Collaboration : Pauline Macheboeuf, PG group
The peptidoglycan (PG) is the main component of the cell wall, a rigid structure allowing the bacteria to survive to osmotic pressure. For this reason, the enzymes involved in the PG biosynthesis are since decades the best target for antibiotics therapy.
Bacterial complex MreBCD is part of bacterial elangasome, together with RodA and PBP2, they are essential for bacterial rod shape maintenance [1]. The structure of the MreC alone [2] compared to the complex with either PBP2 [3] or MreD [4] revealed possible regulatory role(s) for both MreC and MreD in PG synthesis.
To further get insights into connections between bacterial elongation and division we set-up a synthetic lethality genetic screen taking advantage of a viable P. aeruginosa mreDdown mutant with round morphology (Figure 1). We identified a set of carboxy- and endo-peptidases as synthetic lethal in mreDdown mutant, suggesting intricate interactions with the elangosome core proteins (Figure 2). This project characterizes novel elangosome partners by CRISPRi validations, functional in vivo approaches and morphological profiling by fluorescence microscopy.
Figure 1 : Morphology differences between P.aeruginosa wild-type and mreDdownmutant. Upper panel, bacteria visualized in confocal microscope after membrane staining (scale bar 2µm). Lower panel, cryo-EM images of bacteria freeze and cut (scale bar 200nm).
Figure 2 : Scheme of the two PG synthesis machinery (elongasome and divisome) and PG recycling. Some of the proteins identified in the synthetic lethal screening in a mreDdown mutant are shown in color (green if the mutation is beneficial in the mutant, orange/yellow if the protein deletion is detrimental in mreDdown mutant).