LsrK attenuates the pathogenicity of both the Gram negative bacterium Escherichia coli O157:H7 and Gram positive Staphylococcus aureus

The Escherichia coli LsrK gene encoding a phosphorylase acting on AI-2 quorum sensing signal molecules was recombinantly expressed in the E. coli BL21(DE3). Its role on affecting the pathogenicity of both Gram negative and positive pathogens was investigated using two representative enterohemorrhagic bacteria, the E. coli O157:H7 and Staphylococcus aureus . The recombinant LsrK catalyzed degradation of the typical AI-2 signal molecule 4,5-dihydroxy-2,3-pentanedione and decreased the transcript levels of multiple virulence factors in the two bacteria ( fliC, ycgR, eaeA , ompX , ycgR , and eaeA in E. coli O157:H7 and sea , eta , hlα , sdrE , bbp , and cna in S. aureus , respectively). Interestingly, LsrK inhibited formation of the biofilm in E. coli but promoted this process in S. aureus , which might be partially related to transcription repression of SaaR involved in biofilm generation. LsrK also reduced the swimming motility, hemolytic ability, cytotoxicity, and the acid-tolerating ability of the two pathogenic bacteria. These collectively suggested that LsrK could serve as a promising enzyme in combating Gram negative and positive pathogenic bacteria infection.