Herbert Schellhorn

, PhD

Associate Professor, Pathology and Molecular Medicine

Member, Pathology and Molecular Medicine

Associate Professor, Biology

McMaster University
541 Life Sciences Building
905-525-9140 ext. 27316
schell@mcmaster.ca

Education and Professional Standing

• PhD Microbiology, North Carolina State University, 1988
• MSc Microbiology, University of Guelph, 1984

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Interests

Increasing our knowledge regarding regulation of bacterial genes that are specifically expressed in response to nutrient deprivation or other stress is crucial for understanding basic mechanisms of bacterial pathogenesis and environmental adaptation. In recent years, much has been learned about a key-conserved regulator, RpoS, that is required for the expression of a large number (over 60) of stress-induced genes. RpoS is known to be a virulence factor and so it is likely that one or more of the functions it regulates are important in adaptation of pathogenic bacteria to the host environment. There many unanswered questions regarding both the regulation of RpoS and the identity of genes it regulates. To address the latter point, we are using genetic and molecular biology tools to examine the expression of a large number of RpoS-dependent genes that we have identified in my laboratory. By simultaneously characterizing many RpoS-dependent genes, we will be able to identify key common regulatory signals of these genes that distinguishes their regulation from so-called "housekeeping" genes that are required for normal growth. The functions of approximately one half of the genes is not known - we will employ the computer tools of the rapidly advancing field of genomics, in addition to experimentation, to gain insight into the roles of these genes.

In addition to identifying RpoS-dependent genes, we are investigating specific questions that have arisen from our previous studies regarding lysine decarboxylase, transaldolase and catalase expression. Each of these stationary-specific genes are probably important in helping the cell adapt to stress conditions since we have found that they are expressed only in stationary phase when cells are in a starved state - they are not expressed under normal conditions.

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Selected Publications

• Dong, T., and H.E Schellhorn. 2008. Control of RpoS in global gene expression of Escherichia coli inminimal media.  Molecular Genetics and Genomics (in press).
• Dong, T., B.K. Coombes and H.E Schellhorn. 2008. Role of RpoS in virulence of Citrobacter rodentium. Infection and Immunity (in press).
• Li Y, Shi CX, Rosenfeld J, Mossman KL, Boo YC, Schellhorn HE. 2008. Restoration of vitamin C synthesis in transgenic Gulo-/- mice by helper-dependent adenoviral-based expression of gulonolactone oxidase. Human Gene Therapy. (in press)
• Dong, T., M. Kirchhof, and H.E Schellhorn. 2008. RpoS regulation of exponential phase-specific genes in Escherichia coli K-12. Molecular Genetics and Genomics 279(3):267-77.
• Li, Y.D., and H.E. Schellhorn. 2007.  New Developments and Novel Therapeutic Perspectives for Vitamin C in Research and Nutrition.  Journal of Nutrition 137:2171-84
• Li, Y.D., and H.E. Schellhorn. 2007.  Rapid kinetic microassay for catalase activity. Journal of Biomolecular Techniques, 2007  18:185-7.
• Dong T, C. Joyce and H.E. Schellhorn. 2007. The Role of RpoS in Bacterial Adaptation. In Bacterial Physiology - A Molecular Approach. Walid M. El-Sharoud (ed.) Springer, Heidelberg.
• Li, Y.D., and H.E. Schellhorn. 2006. Can age-related degenerative diseases be ameliorated by administration of vitamin C at pharmacological levels?  Medical Hypotheses 68(6):1315-7  (CIHR)
• Kim H.J., S.I. Lee, D.H. Lee, D. Smith, H. Jo, H.E. Schellhorn and Y.C. Boo. 2006. Ascorbic acid synthesis due to L-gulono-1,4-lactone oxidase expression enhances NO production in endothelial cells. Biochem Biophys Res Commun 345(4):1657-6
• Weerasinghe JP, T. Dong, M.R. Schertzberg, M.G. Kirchhof, Y. Sun, and H.E. Schellhorn 2006. Stationary phase expression of the arginine biosynthetic operon argCBH in Escherichia coli. BMC Microbiol.   22;6:14. (NSERC)
• Shu J, H.E. Schellhorn, and T.M. Murphy. 2006. Stationary phase-induction of G-->T mutations in Escherichia coli. Mutation Research  596(1-2):106-12.
• Chen,G. and H.E. Schellhorn. 2004. Positive selection for loss of RpoS function in Escherichia coli Mutation Research 554: 193-203.
• Ha, M.N., F.L Graham, C.K. D’Souza, W.J. Muller, S.A. Igdoura, and H.E. Schellhorn.  2004. Functional rescue of vitamin C synthesis deficiency in human cells using adenoviral-based expression of murine L-gulono-γ -lactone oxidase (GULO). Genomics. 83(3):482-92.
• Vijayakumar, S.R., C.L. Patten, M.G. Kirchhof, and H.E. Schellhorn. 2004. Identification of RpoS regulated genes in Escherichia coli Journal of Bacteriology.  186:8499-50.
• Patten, C.L., M.G. Kirchhof, R.A. Morton, and H.E. Schellhorn. 2004. Microarray analysis of RpoS-mediated gene expression in Escherichia coli K-12. Molecular Genetics and Genomics. 272:580-91.