Figure 8.

Biosurfactant secretion becomes exploitable in a biosurfactant secreting strain that lacks the native rhlAB regulation (the inducible strain rhlA⁻ P_BADrhlAB). (A) Unlike the wild-type (fig 2C), rhlA⁻ P_BADrhlAB is rapidly outcompeted by rhlA⁻ and colonies lose swarming over four days of consecutive passages. The experiment was also conducted by swapping fluorescent labels to show the outcome is independent of the fluorescent protein used. (B) Cell count ratios measured from the competition experiments confirm that strain rhlA⁻ P_BADrhlAB has a strong competitive disadvantage against rhlA⁻ (blue), while WT cells do not (red). (C) The productivity of swarming colonies (number of cells in colony) comprising a mixture of rhlA⁻P_BADrhlAB and rhlA⁻ is comparable to that of the wild-type at day 1 but decreases down to a level comparable to that of rhlA⁻ at day 4.