Construction RpoS Gene Deletion Mutant Of Salmonella Enteritidis And Its Characteristics

Salmonella enteritidis is a kind of intestinal pathogenic bacteria. It’s easy to infect dairy foods, meat and fish. In the process of grow, food processing and infect the host, bacteria needs to response many environmental stresses. At this time, there is a kind of injury and sublethal bacteria, after a period of time to recover its biological activity, and to leave the food safety hidden trouble. Because of there is less research about the stress response mechanism and injury recovery mechanism of S.E., it is difficult to detect this bacteria.While S.E. response to stress conditions, will priming the homologous regulation factors to regulate the expression of related genes, and adapt to the new environmental.σs factor is such a transcriptional regulation factor, which controls the expression of many genes of the stationary phase and interrelated adversity stress conditions, but its mechanism of action is complicated.This study was to construct mutant by knocking-out rpoS gene of salmonella enteritidis, with the help of the λ-red recombinant system. Investigation the survival ability of wild type strains and rpoS deletion mutant under the stress environment of high temperature, acids, hyper osmosis, hydrogen peroxide, injure of machine, etc. At the same time, compared both stress response of ultra high pressure (UHP) processing and the information of recovery after injured. Preliminarily studied the effect and information of stress regulation of rpoS gene when the stress environment.Thus, settle the foundation for further understanding the mechanism of response to stresses of σs factor, and the injury recovery mechanism of S.E..The main results of this research were as follows:1) rpoS gene of S.E. was successfully knocked-out with the help of the λ-red recombinant system. Constructed rpoS gene deleted mutant-S.E./ΔrpoS strains.2) There is no significant difference of the growth curves between the rpoS mutant and wild-type strains in LB culture media at37℃ (P>0.05). But the survival ability of S.E./Δ rpoS strains was significantly lower than wild-type strains under stress conditions of45℃、pH4.0、2%NaCl and1mM H2O2(P<0.05). So the experimental results can be preliminary show that the effect of survival ability is not obvious while salmonella enteritidis loss rpoS gene, but σs factor participates regulation of the stress response and plays an important role for salmonella enteritidis to stress environments which were above-mentioned.3) Pressure is the main factor to injured S.E. by UHP. To compared wild-type strains and S.E./ΔrpoS strains under high-pressure found that σs factor may be participates in regulation and produces effect. The recovery time of S.E. which injured by UHP is2h by two-step overlay method, and the recovery time of S.E./ΔrpoS strains which injured by UHP is5h, So it is shows that the recovery ability of S.E.is stronger than S.E./ΔrpoS strains, also can demonstrate that it is significant to affected the recovery ability of salmonella enteritidis while losing rpoS gene.