Dr. Keith Poole is a Professor in the Department of Biomedical and Molecular Sciences (DBMS) and past Head of the Department of Microbiology and Immunology (2005-2011) and past Associate Head of DBMS (2011-2012). He received his BSc (1980) and PhD (1986) degrees in Microbiology from the University of British Columbia working in the area of Pseudomonas outer membranes under the tutelage of R.E.W. (Bob) Hancock. This was followed by a 2-year stint as a postdoctoral fellow in the laboratory of Prof. Dr. Volkmar Braun at the University of Tuebingen, working on the molecular biology of a hemolysin from Serratia marcescens. Dr. Poole joined the department of Microbiology and Immunology at Queen’s University in 1988, working first on the molecular biology of siderophore-mediated iron acquisition in Pseudomonas aeruginosa and, later, on efflux-mediated multidrug resistance and bacterial stress responses as determinants of antimicrobial resistance, also in P. aeruginosa. He is a past recipient of the Queen’s University Prize for Excellence in Research (2005), Cystic Fibrosis Canada’s Robbie Award (2014) and their Marsha Morton Scholarship (1999), as well as the Canadian Society of Microbiologists’ Fisher Scientific Award (1996). He was elected as a Fellow of the American Academy of Microbiology in 2007.
Dr. Poole has consulted widely with industry on efflux-mediated antimicrobial resistance. He has published 150 papers and book chapters and has delivered more than 100 invited presentations. He is also a past member of the editorial boards of Antimicrobial Agents and Chemotherapy (1997-2006) and Journal of Antimicrobial Chemotherapy (2004-2009).
From efflux to stress: the evolution of multidrug resistance in Pseudomonas aeruginosa
Keith Poole, Department of Biomedical and Molecular Sciences, Queen’s University.
Antibiotic resistance continues to plague antimicrobial chemotherapy of infectious disease, no more so than in the opportunistic human pathogen P. aeruginosa. Efflux mechanisms, particularly broadly-specific multidrug efflux systems, are important contributors to the intrinsic and acquired resistance of this organism. Despite their contribution to resistance, however, it has long been suggested that antimicrobial efflux is not their intended function. Recent work confirms this, and it is now established that these multidrug efflux systems are components of environmental stress responses and, moreover, that stress responses are important determinants of antimicrobial resistance, not only in P. aeruginosa but also in other disease-causing bacteria. This raises the spectre of the environment driving resistance development in the absence of antimicrobial selective pressure and highlights the possible need to target these stress response resistance determinants therapeutically. Examples of stress responses, including efflux mechanisms, as determinants of antimicrobial resistance in P. aeruginosa will be presented and our early efforts at targeting these to enhance the organism’s antimicrobial susceptibility will be highlighted.
This award is made possible by the
financial support of Canadian Science
Publishing (publisher of the NRC
Research Press journals). Their commitment and service to microbiological research and teaching in Canada is greatly appreciated.
2014 Armand-Frappier Gold Metal Award Lecture
Ragunath Singaravelu, University of Ottawa, ON
Ragunath Singaravelu is a virologist studying currently completing his Ph.D. in Microbiology and Immunology in the lab of Dr. John Pezacki at the National Research Council of Canada in Ottawa. He obtained his B.Sc. in Biochemistry and B.A.Sc. in Chemical Engineering at University of Ottawa, where he trained in the labs of Dr. Tony Durst and Dr. Daniel Figeys. His doctoral thesis work has focused on understanding the role of hepatic lipid metabolism in hepatitis C virus (HCV) pathogenesis.
An emerging focus in immunology is the relevance of lipid metabolism in innate immunity. Recent work demonstrated a novel role for the macrophage secreted oxysterol, 25-hydroxycholesterol (25HC), in the host antiviral response and interferon signalling. While these studies demonstrate 25HC inhibits viral-cell fusion through modification of cellular membranes, it is unclear whether 25HC possesses additional membrane-independent antiviral functions. We have previously shown that 25HC represses hepatitis C virus (HCV) replication through repression of coding genes associated with lipid metabolism in hepatocytes. We demonstrate that 25HC activates the expression of microRNAs, miR-130b and miR-185, in hepatitis C virus (HCV) infected hepatoma cells. We show that miR-185 and miR-130b overexpression potently inhibits HCV replication. Conversely, miR-130b inhibition increases viral replication. miR-185 directly regulates SREBP2, a master transcriptional regulator of cholesterol biosynthesis, as well as SCD, a key enzyme in the synthesis of unsaturated fatty acids. Similarly, miR-130b regulates the expression of LDLR, a crucial receptor for cholesterol uptake. The miRNAs' antiviral activity is consistent with the previously reported crucial roles of SREBP2, SCD, and LDLR in the HCV life cycle. HCV hijacks hepatic lipid metabolism to facilitate its pathogenesis; clinically, these HCV-induced metabolic alterations results in steatosis for over 50% of patients. Interestingly, we demonstrate that HCV infection down-regulates miR-185 and miR-130b expression. Coherent anti-Stokes Raman scattering microscopy demonstrates that inhibition of miR-185 or miR-130b activity results in lipid accumulation – highlighting a novel mechanism of HCV-induced steatosis. As there is increasing evidence that cholesterol and unsaturated fatty acids play a critical role in viral entry and replication, 25HC’s activation of miRNAs repressing LDLR, SCD, and SREBP2 expression may play a role in the broad antiviral response. Furthermore, HCV’s repression of miR-130b and miR-185 represents a novel mechanism of innate immune evasion. Our data highlight miRNAs as a novel link between lipid metabolism and innate immunity.
This lecture is made possible with the financial support of
Canadian Society of Microbiologists. Their commitment and service to microbiological research and teaching in Canada is greatly appreciated.
2014 Fisher Scientific Award
Catherine Paradis-Bleau, Université de Montréal, QC
After a B. Sc. in Biology with a major in Microbiology at the Université de Sherbrooke (1998-2001), Dr. Paradis-Bleau did a M. Sc. and Ph.D. in Microbiology-Immunology at the Université Laval under the supervision of Dr. Roger C. Levesque (2002-2007). For her doctoral work she studied bacterial cell division proteins and cell wall biogenesis enzymes from the opportunistic pathogen Pseudomonas aeruginosa as bacterial targets, and phage lysis proteins as new antibacterial agents. Her thesis work allowed her to win the Canadian graduate student microbiologist of the year award from the Canadian Society of Microbiologists. She then moved to Boston for a first postdoctoral training at Harvard Medical School to study of the host innate immune response to P. aeruginosa pulmonary infection in the genetic background of cystic fibrosis (2007-2008). She decided to go back to fundamental bacteriology to build my her scientific niche and joined the lab of Thomas G. Bernhardt at Harvard Medical School for a second postdoctoral training (2008-2012). She then used bacterial genetic and molecular microbiology to study gram-negative bacterial envelope assembly and discovered many novel factors involved in this process. She opened my herlab in the Department of Microbiology, Infectiology and Immunology of the Université de Montréal at the end of the year 2012 that aims at understanding the physiological and molecular role of the novel factors involved in gram-negative bacterial envelope assembly.
Bacterial envelope assembly: recent advances from bacterial genetics and antibiotic-independent phenotypic screens
Catherine Paradis-Bleau, Department of Microbiology, Infectiology and Immunology, Université de Montréal, QC, CA.
Bacterial envelopes are complex structures that present both challenges and opportunities for fundamental discoveries and therapeutic interventions. Many of our most successful antibiotics target bacterial envelope assembly. Ironically, most of our knowledge about envelope assembly has come from using these antibiotics as functional probes. To shed light on bacterial envelope assembly, I used the gram-negative bacterium Escherichia coli as a model system and first studied cell wall assembly by the penicillin-binding proteins (PBPs). The development of a reciprocal synthetic lethal screen approach permitted the discovery of the outer membrane lipoproteins LpoA and LpoB as the first PBP regulators. LpoA and LpoB are essential cofactors of the main cell wall assembly enzymes PBP1A and PBP1B. They directly interact with their cognate PBP, forming specific transenvelope complexes critical for cell wall assembly in vivo. This demonstrates that the PBPs of Gram-negative bacteria need protein cofactors located in the outer membrane to activate and guide their enzymatic activity. I then completed a project aiming at identifying the complete set of E. coli factors required for envelope integrity. The design and optimization of a novel phenotypic assay combined with genomic-scale analysis allowed the discovery of 102 genes of unknown function that appear to be important for envelope assembly. I selected the factor ElyC for initial studies because it has a domain of unknown function predicted to be in the periplasm that is highly conserved among bacteria. I demonstrated that ElyC is required for cell wall assembly at room temperature and involved ElyC in the metabolism of the precursor undecaprenyl-P, a lipid carrier essential for the assembly of many bacterial envelope components such as cell wall and enterobacterial common antigen. Functional studies of the other factors involved in envelope assembly should broaden our understanding of this process and identify new vulnerabilities to target with drugs.
This lecture is made possible with the financial support of Fisher Scientific. Their commitment and service to microbiological research and teaching in Canada is greatly appreciated.
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