The Effect Of Psp System Under Desiccation Stress Of Cronobacter Malonaticus

Cronobacter malonaticus is widely pathogenic in infants,children and immunocompromised adults,causing clinical symptoms such as septicaemia,necrotizing enterocolitis and meningitis.Meanwhile,the strong desiccation tolerance allows Cronobacter spp.to survive in foods with low water activity for long periods of time,increasing the risk of human infection.However,the mechanism of desiccation tolerance of Cronobacter spp.is not well understood.The phage shock protein(Psp)family can respond to avariety of environmental changes,maintain the stability of the intracellular environment,and protect the body from damage.The Psp family has been reported many times to be related to the envelope stress response,but the role of this family in Cronobacter spp.has not been clarified.In this research,we selected C.malonaticus wild type and Psp system mutant strains(?psp A,?psp B,?psp C and ?psp G)as the experimental subjects.Firstly,transcriptome data were systematically analyzed,and q RT-PCR was used to verify that the psp A,psp B,psp C and psp G genes could be significantly expressed under desiccation treatment.Secondly,bioinformatics analysis was carried out to elucidate the physicochemical and molecular properties of Psp family proteins.Then the phenotypic comparison showed that the survival rate of the mutant strains was obviously lower than that of the wild type;the knockout of psp A,psp B,psp C and psp G genes affected the biofilm formation ability;the deletion of psp A and psp G genes affected the motility ability under desiccation stress and so on.The above results preliminally proved that Psp system is an important regulatory system for the resistance of C.malonaticus to desiccation stress.Finally,the psp A,psp B,psp C and psp G genes were cloned by using genetic engineering technology,and recombinant plasmids p ET28a-EGFP-Psp A,p ET28a-EGFP-Psp B,p ET28a-EGFP-Psp C and p ET28a-EGFP-Psp G were successfully constructed and their recombinant protein were induced,which provided an experimental basis for the subsequent research on the characteristics and functions of Psp family.