The irpT gene influences the multiple stresses tolerance by affecting cytochrome c in Lactococcus lactis N8

Lactococcus lactis, an internationally recognized safe species of Gram-positive bacteria, produces a variety of antimicrobial peptides. In this study, we examined the irpT gene of L. lactis N8 and its influence on the bacterial stress response. We used the Cre–loxP system to knock out the irpT gene from the L. lactis N8Δply10300 genome. The mutant strains L. lactis N8Δply10300 and L. lactis N8Δply10300ΔirpT showed higher nisin tolerance and nisin production than the wild-type strain L. lactis N8, and also obtained tolerance for multiple stressors. The biological characteristics of the irpT gene and its encoded protein in L. lactis N8 were investigated. Deletion of the irpT gene significantly reduced the content of cytochrome c, enhanced the tolerance of the strain to various environmental stresses, resulted in increased antimicrobial peptide nisin production and improved nisin resistance. Deletion of irpT gene conferred resistance to multiple stressors, including lysozyme, lactic acid, and antibiotics, and demonstrated resistance against multiple bacteriostatic mechanisms. Our findings lay the foundation for further research into the physiological processes of stress resistance in lactic acid bacteria.