Altered regulation of septal peptidoglycan synthesis modulates β-lactam susceptibility in Pseudomonas aeruginosa
- 1Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- 2Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
Abstract
Bacterial cell division requires precise regulation of septal peptidoglycan (PG) synthesis by the essential SEDS-bPBP synthase FtsWI. Activation of FtsWI is thought to occur through an allosteric cascade initiated by the late-arriving divisome protein FtsN and transmitted via the FtsQ-FtsL-FtsB (FtsQLB) complex, but the molecular details of this process remain incompletely defined and differ across species. Here, using the conditional essentiality of ftsN in Pseudomonas aeruginosa, we identify substitutions in the non-enzymatic pedestal domain of FtsI that bypass the requirement for FtsN. These mutations restore cell division in ΔftsN cells, suppress dominant-negative phenotypes of activation-defective ftsL alleles, and reduce cell length in an otherwise wild-type background, demonstrating that they alter FtsWI regulation to overcome the requirement for stimulation by both FtsN and FtsQLB. Mapping these mutations onto the P. aeruginosa FtsQLBWI structure reveals that they cluster on distinct surfaces of the pedestal domain. Because some of these substitutions have been identified in clinical P. aeruginosa isolates with increased aztreonam resistance, we next asked whether these regulatory substitutions alter β-lactam susceptibility. Variants at the FtsI-FtsL interface modestly reduce susceptibility to multiple β-lactam antibiotics, whereas a variant on the opposite face of the pedestal domain produces striking FtsN-dependent hypersusceptibility to the same molecules. These findings show that the FtsI pedestal domain plays a central role in the regulation of FtsWI and reveal a previously unrecognized relationship between divisome regulation and β-lactam susceptibility. More broadly, our work identifies the pedestal domain as a regulatory hub that integrates multiple inputs controlling septal PG synthesis and highlights its potential relevance to β-lactam resistance in clinical P. aeruginosa isolates. Author summary: Bacterial cell division is driven by the coordinated activation of septal peptidoglycan synthesis, but the regulatory mechanisms that govern this process remain poorly understood. Here we identify mutations in the non-enzymatic pedestal domain of the septal transpeptidase FtsI that bypass the requirement for the activation factor FtsN in Pseudomonas aeruginosa. These substitutions reveal that the pedestal domain integrates regulatory inputs from both FtsN and the FtsQLB complex to control FtsWI activation. Notably, substitutions at the FtsI-FtsL interface modestly reduce susceptibility to multiple β-lactam antibiotics that specifically target FtsI, whereas a mutation on the opposite face renders P. aeruginosa hypersusceptible to these agents. These findings uncover a previously unrecognized link between divisome regulation and β-lactam susceptibility and suggest that altered activation of septal peptidoglycan biosynthesis represents a noncanonical contributor to antibiotic resistance in P. aeruginosa.
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BibTeX
@article{colautti2026altered,
title = {{Altered regulation of septal peptidoglycan synthesis modulates β-lactam susceptibility in Pseudomonas aeruginosa}},
author = {Jake Colautti and Alexander C. Anderson and Wyatt P. K. Clark and Lindsey S. Marmont},
journal = {PLOS Genetics},
year = {2026},
month = sep,
doi = {10.1371/journal.pgen.1012319},
url = {https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1012319},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Altered regulation of septal peptidoglycan synthesis modulates β-lactam susceptibility in Pseudomonas aeruginosa
AU - Jake Colautti
AU - Alexander C. Anderson
AU - Wyatt P. K. Clark
AU - Lindsey S. Marmont
PY - 2026
DA - 2026/09/28
JO - PLOS Genetics
DO - 10.1371/journal.pgen.1012319
UR - https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1012319
AB - Bacterial cell division requires precise regulation of septal peptidoglycan (PG) synthesis by the essential SEDS-bPBP synthase FtsWI. Activation of FtsWI is thought to occur through an allosteric cascade initiated by the late-arriving divisome protein FtsN and transmitted via the FtsQ-FtsL-FtsB (FtsQLB) complex, but the molecular details of this process remain incompletely defined and differ across species. Here, using the conditional essentiality of ftsN in Pseudomonas aeruginosa, we identify substitutions in the non-enzymatic pedestal domain of FtsI that bypass the requirement for FtsN. These mutations restore cell division in ΔftsN cells, suppress dominant-negative phenotypes of activation-defective ftsL alleles, and reduce cell length in an otherwise wild-type background, demonstrating that they alter FtsWI regulation to overcome the requirement for stimulation by both FtsN and FtsQLB. Mapping these mutations onto the P. aeruginosa FtsQLBWI structure reveals that they cluster on distinct surfaces of the pedestal domain. Because some of these substitutions have been identified in clinical P. aeruginosa isolates with increased aztreonam resistance, we next asked whether these regulatory substitutions alter β-lactam susceptibility. Variants at the FtsI-FtsL interface modestly reduce susceptibility to multiple β-lactam antibiotics, whereas a variant on the opposite face of the pedestal domain produces striking FtsN-dependent hypersusceptibility to the same molecules. These findings show that the FtsI pedestal domain plays a central role in the regulation of FtsWI and reveal a previously unrecognized relationship between divisome regulation and β-lactam susceptibility. More broadly, our work identifies the pedestal domain as a regulatory hub that integrates multiple inputs controlling septal PG synthesis and highlights its potential relevance to β-lactam resistance in clinical P. aeruginosa isolates. Author summary: Bacterial cell division is driven by the coordinated activation of septal peptidoglycan synthesis, but the regulatory mechanisms that govern this process remain poorly understood. Here we identify mutations in the non-enzymatic pedestal domain of the septal transpeptidase FtsI that bypass the requirement for the activation factor FtsN in Pseudomonas aeruginosa. These substitutions reveal that the pedestal domain integrates regulatory inputs from both FtsN and the FtsQLB complex to control FtsWI activation. Notably, substitutions at the FtsI-FtsL interface modestly reduce susceptibility to multiple β-lactam antibiotics that specifically target FtsI, whereas a mutation on the opposite face renders P. aeruginosa hypersusceptible to these agents. These findings uncover a previously unrecognized link between divisome regulation and β-lactam susceptibility and suggest that altered activation of septal peptidoglycan biosynthesis represents a noncanonical contributor to antibiotic resistance in P. aeruginosa.
SN - 1553-7404
ER -