"It appears that a product of cell death can help these swarmer cells sense their environment and determine if this is a good place to settle," said IU Bloomington postdoctoral fellow Ccile Berne, the paper's lead author.
As is often the case in science, the discovery was a result of serendipity.
"We initially noticed that by mixing two crowded cultures of the bacterium, we would get less biofilm formation," Berne said. "This got us thinking about the fact that throughout the living world, high population density stimulates dispersal. We set out to test whether bacteria were producing something that allowed them to switch between these two very different states of bacterial life, staying put in a biofilm or dispersing to colonize new surfaces. We found that eDNA released by dead cells as they lyse, or blow up, was binding directly to the holdfast of the newborn swarmer cells and making it less sticky. It's kind of like having a sticky substance on your fingertip and covering it with dust -- once the holdfast is coated with eDNA, it can't stick to a new surface, so the cell will be more likely to swim away."
The researchers don't know for certain whether the escape behavior of swarmer cells is a result of happenstance -- a happy accident that the holdfasts and eDNA interact -- or whether the interaction represents an active process that has been modified and fine-tuned through natural selection. Irrespective, more cells will die in worse environments, producing more eDNA, and stimulating more dispersal of the swarmer cells.
"Responding to relatives' eDNA makes a lot of sense for a bacterium because the DNA will be almost identical," Brun said. "What may be good for one bacterial species may be bad for another and vice versa. So you would not want to respond to DNA from another species, which has a different sequence than your and your siblings' DNA. What better way to sense whether the environment is ba
|Contact: David Bricker|