Two-Step Assembly Dynamics of theBacillussubtilisDivisome

Abstract

Cell division in bacteria is carried out by about a dozen proteins which assemble at midcell and form a complex known as the divisome. To study the dynamics and temporal hierarchy of divisome assembly in Bacillus subtilis, we have examined the in vivo localization pattern of a set of division proteins fused to green fluorescent protein in germinating spores and vegetative cells. Using time series and time-lapse microscopy, we show that the FtsZ ring assembles early and concomitantly with FtsA, ZapA, and EzrA. After a time delay of at least 20% of the cell cycle, a second set of division proteins, including GpsB, FtsL, DivIB, FtsW, Pbp2B, and DivIVA, are recruited to midcell. Together, our data provide in vivo evidence for two-step assembly of the divisome. Interestingly, overproduction of FtsZ advances the temporal assembly of EzrA but not of DivIVA, suggesting that a signal different from that of FtsZ polymerization drives the assembly of late divisome proteins. Microarray analysis shows that FtsZ depletion or overexpression does not significantly alter the transcription of division genes, supporting the hypothesis that cell division in B. subtilis is mainly regulated at the posttranscriptional level.

Control of cell division in Streptococcus pneumoniae by the conserved Ser/Thr protein kinase StkP

“…FtsA, together with FtsZ, is one of the earliest proteins to localize at the division sites, whereas DivIVA arrives somewhat later (43,44). Interestingly, we now have shown that StkP phosphorylates DivIVA and FtsA in vitro (Fig.…”

“…5), consistent with the observation that new PG insertion at midcell provides the signal recognized by StkP's PASTA domains. This timing of localization resembles the assembly of cell-division proteins by discrete steps that has been shown to occur in the model organisms (44,49).…”

Positive control of cell division: FtsZ is recruited by SsgB during sporulation ofStreptomyces

“…Hence, in contrast to the principle that FtsZ is typically the first divisome component to arrive at division sites followed by the sequential recruitment of the cytokinetic machinery (Goehring and Beckwith 2005; Dajkovic and Lutkenhaus 2006;Gamba et al 2009), in Streptomyces, SsgB arrives prior to FtsZ at the septum site. This was further demonstrated by timelapse imaging, and was corroborated by the observation that FtsZ ladder formation depends on SsgA and SsgB, while SsgB localizes at septum sites independently of FtsZ.…”

“…The Z ring then mediates the recruitment of the cell division machinery or divisome to the mid-cell position (for review, see Goehring and Beckwith 2005;Adams and Errington 2009). Recent evidence suggests that this is a two-step mechanism, with a significant lag in Bacillus between the formation of the Z ring associated with FtsA, ZapA, and EzrA and the recruitment of the other components of the cytokinetic machinery, such as FtsL, FtsW, DivIB, and DivIVA (Gamba et al 2009). The process of Z-ring (dis)assembly during division is actively controlled (for review, see Romberg and Levin 2003).…”

Preparation and Characterization of Bacterial Protein Complexes for Structural Analysis

“…There are many well-documented examples of this in microbial systems, including the co-localization of enzymes associated with sequential steps within an enzymatic pathway, sometimes found as a hetero-oligomeric complex (Klem and Davisson, 1993); the association of proteins to effect cell division (Gamba et al, 2009); the assembly of proteins into complexes to create pores or channels in order to import or export molecules through one or more membranes (Collins et al, 2007); and the control of gene expression through the modulation of both transcription (Rutherford et al, 2009) and translation (Yu et al, 2009). These protein-protein interactions span a wide range of timescales and affinities adapted to their specific biological roles.…”