How do bacteria swim? Brown physicis...(ys more important the smaller the object...)

The researchers also discovered another clue to the swimming behavior: Caulobacter's swimming circles grew tighter as the bacterium got closer to a surface boundary, in this case a glass slide. The tighter circle, the team found, is the result of more drag being exerted on the microbe as it swims closer to the surface. When the microbe was farther away from the surface, it encountered less drag, and its swimming circle was wider, the group learned.

It's this zigzagging effect that helps explain why "most of the time, these cells are not as close to the surface as they are predicted to be," Tang said. "The reason is Brownian motion, because they are jumping around."

That finding is important, because it helps explain the feedings areas for simple-celled organisms. Perhaps more importantly, it may help scientists understand how bacteria ultimately arrive at a surface and adhere to it. The applications range from better understanding the flow and adhesion of platelets in the bloodstream to greater insights into how contaminants are captured as they percolate through the soil.

"As it turns out, swimming is an important mechanism to that adhesion process," Tang said.

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