Study Of AI-2Signal Molecule In Lactic Acid Bacteria From Koumiss

Activity of AI-2signal molecule in eleven lactic acid bacterias was study in quorum sensing angle. Firstly, the best vacuum freeze drying protective agent was choiced for reporter strain Vibrio harveyi BB170by orthogonal test of four factors and three levels. Secondly, the AI-2activity of eleven strains of lactic acid bacteria at different culture time were tested.Thirdly, the changes of AI-2activity were tested when two representative strains of lactic acid bacteria were added to yeast metabolites and co-cultured with yeast to lay the foundation for the research of symbiosis mechanism of lactic acid bacteria and yeast.The best formula of composite protective agent of reporter strain Vibrio harveyi BB170was:10%skim milk,1%L-sodium glutamate,2%sucrose and1.25%glucose.The fluorescence intensity of bacterial powder reached to216804AU and can still reached to39203AU placed at room temperature after two months.Test results about the AI-2activity of eleven lactic acid bacterias showed that1-3and1-3-1can’t produce AI-2, the remaining nine strains such as LC5,2-1can produce AI-2. Furthermore,the strain6-1-1and remaining eight strains began to produce in stable phase and exponential phase respectively.The influence of the yeast YE4、J6、J11、J23-1metabolites on the production of AI-2in LC5and2-1were different. Metabolites of four yeasts had a certain role in promoting the AI-2production of LC5in a specified period of time. However, YE4played a driving role only and remaining strains played inhibitory action for2-1.After four yests with LC5and2-1were co-cultured,YE4had a promoting effect on LC5co-cultured13h and without affecting in the rest of the time; The remaining three yeasts and all four yeasts showed inhibition for LC5and2-1respectively.