The Study On Desiccation Tolerance And Relavent Genes Of Cronobacter Sakazakii

Cronobacter sakazakii(C.sakazakit)belong to the Enterobacteriaceae,Cronobacter.C.sakazakii is a gram-negative,peritrichous,motile,non-spore forming facultative anaerobic bacteria.And it's a kind of opportunistic pathogen that can survive in human and animal intestines.C.sakazakii can be isolated from a wide variety of food matrix.Thus,C.sakazakii can infect human,especially for low-birth-weight neonates,infants,immunocompromised adults and old people,by environment contact or daily eating.Because of the great harm to human,the studies of C.sakazakii centered on the pathogenicity and the virulence factors.Moreover,the excellent desiccation tolerance can make C.sakazakii exist in low water activity foods in long-term which may cause the increasing risk of human infection.The desiccation tolerance mechanism of C.sakazakii has not been clear so far.This research focused on the desiccation tolerance mechanism of C.sakazakii isolated from various food matrix.In this study,Multiple Locus Sequence Typing(MLST)was performed to classify the forty-five C.sakazakii strains into nineteen STs.Relevance between sequence types and desiccation tolerance were discussed and the result indicated that the desiccation tolerance of different strains was not consistent with the sequence type.In C.sakazakii genome,ten genes involved in osmoprotectants synthesis or transport were selected to investigate whether these genes were responsible for cytoprotection in the dry environment by qRT-PCR.And the different expression in strains with diverse desiccation tolerance was compared.The difference expression in strains with different desiccation tolerance suggest that these genes paly a regulatory role in the drying resistance process.Furthermore,biofilm-forming ability of these strains was also detected and the results showed that there was a positive correlation between biofilm formation and desiccation tolerance.Finally,the quantitative proteome analysis on the different desiccation tolerance strainsshow that the proteins associated with ribosomal subunit proteins,K+ transport protein Kup,betaine synthesis related proteins,compatible solutes transport,Fe-S cluster related proteins,lipopolysaccharide biosynthesis,lipid metabolism,and some proteins related to stress response were up-regulated.The enzymes associated with glycogen synthesis were down-regulated well as the enzymes associated with arginine synthesis was down-regulated.Furthermore,the up-regulated proteins associated with uptaking and usage of exogenous nitrogen source was found,which may be related to the supply of nitrogen in the process of amino acids and proteins synthesis in vivo.