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 copperresponsive 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.

Control of Copper Resistance and Inorganic Sulfur Metabolism by Paralogous Regulators in Staphylococcus aureus

“…Microarray experiments in S. aureus SH1000 reveal that the expression of CsoR is not strongly induced by copper stress, unlike the situation in M. tuberculosis (13,50); as a result, constitutively expressed CsoR might play a role in buffering "free" Cu(I) in S. aureus in the Ϸ10 Ϫ18 M range. On the other hand, the gene encoding the likely copper chaperone CopZ just downstream from copA (Fig.…”

A Multicopper Oxidase Is Required for Copper Resistance in Mycobacterium tuberculosis

“…Previously, quantitative RT-PCR experiments showed that mmcO transcription is increased by addition of copper (40) and is regulated by the copper-responsive RicR protein (41). To examine how MmcO protein levels changed in M. tuberculosis under copper stress, we utilized the avirulent M. tuberculosis strain mc 2 6230 and its isogenic ⌬mmcO mutant.…”

mosR , a Novel Transcriptional Regulator of Hypoxia and Virulence in Mycobacterium tuberculosis

“…Before DNA microarray hybridizations, doublestranded cDNA was synthesized from 10 g of total RNA using the SuperScript Double-Stranded cDNA Synthesis Kit (Invitrogen), as directed by the manufacturer, in the presence of 250 ng genome-directed primers (41,49). The doublestranded cDNA was cleaned up and labeled following the NimbleGen gene expression analysis protocol (NimbleGen Systems, Inc., Madison, WI) and hybridized to NimbelGen-manufactured microarrays following a protocol we established earlier (49). In this microarray, each of the 3,989 open reading frames in the genome of M. tuberculosis strain H37Rv was represented by 19 probes of 60-mer oligonucleotides.…”