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The global responses of Mycobacterium tuberculosis to physiological levels of copper.

ABSTRACT: Copper (Cu) is a required micronutrient, but it is highly toxic at high concentrations. Therefore, the levels of Cu must be tightly regulated in all living cells. The phagosome of Mycobacterium tuberculosis has been shown to have variable levels of Cu. Previously, we showed that M. tuberculosis contains a copper-sensitive operon, cso, that is induced during early infection in mice. In this study, we showed that ctpV, a gene in the cso operon, is a copper-responsive gene and most likely encodes an efflux pump for Cu. Furthermore, the transcription of key genes in the cso operon is induced by Cu ions and not by other ions, such as Ni and Zn ions. To elucidate copper-responsive genes other than those in the cso operon, we utilized DNA microarrays to profile mycobacterial responses to physiological levels of Cu. A transcriptome analysis identified a novel set of 30 copper-responsive genes in M. tuberculosis, one-half of which were induced only when toxic levels of Cu were added. Interestingly, several transcriptional regulators, including the furA gene, were induced during toxic Cu exposure, indicating that there was a generalized response to oxidative stressors rather than a Cu-specific response. In general, the Cu-induced transcriptome generated should help elucidate the role of the Cu response in maintaining M. tuberculosis survival during infection and could provide novel targets for controlling this virulent pathogen.

SUBMITTER: Ward SK

PROVIDER: S-EPMC2293257 | biostudies-other | 2008 Apr

REPOSITORIES: biostudies-other

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The global responses of Mycobacterium tuberculosis to physiological levels of copper.

Ward Sarah K SK Hoye Elizabeth A EA Talaat Adel M AM

Journal of bacteriology 20080208 8

Copper (Cu) is a required micronutrient, but it is highly toxic at high concentrations. Therefore, the levels of Cu must be tightly regulated in all living cells. The phagosome of Mycobacterium tuberculosis has been shown to have variable levels of Cu. Previously, we showed that M. tuberculosis contains a copper-sensitive operon, cso, that is induced during early infection in mice. In this study, we showed that ctpV, a gene in the cso operon, is a copper-responsive gene and most likely encodes a ...[more]

PMID: 18263720

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Project description:Purpose: CsoR, a copper responsive negative regulator of Mycobacterium tuberculosis has been shown to respond to copper and bind to its own regulon in in vitro experiments. Here we examine the role of CsoR in vivo by examining the impact of deletion of csoR on the host transcriptome. Methods: csoR was knocked out of M. tuberculosis H37Rv using the specialized transduction method developed by Bardarov et al (2002), followed by removal of the hygromycin marker with plasmid pYUB870. Both wild type and confirmed csoR knockout were grown in copper free Sauton's media to late log phase before harvesting for transcriptomic studies. RNA was extracted using a modified Trizol method prior to DNAse treatment and rRNA depletion. Sequencing was done on an Illumina HiSeq 2000, filtered for quality using the FASTX-Toolkit, and mapped using Bowtie, and counts per locus generated with BedTools in the Galaxy platform. Differential expression analysis was carried out in edgeR with significantly differentially expressed genes being identified as those with ≥|2| fold differential expression between ΔcsoR and wild type strains, and an FDR < 0.05. Results: We found that 223 genes were differentially expressed between the ΔcsoR and wild type strains, 52 induced and 71 repressed. Differential expression of 10 of these genes, 6 induced and 4 repressed, was confirmed by qRT-PCR using SYBR green methodology. The only copper responsive genes identified were those within the csoR operon: csoR, Rv0968, ctpV, Rv0970, suggesting that csoR may only regulate its own operon in response to copper. Genes in the RicR regulon, another copper responsive transcriptional regulator, were not significantly differentially expressed, but some of these copper inducible genes were slightly down regulated suggesting that copper levels may be lower in the mutant strain as compared to wild type. Notably, 44 of the 48 members of the dosR regulon, responsive to hypoxic and NO stress, were induced in the mutant vs wild type suggesting that csoR is necessary for maintaining homeostasis, likely through copper regulation, within the cell. Conclusions: We have shown that CsoR is likely only directly regulating its own operon in response to copper, however it is required to maintain homeostasis, preventing a hypoxia-type stress response in the absense of copper.

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The global responses of Mycobacterium tuberculosis to physiological levels of copper.

Publications

The global responses of Mycobacterium tuberculosis to physiological levels of copper.

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