Quorum-sensing behavior of Lactobacillus paracasei HD1. 7

Abstract:

Abstract:［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. 3311g/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．

Key words:Keywords: Lactobacillus paracasei HD1.7，paracin1.7，quorum-sensing，bacterial density