Local peptidoglycan composition defines division site selection in Streptococcus pneumoniae

Accurate division site placement is essential for bacteria to produce viable daughter cells. In the ovoid-shaped Streptococcus pneumoniae, previous work showed that division site placement depends on both the protein MapZ and chromosome segregation, although specific mechanisms remain unclear. Here we imaged fluorescently labelled S. pneumoniae, observing division site placement at the cell equator, the widest part of the cell, not at the mid-cell. Disruption of chromosome segregation neither affected MapZ nor divisome positioning, suggesting that division site selection can occur independently of chromosome segregation. MapZ localization depends on the sequential recruitment of two peptidoglycan decarboxylases, DacA and DacB, to the division site. DacA and DacB activity during early peptidoglycan synthesis generates a distinctive, tetrapeptide signature required for MapZ binding. As the cell cycle progresses, this signature becomes enriched at cell equators, recruiting MapZ so that these equators eventually serve as the division site in daughter cells. These findings update the mechanism of division site placement in S. pneumoniae.