Movement Dynamics of Divisome and Penicillin-Binding Proteins (PBPs) in Cells of Streptococcus pneumoniae

Perez, A. J.; Cesbron, Y.; Shaw, S. L.; Bazan Villicana, J.; Tsui, H.-C. T.; Boersma, M. J.; Ye, Z. A.; Tovpeko, Y.; Dekker, C.; Holden, S.; Winkler, M. E.

doi:10.1101/429217

bioRxiv · 10.1101/429217

Movement Dynamics of Divisome and Penicillin-Binding Proteins (PBPs) in Cells of Streptococcus pneumoniae

Perez, A. J.·Cesbron, Y.·Shaw, S. L.·Bazan Villicana, J.·Tsui, H.-C. T.·Boersma, M. J.·Ye, Z. A.·Tovpeko, Y.·Dekker, C.·Holden, S.·Winkler, M. E.

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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 (Spn). 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 {Delta}mapZ 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 Spn 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 Spn.\n\nSignificanceThis study answers two long-standing questions about FtsZ dynamics and its relationship to septal PG synthesis in Spn for the first time. In previous models, FtsZ concertedly moves from midcell septa to MapZ rings that have reached the equators of daughter cells. Instead, the results presented here show that FtsZ, FtsA, and EzrA filaments/bundles move continuously out from early septa as part of MapZ rings. In addition, this study establishes that the movement of bPBP2x:FtsW complexes in septal PG synthesis depends on and likely mirrors new PG synthesis and is not correlated with the treadmilling of FtsZ filaments/bundles. These findings are consistent with a mechanism where septal FtsZ rings organize directional movement of bPBP2x:FtsW complexes dependent on PG substrate availability.

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Perez, A. J., Cesbron, Y., Shaw, S. L., Bazan Villicana, J., Tsui, H.-C. T., Boersma, M. J., Ye, Z. A., Tovpeko, Y., Dekker, C., Holden, S., Winkler, M. E.. 2018-09-27. Movement Dynamics of Divisome and Penicillin-Binding Proteins (PBPs) in Cells of Streptococcus pneumoniae. https://doi.org/10.1101/429217

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