KyuHong Cho | Microbiology | SIU

KyuHong Cho

Assistant Professor

Research Specialities: Group A Streptococcal Virulence Factors. S. pyogenes is a strict human pathogen that causes diseases ranging from mild infections such as strep throat or impetigo to life threatening diseases like necrotizing fasciitis or toxic shock syndrome. Different disease manifestations seem to be caused by different types of regulation of virulence factors in different tissues; S. pyogenes uses many regulators including 11 - 13 two component systems and several stand-alone response regulators. Our future studies will be focused on the regulation of virulence factors such as the thermoregulation of capsule expression and regulation of CAMP factor expression as model systems for the virulence gene regulation byS. pyogenes. Another interest of our research is to study genes such as gidA and cvfA which are necessary for the virulence of S. pyogenes but whose functions are not well known. The S. pyogenes genome contains hundreds of genes whose functions are unknown.

Education:

PhD, 2001, University of Illinois

Courses Taught:

MICR 201: Elementary Microbiology
MICR/MBMB 421: Biotechnology
MICR/MBMB 481: Diagnostic and Applied Microbiology Laboratory
Tutor: Southern Illinois University School of Medicine Year One Curriculum

Research Interests:

Thermoregulation of Capsule Production. Streptococcus pyogenes is a human pathogen that infects many different tissues including skin, throat, blood, female urogenital tract, and lower gastrointestinal tract. These tissues exhibit different temperatures ranging from 25°C to 37°C. Thus, S. pyogenes is expected to control its physiology and the expression of virulence factors according to temperature variations in order to infect and survive in those tissues. During a study of the streptococcal capsule, we found that the capsule expression is thermoregulated; the capsule production by a S. pyogenes strain was higher at room temperature (20°C ~ 25°C) than that at 37°C. The capsule is one of the major virulence factors involved in the initial colonization on skin and throat and in the escape from the host immune system. Based on the phenotype of the temperature-regulated capsule production, we study the molecular mechanism of this thermoregulation.

CvfA. Streptococcus pyogenes, a multiple-auxotrophic human pathogen, regulates virulence gene expression according to nutritional availability during various stages of infection process or in different infection sites. We discovered that CvfA influenced the expression of virulence genes according to growth phase and nutritional status. The influence of CvfA in C medium, rich in peptides and poor in carbohydrates, was most pronounced at the stationary phase. Under these conditions, up to 30% of the transcriptome exhibited altered expression; the expression of multiple virulence genes were altered including those encoding streptokinase, CAMP factor, streptolysin O, M protein (more abundant in the CvfA(-) mutant), SpeB, mitogenic factor, and streptolysin S (less abundant). The increase of carbohydrates or peptides in media restored the expression of the virulence genes in the CvfA(-) mutant to wild-type levels (emm, ska, and cfa by carbohydrates; speB by peptides). Even though the regulation of gene expression dependent on nutritional stress is commonly linked to the stringent response, levels of ppGpp were not altered by deletion of cvfA. Instead, CvfA interacted with enolase, implying that CvfA, a putative RNase, controls the transcript decay rates of virulence factors or their regulators according to nutritional status. The virulence of CvfA(-) mutants was highly attenuated in murine models, indicating that CvfA-mediated gene regulation is necessary for the pathogenesis of S. pyogenes. Taken together, the CvfA-enolase complex in S. pyogenes is involved in the regulation of virulence gene expression by controlling RNA degradation according to nutritional stress.

Publications:

Articles in Professional Journals

• Cho, K.H., Wright J., Svencionis, J. and Kim, J.H. 2013. The prince and the pauper. Which one is real? The problem of secondary mutation during mutagenesis in Streptococcus pyogenes. Virulence. 4(8), 1-2. Link
• Kim, J.H., Roy, A., Jouandot D 2nd and Cho, K.H. 2013. The glucose signaling network in yeast. Biochimica et Biophysica Acta. doi:pii:S0304-4165(13)00338-3. 10.1016/j.bbagen.2013.07.025. PubMed link
• Cho, K.H. and Kang, S.O. 2013. Streptococcus pyogenes c-di-AMP phosphodiesterase, GdpP, influences SpeB processing and virulence. PLOS ONE 8(7): e69425. doi:10.1371/journal.pone.0069425. Link
• Tesorero, R.A., Yu, N., Wright, J.O., Svencionis, J.P., Cheng Q., Kim, J.H. and Cho, K.H. 2013. Novel regulatory small RNAs in Streptococcus pyogenes. PLOS ONE. 8(6):e64021. doi:10.1371/Journal.pone.0064021. Link
• Roy, A., Shin Y.J., Cho, K.H. and Kim, J.H. 2013. Mth1 Regulates Expression of the Glucose Transporter Genes by Modulating the Interaction of Rgt1 with Ssn6-Tup1 in yeast. Molecular Biology of the Cell 24(9), 1493-503. Link
• Kang, S.O., Wright, J.O., Tesorero, R.A., Lee, H., Beall, B. and Cho, K.H. 2012. Thermoregulation of Capsule Production by Streptococcus pyogenes. PLoS ONE 7(5): e37367. doi:10.1371/journal.pone.0037367. Link
• Kang, S.O., Caparon, M.G. and Cho, K.H. 2010. Virulence Gene Regulation By CvfA, A Putative RNase: The CvfA-Enolase Complex In Streptococcus pyogenes Links Nutritional Stress, Growth Phase Control And Virulence Gene Expression. Infect. Immun. 78:2754-67. PubMed link
• Yu, N., Cho, K.H., Cheng, Q. and Tesorero, R.A. 2009. A Hybrid Computational Approach for the Prediction of Small Non-coding RNAs from Genome Sequences. 2009 International Conference on Computational Science and Engineering:1071-76.
• Cho, K.H. and Caparon, M.G. 2008. tRNA Modification by GidA/MnmE is Necessary for Streptococcus pyogenes Virulence: a New Strategy to Make Live Attenuated Strains. Infect Immun. 76(7):3176-86. PubMed link
• Cho, K.H. and Caparon, M.G. 2005. Patterns of virulence gene expression differ between biofilm and tissue community of Streptococcus pyogenes. Mol. Micro. 57(6):1545-1556. PubMed link
• Nyberg, P., Sakai, T., Cho, K.H. , Caparon, M.G., Fassler, R. and Bjorck, L. 2004. Interactions with fibronectin attenuate the virulence of Streptococcus pyogenes. EMBO J. 19;23(10):2166-2174. PubMed link
• Cho, K.H. and Salyers, A.A. 2001. Biochemical analysis of interactions between outer membrane proteins that contribute to starch utilization by Bacteroides thetaiotaomicron. J. Bacteriol. 183:7224-7230. PubMed link
• Cho, K.H., Cho, D.L., Wang, G-R. and Salyers, A.A. 2001. New regulatory gene that contributes to control ofBacteroides thetaiotaomicron starch utilization genes. J. Bacteriol. 183:7198-7205. PubMed link
• Shipman, J.A., Cho, K.H. , Siegel, H.A. and Salyers, A.A. 1999. Physiological characterization of SusG, an outer membrane protein essential for starch utilization by Bacteroides thetaiotaomicron. J. Bacteriol. 181:7206-7211. PubMed link
• Cho, K.H., Cho, Y.K., Hong, S.S. and Lee, H.S. 1995. Isolation of microorganism with high productivity and cultivation optimization for lactic acid production. Kor. J. Appl. Microbiol. Biotechnol. 23:6-11.
• Cho, Y.K., Cho, K.H., Hong, S.S. and Lee, H.S. 1995. Optimization of medium components for lactic acid production. Kor. J. Appl. Microbiol. Biotechnol. 23:12-16.