Personality and mood swings in bacteria
Bacteria can control where they go using a signaling network of protein molecules. Scientists at AMOLF have developed a microscopy method that allows them to see how individual bacteria use this network to make decisions. They discovered that bacteria are surprisingly diverse in personality and mood. The team published its findings in the scientific journal eLife on December 12, 2017.
Bacteria, being single-celled organisms, do not have a nervous system, but are able to control their movements using a network of protein molecules that interact in a special way, much like the nerve cell circuits in our brain. “For example E.coli, a harmless bacterium that lives in our gut, ‘knows’ how to interrupt its otherwise straight swimming motion by occasional tumbles that sets it off in a new, random direction,” says Tom Shimizu, group leader of AMOLF’s Systems Biology group. “E.coli uses sensor proteins to detect things like food molecules or toxic chemicals to decide whether life is getting better or worse as it swims, and controls how often it tumbles to make sure it ends up in a good place.”
Zooming in on single cells
For many years, researchers have studied how these molecular circuits in bacteria like E.coli respond to changes in their surroundings, but this relied on experiments where the signal had to be averaged over hundreds of cells. Johannes Keegstra, a PhD student in the group of Shimizu, led the effort to develop a microscopy method that enables researchers to see how the protein network in each individual bacterium responds to changes in the environment, for example, the abundance of food.
The bacteria used in the experiments had exactly the same DNA sequence (like identical twins) and were also grown under identical conditions. Nevertheless, the researchers discovered that the protein network in each of them behaves differently in the same chemical environment. “Each bacterium seems to have its own personality,” Keegstra says. “For example, we found that the chemical concentration to which bacteria respond, varies considerably between bacteria.”