Movement dynamics of divisome proteins and PBP2x:FtsW in cells of Streptococcus pneumoniae

Abstract

Bacterial cell division and peptidoglycan (PG) synthesis are orchestrated by the coordinated dynamic movement of essential protein complexes. Recent studies show that bidirectional treadmilling of FtsZ filaments/bundles is tightly coupled to and limiting for both septal PG synthesis and septum closure in some bacteria, but not in others. Here we report the dynamics of FtsZ movement leading to septal and equatorial ring formation in the ovoid-shaped pathogen, Streptococcus pneumoniae. Conventional and single-molecule total internal reflection fluorescence microscopy (TIRFm) showed that nascent rings of FtsZ and its anchoring and stabilizing proteins FtsA and EzrA move out from mature septal rings coincident with MapZ rings early in cell division. This mode of continuous nascent ring movement contrasts with a failsafe streaming mechanism of FtsZ/FtsA/EzrA observed in a ΔmapZ mutant and another Streptococcus species. This analysis also provides several parameters of FtsZ treadmilling in nascent and mature rings, including treadmilling velocity in wild-type cells and ftsZ(GTPase) mutants, lifetimes of FtsZ subunits in filaments and of entire FtsZ filaments/bundles, and the processivity length of treadmilling of FtsZ filament/bundles. In addition, we delineated the motion of the septal PBP2x transpeptidase and its FtsW glycosyl transferase-binding partner relative to FtsZ treadmilling in S. pneumoniae cells. Five lines of evidence support the conclusion that movement of the bPBP2x:FtsW complex in septa depends on PG synthesis and not on FtsZ treadmilling. Together, these results support a model in which FtsZ dynamics and associations organize and distribute septal PG synthesis, but do not control its rate in S. pneumoniae.

BactMAP: An R package for integrating, analyzing and visualizing bacterial microscopy data

“…This is confirmed by the trajectories recorded by iSBatch (Figure b). Interestingly, the timing of movement from mid‐cell to the quarter positions of the cell is not completely the same in the left and the right side of the cell, as was also shown by Perez et al, . As shown in Figure c, the FtsZ‐RFP tracks are short and sometimes even static.…”

“…This is confirmed by the trajectories recorded by iSBatch ( Figure 5b). Interestingly, the timing of movement from mid-cell to the quarter positions of the cell is not completely the same in the left and the right side of the cell, as was also shown by Perez et al, 2019. As shown in Figure 5c, the FtsZ-RFP tracks are short and sometimes even static. It is not surprising that we do not observe treadmilling in these conditions, since we imaged the cells in HiLo-mode (highly inclined and laminated optical sheet mode) where we focused on the middle of the cell and not in TIRF mode as performed by (Perez et al, 2019).…”

“…As shown in Figure c, the FtsZ‐RFP tracks are short and sometimes even static. It is not surprising that we do not observe treadmilling in these conditions, since we imaged the cells in HiLo‐mode (highly inclined and laminated optical sheet mode) where we focused on the middle of the cell and not in TIRF mode as performed by (Perez et al, ). While these conditions are good to follow DnaX and to see the general localization of FtsZ, we miss the focus on the edge of the cell and thereby the movement of FtsZ along the Z‐ring.…”

BactMAP: an R package for integrating, analyzing and visualizing bacterial microscopy data

“…This is confirmed by the trajectories recorded by iSBatch ( Figure 5B). Interestingly, the timing of movement from mid-cell to the quarter positions of the cell is not completely the same in the left and the right side of the cell, as was also shown by (Perez et al, 2019). As shown in Fig.…”

Spatio-temporal control of DNA replication by the pneumococcal cell cycle regulator CcrZ

“…Another S. pneumoniae specific protein, called MapZ was shown to guide Z-ring formation, analogous to the Min system in other bacteria 32,33 . During cell growth, nascent MapZ rings are pushed apart by septal peptidoglycan synthesis, allowing for FtsZ polymers to continuously assemble at the newly formed septum 34 .…”