molybdenum-cofactor and Tuberculosis

The Rangipo strain of Mycobacterium tuberculosis achieved notoriety in New Zealand due to its role in several tuberculosis (TB) outbreaks. Why this strain should be the source of relatively large clusters of the disease is unknown. In this work, we performed an in-depth analysis of the genome of the Rangipo strain to determine whether it offers clues to understanding its prevalence.. Next-generation sequencing was performed on nine isolates which matched the Rangipo genotypic profile. Sequence reads were assembled against the H37Rv reference genome and single-locus variants identified. Unmapped reads were compared against the genome sequences of other M. tuberculosis strains, in particular CDC1551, Haarlem and Erdman.. Across the nine Rangipo strains, a total of 727 single-locus variants were identified with respect to H37Rv, of which 700 were common to all Rangipo strains sequenced. Within the common variants, 386 were non-synonymous, with 12 occurring in genes associated with M. tuberculosis virulence. Next-generation and Sanger sequencing determined the presence of three genes in the Rangipo isolates, which are absent in H37Rv, but which have been reported to be important for the pathogenicity of M. tuberculosis. The differentially encoded Rangipo genes consisted of transcriptional regulator EmbR2, and molybdopterin cofactor biosynthesis proteins A and B. The Rangipo strain also harbours an extended DNA helicase and an additional adenylate cyclase.. Our study provides new insights into the genomic content of the New Zealand Rangipo strain of M. tuberculosis and highlights the presence of additional virulence-related loci not found in H37Rv.

Topics: Bacterial Proteins; Carrier State; Coenzymes; Disease Outbreaks; Genetic Loci; Genetic Variation; Genome, Bacterial; Genotype; High-Throughput Nucleotide Sequencing; Humans; Metalloproteins; Molybdenum Cofactors; Mycobacterium tuberculosis; New Zealand; Pteridines; Tuberculosis; Virulence; Whole Genome Sequencing

The unique ability of the tuberculosis (TB) bacillus, Mycobacterium tuberculosis, to persist for long periods of time in lung hypoxic lesions chiefly contributes to the global burden of latent TB. We and others previously reported that the M. tuberculosis ancestor underwent massive episodes of horizontal gene transfer (HGT), mostly from environmental species. Here, we sought to explore whether such ancient HGT played a part in M. tuberculosis evolution towards pathogenicity. We were interested by a HGT-acquired M. tuberculosis-specific gene set, namely moaA1-D1, which is involved in the biosynthesis of the molybdenum cofactor. Horizontal acquisition of this gene set was striking because homologues of these moa genes are present all across the Mycobacterium genus, including in M. tuberculosis. Here, we discovered that, unlike their paralogues, the moaA1-D1 genes are strongly induced under hypoxia. In vitro, a M. tuberculosis moaA1-D1-null mutant has an impaired ability to respire nitrate, to enter dormancy and to survive in oxygen-limiting conditions. Conversely, heterologous expression of moaA1-D1 in the phylogenetically closest non-TB mycobacterium, Mycobacterium kansasii, which lacks these genes, improves its capacity to respire nitrate and grants it with a marked ability to survive oxygen depletion. In vivo, the M. tuberculosis moaA1-D1-null mutant shows impaired survival in hypoxic granulomas in C3HeB/FeJ mice, but not in normoxic lesions in C57BL/6 animals. Collectively, our results identify a novel pathway required for M. tuberculosis resistance to host-imposed stress, namely hypoxia, and provide evidence that ancient HGT bolstered M. tuberculosis evolution from an environmental species towards a pervasive human-adapted pathogen.

Topics: Animals; Bacterial Proteins; Coenzymes; Female; Gene Expression Regulation, Bacterial; Gene Transfer, Horizontal; Humans; Hypoxia; Metalloproteins; Mice; Mice, Inbred C57BL; Molybdenum Cofactors; Mycobacterium; Mycobacterium tuberculosis; Nitrates; Oxygen; Pteridines; Tuberculosis