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The protonmotive force is required for maintaining ATP homeostasis and viability of hypoxic, nonreplicating Mycobacterium tuberculosis.

ABSTRACT: The persistence of Mycobacterium tuberculosis despite prolonged chemotherapy represents a major obstacle for the control of tuberculosis. The mechanisms used by Mtb to persist in a quiescent state are largely unknown. Chemical genetic and genetic approaches were used here to study the physiology of hypoxic nonreplicating mycobacteria. We found that the intracellular concentration of ATP is five to six times lower in hypoxic nonreplicating Mtb cells compared with aerobic replicating bacteria, making them exquisitely sensitive to any further depletion. We show that de novo ATP synthesis is essential for the viability of hypoxic nonreplicating mycobacteria, requiring the cytoplasmic membrane to be fully energized. In addition, the anaerobic electron transport chain was demonstrated to be necessary for the generation of the protonmotive force. Surprisingly, the alternate ndh-2, but not -1, was shown to be the electron donor to the electron transport chain and to be essential to replenish the [NAD(+)] pool in hypoxic nonreplicating Mtb. Finally, we describe here the high bactericidal activity of the F(0)F(1) ATP synthase inhibitor R207910 on hypoxic nonreplicating bacteria, supporting the potential of this drug candidate for shortening the time of tuberculosis therapy.

SUBMITTER: Rao SP

PROVIDER: S-EPMC2575262 | biostudies-other | 2008 Aug

REPOSITORIES: biostudies-other

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The protonmotive force is required for maintaining ATP homeostasis and viability of hypoxic, nonreplicating Mycobacterium tuberculosis.

Rao Srinivasa P S SP Alonso Sylvie S Rand Lucinda L Dick Thomas T Pethe Kevin K

Proceedings of the National Academy of Sciences of the United States of America 20080812 33

The persistence of Mycobacterium tuberculosis despite prolonged chemotherapy represents a major obstacle for the control of tuberculosis. The mechanisms used by Mtb to persist in a quiescent state are largely unknown. Chemical genetic and genetic approaches were used here to study the physiology of hypoxic nonreplicating mycobacteria. We found that the intracellular concentration of ATP is five to six times lower in hypoxic nonreplicating Mtb cells compared with aerobic replicating bacteria, mak ...[more]

PMID: 18697942

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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.

Project description:BACKGROUND:The DevR(DosR) regulon is implicated in hypoxic adaptation and virulence of Mycobacterium tuberculosis. The present study was designed to decipher the impact of perturbation in DevR-mediated signaling on these properties. METHODOLOGY/PRINCIPAL FINDINGS:M. tb complemented (Comp) strains expressing different levels of DevR were constructed in Mut1* background (expressing DevR N-terminal domain in fusion with AphI (DevR(N)-Kan) and in Mut2?devR background (deletion mutant). They were compared for their hypoxia adaptation and virulence properties. Diverse phenotypes were noted; basal level expression (?5.3±2.3 µM) when induced to levels equivalent to WT levels (?25.8±9.3 µM) was associated with robust DevR regulon induction and hypoxic adaptation (Comp 9* and 10*), whereas low-level expression (detectable at transcript level) as in Comp 11* and Comp15 was associated with an adaptation defect. Intermediate-level expression (?3.3±1.2 µM) partially restored hypoxic adaptation functions in Comp2, but not in Comp1* bacteria that co-expressed DevR(N)-Kan. Comp* strains in Mut1* background also exhibited diverse virulence phenotypes; high/very low-level DevR expression was associated with virulence whereas intermediate-level expression was associated with low virulence. Transcription profiling and gene expression analysis revealed up-regulation of the phosphate starvation response (PSR) in Mut1* and Comp11* bacteria, but not in WT/Mut2?devR/other Comp strains, indicating a plasticity in expression pathways that is determined by the magnitude of signaling perturbation through DevR(N)-Kan. CONCLUSIONS/SIGNIFICANCE:A minimum DevR concentration of ?3.3±1.2 µM (as in Comp2 bacteria) is required to support HspX expression in the standing culture hypoxia model. The relative intracellular concentrations of DevR and DevR(N)-Kan appear to be critical for determining dormancy regulon induction, hypoxic adaptation and virulence. Dysregulated DevR(N)-Kan-mediated signaling selectively triggers the PSR in bacteria expressing no/very low level of DevR. Our findings illustrate the important role of appropriate two-component-mediated signaling in pathogen physiology and the resilience of bacteria when such signaling is perturbed.

Dataset Information

The protonmotive force is required for maintaining ATP homeostasis and viability of hypoxic, nonreplicating Mycobacterium tuberculosis.

Publications

The protonmotive force is required for maintaining ATP homeostasis and viability of hypoxic, nonreplicating Mycobacterium tuberculosis.

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