Changes in energy metabolism ofMycobacterium tuberculosisin mouse lung and underin vitroconditions affecting aerobic respiration

Abstract

Transcription profiling of genes encoding components of the respiratory chain and the ATP synthesizing apparatus of Mycobacterium tuberculosis was conducted in vivo in the infected mouse lung, and in vitro in bacterial cultures subjected to gradual oxygen depletion and to nitric oxide treatment. Transcript levels changed dramatically as infection progressed from bacterial exponential multiplication (acute infection) to cessation of bacterial growth (chronic infection) in response to host immunity. The protonpumping type-I NADH dehydrogenase and the aa3-type cytochrome c oxidase were strongly down-regulated. Concurrently, the less energy-efficient cytochrome bd oxidase was transiently upregulated. The nitrate transporter NarK2 was also up-regulated, indicative of increased nitrate respiration. The reduced efficiency of the respiratory chain was accompanied by decreased expression of ATP synthesis genes. Thus, adaptation of M. tuberculosis to host immunity involves three successive respiratory states leading to decreased energy production. Decreased bacterial counts in mice infected with a cydC mutant (defective in the cytochrome bd oxidase-associated transporter) at the transition to chronic infection provided initial evidence that the bd oxidase pathway is required for M. tuberculosis adaptation to host immunity. In vitro, NO treatment and hypoxia caused a switch from transcription of type I to type II NADH dehydrogenase. Moreover, cytochrome bd oxidase expression increased, but cytochrome c oxidase expression decreased slightly (nitric oxide) or not at all (hypoxia). These specific differences in respiratory metabolism during M. tuberculosis growth arrest in vitro and in vivo will guide manipulation of in vitro conditions to model bacterial adaptation to host immunity. nitric oxide treatment ͉ transcriptional profiling ͉ dormancy ͉ hypoxia M ycobacterium tuberculosis is an airborne bacterial pathogen causing a chronic lung infection that passes through several stages. In most infected persons, host defenses either clear infection or drive it into a chronic latent state that is potentially long-lasting. Weakening of host immunity can result in release from latency and reactivation of disease. It has been suggested that various stages of M. tuberculosis infection are associated with different physiological states of the pathogen (1-5). Work with murine infection models shows that adaptation of M. tuberculosis to host immunity involves replacement of sugars by fatty acids as a carbon and energy source (6, 7). Respiration may also be an important aspect of energy metabolism involved in M. tuberculosis adaptation to host immunity, because respiration in bacteria is a flexible process that changes as microorganisms respond to environmental stresses (reviewed in refs. 8 and 9). However it is not known whether bacterial pathogens, including M. tuberculosis, reroute electron flow during the infection of a host animal.One model for studying M. tuberculosis adaptation to host immunity involves infecting mice with tubercle...

Effect of Anaerobic Growth on Quinolone Lethality with Escherichia coli

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Evidence for complex interactions of stress-associated regulons in an mprAB deletion mutant of Mycobacterium tuberculosis

“…NarK2 (Rv1737c) is important for nitrate reductase activity (Sohaskey & Wayne, 2003), and may be involved in adaptation to nitric oxide stress in macrophages (Shi et al, 2005). RpfC is one of five M. tuberculosis proteins with similarity to Rpf (resuscitation-promoting factor) of Micrococcus luteus, which are important for stimulation of growth of M. tuberculosis in broth, in recovery of dormant mycobacteria, and in virulence (Downing et al, 2005;Mukamolova et al, 2002;Tufariello et al, 2006).…”

Gramicidin S identified as a potent inhibitor for cytochrome bd‐type quinol oxidase

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