Figure 1.

Pseudomonas aeruginosa synthesizes and secretes rhamnolipid biosurfactants required for swarming motility. (A) The wild-type Pseudomonas aeruginosa regulates the expression of rate-limiting enzyme RhlA using a mechanism called metabolic prudence that integrates nutrient sensing and quorum sensing. (B) Metabolic prudence ensures that rhamnolipids are secreted only when carbon is in excess and population density is high. (C) In this study, we use a genetically engineered inducible strain where RhlA expression is under regulation of the L-arabinose inducible promoter P_BAD. (D) The inducible construct circumvents metabolic prudence and provides an experimental handle to modulate biosurfactant synthesis and investigate swarming cooperation thoroughly.