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Peer-reviewedCC BYNature Microbiology

The penicillin-binding protein PBP1b fortifies the Escherichia coli division site against osmotic rupture

  • Paula P. Navarro1,2,3,4
  • Andrea Vettiger5,6
  • Roman Hajdu7
  • Virly Y. Ananda8,9
  • Alejandro Lopez-Tavares8
  • Ernst W. Schmid10
  • Johannes C. Walter10,11
  • Martin Loose7
  • Luke H. Chao12,9
  • Thomas G. Bernhardt13,14
14 affiliations
  1. 1Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland. [email protected]
  2. 2Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA. [email protected]
  3. 3Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA. [email protected]
  4. 4Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA. [email protected]
  5. 5Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland. [email protected]
  6. 6Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA. [email protected]
  7. 7Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
  8. 8Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
  9. 9Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
  10. 10Department of Biological Chemistry & Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
  11. 11Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA
  12. 12Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
  13. 13Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA. [email protected]
  14. 14Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA. [email protected]
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Abstract

A multi-protein system called the divisome promotes bacterial division. This apparatus synthesizes the peptidoglycan (PG) cell wall layer that forms the daughter cell poles and protects them from osmotic lysis. In the model Gram-negative bacterium Escherichia coli , PG synthases called class A penicillin-binding proteins (aPBPs) have been proposed to play crucial roles in division. However, there is limited experimental support for aPBPs playing a specialized role in division that is distinct from their general function in the expansion and fortification of the PG matrix. Here, we present in situ cryogenic electron tomography data indicating that the aPBP-type enzyme PBP1b is required to produce a wedge-like density of PG at the division site. Furthermore, atomic force and live cell microscopy showed that loss of this structure weakens the division site and renders it susceptible to lysis. Surprisingly, we found that the lipoprotein activator LpoB needed to promote the general function of PBP1b was not required for normal division site architecture or its integrity. Additionally, we show that of the two PBP1b isoforms produced in cells, it is the one with an extended cytoplasmic N-terminus that functions in division, likely via recruitment by the FtsA component of the divisome. Altogether, our results demonstrate that PBP1b plays a specialized, LpoB-independent role in E. coli cell division involving the biogenesis of a PG structure that prevents osmotic rupture. The conservation of aPBPs with extended cytoplasmic N-termini suggests that other Gram-negative bacteria may use similar mechanisms to reinforce their division site.

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Cite

BibTeXRIS
BibTeX
@article{navarro2026penicillinbinding,
  title = {{The penicillin-binding protein PBP1b fortifies the Escherichia coli division site against osmotic rupture}},
  author = {Paula P. Navarro and Andrea Vettiger and Roman Hajdu and Virly Y. Ananda and Alejandro Lopez-Tavares and Ernst W. Schmid and Johannes C. Walter and Martin Loose and Luke H. Chao and Thomas G. Bernhardt},
  journal = {Nature Microbiology},
  year = {2026},
  month = jul,
  doi = {10.1038/s41564-026-02403-6},
  url = {https://doi.org/10.1038/s41564-026-02403-6},
  note = {CC BY},
}
RIS
TY  - JOUR
TI  - The penicillin-binding protein PBP1b fortifies the Escherichia coli division site against osmotic rupture
AU  - Paula P. Navarro
AU  - Andrea Vettiger
AU  - Roman Hajdu
AU  - Virly Y. Ananda
AU  - Alejandro Lopez-Tavares
AU  - Ernst W. Schmid
AU  - Johannes C. Walter
AU  - Martin Loose
AU  - Luke H. Chao
AU  - Thomas G. Bernhardt
PY  - 2026
DA  - 2026/07/03
JO  - Nature Microbiology
DO  - 10.1038/s41564-026-02403-6
UR  - https://doi.org/10.1038/s41564-026-02403-6
AB  - A multi-protein system called the divisome promotes bacterial division. This apparatus synthesizes the peptidoglycan (PG) cell wall layer that forms the daughter cell poles and protects them from osmotic lysis. In the model Gram-negative bacterium Escherichia coli , PG synthases called class A penicillin-binding proteins (aPBPs) have been proposed to play crucial roles in division. However, there is limited experimental support for aPBPs playing a specialized role in division that is distinct from their general function in the expansion and fortification of the PG matrix. Here, we present in situ cryogenic electron tomography data indicating that the aPBP-type enzyme PBP1b is required to produce a wedge-like density of PG at the division site. Furthermore, atomic force and live cell microscopy showed that loss of this structure weakens the division site and renders it susceptible to lysis. Surprisingly, we found that the lipoprotein activator LpoB needed to promote the general function of PBP1b was not required for normal division site architecture or its integrity. Additionally, we show that of the two PBP1b isoforms produced in cells, it is the one with an extended cytoplasmic N-terminus that functions in division, likely via recruitment by the FtsA component of the divisome. Altogether, our results demonstrate that PBP1b plays a specialized, LpoB-independent role in E. coli cell division involving the biogenesis of a PG structure that prevents osmotic rupture. The conservation of aPBPs with extended cytoplasmic N-termini suggests that other Gram-negative bacteria may use similar mechanisms to reinforce their division site.
SN  - 2058-5276
ER  -