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Mackenzie, J. S.

Publications and source records attributed to Mackenzie, J. S..

2 recordsLinked to original sources
bioRxiv2021

Mycobacterium tuberculosis senses host Interferon- gamma via the membrane protein MmpL10

Mycobacterium tuberculosis (Mtb) is one of the most successful human pathogens and remains a leading cause of death from infectious disease. Interferon-{gamma} (IFN-{gamma}) is a central regulator of the immune defense against Mtb. Several cytokines have been shown to increase virulence of other bacterial pathogens, leading us to investigate whether IFN-{gamma} has a direct effect on Mtb. We found that both recombinant and T-cell derived IFN-{gamma} rapidly induced a dose-dependent increase in the oxygen consumption rate (OCR) of Mtb, consistent with increased bacterial respiration. This was also observed in clinical strains, but not in the vaccine strain Bacillus Calmette-Guerin (BCG), and did not occur for other cytokines tested, including TNF-. IFN-{gamma} binds to the cell surface of intact Mtb, but not BCG, whilst TNF- binds to neither. Mass spectrometry analysis identified mycobacterial membrane protein large 10 (MmpL10) as the transmembrane binding partner. Consistent with this, IFN-{gamma} binding and the OCR response was absent in a Mtb {Delta}mmpl10 strain and restored by complementation of the mutant strain. RNA-sequencing of IFN-{gamma} exposed Mtb revealed a distinct transcriptional profile, including genes involved in virulence and cholesterol catabolism. Finally, exposure of Mtb cells to IFN-{gamma} resulted in sterilization of bacilli treated with isoniazid (INH), indicating clearance of phenotypically resistant bacteria that persist in the presence of INH alone. Our data suggest a novel mechanism allowing Mtb to respond to host immune activation that may be important in the immunopathogenesis of TB and have use in novel eradication strategies. One-Sentence SummaryIFN-{gamma} is a critical component of effective immune defense in human tuberculosis yet its causative agent, Mycobacterium tuberculosis it able to sense this cytokine and increase virulence and respiration in response.

microbiology↗
bioRxiv2021

Mycobacterium tuberculosis H2S functions as a sink to modulate central metabolism, bioenergetics, and drug susceptibility

H2S is a potent gasotransmitter in eukaryotes and bacteria. Host-derived H2S has been shown to profoundly alter M. tuberculosis (Mtb) energy metabolism and growth. However, compelling evidence for endogenous production of H2S and its role in Mtb physiology is lacking. We show that multidrug-resistant and drug-susceptible clinical Mtb strains produce H2S, whereas H2S production in non-pathogenic M. smegmatis is barely detectable. We identified Rv3684 (Cds1) as an H2S-producing enzyme in Mtb and show that cds1 disruption reduces, but does not eliminate, H2S production, suggesting the involvement of multiple genes in H2S production. We identified endogenous H2S to be an effector molecule that maintains bioenergetic homeostasis by stimulating respiration primarily via cytochrome bd. Importantly, H2S plays a key role in central metabolism by modulating the balance between oxidative phosphorylation and glycolysis, and functions as a sink to recycle sulfur atoms back to cysteine to maintain sulfur homeostasis. Lastly, Mtb-generated H2S regulates redox homeostasis and susceptibility to anti-TB drugs clofazimine and rifampicin. These findings reveal previously unknown facets of Mtb physiology and have implications for routine laboratory culturing, understanding drug susceptibility, and improved diagnostics.

microbiology↗