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The Mycomembrane Differentially and Heterogeneously Restricts Antibiotic Permeation

Irene Lepori1, Kiserian Jackson1,2, Zichen Liu3,4

  • 1Department of Microbiology, University of Massachusetts, Amherst, Massachusetts 01003, United States.

ACS Infectious Diseases
|June 5, 2025
PubMed

Insights

The mycobacterial outer membrane selectively blocks antibiotic entry, acting as a cell-specific barrier. This finding, using the Peptidoglycan Accessibility Click-Mediated AssessmeNt (PAC-MAN) method, reveals differential drug permeation in Mycobacterium tuberculosis.

Area of Science:

  • Microbiology
  • Cell Biology
  • Drug Discovery

Background:

  • The outer mycomembrane of Mycobacterium tuberculosis is widely considered a primary barrier to antibiotic treatment.
  • Previous studies supporting this hypothesis relied on indirect evidence or bulk population measurements.

Purpose of the Study:

  • To investigate the role of the mycobacterial mycomembrane as a barrier to antibiotic entry using a novel method.
  • To determine if the mycomembrane exhibits differential permeability to various molecules and antibiotics.

Main Methods:

  • Utilized the Peptidoglycan Accessibility Click-Mediated AssessmeNt (PAC-MAN) method to trap azide-modified small molecules within the peptidoglycan layer of live mycobacteria.
  • Applied PAC-MAN to analyze the differential restriction of fluorophores and antibiotic derivatives by the mycomembrane.

Main Results:

  • The mycomembrane was shown to differentially restrict access of fluorophores and antibiotic derivatives in both M. tuberculosis and M. smegmatis.
  • Discrimination was observed between different classes of antibiotics and within the fluoroquinolone family.
  • Analysis of subpopulations revealed heterogeneous restriction of certain fluorophores and vancomycin by the mycomembrane.

Conclusions:

  • The mycobacterial mycomembrane acts as a dynamic, molecule- and cell-specific barrier to antibiotic permeation.
  • This finding has significant implications for understanding antibiotic resistance and developing new therapeutic strategies against tuberculosis.
Keywords:
antibioticsbioorthogonal click chemistrycell envelopepermeabilitytuberculosis

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