Energetics of respiration and oxidative phosphorylation in mycobacteria

The genus Mycobacterium comprises a group of obligately aerobic bacteria that have adapted to inhabit a wide range of intracellular and extracellular environments. A fundamental feature in this adaptation is the ability to respire and generate energy from variable sources or to sustain metabolism in the absence of growth. Early studies on respiration demonstrated that Mycobacterium tuberculosis H37Rv, grown in the lungs of infected mice, had high rates of endogenous respiration that were not stimulated by exogenous substrates (e.g., acetate, pyruvate, glucose, glycerol, lactate) (1). In contrast, cells grown in vitro respired these substrates at high rates. Fatty acids, however, stimulated the respiration of in vivo-grown M. tuberculosis, suggesting for the first time that M. tuberculosis switches to different energy sources in host tissues to fuel respiration. These early studies pointed to the fact that electron donor utilization and respiration are precisely controlled in M. tuberculosis, not only in response to growth rate, but also in response to the carbon and energy sources used for growth. The pioneering work of Brodie and colleagues on Mycobacterium phlei established much of the primary information on the electron transport chain and oxidative phosphorylation system in mycobacteria (reviewed in reference 2).