Cell Cycle Machinery in Bacillus subtilis

Abstract

Bacillus subtilis is the best described member of the Gram positive bacteria. It is a typical rod shaped bacterium and grows by elongation in its long axis, before dividing at mid cell to generate two similar daughter cells. B. subtilis is a particularly interesting model for cell cycle studies because it also carries out a modified, asymmetrical division during endospore formation, which can be simply induced by starvation. Cell growth occurs strictly by elongation of the rod, which maintains a constant diameter at all growth rates. This process involves expansion of the cell wall, requiring intercalation of new peptidoglycan and teichoic acid material, as well as controlled hydrolysis of existing wall material. Actin-like MreB proteins are the key spatial regulators that orchestrate the plethora of enzymes needed for cell elongation, many of which are thought to assemble into functional complexes called elongasomes. Cell division requires a switch in the orientation of cell wall synthesis and is organised by a tubulin-like protein FtsZ. FtsZ forms a ring-like structure at the site of impending division, which is specified by a range of mainly negative regulators. There it recruits a set of dedicated division proteins to form a structure called the divisome, which brings about the process of division. During sporulation, both the positioning and fine structure of the division septum are altered, and again, several dedicated proteins that contribute specifically to this process have been identified. This chapter summarises our current understanding of elongation and division in B. subtilis, with particular emphasis on the cytoskeletal proteins MreB and FtsZ, and highlights where the major gaps in our understanding remain.

Rules and Exceptions: The Role of Chromosomal ParB in DNA Segregation and Other Cellular Processes

“…Elongated cells were detected in populations of strains deprived of Spo0J or both, Spo0J and Soj, but not in the strain lacking only Soj [70]. In B. subtilis, two systems controlling cell division were described (for a review, see [185]). The Min system hampers the formation of the cytokinetic Z-ring composed of tubulin like FtsZ protein close to the cell poles [186].…”

Geometric principles underlying the proliferation of a model cell system

“…Its most critical general role lies in osmoregulation, 52 enabling bacterial cells in dilute environments to withstand the turgor pressure generated 53 by the high osmolarity of the cytoplasm (Rojas and Huang, 2017). A large number (~30) of 54 normally essential genes are required for synthesis of the material of the wall, and its spatial 55 regulation during cell growth and division (Errington and Wu, 2017;Zhao et al, 2017). 56 In the light of the multiplicity of important functions for the wall it is surprising that under 57 certain conditions (isotonic to avoid osmotic lysis) many bacteria, both Gram-positive and 58 Gram-negative, that normally have a cell wall, can thrive in a wall-less state, called the L- Errington et al, 2016).…”

Armeniaspirols inhibit the AAA+ proteases ClpXP and ClpYQ leading to cell division arrest in Gram-positive bacteria

“…The key divisome protein FtsZ increased significantly upon treatment with 1. FtsZ polymerizes at the mid-cell forming a dynamic ring upon which additional divisome proteins are scaffolded to guide septum synthesis between daughter cells 55,56 . Additionally the highly abundant chaperones GroEL, DnaK, and Tig, known to play a role in FtsZ function, also increased 40,[57][58][59][60][61][62] .…”