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Abstract Bacterial peptidoglycan (PG) synthesis requires strict spatiotemporal organization to reproduce specific cell shapes. In ovoid‐shapedStreptococcus 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 examinedSpncells 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.
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Revisiting peptidoglycan sensing: interactions with host immunity and beyond
The interaction between host immunity and bacterial cells plays a pivotal role in a variety of human diseases. The bacterial cell wall component peptidoglycan (PG) is known to stimulate an immune response, which makes PG a distinctive recognition element for unveiling these complicated molecular interactions. Pattern recognition receptor (PRR) proteins are among the critical components of this system that initially recognize molecular patterns associated with microorganisms such as bacteria and fungi. These molecular patterns are mostly embedded in the bacterial or fungal cell wall structure and can be released and presented to the immune system in various situations. Nonetheless, detailed knowledge of this recognition is limited due to the diversity among the PG polymer and its fragments; the subsequent responses by multiple hosts add more complexity. Here, we discuss how our understanding of the role and molecular mechanisms of the well-studied PRR, the NOD-like receptors (NLRs), in the human immune system has evolved in recent years. We highlight the instances of other classes of proteins with similar behavior in the recognition of PG that have been identified in other microorganisms such as yeasts. These proteins are particularly interesting because a network of cellular interactions exists between human host cells, bacteria and yeast as a part of the normal human flora. To support our understanding of these interactions, we provide insight into the chemist's toolbox of peptidoglycan probes that aid in the investigations of the behaviors of these proteins and other biological contexts relevant to the sensing and recognition of peptidoglycan. The importance of these interactions in human health for the development of biomarkers and biotherapy is highlighted.
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- Award ID(s):
- 1554967
- PAR ID:
- 10274942
- Date Published:
- Journal Name:
- Chemical Communications
- Volume:
- 56
- Issue:
- 87
- ISSN:
- 1359-7345
- Page Range / eLocation ID:
- 13313 to 13322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d0cc02605k
