Organization of peptidoglycan synthesis in nodes and separate rings at different stages of cell division of Streptococcus pneumoniae

• Published in: Molecular microbiology Vol. 115; no. 6; pp. 1152 - 1169
• Main Authors: Perez, Amilcar J., Boersma, Michael J., Bruce, Kevin E., Lamanna, Melissa M., Shaw, Sidney L., Tsui, Ho‐Ching T., Taguchi, Atsushi, Carlson, Erin E., VanNieuwenhze, Michael S., Winkler, Malcolm E.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-06-2021
• Subjects: Amino acids; Antibiotics; Cell division; Elongation; Fluorescence; fluorescent D‐amino acids (FDAAs); FtsX localization; FtsZ localization; Labeling; Nodes; Penicillin; penicillin‐binding proteins (PBPs); Peptidoglycans; peripheral (elongation) peptidoglycan synthesis; Proteins; septal peptidoglycan synthesis; Streptococcus infections; Streptococcus pneumoniae; Synthesis; septal peptidoglycan synthesis; fluorescent D-amino acids (FDAAs); penicillin-binding proteins (PBPs); FtsZ localization; peripheral (elongation) peptidoglycan synthesis; FtsX localization
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.14659

Bacterial peptidoglycan (PG) synthesis requires strict spatiotemporal organization to reproduce specific cell shapes. In ovoid‐shaped Streptococcus pneumoniae (Spn), septal and peripheral (elongation) PG synthesis occur simultaneously at midcell. To uncover the organization of proteins and activities that carry out these two modes of PG synthesis, we examined Spn cells vertically oriented onto their poles to image the division plane at the high lateral resolution of 3D‐SIM (structured‐illumination microscopy). Labeling with fluorescent D‐amino acids (FDAA) showed that areas of new transpeptidase (TP) activity catalyzed by penicillin‐binding proteins (PBPs) separate into a pair of concentric rings early in division, representing peripheral PG (pPG) synthesis (outer ring) and the leading‐edge (inner ring) of septal PG (sPG) synthesis. Fluorescently tagged PBP2x or FtsZ locate primarily to the inner FDAA‐marked ring, whereas PBP2b and FtsX remain in the outer ring, suggesting roles in sPG or pPG synthesis, respectively. Pulses of FDAA labeling revealed an arrangement of separate regularly spaced “nodes” of TP activity around the division site of predivisional cells. Tagged PBP2x, PBP2b, and FtsX proteins also exhibited nodal patterns with spacing comparable to that of FDAA labeling. Together, these results reveal new aspects of spatially ordered PG synthesis in ovococcal bacteria during cell division.
High‐resolution images of vertically oriented Streptococcus pneumoniae cells reveal concentric rings of PBP transpeptidase (TP) activity corresponding to the leading edge of the septal annulus (inner ring) and the midcell outer ring of elongating peptidoglycan (PG) synthesis. The rings serve as fiducial markers for assigning proteins to the septal (PBP2x and FtsZ) or elongation (PBP2b, FtsX) PG synthesis machines. In predivisional cells, PG synthesis proteins and PBP transpeptidase activity are arranged in patterns of regularly spaced nodes, whose spacing is perturbed in mutants.