Effects Of CodY Gene On Environmental Tolerance And Pathogenicity In Staphylococcus Aureus

Staphylococcus aureus is an important zoonotic pathogen,and its pathogenicity is the m ain factor endangering human health,causing a series of acute and chronic infections.Also,S.aureus is easy to produce biofilms,and can withstand high temperature,low temperatur e,drying,oxidation and osmotic pressure and other adverse environments.S.aureus in the biofilm-state could adhere to living or non-living surfaces,enhanceing S.aureus resistance to environmental stress.In recent years,relevant studies have found that the transcriptional regulatory factor CodY can be involved in regulating the mechanism of responsing to nutri tional control,and regulating the metabolic pathway in S.aureus.However,it remains uncl ear whether CodY can regulate S.aureus resistance to environmental stress,how it affects biofilm formation and related pathogenicity.Therefore,the effects of codY on environment al tolerance and pathogenicity of S.aureus were investigated in this study.A strain of S.aureus RMSA24(wild strain,WT)isolated from raw cow milk in the labor atory and codY-mutant strain(M-codY)constructed on the basis of WT in the laboratory in the early stage were selected as research objects.The effects of codY on environmental tole rance and pathogenicity of S.aureus were investigated through transcriptome sequencing,constructing a complement-strain environmental tolerance test,biofilm formation assays,h emolysis test and RT-q PCR.The main research achievements are as follows:1.Transcriptome sequencing was performed on WT and M-codY,among which 255 gen e transcripts were defined as differentially expressed genes.The mutation of codY up-regul ated 183 DEGs and down-regulated 72 DEGs.A total of 2371 genes did not change signifi cantly in the overlap regions of the Venn diagram.In addition,it was found that the environ ment related-heat shock protein related genes(gro L,dan J)and the biofilm-related genes(i sa A,fnb A,fnb B and spa)were downregulated,and hemolysin genes(hla,hld,hlg B and hlg C)were up-regulated.Quantitative PCR showed that gro L,dan J,isa A,fnb A,fnb B,spa,ica A and arl R were reduced by 5.2,3.9,7.3,6.25,2.3 and 7.7 times,respectively.hla,hld,hlg B and hlg C were increased by 4.8,1.9,3.9 and 2.3 times,respectively.2.In this study,the complement strain C-codY of was constructed by homologous recom bination technology.the growth curves of wild strain WT,mutant strain M-codY and compl ement strain C-codY were basically the same.3.The environmental tolerance test showed that the ability of resistance to high temperat ure,dryness and oxidation of M-codY was significantly lower than that of WT and C-codY.M-codY had higher resistance to low temperature than WT and C-codY.There was no sign ificant difference in the ability of resisting osmotic stress among the three strains.4.The biofilm formation ability of mutant M-codY was significantly lower than that of wild WT and complement C-codY,The hemolytic ability of mutant M-codY was significan tly higher than that of wild WT and complement C-codY.In conclusion,this study explored the influence of codY on environmental tolerance and pathogenicity of S.aureus,which may provide a new direction for the prevention and treat ment of S.aureus infection.