Effect Of Lysogenic Infection Of Stx Phage On Acid-Resistant Of Escherichia Coli Mg1655

Shiga toxin-producing Escherichia coli (STEC) strains are common foodborne enteric pathogens associated with diarrhea, hemorrhagic colitis and hemolytic uremic syndrome (HUS) E.coli O157:H7is the most representative serotype of them, It can cause severe disease through Shiga toxin, hemolysin and adhesin in humans. Acid resistance(AR) is considered as a virulence factor, because it contributes to the low infective dose.E. coli O157:H7can survive acid environmental stresses such as the human stomach which pH ranges from1.5to3.0, and some genes of E.coli will be induced to express in order to maintain homeostasis. it is easy to pollute the acid food and some leavened food, So the study on acid resistance of E.coli has aroused people’s attention.The glutamate decarboxylase (GAD) system is the most efficient acid resistance mechanism in E. Coli. In order to confirm and analyze the relationship among these acid genes,We inactivated gadE and hdeBAD in E. coli MG1655by means of lambda red recombinase method, and compared transcription profiles of the mutant with wild type in the exponential by realtime-PCR.We find that the inactivation of gadE can cause downregulated the expression of gadA,gadB,hdeA,hdeB in GAD system.Also, the Survival of the two mutant strains are decline. This study further shows that the gadE is an important regulatory factor in glutamate-dependent acid resistance system. Inactivation of hdeBAD has no effect on the expression of gadE, exemplifying the regulative effects are not mutual.The phage is ubiquitous in circumstances, Previous research have found that the expression of Acid-resistant gene has also upgregulate in lysogen compared to previous, such as gadE,hdeA, In order to confirm the effect of Stx phage on E.coli, we carried out a series of experiments to find the truth, we infect the E.coli K-12MG1655using the Min27Phage isolated from brash piglet and comparing the variation tendency between lysogenic bacterium and nonlysogenic ones in acid environment.we found that, the phage really cause the rise in gene expression of acid-resistance gene:gadE,moreover, the viability of lysogenic bacterium is also enhanced, We can fetter out details that the Stx phage can effect physiological property of the host bacteria indeed. So, The Stx phage should be highlighted not just only for its ability to product the toxin but also other roles.