Abstract
Bacterial cell division is a fundamental process that requires the coordinated actions of a number of proteins which form a complex macromolecular machine known as the divisome. The membrane-spanning proteins DivIB and its orthologue FtsQ are crucial divisome components in Gram-positive and Gram-negative bacteria respectively. However, the role of almost all of the integral division proteins, including DivIB, still remains largely unknown. Here we show that the extracellular domain of DivIB is able to bind peptidoglycan and have mapped the binding to its β subdomain. Conditional mutational studies show that divIB is essential for Staphylococcus aureus growth, while phenotypic analyses following depletion of DivIB results in a block in the completion, but not initiation, of septum formation. Localisation studies suggest that DivIB only transiently localises to the division site and may mark previous sites of septation. We propose that DivIB is required for a molecular checkpoint during division to ensure the correct assembly of the divisome at midcell and to prevent hydrolytic growth of the cell in the absence of a completed septum.
Highlights
Bacterial cell division is a fundamental process that requires the coordinated actions of a number of proteins which form a complex macromolecular machine known as the divisome
Many components of the divisome have been shown to be essential for viability: 10 genes involved in cell division are essential in Bacillus subtilis (Kobayashi et al, 2003), Escherichia coli (Buddelmeijer and Beckwith, 2002) and Caulobacter crescentus (Goley et al, 2011), while eight division genes are essential in Streptococcus pneumoniae (Song et al, 2005; van Opijnen et al, 2009)
The divisome is composed of FtsZ-associated proteins (FtsA, ZapA, FtsE/X, [ZipA ZapB ZapC; E. coli], [EzrA, SepF; B. subtilis]), and membrane-spanning proteins, many of which are involved in the biosynthesis of septal peptidoglycan (Errington et al, 2003; Schmidt et al, 2004; Ishikawa et al, 2006; Ebersbach et al, 2008)
Summary
Cell division in bacteria requires the coordinated action of a number of proteins which form a complex macromolecular machine known as the divisome (Errington et al, 2003).Many components of the divisome have been shown to be essential for viability: 10 genes involved in cell division are essential in Bacillus subtilis (Kobayashi et al, 2003), Escherichia coli (Buddelmeijer and Beckwith, 2002) and Caulobacter crescentus (Goley et al, 2011), while eight division genes are essential in Streptococcus pneumoniae (Song et al, 2005; van Opijnen et al, 2009). While key components of the divisome, such as FtsZ, are highly conserved throughout bacterial species, others have diverged significantly (Angert, 2005). This diversity of cell division mechanisms carried out by the set of cell division proteins that comprise the divisome in each species is likely to be influenced by bacterial shape and envelope structures. Most studies of cell division have focused on the rod-shaped model organisms E. coli and B. subtilis. Using coccus-shaped bacteria to study cell division may prove a simpler model due to the lack of cylindrical elongation of the cell wall and elimination of potential overlapping roles of cell wall synthesis machineries (Turner et al, 2010)
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