Bacterial Cell-Wall Evolution

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The peptidoglycan or cell wall gives the bacteria a rigid structure, protects it from bursting due to osmotic pressure and contributes to cell shape. Bacterial cell shape is highly dynamic and cells are able to change from rod to spiral to round morphologies depending on their environment. These cell shape changes can be a transition that can happen on the developmental time scale, during a single cell cycle or it can become permanent through the course of bacterial evolution to respond to new environmental constraints. For example, I recently described the past evolution of nasopharyngeal bacteria (herein Neisseria meningitidis and Moraxella catarrhalis). Both species have undergone a similar cell-shape transition from rod to coccus during their adaptation to this ecosystem. As a consequence, changes in the structure of their cell-wall could be observed. By taking an evolutionary approach to detect specific genetics events, it is possible to expose the function of some proteins that could be involved in these phenotypic alterations. In the context of this study, we were able to shed light on an unrevealed role of YacF (ZapD), deleted in all cocci, as a coordinator of bacterial cell elongation and division. But the precise molecular mechanism is still unknown. The long-term goal of the research program is to better understand the regulation of the cell-wall by discovering new players and describe the importance of these regulation phenomena in the bacterial cell cycle. In this proposal, we aim at describing in depth the molecular mechanisms behind YacF coordination of the cell cycle in bacilli. We will test the hypothesis that YacF is timely inhibiting cell division during the course of cellular elongation. In addition, we will build a bioinformatics tool that will allow the detection of subtle modifications such as amino-acids change that happen during bacterial evolution. In this case, we want to describe mutations concomitant with the coccoid transition that could have changed protein function, protein-protein interaction or genes regulation. Finally, using similar evolutionary type of methods as we used in the Neisseriaceae or Moraxellaceae family, we will reveal other players implicated in the cell-wall regulation by searching for natural morphological aberration (herein Simonsiella muelleri). Equipped with multi-disciplinary expertise from bioinformatics, genomics and molecular biology to microbial ecology, we aim at understanding the mechanisms behind bacterial cell-wall evolution and the reasons of such changes. A better understanding of these mechanisms will ultimately allow improvement of industrially important bacterial strains or the development of new approaches towards bacterial population control that could be applicable to numerous fields such as agriculture, biotechnology and medicine.