Study On Relationship Between Production Of Antibacterial Substances And LuxS/AI-2Mediated Quorum Sensing System In Lactobacillus Plantarum HE-1Co-culture With LABs

LABs used in this study were isolated from koumiss of Ximeng region in Inner Mongolia. First, Spot-on-lawn method is used on solid medium to find Lactobacillus plantarum HE-1and Enterococcus faecium HE-432which have the potential to produce antimicrobial substances, and find out the best indicator bacteria for subsequent testing. Secondly, design15co-cultured combination that using similar and different species of LABs as stimulating factors and use agar-well diffusion test to detect the antimicrobial resistance of co-cultured supernatant. Third, choose the co-cultured supernatant which can inhibit indicator bacteria to detect AI-2signaling molecule, looking for the correspondence between AI-2signal molecule and antibacterial substances on time and amount. Fourth, explore the relationship between biofilm formation and antimicrobial substances production to make L. plantarum HE-1become probiotics. Fifth, LABs producing antibacterial substances were verified by molecular biology to have luxS gene fragment and prove AI-2signal molecule can be produced. Experimental results show: Enterococcus、Lactobacillus、Lactococcus、Pediococcus、Staphylococcus、Bacillus、 Escherichia and Micrococcus could be inhibited by the antimicrobial substances of L. plantarum HE-1, and selected the E. coli as best indicateor for follow-up experiment instructions. Second,11co-cultured combination could inhibit the growth of indicator bacteria L. plantarum HE-1co-cultured with E. faecium HE-521producing antimicrobial substances reached a maximum of17.84mm bacteriostatic ring; L. plantarum HE-1co-cultured with Enterococcus, Lactobacillus, Lactococcus, Pediococcus, Staphylococcus, Bacillus could induce to produce antibacterial substances;11co-cultured combination produced antibiotic substances at9h, L. plantarum HE-1single cultured in liquid did not produce antibacterial substances. Third,4co-cultured combination which induce the production of antibiotics were generated AI-2signal molecules at9h, and formed a peak in the range of6h to15h, the relative fluorescence intensity of AI-2signal molecular co-cultrued in9h was larger than L. plantarum HE-1cultured alone. There was corresponding relation between producing antibacterial substances and AI-2in time and amount. Forth, biofilm formation was closely related to the AI-2/LuxS quorum sensing system. The homology analysis of luxS gene further demonstrated that AI-2was produced by L. plantarum HE-1.