Study On Gene Hmp In Cronobacter Under Hydrogen Peroxide And Nitric Oxide Stress

Cronobacter species are a group of gram-negative bacteria which contribute to some fatal disease such as necrotizing colitis,septicemia,and neonatal meningitis,mainly existing in infant formula milk powder.Meanwhile,Cronobacter spp.has a strong ability to resist adversity,such as acid,alkali and high temperature,etc.At present time,there are no effective solutions to these diseases caused by it,but only to solve the infection at the source.Therefore,it is it a great significance to explore its virulence factors and understand its self-regulation mechanism under adverse conditions.Flavohemoglobin,which expressed by hmp,could eliminate nitric oxide in most microorganism to protect them.In this research,we selected Cronobacter malonaticus wild type and its knock-out strain ?hmp as the experimental strains to explore the growth,cell activity,cell shape,biofilm formation of bacteria and the mechanism of these phenomenon.Firstly,the bacteria were suppressed under oxidative stress.The growth rate,cell viability and biofilm formation ability of the mutant were higher than those of the wild type.The cell morphology of the wild strain was more seriously damaged,and the expression of gene hmp was decreased under the condition of oxidative stress.Besides,reactive oxygen species of wild type was higher than that of mutant strain,which is due to the stronger reducibility of wild type.Secondly,under nitric oxide stress,the inhibition rate of the mutant was higher than that of the wild strain,and the cell viability and biofilm formation ability were lower.Furthermore,the cell morphological damage of mutant was more serious than that of wild type,and the expression of gene hmp would increase under nitric oxide stress.Finally,the damage to the bacteria is greatly increased under nitric oxide and hydrogen peroxide treatment.In addition,the growth rate of wild strain was higher than that of mutant strain.Mutant strains sustained more severe damage and produced more reactive oxygen species than wild type.The expression of gene hmp also increased under nitric oxide and hydrogen peroxide treatment.The results showed that hmp of C.malonaticus would promote the oxidative damage it suffered and protect it from nitric oxide damage.This study concentrated on the stress of C.malonaticus treated with nitric oxide and hydrogen peroxide and discussed the function of hmp.The results would provide a theoretical basis for further understanding of its pathogenic mechanism,effective prevention and control of its pollution in food industry.