The role of luxS in Escherichia coli biofilm formation: A link between quorum sensing and central metabolism

The mechanism of Escherichia coli biofilm formation has been studied extensively, and is commonly used as a model for biofilm formation by other Gram negative bacteria. E. coli biofilms are frequently found on indwelling medical devices, and have been known to cause a number of infections including chronic urinary tract infections, chronic bacterial prostatitis, and pelvic inflammatory disease. The resistance of E. coli biofilms to antibiotics is a critical concern. Once a biofilm is established, the infection is almost impossible to treat. Since bacteria within a biofilm encounter relatively high cell concentrations, it is likely that quorum sensing, or bacterial cell-to-cell communication, plays an important role in biofilm formation and maturation. If we can better understand the role of quorum sensing in biofilm formation, it may become possible to develop a treatment that inhibits biofilm formation, thus preventing infection.; In the present study, the role of LuxS-based quorum sensing in E. coli biofilm formation was examined using a luxS-null strain. The LuxS-based quorum sensing system was found to play a significant role in biofilm formation, both through its role in autoinducer-2 (AI-2) production and its role in central metabolism. The DeltaluxS strain was unable to form a mature biofilm due to the down-regulation of the fliC gene, which encodes the flagellar structural protein. The attached E. coli DeltaluxS cells produced an excess of extracellular matrix (ECM), most likely due to the up-regulation of the metR gene, which encodes a transcriptional regulator of several genes involved in methionine synthesis. The DeltaluxS strain was also shown to produce less S-Adenosylmethionine (SAM) than its parent strain, which resulted in a slowed growth rate and a cell division defect.