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Updated: Jun 28, 2025
Analysis of the Lipid Composition of Mycobacteria by Thin Layer Chromatography
Published on: April 16, 2021
Lipoarabinomannan modification as a source of phenotypic heterogeneity in host-adapted Mycobacterium abscessus
Kavita De1, Juan M Belardinelli1, Arun Prasad Pandurangan2
1Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523-1682.
Abstract:
Mycobacterium abscessus is increasingly recognized as the causative agent of chronic pulmonary infections in humans. One of the genes found to be under strong evolutionary pressure during adaptation of M. abscessus to the human lung is embC which encodes an arabinosyltransferase required for the biosynthesis of the cell envelope lipoglycan, lipoarabinomannan (LAM). To assess the impact of patient-derived embC mutations on the physiology and virulence of M. abscessus, mutations were introduced in the isogenic background of M. abscessus ATCC 19977 and the resulting strains probed for phenotypic changes in a variety of in vitro and host cell-based assays relevant to infection. We show that patient-derived mutational variations in EmbC result in an unexpectedly large number of changes in the physiology of M. abscessus, and its interactions with innate immune cells. Not only did the mutants produce previously unknown forms of LAM with a truncated arabinan domain and 3-linked oligomannoside chains, they also displayed significantly altered cording, sliding motility, and biofilm-forming capacities. The mutants further differed from wild-type M. abscessus in their ability to replicate and induce inflammatory responses in human monocyte-derived macrophages and epithelial cells. The fact that different embC mutations were associated with distinct physiologic and pathogenic outcomes indicates that structural alterations in LAM caused by nonsynonymous nucleotide polymorphisms in embC may be a rapid, one-step, way for M. abscessus to generate broad-spectrum diversity beneficial to survival within the heterogeneous and constantly evolving environment of the infected human airway.
Insights
Mutations in the embC gene of Mycobacterium abscessus alter its lipoarabinomannan (LAM) structure, affecting its physiology and interaction with immune cells. These embC variations provide a mechanism for M. abscessus to adapt and survive in the human lung.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Mycobacterium abscessus causes chronic lung infections.
- The embC gene is crucial for lipoarabinomannan (LAM) biosynthesis and under evolutionary pressure in human lung infections.
Purpose of the Study:
- To investigate the impact of patient-derived embC mutations on M. abscessus physiology and virulence.
- To understand how embC variations affect LAM structure and M. abscessus-host interactions.
Main Methods:
- Introduced patient-derived embC mutations into an isogenic M. abscessus background.
- Assessed phenotypic changes using in vitro and host cell-based assays.
- Analyzed LAM structure, bacterial motility, biofilm formation, and host cell responses.
Main Results:
- Mutations in embC led to novel LAM forms with truncated arabinan domains and altered mannoside chains.
- Mutant strains exhibited significant changes in cording, sliding motility, and biofilm formation.
- Mutants displayed altered replication rates and inflammatory responses in human macrophages and epithelial cells.
Conclusions:
- EmbC mutations significantly alter M. abscessus physiology and virulence by modifying LAM structure.
- Distinct embC mutations result in varied pathogenic outcomes, suggesting a rapid adaptation mechanism.
- LAM structural diversity driven by embC polymorphisms aids M. abscessus survival in the human airway.
