Study On The Effect Of Escherichia Coli Nissle 1917(EcN) Capsular Polysaccharide On Biofilm Formation

Microbial biofilm is a membrane-like structure formed by the interaction between bacteria and the surface of an object,and this special structure can provide protection for bacteria.The formation of biofilm is not only the key to pathogenic bacteria causing disease to the host body,but also one of the important reasons why probiotics are endowed with probiotics.Escherichia coli Nissle 1917(EcN),as a typical probiotic,is not immunogenic and can be well tolerated by the human body.It can prevent and treat many types of intestinal diseases.EcN has a good biofilm formation ability.The formation of biofilm greatly promotes the long-term and persistent colonization of EcN in the intestinal mucosa,and inhibits the colonization of pathogens in the host through competition.The capsular polysaccharide(Heparosan)on the surface of EcN cells is an acidic polysaccharide whose chemical structure is similar to heparin and heparan sulfate.Capsular polysaccharides endow bacteria with a variety of biological activities and functions,and can form a protective layer outside the cell wall,thereby protecting bacteria from a variety of environmental stress factors.The synthesis mechanism and regulation mechanism of EcN capsular polysaccharide are relatively complicated.The function of the EcN capsular polysaccharide synthesis gene kfiA has not been fully explained,and the capsular polysaccharide seems to be closely related to the formation of EcN biofilm.In order to explore the relationship between capsular polysaccharides and EcN biofilms,this topic takes the EcN strain kfiA gene and EcN capsular polysaccharides as the research objects,and analyzes the effects of kfiA genes and EcN capsular polysaccharides on EcN biofilms.The results of the study showed that the kfiA gene is a key gene for the synthesis of EcN capsular polysaccharides,and the deletion of the kfiA gene prevents EcN from synthesizing capsular polysaccharides.Further studies have found that the absence of EcN capsular polysaccharides increases the isoelectric point of EcN,promotes the adsorption of EcN to biological macromolecules,and enhances the initial adhesion ability of EcN and the ability of biofilm formation.EcN capsular polysaccharides can be decomposed into unsaturated disaccharides by heparin lyase III.In order to further prove that the absence of EcN capsular polysaccharide can promote the formation of EcN biofilm,this study used heparin lyase III to remove the capsular polysaccharide on the surface of EcN cells.The results showed that after the loss of capsular polysaccharide,the antoaggregation ability,initial adhesion ability and biofilm formation ability of EcN were significantly enhanced.In summary,we conclude that the kfiA gene,as a key gene for the synthesis of EcN capsular polysaccharide,can affect the formation of EcN biofilm.The deletion of the kfiA gene of the EcN strain results in the inability to synthesize capsular polysaccharides,which increases the isoelectric point of EcN,and enhances the antoaggregation ability,initial adhesion ability and biofilm formation ability of EcN,which promotes EcN biofilm formation.form.