The Research Of Regulatory Mechanism Of Biofilm In Escherichia Coli Isolated From Dairy Cow With Mastitis

Cow mastitis is not only a disease with high incidence of dairy cows,but also a disease that causes high losses in the global dairy industry.Mastitis due to pathogenic bacteria infection or external stimulation leads to inflammation of breast tissue.Studies have shown that about 150 kinds of pathogenic microorganisms are related to dairy cow mastitis,among which Escherichia coli is one of the important pathogens of dairy cow mastitis.The formation of biofilm is considered to be a selective advantage of the pathogen causing mastitis in dairy cows,which promotes the persistent survival of bacteria in the mammary gland.The formation of biofilm may play an important role in the pathogenesis of mastitis in dairy cows.At present,some studies have reported the effect of lactose,the only sugar in milk,on the biofilm formation of Staphylococcus aureus and Streptococcus in dairy cows mastitis.Moreover,there are many studies on the regulation mechanism of LuxS/AI-2 in E.coli MG1655 strain and avian pathogenic E.coli.However,in Escherichia coli of dairy cow mastitis,the regulation mechanism of lux S on the expression of genes related to biofilm is rarely reported at home and abroad.This study used exogenous addition of different concentrations of lactose,glucose and galactose to carry out in vitro membrane formation experiments,through gene knockout,replenishment,RT-qPCR experimental techniques.It was revealed that lactose must be absorbed and cleaved by lactose operon to produce glucose and galactose,and then down-regulate the transcription level of biofilm-forming genes csgA,fliC,wcaF and fimA,and inhibit the biofilm formation of Escherichia coli with mastitis.In addition,the important role of Lux S/AI-2 quorum sensing system in the biofilm formation of Escherichia coli in dairy cow mastitis was preliminarily explained by gene knockout,gene replenishment,in vitro film formation experiment and exercise experiment.Therefore,our findings will provide a new theoretical and experimental basis for the prevention and treatment of cow mastitis caused by biofilm positive Escherichia coli.