Study On Molecular Mechanism Of Adaptation In Lactobacillus Casei Zhang To Amoxicillin

Lactobacillus(L.)casei Zhang is a probiotic strain with excellent traits,which was isolated from traditional fermented sour milk collected from a herdsman's house in Xilinguole,Inner Mongolia.L.casei Zhang has great ability to adapt and resist environmental stresses,such as acid and bile salts.Amoxicillin has often used clinically to treat diseases such as bacterial infections,it has become a new type of stress toward probiotics.In this study,the evolutionary strain L.casei Zhang-A-600 was selected as the research object.First,the growth characteristics of the adaptive strain L.casei Zhang-A-600 and the parental strain L.casei Zhang were studied,and then iTRAQ?based proteomic technology combined with cre-loxP gene knockout were used to explore the molecular mechanism of the adaptation of L.casei Zhang's toward the amoxicillin environment.The results are as follows:(1)Phenotypic characteristics showed that the growth trend of L.casei Zhang-A-600 was different from that of the parental strain.The results of viable cell count and OD600nm values showed that the growth rate of the adapted strain was much higher than that of the parental strain.(2)Proteomic results indicated that L.casei Zhang-A-600 had a total of 72 differential expressed proteins compared with the parental strain,of which 38 proteins were significantly up-regulated(>2-fold,P<0.05)and 34 proteins were significantly down-regulated(<-2-fold,P<0.05).Annotation and functional classification by using KEGG and COG databases revealed that the differential expressed proteins were mainly stress proteins,carbohydrates,and amino acid transport and metabolism related proteins.(3)The gene knockout results showed that the mutants L.casei Zhang-A-600-?045 8 and L.casei Zhang-A-600-?0521 had the different phenotypic characteristics with the wild-type strain L.casei Zhang-A-600 in OD600nm,indicating that the two genes may play a role in the amoxicillin adaptation of L.casei Zhang.Proteomics technology is a powerful tool for studying the resistance mechanism of probiotics.On the one hand,this study can lay a solid theoretical foundation for the screening of stress-resistant probiotics.On the other hand,it can also provide necessary theoretical guidance for optimizing and improving industrial production processes involving probiotics.