University of Illinois researchers have designed a new system for studying bacterial locomotion. As described in the September issue of Nature Methods, physics professors Yann Chemla and Ido Golding, designed a microfluidic chamber in which the bacteria could swim, and allow the researchers to introduce stimuli - such as chemical attractants - to observe directional changes.

The team installed optical traps using lasers, which confine individual cells to a specific area - but allow the bacteria to roam free within the space - without impeding the rotation or movement of the bacterium's flagella. Essentially they've designed a microscopic treadmill on which the bacteria can 'run'. The addition of fluorescent markers enhance the visualization under a microscope.

The researchers commented that earlier methods of studying the locomotion of bacteria, have only been able to follow the individual cells for about 30 seconds. During that limited time frame, it was nearly impossible to determine what cues are spurring a cell to move in a given direction. They have found that this new method addresses both of these problems without altering the normal behavior of the bacterium.

“Because the cell is immobilized, what we do is change the environment around it,” Chemla said. “We can set up a flow cell that has two different concentrations of some chemical, for example, and see how the bacterium responds. Technically we’re moving the swimming pool relative to the swimmer,” he said.

For more information: http://news.illinois.edu/news/09/1005bacteria.html