Growth and division of Streptococcus pneumoniae: localization of the high molecular weight penicillin‐binding proteins during the cell cycle

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Abstract
Summary: The bacterial peptidoglycan, the main component of the cell wall, is synthesized by the penicillin‐binding proteins (PBPs). We used immunofluorescence microscopy to determine the cellular localization of all the high molecular weight PBPs of the human pathogen Streptococcus pneumoniae, for a wild type and for several PBP‐deficient strains. Progression through the cell cycle was investigated by the simultaneous labelling of DNA and the FtsZ protein. Our main findings are: (i) the temporal dissociation of cell wall synthesis, inferred by the localization of PBP2x and PBP1a, from the constriction of the FtsZ‐ring; (ii) the localization of PBP2b and PBP2a at duplicated equatorial sites indicating the existence of peripheral peptidoglycan synthesis, which implies a similarity between the mechanism of cell division in bacilli and streptococci; (iii) the abnormal localization of some class A PBPs in PBP‐defective mutants which may explain the apparent redundancy of these proteins in S. pneumoniae.