Étude du rôle fonctionnel des hydrolases du peptidoglycane chez Lactobacillus plantarum
(2013)
Files
Thèse_Thomas_Rolain.pdf
Open Access - Adobe PDF
- 29.63 MB
Details
- Authors
- Supervisors
- Hols, Pascal
- Abstract
- (en) Cell wall is an essential structure for the survival of bacteria, as it determines cell shape, and also preserves cell integrity from internal osmotic pressure. In Gram-positive bacteria, peptidoglycan (PG) is a major component of the cell wall. This polymer consists in the disaccharide repeat N-acetylmuramic acid-(β-1,4)-N-acetylglucosamine (MurNAc-GlcNAc) connected to a peptidic stem which is linked to MurNAc. Although this structure is highly resistant and rigid, it needs to be relaxed to allow different processes to take place such as daughter cell separation, cell-wall turnover, sporulation and germination, biofilm formation. To this end, bacteria produce a variety of enzymes called peptidoglycan hydrolases (PGH) that are able to cleave PG. In this work, we characterized the PGH complement of Lactobacillus plantarum by performing a systematic gene deletion strategy. From twelve predicted PGH-encoding genes, nine could be individually inactivated and their corresponding mutant strains were characterized regarding their cell morphology, growth, and autolysis under various conditions. Characterization of mutant strains in a range of conditions showed that four PGHs (Acm2, Lys2, LytA, and LytH) play important roles either in the cell cycle or in the autolysis process of L. plantarum. Among them, the N-acetylglucosaminidase Acm2 was demonstrated to be required for the ultimate step of cell separation of daughter cells, whereas the D,L-endopeptidase LytA appeared to be required for cell shape maintenance and cell-wall integrity. Finally, our data also revealed that O-glycosylation of the AST domain of Acm2 and to a lesser extent, the domain itself negatively impact on its PGH activity whereas the SH3b domains are necessary for Acm2 activity as well as its binding to the PG through recognition of glucosamine as the minimal binding motif. To the best of our knowledge, this is the first time that O-glycosylation is shown to control the activity of a bacterial enzyme.
- Affiliations
Citations
Rolain, T. (2013). Étude du rôle fonctionnel des hydrolases du peptidoglycane chez Lactobacillus plantarum. https://hdl.handle.net/2078.5/203599