Motility is a key virulence determinant in Pseudomonas aeruginosa. Pseudomonas aeruginosa has three distinct methods of moving across or through a medium. Rhamnolipids are particularly important in swarming motility where they are postulated to lower the surface tension of the surface through their surfactant properties, allowing the bacterial cell to swarm. New evidence suggests that rhamnolipids are necessary to allow Pseudomonas aeruginosa cells to overcome attachment mediated by type IV pili. There is some discrepancy between the role of HAAs and RHLs in swarming motility. Some studies use a rhlA mutation to assess the effect on motility, which prevents the formation of HAAs and rhamnolipids. Studies that use a rhlB mutant show that Pseudomonas aeruginosa can swarm in the absence of rhamnolipids, but HAAs are absolutely necessary for swarming. Rhamnolipids have been proposed to be important in regulating swarm tendril formation.
Rhamnolipids and HAAs are also implicated in twitching motility, similarly the surfactant is thought to lower the surface tension allowing cells to move across the substratum. However, the role of rhamnolipids in twitching motility may be nutritionally conditional.