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I've wondered how micro-organisms perceive the larger world, it's forces and the consequences the relatively massive forces have on such tiny objects.

Let's say E coli (0.5 micro meters width, 2 micro-meters length) in a pure stream of water, moving with an acceleration of 2 m/s^2.

I've used a micro-organism in this question solely to validate perception. From a biological viewpoint, the microbe may not percieve the forces, nevertheless, what are the effects on the body.

I'm interested in the effects on a small scale on any micro-object.

George Elov
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  • That's a very broad question, so it's likely to get closed, unless you can narrow it down to something very specific. But (for example) at the scale of micro-organisms, water seems a lot more viscous than it does at our scale. – PM 2Ring Apr 03 '19 at 17:45
  • You may wish to search for descriptions of shear-induced damage of biological cells. Cells can't be quickly brought through very small apertures because they'd be lysed (torn apart) by the differential pressure. Sonication has the same effort (and is commonly used to lyse cells deliberately). – Chemomechanics Apr 03 '19 at 21:08

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As pointed out by PM 2Ring, as animals get smaller, the effects of the viscosity of the water become greater. A human pushes his or her way through the water; a goldfish wiggles their way through the water, and an animal the size of a water flea (1/10th of an inch, or less) crawls through the water as if it were pancake syrup (to us). A big paramecium (1/100th of an inch or less) engages the water with its cilia and drags itself through it.

To a bacterium, water becomes a matrix in which it is embedded and although there are bacteria with single whip-like cilia for propulsion, their mobility is limited. When the water/matrix is accelerated, they are carried along with it unless the force causing the acceleration is (by our standards) really big- hundreds to thousands of G's. In this case, they sink through the water in the opposite direction of the G force and can also get sheared open and destroyed when the force varies strongly with position on a scale length of order ~several bacterium lengths or less.

niels nielsen
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