Impact of small RNA RaoN on nitrosative-oxidative stress resistance and virulence of Salmonella enterica serovar Typhimu
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Impact of small RNA RaoN on nitrosative-oxidative stress resistance and virulence of Salmonella enterica serovar Typhimurium Sinyeon Kim1,2 and Yong Heon Lee3* 1
School of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea Department of Bioscience and Biotechnology, Konkuk University, Seoul 05029, Republic of Korea 3 Department of Biomedical Laboratory Science, Dongseo University, Busan 47011, Republic of Korea 2
(Received Jan 14, 2020 / Revised Feb 13, 2020 / Accepted Mar 5, 2020)
RaoN is a Salmonella-specific small RNA that is encoded in the cspH-envE intergenic region on Salmonella pathogenicity island-11. We previously reported that RaoN is induced under conditions of acid and oxidative stress combined with nutrient limitation, contributing to the intramacrophage growth of Salmonella enterica serovar Typhimurium. However, the role of RaoN in nitrosative stress response and virulence has not yet been elucidated. Here we show that the raoN mutant strain has increased susceptibility to nitrosative stress by using a nitric oxide generating acidified nitrite. Extending previous research on the role of RaoN in oxidative stress resistance, we found that NADPH oxidase inhibition restores the growth of the raoN mutant in LPS-treated J774A.1 macrophages. Flow cytometry analysis further revealed that the inactivation of raoN leads to an increase in the intracellular level of reactive oxygen species (ROS) in Salmonella-infected macrophages, suggesting that RaoN is involved in the inhibition of NADPH oxidase-mediated ROS production by mechanisms not yet resolved. Moreover, we evaluated the effect of raoN mutation on the virulence in murine systemic infection and determined that the raoN mutant is less virulent than the wild-type strain following oral inoculation. In conclusion, small regulatory RNA RaoN controls nitrosativeoxidative stress resistance and is required for virulence of Salmonella in mice. Keywords: small RNA RaoN, oxidative stress, nitrosative stress, ROS, RNS, intramacrophage growth, virulence, Salmonella enterica serovar Typhimurium Introduction Salmonella enterica serovar Typhimurium is a Gram-negative facultative intracellular pathogen associated with foodborne gastroenteritis in humans. This serovar also causes a *For correspondence. E-mail: [email protected]; Tel.: +82-51-320-1912; Fax: +82-51-320-2721 Copyright G2020, The Microbiological Society of Korea
murine systemic disease similar to human typhoid fever by infection with S. enterica serovar Typhi (Monack et al., 2004; Haraga et al., 2008; Johnson et al., 2018). During systemic infection of mice, S. enterica serovar Typhimurium survives the acidic pH of the stomach before passage to the small intestine, where this pathogen specifically invades M cells overlying the lymphoid follicles of Peyer’s patches. Subsequently, the bacteria preferentially infect phagocytes, which then spread into the draining mesenteric lymph nodes and disseminate via the bloodstream to the spleen and liver
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