Abstract: This study aimed to construct a histidine protein kinase gene (prcK) deletion mutant of Lactobacillus paracasei HD1.7 for providing an experiment tool for research on the function of the prcK gene. In this research, homologous recombination method was used. Plasmid pKLKRT (including prcK::Tetr) was constructed and used to transform L. paracasei HD1.7 by eletroporation. The prcK::Tetr in place of prcK was integrated into the chromosome of L. paracasei HD1.7 by homologous recombination. One strain that grew only on plates with tetracycline but not on plates with ampicillin was selected. The PCR amplification and endonuclease digestion analysis indicated that plasmid pKLKRT was successfully constructed and introduced into L. paracasei HD1.7. The prcK gene deletion mutant was confirmed by PCR amplification. In conclusion, a prcK gene deletion mutant of L. paracasei HD1.7 has been successfully constructed by homologous recombination, which will lay the basis for understanding the molecular mechanism of the quorum sensing-related genes in L. paracasei HD1.7.

Key words: Lactobacillus paracasei, bacteriocin, histidine protein kinase, homologous recombination