Encapsulation of the septal cell wall protects Streptococcus pneumoniae from its major peptidoglycan hydrolase and host defenses

During their cell cycle, Gram-positive bacteria can be frequently found surrounded by a cellular envelope, which includes glycopolymers such as peptidoglycan, wall teichoic acids or capsular polysaccharides, whose composition is adjusted to the external insults they may find. The clarification of how bacteria tune synthesis of these three macromolecules, which act as defensive layers, ensuring efficient enclosing of bacteria and their protection from the surrounding medium, will permit a better understanding of how bacteria propagate and may pave the way to the intelligent design of anti-infective strategies. In this manuscript, we have determined how Wzg, a candidate for the Streptococcus pneumoniae ligase that attaches capsular polysaccharides to the bacterial cell wall, is directed to the division septum to ensure the full encapsulation of bacteria. Perturbation of this process result in bacteria with reduced protection from external peptidoglycan binding receptors (such as the pneumococcal major hydrolase) and impaired in their ability to survive within the infected host.