Cell Diameter inBacillus subtilisis Determined by the Opposing Actions of Two Distinct Cell Wall Synthetic Systems

Abstract

20Rod shaped bacteria grow by adding material into their cell wall via the action of two spatially distinct enzymatic systems: 21The Rod system moves around the cell circumference, while the class A penicillin-binding proteins (aPBPs) are 22 unorganized. To understand how the combined action of these two systems defines bacterial dimensions, we examined how 23 each system affects the growth and width of Bacillus subtilis, as well as the mechanical anisotropy and orientation of 24 material within their sacculi. We find that rod diameter is not determined by MreB, rather it depends on the balance between 25 the systems: The Rod system reduces diameter, while aPBPs increase it. RodA/PBP2A can both thin or widen cells, 26 depending on its levels relative to MreBCD. Increased Rod system activity correlates with an increased density of directional 27MreB filaments, and a greater fraction of directionally moving PBP2A molecules. This increased circumferential synthesis 28 increases the amount of oriented material within the sacculi, increasing their mechanical anisotropy and reinforcing rod 29 shape. Together, these experiments explain how the combined action of the two main cell wall synthetic systems build rods 30 of different widths, a model that appears generalizable: Escherichia coli containing Rod system mutants show the same 31 relationship between the density of directionally moving MreB filaments and cell width.

Establishing Rod-Shape from Spherical, Peptidoglycan-Deficient Bacterial Spores

“…1H). Consistent with a recent report that cells reduce their diameter when the Rod system becomes dominant over aPBPs (28), emerging cells continued to grow in length but shrink in width in Phase II (Fig. S3).…”

Lipid Anchoring of Archaeosortase Substrates and Mid-Cell Growth in Haloarchaea

“…Therefore, it is possible that our SLG-msfGFP fusion is actually blocking the transport of or interaction with other yet unknown surface proteins essential for shape maintenance. The concept of having different classes of surface-modifying proteins counteracting each other has been demonstrated in bacteria, where different classes of Penicillin Binding Proteins (PBPs) act on the peptidoglycan cell wall to control cell width homeostasis in rod-shaped cells (29). Interestingly, just like ovococcoid bacteria that are capable of mid-cell elongation and also lack a clear dedicated elongation machinery, haloarchaea may be also employing cytoskeletal polymers to direct different sub-complexes for cell elongation and cell division (30).…”

Single rod-shaped cell fluctuations from stochastic surface/volume growth rates

“…While it is evident that both volume and surface accretion must affect bacterial shape homeostasis, the role of the coupling between the two remains an open question. From a cellular metabolism perspective, to a first approximation volume growth relates to the production of all proteins and metabolites increasing cellular biomass, while surface growth relates to those proteins specifically needed for building the cell wall and the outer membrane [19]. Since both the energy and the ribosomes required for both processes are usually limiting factors [15], the bacterial cell has to perpetually solve a resource allocation problem to maintain the right balance between bulk and surface-specific synthesis and thus maintain shape homeostasis between successive divisions.…”