Objective   To study the effect of luxS gene on biofilm formation in knocked-out Escherichia coli (E. coli).     Methods   Clinically isolated E. coli S17 was used as the target in this study .The upstream and downstream sequences of luxS

and kana-resistance gene of pEGFP-N1 were amplified by PCR

cloned into T plasmid pAT2 vector and pAT2-kana. Homologous recombinant plasmids pAT2-△luxS were then constructed. After the pAT2-△luxS were transformed into E. coli and amplified

fragments of homologous recombinant plasmids were obtained by restricted enzyme reaction and transformed to E. coli S17. Effect of luxS gene on biofilm formation in knocked-out E. coli in 96-well plates was analyzed with crystal violet staining.    Results   A total of 1678 luxS fragments were amplified by PCR with correct sequences. A E. coli S17 strain without luxS gene was established with an OD of 1.51±0.09 and 0.43±0.13

respectively.    Conclusion    The luxS gene plays an important role in regulation of biofilm formation in E. coli.