Study On The Mechanisms Of Linoleic Acid Inhibiting The Growth Activity Of Lactobacillus

Recent studies have shown that dietary nutrients cause diseases in humans by affecting the enteric microorganism.As a polyunsaturated fatty acid(PUFA),Linoleic acid is an essential substance in human physiological activities.However,excessively high content of PUFA is harmful to human intestinal flora,especially Lactobacillus with probiotic function.The reason why PUFA in the diet affects Lactobacillus activity have been seldom studied.In the present study,linoleic acid was used to study the mechanism of its inhibition function against Lactobacillus activity.The Lactobacillus strains affected by linoleic acid were screened out,then the minimum inhibitory concentration of linoleic acid was determined.The comprehensive analysis was performed by the in vitro and in vivo experiments.First,flow cytometry and fluorescence microscopy were used to observe the degree of cell membrane damage of Lactobacillus,and the cell structure was further observed by scanning electron microscope and transmission electron microscope.Then,we determined the impact of linoleic acid on the growth trend of Lactobacillus for 10 hours and the metabolites content in bacterial suspension.After that,we counted the number of viable bacteria of Lactobacillus under the intervention of linoleic acid in vitro simulates the gastrointestinal environment.Based on the in vitro experimental results in the simulated gastrointestinal tract,in vivo experiments were conducted to verify whether linoleic acid would also inhibit the growth activity of Lactobacillus.The RT-PCR method was used to detect the gene content of Lactobacillus in the feces of mice.Then,the fluorescently labeled Lactobacillus was administrated to the mice.After 24 hours,the survival of Lactobacillus in each part of the intestine of the mice was observed using a fluorescence microscope.The results showed that the strain most affect by linoleic acid was Lactobacillus rhamnosus(L.rhamnosus)among eight different species of Lactobacillus.At a concentration of linoleic acid of 50 ?g/m L,the cell membrane of L.rhamnosus was damaged and the cell structure changed.The growth of L.rhamnosus was slow and the key metabolites leaked into the liquid within 10 hours.The activity of L.rhamnosus in the simulated intestinal fluid in vitro decreased sharply.In animal experiments,the gene content of L.rhamnosus in the feces of mice fed with linoleic acid was relatively low.Under a fluorescent microscope,the number of fluorescently labeled L.rhamnosus decreased intensively,especially in the ileum and colon.Studies in vitro and in vivo indicated that linoleic acid could can inhibit the growth activity of Lactobacillus.The mechanism of action is that linoleic acid destroys the cell membrane of Lactobacillus,which affects the normal metabolism of bacteria and eventually leads to its death.This study aims to clarify the mechanism of linoleic acid's inhibition of the growth activity of Lactobacillus,and to understand the relationship between dietary nutrients and probiotics,and develop scientific and effective functional food.