The mycomembrane differentially and heterogeneously restricts antibiotic permeation

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 evidence for mycomembrane impermeability relied on indirect or bulk population studies.

Purpose of the Study:

• To investigate the role of the mycobacterial mycomembrane as a selective barrier to small molecules.
• To assess differential permeability of the mycomembrane to various compounds, including antibiotics.

Main Methods:

• Utilized the Peptidoglycan Accessibility Click-Mediated Assessment (PAC-MAN) method to trap molecules within the peptidoglycan layer of live mycobacteria.
• Applied PAC-MAN to analyze the mycomembrane's restriction of fluorophores and antibiotic derivatives in both Mycobacterium tuberculosis and Mycobacterium smegmatis.

Main Results:

• The mycobacterial mycomembrane differentially restricts the entry of various fluorophores and antibiotic derivatives.
• Discrimination was observed between different classes of antibiotics and even within the fluoroquinolone family.
• Heterogeneous restriction of certain molecules, including vancomycin, was noted across sub-populations.

Conclusions:

• The mycobacterial mycomembrane acts as a selective barrier, controlling the permeation of specific molecules.
• This cell-specific and molecule-specific barrier function has significant implications for developing effective tuberculosis therapies.