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I was wondering what actually happens during the tumbling process of a "run and tumble" process. When the bacteria stops to tumble and reorient itself, is that an active process, or is the reorientation due to thermal rotationnal diffusion?

Cheers,

Nico

user30584
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  • That is a biological question – Henry Oct 04 '13 at 23:06
  • Also "a bacteria" and "the bacteria stops" make no sense since "bacteria" is plural. – Olin Lathrop Oct 04 '13 at 23:38
  • @OlinLathrop: Please substitute bacterium for bacteria throughout OP's question then. – Pieter Geerkens Oct 05 '13 at 03:34
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    @PieterGeerkens What? Don't you know that Harvard plays its football games at a diverse range of "stadia" (according to Tom Lehrer in "Fight Fiercely Harvard!") :)! I myself prefer bacteriums if they must visit me, but preferably none at all (aside from the ones we need on our skin and in our gut). – Selene Routley Oct 05 '13 at 04:25
  • @Pieter: No, that is something the OP should do. I don't want people to learn that being sloppy is OK since other people will fix it for you. – Olin Lathrop Oct 05 '13 at 14:45
  • Would http://biology.stackexchange.com/ be a better home for this question? – Qmechanic Oct 05 '13 at 15:31
  • @OlinLathrop: You missed my sarcasm - such an edit would often be rejected as too minor, and your comment was a tad pedantic also. – Pieter Geerkens Oct 05 '13 at 15:32
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    This question appears to be off-topic because it is about biology – Jim Oct 10 '13 at 13:31

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In all phases of matter there exists energy carried by the individual particles that gives bulk behavior and average quantities like average kinetic energy and temperature which depends on it.

Your question is very general and I will answer for the phase of matter called gas. There the kinetic energy of the individual gas molecules is random and can be seen in what is called Brownian motion of dust particles.

enter image description here

This is a simulation of the Brownian motion of a big particle (dust particle) that collides with a large set of smaller particles (molecules of a gas) which move with different velocities in different random directions.

A dust particle is inactive, i.e. cannot convert internal energy to motion and affect its course. It follows a random path forever. A bacterium is alive, has internal energy it can convert to motion and could overcome the random bufferings of the air molecules and give a direction to its course or stay at rest with respect to gravity. It is an active choice of the bacterium.

anna v
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  • "Your question is very general"---I don't think his question was general. I think it was about bacteria. – Brian Moths Oct 05 '13 at 03:10
  • @NowIGetToLearnWhatAHeadIs it does not specify in what medium. air? blood? bones? – anna v Oct 05 '13 at 03:12
  • @NowIGetToLearnWhatAHeadIs and moreover the Brownian motion idea is also very general and must be applicable to bacteriums in at least some way. Laboratory realisations of a Maxwell Daemon actually use pollen and bacterium sized particles buffeted in this way rather than build a Maxwell Daemon that works with molecules themselves (the measurement and logic circuits would be overwhelmed otherwise by the high speeds). What a thoroughly awesome applet, Anna! – Selene Routley Oct 05 '13 at 04:27