Epr plays a key role in DegU-mediated swarming motility of Bacillus subtilis

Epr, a minor extracellular protease, is involved in the swarming motility of Bacillus subtilis. It does so by providing essential signals required for swarming. It has also been demonstrated that DegU is required for swarming and that it occurs at very low levels of DegU approximately P and is inhibited at high levels of DegU approximately P. In this study, we show that maximal epr expression is observed at very low concentrations of DegU approximately P, whereas it is repressed at high DegU approximately P. A parallel effect of DegU approximately P levels on swarming motility is also observed, where very low levels of DegU approximately P support swarming and excessive DegU approximately P abolishes swarming. We further demonstrate that the defect of swarming motility in a degU(-) strain can be rescued, albeit incompletely, by increased expression of an exogenous epr gene. We also show that an additional extracellular factor(s), apart from epr, regulated by DegU, is required for robust swarming.