Analysis of regulation role of sRNA (istR) in Salmonella resistant to reactive nitrogen and oxygen intermediates

Abstract:

Salmonella is a facultative intracellular pathogen that is associated with gastroenteritis, septicemia, and typhoid fever. It survives and replicates in macrophages during the course of infection and can be exposed to a number of stressful environments during its life cycle. Among the major antimicrobial products of macrophages are reactive intermediates of the oxidation of nitrogen (RNI) and the reduction of oxygen (ROI) which belong to oxygen-dependent antimicrobial systems of phagocytic cells. Resistance to ROI and RNI is a key feature of Salmonella virulence in vivo. Bacterial small non-coding RNA (sRNA) plays diverse physiological roles in stress responses, regulation of metabolism, control of bacterial envelope composition and bacterial virulence. In this study, we studied regulatory function of salmonella sRNA istR associated with resistance of S. enterica serovar Enteritidis to RNI and ROI. We constructed an istR-deletion mutant of SE2472 (SE2472△istR) using the red recombination system. The △istR mutant of SE2472 was complemented by cloned the wild-type allele of istR into plasmid pHDB3. To study the contribution of istR to the resistance of Salmonella enteritidis to RNI and ROI, we studied the differences of the survival rate of wild type SE2472, SE2472△istR mutant and complement strain to NaNO2 (pH 5.0, 20 mmol/L) and H2O2. The SE2472△istR was more sensitive to the bactericidal activity of NaNO2 (pH 5.0, 20 mmol/L) than wild type SE2472, but there is no difference in survival rate in the present of H2O2. To confirm the results, we constructed the complement plasmid and transferred it into SE2472△istR to rescue the survival defect. Results showed that the survival defect of SE2472△istR was rescued well when complement strain grown with NaNO2. The study of survival rate of the wild type SE2472 and istR deletion mutant in the presence of NaNO2 (pH 5.0, 20 mmol/L) and H2O2 demonstrated that sRNA istR acts as an important regulator of the resistance of SE oxygen-dependent antimicrobial systems.