New insights into the Undecaprenol monophosphate recycling pathway of Streptococcus pneumoniae

Recycling of undecaprenol pyrophosphate is critical to regenerate the pool of undecaprenol monophosphate required for cell wall biosynthesis. Undecaprenol pyrophosphate is dephosphorylated by membrane-associated undecaprenyl pyrophosphate phosphatases such as UppP or type 2 Phosphatidic Acid Phosphatases (PAP2) and then transferred across the cytoplasmic membrane by Und-P flippases such as PopT (DUF368-containing protein) or UptA (a DedA family protein). While the deletion of uppP in S. pneumoniae has been reported to increase susceptibility to bacitracin and reduce infectivity in a murine infection model, the presence of PAP2 family proteins or Und-P flippases and their potential interplay with UppP in S. pneumoniae remained unknown. In this report, we identified two PAP2 family proteins and a DUF368-containing protein and investigated their roles together with that of UppP in cell growth, cell morphology and susceptibility to bacitracin in S. pneumoniae. Our results suggest that the undecaprenol monophosphate recycling pathway in S. pneumoniae could result from a functional redundancy between UppP, the PAP2-family protein Spr0434 and the DUF368-containing protein Spr0889.