Syracuse

In every living organism, cell division requires accurate identification of the division site and placement of the division machinery. In bacteria, this process is traditionally considered to begin with the polymerization of the highly conserved tubulin-like protein FtsZ into a ring that locates precisely at midcell 1 . Over the last decades, several systems have been reported to regulate the spatiotemporal assembly and placement of the FtsZ-ring 2-5 . However, the human pathogen Streptococcus pneumoniae, as many other organisms, is devoid of these canonical systems and the mechanisms of positioning of the division machinery remain unknown 4,6 . Here we characterize a novel factor that locates at the division site before FtsZ and guides septum positioning in the pneumococcus. MapZ (Midcell Anchored Protein Z) forms ring structures at the cell equator and moves apart as the cell elongates, therefore behaving as a permanent beacon of division sites. MapZ then positions the FtsZ-ring through direct protein-protein interactions. MapZ-mediated