Type IV Pili-Dependent Motility as a Tool to Determine the Activity of c-di-GMP Modulating Enzymes in Myxococcus xanthus.

The nucleotide-based second messenger bis-(3'-5')-cyclic dimeric GMP (c-di-GMP) regulates multiple processes in bacteria including cellular motility. The rod-shaped Myxococcus xanthus cells move in the direction of their long axis using two distinct motility systems: type IV pili (T4P)-dependent motility and gliding motility. Manipulation of the c-di-GMP level by expression of either an active, heterologous diguanylate cyclase or an active, heterologous phosphodiesterase causes defects in T4P-dependent motility without affecting gliding motility. As both an increased and a decreased level of c-di-GMP affect T4P-dependent motility, M. xanthus represents a good model system to assess enzyme activity of diguanylate cyclases and phosphodiesterases using T4P-dependent motility as a readout. Here, we describe the assay, which allows correlating diguanylate cyclase and phosphodiesterase activity with T4P-dependent motility in M. xanthus.