Preliminary Study Of Sensing Behavior Of Production Bacteriocin Paracin1.7 Strains Quorum

Lactobacillus paracasei HD1.7 was isolated from Chinese sauerkraut juice in 2003. It had been proved that the strain can produce a kind of non-acid antimicrobial peptide, which had broad spectrum of inhibition. It is supposed that the production of Paracinl.7 may be regulated by the quorum sensing system of L.paracasei HD1.7. For this hypothesis, the topic will prove it in the physiological level. The issue makes the demonstration about the relationship between the quorum-sensing of HD1.7 and Paracinl.7 accumulation by two aspects.On the one hand, Research on the diversification of the antibacterial activity of bacteriocin Paracin1.7 in a different cell density. Studies have shown that the antibacterial activity of Paracinl.7 was closely related to the cell density of HD1.7 by fermentation in different culture conditions. On this basis, after adding low-density concentrations and high-density concentrations of autoinducer, it was showed that the autoinducer whose concentration was the main factor of affecting bacteriocin Paracinl.7 accumulation; Meanwhile, based on the conclusion that the concentration of signaling molecules is as different as the cell density of HD1.7 by fermentation, after adding different concentrations of autoinducer (bacterial density is 106,107,108å'Œ109A/mL), it was found that Paracinl.7 as the autoinducer self-induced dominated in regulation. By assuming high density, the study showed that the activity of bacteriocin Paracinl.7 was increased with the cell density of HD1.7 in a certain cell density range (<108A/mL) However, once beyond it (>108A/mL), the expression of antibacterial activity was not increased with the cell density, even suppress the activity of bacteriocin Paracinl.7, which proved that the quorum-sensing system of L.paracasei HD1.7 regulated the expression of antibacterial activity of bacteriocin Paracinl.7, and Paracin1.7 as the autoinducer self-induced dominated in regulation.On the other hand, Comparing the production of the bacteriocin between the original strain HD1.7 and the mutant strain YTT-N11 in the same cell density. YTT-N11 was obtained by NTG mutagenesis of the HD1.7, and then made the strains HD1.7 and YTT-N11 fermentation at the same conditions. It was showed that the production of two strains were significantly different, the strain N11 is 6.99 times of the original strain on bacteriocin Paracin1.7 accumulation. As a result, we obtained YTT-N11, a high-yielding strain of producing bacteriocin Paracinl.7, which will provide a good foundation for the regulation of bacteriocin Paracin1.7 by the quorum-sensing of HD1.7 at the molecular level.The results above are the direct experimental evidence that QS system has been regulated on biosynthesis of bacteriocin Paracin1.7 for the first time, which will provide the technical guidance for obtaining high-yielding of bacteriocin Paracin1.7. An amount of data in this study would support the idea and this work will be very significant because of the few data in this field. In this way, we will have more acquaintance with the mechanism of bacteriocin Paracin1.7, and provide a theoretical basis for the control of bacteriocin System and the optimization of bacteriocin production, which make Paracin1.7 and its synthesis system having more extensive development and space.In order to complete the study, it should be analyzing he process and manner of the QS system regulating the expression of Paracin1.7.