AUTHOR=Ma Ruoyao , Farrell Damien , Gonzalez Gabriel , Browne John A. , Nakajima Chie , Suzuki Yasuhiko , Gordon Stephen V. 

TITLE=The TbD1 Locus Mediates a Hypoxia-Induced Copper Response in Mycobacterium bovis

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.817952

DOI=10.3389/fmicb.2022.817952

ISSN=1664-302X

ABSTRACT=<p>The <italic>Mycobacterium tuberculosis</italic> complex (MTBC) contains the causative agents of tuberculosis (TB) in mammals. The archetypal members of the MTBC, <italic>Mycobacterium tuberculosis</italic> and <italic>Mycobacterium bovis</italic>, cause human tuberculosis and bovine tuberculosis, respectively. Although <italic>M. tuberculosis</italic> and <italic>M. bovis</italic> share over 99.9% genome identity, they show distinct host adaptation for humans and animals; hence, while the molecular basis of host adaptation is encoded in their genomes, the mechanistic basis of host tropism is still unclear. Exploration of the <italic>in vitro</italic> phenotypic consequences of known genetic difference between <italic>M. bovis</italic> and <italic>M. tuberculosis</italic> offers one route to explore genotype–phenotype links that may play a role in host adaptation. The TbD1 (“<italic>Mycobacterium tuberculosis</italic> deletion 1 region”) locus encompasses the <italic>mmpS6</italic> and <italic>mmpL6</italic> genes. TbD1 is absent in <italic>M. tuberculosis</italic> “modern” lineages (Lineages 2, 3, and 4) but present in “ancestral” <italic>M. tuberculosis</italic> (Lineages 1 and 7), <italic>Mycobacterium africanum</italic> lineages (Lineages 5 and 6), newly identified <italic>M. tuberculosis</italic> lineages (Lineages 8 and 9), and animal adapted strains, such as <italic>M. bovis</italic>. The function of TbD1 has previously been investigated in <italic>M. tuberculosis</italic>, where conflicting data has emerged on the role of TbD1 in sensitivity to oxidative stress, while the underlying mechanistic basis of such a phenotype is unclear. In this study, we aimed to shed further light on the role of the TbD1 locus by exploring its function in <italic>M. bovis</italic>. Toward this, we constructed an <italic>M. bovis</italic> TbD1 knockout (ΔTbD1) strain and conducted comparative transcriptomics to define global gene expression profiles of <italic>M. bovis</italic> wild-type (WT) and the ΔTbD1 strains under <italic>in vitro</italic> culture conditions (rolling and standing cultures). This analysis revealed differential induction of a hypoxia-driven copper response in WT and ΔTbD1 strains. <italic>In vitro</italic> phenotypic assays demonstrated that the deletion of TbD1 sensitized <italic>M. bovis</italic> to H<sub>2</sub>O<sub>2</sub> and hypoxia-specific copper toxicity. Our study provides new information on the function of the TbD1 locus in <italic>M. bovis</italic> and its role in stress responses in the MTBC.</p>