| Biofilm has the function of resisting environmental stress and immune defense,and its formation process is regulated by quorum sensing system.As a research hotspot in recent years,researches on biofilms are mostly concentrated in harmful bacteria,and the research on biofilms of lactic acid bacteria remains to be in-depth.In this study,13 strains of lactic acid bacteria were screened for biofilm production,The selected high yield biofilms Lactobacillus plantarum 5-1-2,5-4-1 and Lactobacillus San Francisco 10-2 were selected as research objects,By adding the endogenous and exogenous signal molecule AI-2 in the culture medium,the effects of signal molecules on the growth of lactic acid bacteria,biofilm production,probiotic properties of strains,bacteria and biofilm morphology,extracellular polysaccharide and related genes were determined.(1)Lactobacillus plantarum 5-1-2,5-4-1 and Lactobacillus San Francisco 10-2 were screened from 13 strains of lactic acid bacteria to explore the laws of growth and biofilm formation.During the growth of lactic acid bacteria,the bacterial biofilm gradually accumulates with the growth of the bacteria.When the strain grows into the stable period,the production of the biofilm will reach the highest peak.(2)Adding the endogenous signal molecule AI-2,with the increase in the amount of addition,the medium components were diluted,and the reduction of nutrients resulted in a significant decrease in cell growth and biofilm production(p<0.05),so that the regulating effect of the endogenous signal molecules was concealed.(3)The addition of exogenous signal molecule AI-2 played a significant role in promoting cell growth.The final concentration of 60μmol/L signaling molecule AI-2 has a significant effect on the biofilm formation of Lactobacillus plantarum 5-1-2 and Lactobacillus San Francisco 10-2,and The signal molecule AI-2 with a final concentration of 20μmol/L has a significant promoting effect on Lactobacillus plantarum5-4-1.With the addition of exogenous signal molecule AI-2,the surface of bacterial bacteroids was smoother and smoother,and it helps to increase the cell adhesion;At the same time,it promotes the structure of biofilm more densely,and then increases the stability of biofilm structure;Exopolysaccharide production increased significantly;And the production of exopolysaccharides from the cells increased significantly.The exogenous signal molecule AI-2 can increase the growth ability of the strain at pH 3.5,and the accelerating effect is mainly concentrated in the stable period.Adding the signal molecule AI-2 in a medium containing 1 g/L bile salt promotes the growth of lactic acid bacteria,and has a significant promoting effect on Lactobacillus plantarum 5-1-2 and Lactobacillus San Francisco 10-2 in the stationary phase.Adds a signal molecule with a final concentration of 60 μmol/L,Culture of 7 h and 13 h,It shows a significant promotion of Lactobacillus plantarum 5-4-1 lam C gene expression;Culture of 25 h,It shows a significant promotion of Lactobacillus plantarum 5-1-2 fts H gene expression;Culture of 7 h,It shows a significant promotion of Lactobacillus San Francisco 10-2 ftsH gene expression. |
