mycolate outer membrane

GO:0036407 · Envelope · Membrane · Proposed

A mycolic-acid-rich cell outer membrane in mycobacteria and related Corynebacteriales, containing a lipid bilayer and covalently linked long-chain mycolic acids attached to peptidoglycan through an arabinogalactan network. [GO:0036407]

Synonyms: MOM; mycobacterial outer membrane; mycomembrane

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Essential	Role
mycolic acid	Lipid	part of	`CHEBI:25438`	ESSENTIAL	Forms the mycolate-rich hydrophobic membrane layer and creates the covalently attached inner leaflet when esterified to arabinogalactan. `DOI:10.1016/j.chembiol.2013.11.011` Marrakchi, Lanéelle and Daffé 2014 review mycolic acids as major specific lipid constituents of the mycobacterial cell envelope. `DOI:10.1016/j.tim.2009.12.005` Niederweis et al. 2010 review the lipid architecture proposed for the mycobacterial outer membrane.
extractable mycomembrane lipids	Lipid	part of	Reviewed label only (reviewed name; no accession asserted)	CONDITIONAL	Intercalate with covalently attached mycolates to fill the outer leaflet and tune the hydrophobic surface of the mycomembrane. `DOI:10.1016/j.tim.2009.12.005` Niederweis et al. 2010 review free mycolates and extractable lipids as outer-membrane constituents. `DOI:10.1038/s41598-017-12718-4` Chiaradia et al. 2017 dissected the mycobacterial cell envelope and analyzed native mycomembrane composition.
mycolate outer membrane proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	CONDITIONAL	Provide proteinaceous routes for hydrophilic solute uptake and envelope transport across the mycolate-rich permeability barrier. `DOI:10.1016/j.tim.2009.12.005` Niederweis et al. 2010 review mycobacterial outer-membrane proteins and porin channels.

Taxonomic distribution

NCBITaxon:2 Bacteria — VARIABLE: Mycolate outer membranes occur in mycobacteria and related corynebacteria rather than being shared by all bacteria. [DOI:10.1016/j.tim.2009.12.005]
NCBITaxon:1763 Mycobacterium — COMMON: Mycobacteria are the canonical organisms for the mycolic-acid-rich mycomembrane. [DOI:10.1016/j.tim.2009.12.005]

Canonical examples

NCBITaxon:1772 Mycobacterium smegmatis — Fast-growing mycobacterial model used to dissect native mycomembrane composition and mycolate-rich cell-envelope architecture. [DOI:10.1038/s41598-017-12718-4]
NCBITaxon:1718 Corynebacterium glutamicum — Corynebacterial model in which cryo-electron microscopy directly visualized an outer membrane related to the mycobacterial mycomembrane. [DOI:10.1128/JB.01919-07]

Functions

mycomembrane permeability barrier — The mycolate-rich membrane creates a low-permeability hydrophobic barrier at the outside of the envelope.
- DOI:10.1016/j.tim.2009.12.005 Niederweis et al. 2010 review the mycobacterial outer membrane as a permeability barrier.
porin-mediated hydrophilic uptake — Outer-membrane proteins form channels that let selected hydrophilic solutes cross the otherwise lipid-rich mycolate outer membrane.
- DOI:10.1016/j.tim.2009.12.005 Niederweis et al. 2010 review porins as uptake channels through mycobacterial outer membranes.

Mechanism graphs

Mycolates form a covalently anchored outer membrane (ASSEMBLY)

Long-chain mycolic acids are esterified to arabinogalactan, which links the hydrophobic mycolate layer to peptidoglycan. Extractable lipids and outer-membrane proteins pack into that mycolate-rich membrane to form a low-permeability envelope boundary.

Subject	Predicate	Object	Evidence
mycolic acid	esterifies to	arabinogalactan	`DOI:10.1101/cshperspect.a021113` Alderwick and colleagues 2015 review the mycolyl-arabinogalactan linkage in the mycobacterial cell wall. `DOI:10.1016/j.chembiol.2013.11.011` Marrakchi, Lanéelle and Daffé 2014 review mycolic-acid transfer onto arabinogalactan.
arabinogalactan	anchors to	peptidoglycan-based cell wall	`DOI:10.1101/cshperspect.a021113` Alderwick and colleagues 2015 review how arabinogalactan bridges peptidoglycan and mycolates.
mycolic acid	forms hydrophobic layer of	mycolate outer membrane	`GO:0036407` GO:0036407 defines a mycolic-acid-rich cell outer membrane with long-chain mycolic acids. `DOI:10.1073/pnas.0709530105` Hoffmann et al. 2008 visualized a mycobacterial outer membrane by cryo-electron tomography and vitreous sections.
extractable mycomembrane lipids	pack into	mycolate outer membrane	`DOI:10.1016/j.tim.2009.12.005` Niederweis et al. 2010 review extractable lipids as mycomembrane constituents.
mycolate outer membrane proteins	embed in	mycolate outer membrane	`DOI:10.1016/j.tim.2009.12.005` Niederweis et al. 2010 review protein channels in the mycobacterial outer membrane.
mycolate outer membrane	enables	mycomembrane permeability barrier	`DOI:10.1016/j.tim.2009.12.005` Niederweis et al. 2010 review the mycobacterial outer membrane as the major permeability barrier.

Discussions

CURATION_TODO (RESOLVED): Keep the mycolate outer membrane separate from the whole mycolyl-arabinogalactan-peptidoglycan cell-wall core. GO:0036407 denotes the mycolate-rich outer membrane rather than the full peptidoglycan-arabinogalactan-mycolate cell-wall skeleton. Arabinogalactan and peptidoglycan are therefore graph nodes that explain covalent anchoring, not local component entries for the outer membrane itself.

Evidence

GO:0036407 Gene Ontology cellular-component term for the mycolate outer membrane.
DOI:10.1073/pnas.0709530105 Hoffmann et al. 2008, Disclosure of the mycobacterial outer membrane: cryo-electron tomography and vitreous sections reveal the lipid bilayer structure, Proceedings of the National Academy of Sciences USA.
DOI:10.1128/JB.01919-07 Zuber et al. 2008, Direct visualization of the outer membrane of mycobacteria and corynebacteria in their native state, Journal of Bacteriology.
DOI:10.1016/j.tim.2009.12.005 Niederweis et al. 2010, Mycobacterial outer membranes: in search of proteins, Trends in Microbiology.
DOI:10.1101/cshperspect.a021113 Alderwick et al. 2015, The mycobacterial cell wall: peptidoglycan and arabinogalactan, Cold Spring Harbor Perspectives in Medicine.
DOI:10.1016/j.chembiol.2013.11.011 Marrakchi, Lanéelle and Daffé 2014, Mycolic acids: structures, biosynthesis, and beyond, Chemistry and Biology.

Curation history

2026-09-11T04:39:44Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-11T04:41:56Z codex · EXPANDED_RECORD — Added GO-backed mycomembrane synonymy, cell outer membrane parentage, mycolic-acid, extractable-lipid, and outer-membrane protein components, bacterial and mycobacterial taxonomy, M. tuberculosis and C. glutamicum examples, permeability functions, DOI/GO evidence, an anchored mycolate membrane graph, and a cell-wall core boundary discussion.
2026-09-11T04:49:06Z codex · TIGHTENED_DISCUSSION_ANCHOR — Changed the cell-wall core boundary discussion from a broad components anchor to explicit mycolic-acid and extractable-lipid component anchors.
2026-09-11T04:53:59Z codex · ADDRESS_REVIEW — Resolved PR #412 issues #413 and #414 by citing the Bacteria distribution from the mycomembrane literature and replacing the M. tuberculosis canonical example with a directly supported M. smegmatis example.

Source: data/structures/envelope/mycolate_outer_membrane.yaml