Spatial Dynamics of the Bacterial Cell Wall Synthesis Machinery

Abstract

The bacterial cell wall is a polymeric meshwork that is essential for cell shape. Cytoskeletal filaments spatially organize cell wall synthesis during growth and division. In this thesis, I first provide an introduction to cytoskeletal filaments in bacteria: I review the biochemistry of self-organizing machines that play crucial roles in subcellular organization, in the coordination of cell wall synthesis and DNA segregation, and in fundamental cellular processes like cell growth and division. Next, I detail my study of the subcellular dynamics of the peptidoglycan synthesis machinery in Escherichia coli and Bacillus subtilis, finding that peptidoglycan biogenesis is carried out by two semi-autonomous systems – the Rod system, organized to move circumferentially around the rod-shaped cell by mobile filaments of MreB, and class A penicillin-binding proteins (aPBPs), which appear spatially unorganized, in comparison. This study also identified a new peptidoglycan polymerase, RodA, which is a part of the Rod system. In the last chapter, I detail my studies of the contributions of these two systems to cell growth and cell shape, finding that the balance between them determines the diameter of B. subtilis cells, and that class B penicillin-binding proteins and RodA may also act outside the Rod system.