Bacteria go for a spin

Researchers may have found the mechanism powering a mysterious gliding motion in bacteria.

Bacterial locomotion often relies on appendages. Filamentous structures called flagella propel some microbes, while others glide using pili, extensions that a microbe shoots out from its leading end and then retracts to pull itself forward.

But another form of gliding, first described nearly 3 decades ago, doesn’t involve appendages. To search for the motor, David R. Zusman of the University of California, Berkeley and his colleagues fused a fluorescent protein to a microbial protein known to be necessary for this type of gliding in the rod-shaped bacterium Myxococcus xanthus.

The researchers found that the fluorescent spot remained stationary while the microbe cruised forward. They suspect that the labeled protein is part of an internal protein complex that enables it to push off from the surface. Meanwhile, another protein within this complex appears to track along a helical structure inside the microbe, propelling it forward in a corkscrew motion. The complex forms at the leading edge of the microbe and then disassembles as it moves past it, while a new complex forms farther ahead. The team describes the mechanism in the Feb. 9 Science.

Zusman’s group is now investigating the internal helical structure and determining the proteins within the complex. “Once you know what makes cells move, then you can look for chemicals that can interfere with the movement,” Zusman says. That might be helpful because a microbe’s mobility plays a role in its virulence, he says.