Rhamnolipids mediate detachment of Pseudomonas aeruginosa from biofilms

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Abstract
Summary: The process of detachment, through which bacteria use active mechanisms to leave biofilms and return to the planktonic (free‐living) state, is perhaps the least understood aspect of the biofilm life cycle. Like other stages of biofilm development, detachment is a dynamic, regulated process, controlled by specific genes, and induced by particular environmental cues. In previous work we discovered Pseudomonas aeruginosa variants that exhibit accelerated biofilm detachment. These hyper‐detaching variants arise spontaneously from biofilms at a high frequency, and they exhibit robust detachment under different biofilm growth conditions. Here we show that these variants detach by a mechanism requiring the biosurfactant rhamnolipid and that this detachment mechanism rapidly restores antibiotic sensitivity to separating bacteria. We also show that rhamnolipids can bring about detachment in wild‐type P. aeruginosa biofilms. These findings raise the possibility that this detachment mechanism may be useful as a treatment to disrupt established biofilms. Interestingly, the rhamnolipid‐mediated detachment mechanism involves the formation of cavities within the centre of biofilm structures. Our data suggest a model to explain detachment that occurs via this pattern.