Objective: Paracin 1.7 was a bacteriocin extracted from Lactobacillus paracasei HD1.7. In this study, we investigated quorum-sensing mechanism that regulates the metabolism of Paracin 1.7 in strain HD1.7.
Methods: The antibacterial activity of strain HD1.7 under different growth conditions was analyzed using an agar-well diffusion method, and the cell density was controlled by adjusting nutrient levels in the culture medium.
Results: The antibacterial activity of strain HD1.7 depended on cell density. Strain HD1.7 exhibited the antibacterial activity when the cell density reached a threshold (OD600 of 0.8 and cell dried weight of 0.3311 g/L). Addition of different concentrations of a signaling molecule in the supernatant of the fermentation broth affected the antibacterial activity. After removing the signal molecule, the antibacterial activity was significantly decreased.
Conclusion: Paracin1.7 was the quorum-sensing signaling molecule in the HD1.7 fermentation broth and it could be auto-induced. The antibacterial activity of Paracin1.7 was regulated by the quorum-sensing system in HD1.7.