Department of Molecular and Cellular Biology Faculty . Dr. Cezar Khursigara

Email: ckhursig@uoguelph.ca

Office: SCIE 3248
Ext: 58091
Lab: 3205
Ext: 58904

Khursigara Lab

Molecular and Cellular Imaging Facility

Profile

Starting from a very young age, I have always had a strong interest in biology and the natural world around us. But it was a summer work-study program at Ryerson University where I first became fascinated with the world of bacteria. Under the guidance of Dr. Debora Foster, I studied how pathogenic bacteria such as enteropathogenic and enterohemorrhagic E. coli (EPEC and EHEC) caused disease in humans. This early experience opened my eyes to the world of biological research and showed me how exciting, stimulating and rewarding a laboratory environment could be. I then moved from Toronto to Montreal, where I obtained my Ph.D. from McGill University for my work elucidating the mechanisms of iron-uptake by Gram-negative bacteria, under the supervision of Dr. James Coulton. This experience in combining biochemical, biophysical and structural techniques to characterize protein-protein interactions laid the foundation for my drive to apply a multidisciplinary approach to study bacterial processes. In the course this work I realized how the visualization of molecular interactions using microscopy and high-resolution structural techniques could complement and greatly extend conclusions drawn from more traditional methods. This insight prompted me to move to the United States to work at the National Cancer Institute of the National Institutes of Health (NIH). As a Visiting Fellow in the laboratory of Dr. Sriram Subramaniam, I helped pioneer cutting-edge cryo-electron microscopy techniques alongside molecular and biochemical methods to investigate the molecular architecture of receptor complexes involved in directed bacterial movement, or chemotaxis. My laboratory continues to apply this multidisciplinary approach to the study of a variety of bacterial processes.

Education

B.Sc. Department of Chemistry and Biology, Ryerson University
Ph.D. Department of Microbiology and Immunology, McGill University
PDF. Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health

Research

Bacterial cell biology has seen a renaissance in the past several years that has been spurred in part by advances in imaging techniques. Major advances in fluorescent microscopy, cryo-electron microscopy (2-D) and cryo-electron tomography (3-D) have provided new insight into bacterial ultrastructures that accomplish fundamental processes, such as cell growth and movement. Advances in imaging are also providing evidence that these cellular systems and assemblies are not only highly complex, but generally function in concert to accomplish cellular goals.

The research in our laboratory focuses on elucidating the structure and function of protein complexes involved in complex biological processes. We are particularly interested in the macromolecular assemblies that govern bacterial cell division, cell-to-cell interaction, biofilm formation, motility and chemotaxis. Moreover, with the emergence of a growing number of multi-drug resistant strains of bacteria there is a pressing need to identify new drug targets. Accordingly, these essential bacterial processes provide a number of exciting candidates. My research group is taking a multidisciplinary approach to answer fundamental questions related to these essential cellular processes. By combining cryo-electron microscopy and tomography with biochemical, biophysical, molecular and cellular techniques, our goal is to identify potential therapeutics that can target a broad spectrum of disease-causing bacteria. We also seek to develop novel imaging techniques, including correlative methods using fluorescent and cryo-electron microscopy. We hope that the imaging methods we develop in this research program will transcend bacterial studies and significantly impact applications in diverse biological fields, thus leading to advances in structural biology, nanotechnology, ecology and medicine, among others.

We are currently accepting graduate students who share the lab's vision for understanding bacterial processes and developing cutting-edge imaging methods. Potential students with interests in cellular imaging and electron microscopy, microbiology, molecular and cellular biology, biochemistry, biophysics, and their applications to medically and environmentally relevant problems are encouraged to contact us.

Selected Publications

Park AJ, Murphy K, Krieger J, Brewer D, Taylor P, Habash M, Khursigara CM. A temporal examination of the planktonic and biofilm proteome of whole cell Pseudomonas aeruginosa PAO1 using quantitative mass spectrometry. Molecular and Cellular Proteomics (in press)

Murphy K, Park AJ, Hao Y, Brewer D, Lam SJ, Khursigara CM. Influence of O polysaccharides on biofilm development and outer membrane vesicle biogenesis in Pseudomonas aeruginosa PAO1. Journal of Bacteriology (in press)

Eleftheriou NM, Ge X, Kolesnik J,Falconer SB, Harris RJ, Khursigara C, Brown ED, Brennan JD. Entrapment of Living Bacterial Cells in Low-Concentration Silica Materials Preserves Cell Division and Promoter Regulation. Chem Mater. 2013, 25(23), pp 4798–4805.

Guri A, Griffiths M, Khursigara CM, Corredig M.  The effect of milk fat globules on adherence and internalization of Salmonella Enteritidis to HT-29 cells.   J Dairy Sci. 2012 Sep 26.

Khursigara CM, Lan G, Neumann S, Wu X, Ravindran S, Borgnia MJ, Sourjik V, Milne J, Tu Y, Subramaniam S. (2011) Lateral density of receptor arrays in the membrane plane influences sensitivity of the E. coli chemotaxis response.
EMBO J. May 4;30(9):1719-29.

Li M, Khursigara CM, Subramaniam S, Hazelbauer GL. (2011) Chemotaxis kinase CheA is activated by three neighbouring chemoreceptor dimers as effectively as by receptor clusters.  Mol Microbiol. Feb;79(3):677-85

Khursigara CM, Wu X, Zhang P, Lefman J, Subramaniam S. (2008) Role of HAMP domains in transmembrane signaling by bacterial chemoreceptors. Proceedings of the National Academy of Sciences (USA). 105(43):16555-60.

Khursigara CM, Wu X, Subramaniam S. (2008) Chemoreceptors in Caulobacter crescentus: trimers of receptor dimers in a partially ordered hexagonally packed array. Journal of Bacteriology. 190(20):6805-10.

*Zhang P, *Khursigara CM, Hartnell L, Subramaniam S. (2007) Direct visualization of E. coli chemotaxis receptor arrays using cryo-electron microscopy. Proceedings of the National Academy of Sciences (USA). 104(10):3777-3781. * equal contribution

Pawelek PD, Croteau N, Ng-Thow-Hing C, Khursigara CM, Moiseeva N, Allaire M, Coulton JW. (2006) Structure of TonB in complex with FhuA, E. coli outer membrane receptor. Science. 312(5778):1399-402.

Khursigara CM, De Crescenzo G, Pawelek, PD, Coulton, JW. (2004) Enhanced binding of TonB to a ligand-loaded outer membrane receptor: role of the oligomeric state of TonB in formation of a functional FhuA-TonB complex. Journal of Biological Chemistry. 279(9):7405-12.

Khursigara CM, De Crescenzo G, Pawelek PD, Coulton JW. (2005) Deletion of the proline-rich region of TonB disrupts formation of a 2:1 complex with FhuA, an outer membrane receptor of Escherichia coli. Protein Science. 14(5):1266-73.

Khursigara CM, De Crescenzo G, Pawelek PD, Coulton JW. (2005) Kinetic analyses reveal multiple steps in forming TonB-FhuA complexes from Escherichia coli. Biochemistry. 4(9):3441-53.

Khursigara C, Abul-Milh M, Lau B, Giron JA, Lingwood CA, Barnett Foster DE. (2001) Enteropathogenic Escherichia coli virulence factor bundle-forming pilus has a binding specificity for phosphatidylethanolamine. Infection and Immunity. 69(11):6573-9.

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