Molecular mechanism of swimming speed control in bacteria

• Applicant: Dr. Alexander Böhm (†)
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms
• Term: from 2011 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 206878416

Bacteria like Escherichia coli swim with the help of flagella that can rotate both clockwise and counterclockwise. Rotation is powered by proton influx through membrane spanning motor proteins. By controlling rotation reversals in response to alterations of the chemical composition in their environment bacteria can perform chemotaxis. Recently it has been discovered that in addition E. coli can also modulate its swimming speed in response to external cues. This is mediated by the second messenger cyclic dimeric GMP (c-di-GMP) and the YcgR protein, which upon binding of c-di-GMP interacts with MotA and FliG in the flagellar motor and functions as a brake. It has been suggested that c-di-GMP and YcgR in addition to controlling swimming velocity also influence chemotaxis. This hypothesis will be tested here by studying the behavior of freely swimming bacteria. In addition molecular and physiological aspects of c-di-GMP mediated motor speed control will be studied: The exact interaction surface between YcgR and MotA/FliG will be mapped and mechanistic consequences of YcgR binding to the motor will be assessed. To determine how common swimming velocity control is in the bacterial kingdom it will be tested with simple proof-of-principle experiments whether swimming speed control occurs in additional bacterial species. These experiments are expected to unravel important molecular and physiological aspects of paradigms for bacterial signal transduction and biological nano-machines.

• DFG Programme: Research Grants