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The impact of mab_1638 on the M. abscessus transcriptome [ChIP-seq]

ABSTRACT: Mycobacterium abscessus is a major human pathogen, mostly infecting people with pre-existing pathological lung conditions such as cystic fibrosis. Only little is known about the ways M. abscessus regulates its virulence factors and pathogenesis phenotypes. The production of glycopeptidolipids (GPL) is a major determinant of virulence of this bacterium, with clinical isolates that lack GPL synthesis and export generally exhibiting more aggressive clinical behavior. The current paradigm is that GPL production is abolished in vivo via irreversible, spontaneous mutations taking place as part of in-host evolution. Little is known about the mechanisms or extent to which GPL production may be regulated. We have found an unusual TetR-like transcription factor of M. abscessus, mab_1638, identified via screening of a comprehensive transposon-mutant library, that appears to be a strong positive regulator of the entire GPL biosynthesis and export gene cluster through a combination of direct and indirect mechanisms. The inactivation of mab_1638 by a transposon led to stable and visually obvious rough colony morphology, as well as increased virulence in infection models, characteristic of rough, non-GPL-producers. Transcriptome analysis found the mab_1638:tn mutant to have 118 differentially expressed genes, including the GPL locus. It appears mab_1638 encodes an unusual TetR transcription factor required for the production of GPL in M. abscessus and therefore having a profound effect on virulence traits. This finding raises the important possibility that M. abscessus strains appearing smooth in laboratory growth conditions may nonetheless downregulate GPL-cluster genes in other conditions and thus acquire the phenotypic characteristics of rough strains.

ORGANISM(S): Mycobacteroides abscessus

PROVIDER: GSE287715 | GEO | 2025/07/30

REPOSITORIES: GEO

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Project description:Members of the Mycobacterium (M.) abscessus complex (MABC) are rapidly growing mycobacteria showing smooth and/or rough colony morphotype. While not as virulent as M. tuberculosis, they can cause soft tissue infection and fatal pulmonary disease, especially in patients with cystic fibrosis. Diagnosing MABC pulmonary disease is challenging since the isolation of M. abscessus from respiratory samples is in itself not diagnostic and the clinical features are often non-specific. Immunologic assays, which could aid in the understanding and diagnosis of the disease, are not available. In this study eight rough and six smooth colony morphotype isolates were collected from seven clinical MABC strains and the M. abscessus reference strain ATCC19977, as six strains showed both morphotypes simultaneously and two strains only showed a rough morphotype. Clinical isolates were submitted to whole genome sequencing. Quantitative proteomic analysis was performed on bacterial lysates and the culture supernatant of all 14 isolates. Supernatant proteins present in all isolates were compared in a BLAST search against other clinically significant mycobacterial species to determine species-specific proteins of MABC. In silico B- and T-cell epitope prediction was performed for species-specific proteins. All clinical strains were found to be M. abscessus ssp. abscessus. Six of seven rough colony clinical isolates contained genetic changes in the MAB_4099c gene, which is a likely genetic basis for the rough morphotype. Proteomic analysis detected 3 137 different proteins in total of which 79 proteins were found in the culture supernatants of all isolates. BLAST analyses of these 79 proteins identified 12 of those exclusively encoded by all members of MABC plus M. immunogenum. In silico prediction of epitopes predicted B- and T-cell epitopes in all these 12 species-specific proteins, rendering them promising candidates for future studies on immune pathogenesis and immune diagnostic tools for MABC disease.

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The impact of mab_1638 on the M. abscessus transcriptome [ChIP-seq]

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