The mycomembrane differentially and heterogeneously restricts antibiotic permeation

Abstract

The recalcitrance of Mycobacterium tuberculosis to antibiotic treatment has been broadly attributed to the impermeability of the organisms outer mycomembrane. However, the studies that support this inference have been indirect and/or reliant on bulk population measurements. We previously developed the Peptidoglycan Accessibility Click-Mediated AssessmeNt (PAC-MAN) method to covalently trap azide-modified small molecules in the peptidoglycan cell wall of live mycobacteria, after they have traversed the mycomembrane. Using PAC-MAN we now show that the mycomembrane differentially restricts access of fluorophores and antibiotic derivatives. Mycomembranes of both M. tuberculosis and the model organism M. smegmatis discriminate between divergent classes of antibiotics as well as between antibiotics within a single family, the fluoroquinolones. By analyzing sub-populations of M. tuberculosis and M. smegmatis, we also found that some fluorophores and vancomycin are heterogeneously restricted by the mycomembrane. Our data indicate that the mycomembrane is a molecule- and cell-specific barrier to antibiotic permeation. Abstract Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=108 SRC="FIGDIR/small/630956v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@4bdeb7org.highwire.dtl.DTLVardef@10ade47org.highwire.dtl.DTLVardef@872dceorg.highwire.dtl.DTLVardef@d04b59_HPS_FORMAT_FIGEXP M_FIG C_FIG