A local composition of peptidoglycan drives the division site selection by MapZ in Streptococcus pneumoniae

Abstract

Accurate division site placement is essential for bacterial cells to produce viable daughter cells with proper size and appropriate functional features. In the opportunistic pathogen bacterium Streptococcus pneumoniae, the positioning of the division site has been shown to depend on both the protein MapZ and chromosome segregation. However, the nature of this interplay and the molecular determinants guiding division site localization remained unclear. Here we demonstrated that the division site is positioned at the cell equator, the widest part of the cell body, rather than at mid-cell. In addition, we observed that the localization of MapZ and/or the divisome remain unaffected even in the absence of properly segregated DNA, indicating that chromosome segregation does not contribute to division site selection. Our findings further reveal that MapZ localization depends on the activities of two PG hydrolases DacA and DacB, whose sequential recruitment to the division site during early PG synthesis drives the formation of a distinctive PG signature required for MapZ binding. These results support a model in which MapZ identifies the division site by recognizing a specific PG composition produced only during the early stages of cell division. This PG composition becomes enriched at the cell equators which will eventually serve as the division site of the daughter cells.