers proceeded out to distances of a few microns and then returned to engage the surface again and again, while cells engaging the soft hydrogel tended not to return after leaving. As a result of differences in the duration of engagements and tendency to return to stiff hydrogel and end-tethered layers, swimming E. coli experienced 3 times the integrated dynamic surface contact with stiff coatings compared with softer hydrogels. The striking similarity of swimming behaviors near 16-nm-thick end-tethered layers and 100-μm-thick stiff hydrogels argues that only the outermost several nanometers of a highly hydrated coating influence cell travel. The range of material stiffnesses, cell-surface distance during travel, and time scales of travel compared with run-and-tumble time scales suggests the influence of the coating derives from its interactions with flagella and its potential to alter flagellar bundling. Given that restriction of flagellar rotation is known to trigger increased virulence, bacteria influenced by surfaces in one region may become predisposed to form a biofilm downstream.

Dataset Information

On torque and tumbling in swimming Escherichia coli.

Publications

On torque and tumbling in swimming Escherichia coli.

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