Rhamnolipids from disperse the biofilms of sulfate-reducing bacteria.

Biofilm formation is an important problem for many industries. is the representative sulfate-reducing bacterium (SRB) which causes metal corrosion in oil wells and drilling equipment, and the corrosion is related to its biofilm formation. Biofilms are extremely difficult to remove since the cells are cemented in a polymer matrix. In an effort to eliminate SRB biofilms, we examined the ability of supernatants from PA14 to disperse SRB biofilms. We found that the . supernatants dispersed more than 98% of the biofilm. To determine the biochemical basis of this SRB biofilm dispersal, we examined a series of . mutants and found that mutants , , , and , defective in rhamnolipids production, had significantly reduced levels of SRB biofilm dispersal. Corroborating these results, purified rhamnolipids dispersed SRB biofilms, and rhamnolipids were detected in the . supernatants. Hence, . supernatants disperse SRB biofilms via rhamnolipids. To determine the genetic basis of how the . supernatants disperse SRB biofilms, a whole transcriptomic analysis was conducted (RNA-seq); based on this analysis, we identified four proteins (DVUA0018, DVUA0034, DVUA0066, and DVUA0084) of the . megaplasmid that influence biofilm formation, with production of DVUA0066 (a putative phospholipase) reducing biofilm formation 5.6-fold. In addition, the supernatants of . dispersed the SRB biofilms more readily than protease in M9 glucose minimum medium and were also effective against biofilms of and .