Actin adhesion controls bacterial movement

Actin comet tails propel bacteria through their host cells. Now, Frederick Soo (University of Washington, Seattle, WA) and Julie Theriot (Stanford University, Stanford, CA) suggest that a bug's speed is determined by adhesion between actin and bacterium, not rates of actin polymerization.

The twist was revealed when Soo measured the temperature dependency of Listeria movement and thereby measured the apparent activation energy (E_a) of the rate-limiting step. He noticed that each bacterium had a different E_a. This finding is not predicted by simple polymerization-based models of Listeria movement, which assume that the rate-limiting factor (such as actin concentration) is the same for every bacterium.

Knowing the E_a range for a given population, the authors then predicted the range of speeds for that group at a given...