Journal of Microbiology

Journal Article

Impact of small RNA RaoN on nitrosative-oxidative stress resistance and virulence of Salmonella enterica serovar Typhimurium: Sinyeon Kim , Yong Heon Lee; J. Microbiol. 2020;58(6):499-506. Published online April 11, 2020; DOI: https://doi.org/10.1007/s12275-020-0027-2

Abstract: 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.

Research Support, Non-U.S. Gov't

NOTE] Identification of Chaperones in Freeze Tolerance in Saccharomyces cerevisiae: Mahendran Chinnamara Naicker , I Seul Jo , Hana Im; J. Microbiol. 2012;50(5):882-887. Published online November 4, 2012; DOI: https://doi.org/10.1007/s12275-012-2411-z

Abstract: Exposure to low temperatures reduces protein folding rates and induces the cold denaturation of proteins. Considering the roles played by chaperones in facilitating protein folding and preventing protein aggregation, chaperones must exist that confer tolerance to cold stress. Here, yeast strains lacking individual chaperones were screened for reduced freezing tolerance. In total, 19 of 82 chaperone-deleted strains tested were more sensitive to freeze-thaw treatment than wild-type cells. The reintroduction of the respective chaperone genes into the deletion mutants recovered the freeze tolerance. The freeze sensitivity of the chaperone-knockout strains was also retained in the presence of 20% glycerol.

Retracted Publication

NOTE] Identification of the Vibrio vulnificus htpG Gene and Its Influence on Cold Shock Recovery: Slae Choi , Kyungku Jang , Seulah Choi , Hee-jee Yun , Dong-Hyun Kang; J. Microbiol. 2012;50(4):707-711. Published online August 25, 2012; DOI: https://doi.org/10.1007/s12275-012-2294-z

Abstract: An htpG gene encoding the heat shock protein HtpG was identified and cloned from Vibrio vulnificus. The deduced amino acid sequence of HtpG from V. vulnificus exhibited 71 and 85% identity to those reported from Escherichia coli and V. cholera, respectively. Functions of HtpG were assessed by the construction of an isogenic mutant whose htpG gene was deleted and by evaluating its phenotype changes during and after cold shock. The results demonstrated that recovery of the wild type from cold shock was significantly faster (p<0.05) than that of the htpG mutant, and indicated that the chaperone protein HtpG contributes to cold shock recovery, rather than cold shock tolerance, of V. vulnificus.

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