Differential Activation of
            <i>Escherichia coli</i>
            Chemoreceptors by Blue-Light Stimuli

Wright, S. Joseph; Walia, Bharat; Parkinson, John S.; Khan, Shahid

doi:10.1128/jb.00149-06

Cited by 29 publications

(40 citation statements)

References 53 publications

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“…Images were acquired for 1 s. After a few initial frames of phase-contrast illumination, the laser was switched on, guaranteeing that the start of high-intensity exposure was known. This procedure was used to minimize laser damage to cells during image acquisition, since intense light, especially at short wavelengths, is known to interfere with motor function (32). In order to image stationary filaments on stuck bacteria, cells were exposed to continuous laser illumination; filaments stopped rotating within a few seconds.…”

mentioning

confidence: 99%

On Torque and Tumbling in Swimming Escherichia coli

Darnton¹,

Turner²,

Rojevsky³

et al. 2007

J Bacteriol

413

410

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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-coupleddevice 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.The peritrichous bacterium Escherichia coli executes a random walk: an alternating sequence of runs (relatively long intervals during which the cell swims smoothly) and tumbles (relatively short intervals during which the cell changes course) (8). A cell is propelled by several helical flagellar filaments, each attached by a hook (a universal joint) to a reversible rotary motor (7). During runs, the filaments coalesce into a bundle that pushes the cell forward (24). When viewed from behind the cell, the bundle rotates counterclockwise (CCW), and, to balance the torque, the cell body rotates clockwise (CW). Tumbles are initiated by CW motor rotation (21). Based on studies of Salmonella using dark-field microscopy, it was thought that the motors change direction synchronously, causing the bundle to fly apart (24,25). Based on studies using fluorescence microscopy, it became apparent that different filaments can change directions at different times and that a tumble can result from a change in direction of as few as one filament (30). During a tumble, the reversed filament comes out of the bundle and transforms from normal (a left-handed helix with a pitch of 2.3 m and a diameter of 0.4 m) to semicoiled (a right-handed helix with half the normal pitch but normal amplitude) and then to curly 1 (a right-handed helix with half the normal pitch and half the normal amplitude). The change in direction of the cell's track generated by the tumble occurs during the transformation from normal to semi...

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mentioning

confidence: 99%

On Torque and Tumbling in Swimming Escherichia coli

Darnton¹,

Turner²,

Rojevsky³

et al. 2007

J Bacteriol

413

410

View full text Add to dashboard Cite

show abstract

“…Cultures for behavioral experiments were harvested at mid-exponential phase by centrifugation, washed three times, and re-suspended in a potassium phosphate-EDTA motility buffer containing 5 mM lactate, as respiratory substrate, and 100 M methionine to maintain vigorous swim-tumble bias. The sequences were imaged by a CCD camera mounted on a Nikon Optiphot microscope using a phase contrast objective (40x CF Fluor plan-apochromat, 0.85 numerical aperture) and zoom lens [17]. Due to variations in shutter time, light exposure, filtering and cell culture, the data sets vary among themselves in contrast, intensity and apparent proximity.…”

Section: Resultsmentioning

confidence: 99%

Automatic Tracking of Escherichia Coli Bacteria

Xie¹,

Khan

Shah

2008

Medical Image Computing and Computer-Assisted Intervention – MICCAI 2008

Self Cite

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Abstract. In this paper, we present an automatic method for estimating the trajectories of Escherichia coli bacteria from in vivo phase-contrast microscopy videos. To address the low-contrast boundaries in cellular images, an adaptive kernel-based technique is applied to detect cells in sequence of frames. Then a novel matching gain measure is introduced to cope with the challenges such as dramatic changes of cells' appearance and serious overlapping and occlusion. For multiple cell tracking, an optimal matching strategy is proposed to improve the handling of cell collision and broken trajectories. The results of successful tracking of Escherichia coli from various phase-contrast sequences are reported and compared with manually-determined trajectories, as well as those obtained from existing tracking methods. The stability of the algorithm with different parameter values is also analyzed and discussed.

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“…Our system consisted of a He-Ne continuous wave laser, which provides a bacteria safe 633 nm wavelength light source. According to Wright et al 28 and Taylor et al, 29 blue light influences the motility of bacteria because of the perturbation of electron transport in the body. Thus, the use of lower wavelength, high intensity light sources, e.g., 390-530 nm, leads to slow swimming.…”

Section: Data Acquisition and Analysismentioning

confidence: 99%

Hydrodynamics of a self-actuated bacterial carpet using microscale particle image velocimetry

et al. 2015

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Microorganisms can effectively generate propulsive force at the microscale where viscous forces overwhelmingly dominate inertia forces; bacteria achieve this task through flagellar motion. When swarming bacteria, cultured on agar plates, are blotted onto the surface of a microfabricated structure, a monolayer of bacteria forms what is termed a "bacterial carpet," which generates strong flows due to the combined motion of their freely rotating flagella. Furthermore, when the bacterial carpet coated microstructure is released into a low Reynolds number fluidic environment, the propulsive force of the bacterial carpet is able to give the microstructure motility. In our previous investigations, we demonstrated motion control of these bacteria powered microbiorobots (MBRs). Without any external stimuli, MBRs display natural rotational and translational movements on their own; this MBR self-actuation is due to the coordination of flagella. Here, we investigate the flow fields generated by bacterial carpets, and compare this flow to the flow fields observed in the bulk fluid at a series of locations above the bacterial carpet. Using microscale particle image velocimetry, we characterize the flow fields generated from the bacterial carpets of MBRs in an effort to understand their propulsive flow, as well as the resulting pattern of flagella driven self-actuated motion. Comparing the velocities between the bacterial carpets on fixed and untethered MBRs, it was found that flow velocities near the surface of the microstructure were strongest, and at distances far above, the surface flow velocities were much smaller.

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Differential Activation of Escherichia coli Chemoreceptors by Blue-Light Stimuli

Cited by 29 publications

References 53 publications

On Torque and Tumbling in Swimming Escherichia coli

On Torque and Tumbling in Swimming Escherichia coli

Automatic Tracking of Escherichia Coli Bacteria

Hydrodynamics of a self-actuated bacterial carpet using microscale particle image velocimetry

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