This mode of movement occurs when bundles of flagella moving counterclockwise become unbundled as some of the flagella switch rotational direction. For 10 points each:
[10m] Name this mode of movement exhibited by peritrichous (“pair-ih-TRICK-us”) bacteria like Listeria monocytogenes and E. coli. During chemotaxis, bacteria suppress this kind of motility in favor of directed runs along concentration gradients.
ANSWER: tumbling [or tumbling motility; or word forms of tumble; accept run-and-tumble motion; accept twiddling motion or word forms of twiddle]
[10h] The concentration of this protein’s phosphorylated form controls the direction of flagellar motion. The histidine kinase CheA (“kee-A”) phosphorylates this protein, which binds FliM to stabilize counterclockwise motion and induce tumbling.
ANSWER: CheY (“kee-Y”) [accept CheY-P]
[10e] Run-and-tumble motion can be modeled as a three-dimensional one of these phenomena biased by the direction of flagellar motion. Diffusion without a chemical gradient is also modeled as this kind of process.
ANSWER: random walk [prompt on random processes or stochastic processes; prompt on walks; prompt on Brownian motion or Wiener processes]
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