Conférence scientifique | Centre de recherche du CHU Sainte-Justine
Yves Brun, PhD, titulaire de la Chaire de recherche du Canada 150 sur la biologie cellulaire bactérienne, professeur titulaire, Département de microbiologie, infectiologie et immunologie, Université de Montréal
According to the World Health Organization, the recent dramatic increase in bacterial resistance to antibiotics is one of our most urgent health challenges. By 2050, antimicrobial resistence could be the cause of 10 million deaths per year globally. The best target for antibiotic development has been and continues to be the synthesis of the peptidoglycan cell wall, which is required for bacterial growth and morphogenesis. I will describe new methods of peptidoglycan labeling that allow the detection of sites of peptidoglycan synthesis in live cells and in real time, and their use to study the mechanisms of peptidoglycan synthesis in cell growth and morphogenesis. For example, these methods were used to show that pathogenic Chlamydia have peptidoglycan, ending 50 years of speculation and debate concerning the chlamydial anomaly, and to study the spatio-temporal dynamics of peptidoglycan synthesis at the site of cell division in Bacillus subtilis.
I will describe the mechanisms that control morphological diversity in species related to Caulobacter crescentus that synthesize appendage-like extensions of the cell envelope at distinct sub-cellular positions. I will show that stepwise evolution of a specific domain of a developmental regulator led to the gain of a new function and localization of this protein, which drove the sequential transition in morphology. Our results indicate that evolution of protein function, co-option, and modularity are key elements in the evolution of bacterial morphology. In addition, I will show how evolutionary consideration of the mechanism of growth in the alphaproteobacteria led to the surprising discovery that polar growth, rather than the previously assumed binary fission, is the predominant mode of growth in a large group of the alphaproteobacteria that includes the plant pathogen Agrobacterium tumefaciens and the human pathogen Brucella abortus.