Study On The Effect Of Anti-infection And The Influnce To Intestinal Tract Microbial Population Of Lactobacillus

16SrDNA gene of L.casei.zhang and MG2-1was cloned and analyzed, their fermentation broth,thallus and metabolite were used to carry on the experiment of vitro bacteriostasis.Their oral suspl were fed to mice, mice were innoculated toxic substances. After that the incidence was observed, the fourth day Escherichia coil and lactobacilli were isolated by selective medium. Singular colony bacterial was selected and DNA was extracted, then it was amplified in polymerase chain reaction by ERIC-PCR, then the adhesion experiment of L.casei.zhang and MG2-1 was carried on.The result of 16SrDNA gene sequence analysised is agree with the traditional classification. The characteristic of phenotype, physiology and biochemistry is still the important index of the modern lactobacillus classification, especially to classification of profuse lactobacilli. On the other hand, 16SrDNA gene sequence analysis method is feasible in lactobacilli classification, the lactobacillus oral suspl and metabolizes have stronger bacteriostasis activity, but the thalline is no bacteriostasis activity. The metabolite of lactobacillus has strong heat hardiness, and it can be tolerant of 115℃high temperature. But the degree of acidity highly influenced the bacteriostasis ability of metabolite, and it's bacteriostasis ability would rise while the degree of acidity decreased. The bacteriostasis ability of metabolite would have been lost in neutral condition, and it was not largely influenced by Trypsin and Pepsin.By taken lactobacillus could improve the resistance of infections. L.casei.zhang and MG2-1 were isolated from mice at the fourth day after stop feeding lactobacili .As the effect of antagonism of lactobacilli to the Escherichia coil. Escherichia coil of O157 and K88were not isolated from feeding oral lactobacilli groups. Feeding L.casei.zhang and MG2-1 to mice ,they can attached and grow in the gut.