I know the scientists referred to bacteria in confined spaces but I wonder if they have the same motion in open water sources such as lakes or rivers which are just larger confined spaces? Click here or watch the video or read an excerpt below.
In order to understand what was driving that pattern, Lushi developed a computer model that captured two critical parameters that affect how the bacteria move in a densely packed colony. The first parameter involves the collisions that occur as bacteria try to swim in close quarters. The model showed that, as bacteria bang into each other, the collisions tend to orient individuals in the same direction.
As for the bi-directional motion — with the middle swimmers moving in opposite direction from the ones at the edges — that is a function of fluid flow, the research showed.
Bacteria propel by pushing against the tiny fluid corkscrew-like appendages called flagella. That pushing creates a fluid flow moving opposite the direction of the swimming. The bacteria along the edges of the track are closely aligned by the track’s outer surface. They swim at an angle against that outer surface, which causes the backflow they create to be aimed toward the middle of the track. The swimmers in the middle have to fight the currents generated on either side of them. Eventually, the flow becomes more than they can handle.
“Even though they’re trying to go in the same direction as the ones on the boundaries, they’re being carried backward by the fluid,” Lushi said.