Microaerophilic bacteria transduce energy via oxidative metabolic gearing

Heterotrophic microaerophilic bacteria, a diverse and ubiquitous group, are specialized for growth in O 2 limited environments. Until recently, microaerophilic bacteria have been grouped with obligate aerobic organisms whose metabolic rates slow in response to physiological O 2 limitation. In contrast, microaerophilic bacteria are adapted to maintain essentially constant turnover of primary energy substrates in response to a wide range of physiological O 2. This capacity, oxidative metabolic gearing, allows microaerophilic bacteria to maintain catabolic enzymes, substrates, and cofactors at high steady-state levels. Oxidative metabolic gearing is thus adaptive, as it allows microaerophilic bacteria to respond to changes in physiological O 2 relatively rapidly when compared to aerobic, anaerobic, or facultative microorganisms.