Abstract:

Objective The quorum sensing system is related to bacterial growth profile，virulence，biofilmformation，motility，host immune responses，and resistance to antibiotics. The quorum sensing Escherichia coli（E. coli）regulator C（qseC）is the receptor of the E. coli quorum sensing system，and its effects on the physiologicaland biochemical characteristics of E. coli were not well understood. Methods In the present work，we used theThermotargetron gene targeting system（based on thermophilic mobile group Ⅱ intron）to inactivate the qseC genein E. coli strain HMS174. The phenotypic changes of ΔqseC627s strain，including growth rate，hemolysis，biofilmformation，motility，tolerance to the acidic and alkaline environment，and resistance to antibiotics，were investigated.The present work will draw a clearer picture of the physiological functions of the qseC gene in E. coli. Results The qseC627s locus of E. coli HMS174 was chosen as TeI3c/4c insertion site，the gene inactivation efficiency was100%. Targeting plasmid was cured by successively transferred in LB medium，and the plasmid cure efficiency was100%. Compared to the wild⁃type strain，the mutant ΔqseC627s showed reduced growth rate，maximum bacterialdensity，biofilm formation ability，motility，hemolytic ability，and tolerance to the acidic and alkaline. Further⁃more，compared to the wild type strain，the antibiotic susceptibility assay showed that ΔqseC627s was more resis⁃tant to chloramphenicol，ampicillin，tetracycline，amoxicillin，and metronidazole. Conclusions After the inacti⁃vation of the qseC gene in E. coli HMS174，the phenotype and resistance to external stress of the ΔqseC were sig⁃nificantly changed.

Key words:

escherichia coli, quorum sensing system, thermotargetron, phenotypic changes in mu?tant strain

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