Rapid surface motility in Bacillus subtilis is dependent on extracellular surfactin and potassium ion.

Motility on surfaces is an important mechanism for bacterial colonization of new environments. In this report, we describe detection of rapid surface motility in the wild-type Bacillus subtilis Marburg strain, but not in several B. subtilis 168 derivatives. Motility involved formation of rapidly spreading dendritic structures, followed by profuse surface colonies if sufficient potassium ion was present. Potassium ion stimulated surfactin secretion, and the role of surfactin in surface motility was confirmed by deletion of a surfactin synthase gene. Significantly, this motility was independent of flagella. These results demonstrate that wild-type B. subtilis strains can use both swimming and sliding-type mechanisms to move across surfaces.