Abstract: Abstract： Objective The caseinolytic protease (clp) gene deletion strains and complemented strains of Porphyromonas gingivalis (P.g) W83 were constructed and identified in order to make a foundation for exploring the role and mechanism of clpP gene in the pathogenesis of P.g W83. Methods The primer pair of clpP gene were designed and its upstream and downstream homologous fragments were amplified by PCR, which were cloned into plasmid pUC18. And the erythromycin resistance gene ermB from plasmid pMG36e was inserted as a screening marker to construct a recombinant plasmid，which was electrotransfered into P.g W83 to get the corresponding clpP deficient recombinant strain. The clpP gene fragment was amplified by PCR and ligated with the recombinant plasmid pUC18-△clpP-ermB and electrotransfered into the recombinant strain of P.g so as to construct the corresponding complemented recombinant strain. PCR and electrophoresis were used to identify the correctness of the sequence, and the high-expression strain was screened and selected using a resistant medium. Results The cloned clpP gene fragment was successfully cloned and introduced into the plasmid vector pUC18. The clpP gene deletion strain and the complemented strain of P.g W83 were successfully constructed and could be stably passaged in vitro. Conclusion In this study, the clpP gene deletion strain of P.g W83 was constructed using homologous recombination technology, and the method of using pUC18 plasmid as a vector to construct the complemented strains was established. What we did would help to study the role of clpP gene in the pathogenesis of P.g in future.

Key words: clpP, porphyromonas gingivalis, deletion strain, complemented strain