Two elongasomes generate rod shape in a unicellular microorganism

Cell geometry is genetically inherited by all forms of life. In bacteria, shape is determined by the peptidoglycan and is nearly invariant during the metabolically active vegetative state. Essential morphogenetic complexes, the elongasome and divisome, expand the peptidoglycan along the major and minor axes, respectively, to generate a particular shape. Here, we provide evidence for the presence in Salmonella of two alternative elongasomes that generate a similar (rod) shape. One elongasome is directed by penicillin-binding protein 2 (PBP2) while the other is controlled by PBP2SAL, a pathogen-specific enzyme. In acidic niches, PBP2SAL replaces and renders dispensable PBP2. Our data also demonstrate distinct rates for the two identified elongasomes, with that directed by PBP2SAL exhibiting lower speed