Study On The Effects Of Different Species Of Lactobacillus On ETEC-induced Diarrhea And Its Mechanisms

Diarrhea caused by Enterotoxigenic Escherichia coli(ETEC)severely hindered the development of aquaculture and tourism.The traditional medicines currently in use were narrow in scope of application and had many side effects.Studies have shown that probiotics had the functions of antagonizing pathogenic bacteria,reducing inflammation,and regulating gut microbiota to alleviate diarrhea caused by ETEC.Among them,Lactobacillus rhamnosus,Lactobacillus reuteri,Lactobacillus plantarum,Lactobacillus gasseri and Lactobacillus johnsonii were the five most reported Lactobacillus.However,the comparison of the relieving effects of these five Lactobacilli on the diarrhea caused by ETEC under the same conditions and the differences of their respective effect of mtigation are still unclear..This article aims to compare the differences in the mitigation effects of these five Lactobacilli on the mouse diarrhea caused by ETEC through indicators such as phenotype,immune regulation,short-chain fatty acids,and gut microbiota.And based on the comparative genomics method,the relationship between the mitigation effects of these five Lactobacilli and their own gene composition and functional genes was preliminarily explored.Finally,the clinical effect of the strains with the best mitigation effect in animal experiments was evaluated,providing theoretical basis and data support for the later development and application of probiotic functional products.The main contentss are as follows:Firstly,in order to evaluate the relieving effects of different Lactobacilli on ETEC-induced diarrhea and compare the different ways of relieving diarrhea,a total of 26 strains of five kinds of Lactobacillus were studied by establishing ETEC-infected mouse diarrhea models.The results showed that ETEC infected mice to make their stool water content reach 61.98%,which was 15.25%higher than the control group,causing diarrhea.The relieving ability of Lactobacillus was species-specific.In terms of phenotype and immune regulation,L.plantarum and L.johnsonii had the significant mitigation effect,followed by L.gasseri and L.reuteri,and L.rhamnosus was the worst.In terms of heat-stable enterotoxin,L.johnsonii had the significant relief,and L.rhamnosus was the worst.On aquaporin,L.rhamnosus had the significant relief,and L.reuteri was the worst.In general,at the species level,the mitigation capacity was ranked as:L.plantarum>L.johnsonii>L.gasseri>L.reuteri>L.rhamnosus,and L.plantarum CCFM1143 has the best mitigation effect.Strains with better relief may play a mitigating effect by regulating the abundance of beneficial bacteria,especially the abundance of SCFAs-producing genera,producing SCFAs;Secondly,in order to preliminarily explore the relationship between the mitigation effects of these five Lactobacilli and their own genetic composition and functional genes,the comparative genomic analysis of 26 Lactobacilli showed that the effects of different Lactobacilli on diarrhea were not related to the number of unique genes,the presence or absence and the species of bacteriocin operons,but there was a certain relationship with the evolutionary relationship between the strains within the species.Strains with better mitigation effects had more specific genes related to carbohydrate transport and metabolism,nucleotide transport and metabolism,and cell wall/membrane/plasma membrane synthesis related genes,which were conducive to the adaptation of strains to niche and the production of short-chain fatty acids.Finally,in order to evaluate whether the strain with the best mitigation effect in the mouse diarrhea model was clinically consistent,L.plantarum CCFM1143 was selected for clinical effect evaluation.The results showed that Lactobacillus plantarum CCFM1143 may help regulate the level of short-chain fatty acids by changing the composition of the gut microbiota,thus inhibiting the increase in IL-6 levels and the decrease in MTL levels,and regulating the immune response of patients,thereby improving symptoms and quality of life of patients with diarrhea.Among them,the regulation of IL-6,propionic acid concentration,Bacteroides and Akkermania abundance is similar to the mice experiment results,and can inhibit the increase in the relative abundance of Escherichia-Shigella.