Phosphatidylethanolamine acts as a chemoattractant for the gliding bacterium Myxococcus xanthus

Myxococcus xanthus is a soil bacterium that glides over solid surfaces by an unknown mechanism of motility. In an attempt to identify chemoeffectors for gliding motility, it was discovered that M. xanthus directed movement up gradients of phosphatidylethanolamine (PE) purified from M. xanthus cells. PE acted as a chemoattractant according to the principles of chemotaxis established in swimming enteric bacteria. M. xanthus suppressed direction reversals in the presence of uniform concentrations of PE, a phenomenon known as excitation. Excitation was chemically specific as alterations in the M. xanthus PE fatty acid content increased chemoeffector strength with increasing amounts of the fatty acid C16:1 o5c. In addition, synthetic dilauroyl and dioleoyl PE triggered excitation while other PE species did not. Excitation by dilauroyl PE appeared to be a transduced stimulus as the Dif chemotaxis signal transduction system was essential for the response. Cell-surface appendages called fibrils acted as chemosensors for dilauroyl PE perception. Adaptation, or the restoration of the basal reversal frequency, occurred after 45 minutes of dilauroyl PE exposure and required the Frz chemotaxis signal transduction system. This is the first report of a chemoattractant for the gliding bacteria and the first lipid attractant for bacteria in general. Lipids may be chemoeffectors for the surface motility of diverse bacteria as Pseudomonas aeruginosa also directed twitching motility up PE gradients.