Hydrogenase and ribulose diphosphate carboxylase during autotrophic, heterotrophic, and mixotrophic growth of scotochromogenic mycobacteria

Abstract

Two key autotrophic enzyme systems, hydrogenase and ribulose diphosphate carboxylase, were examined in Mycobacterium gordonae and two other chemolithotrophic, scotochromogenic mycobacteria under different cultural conditions. In all three organisms both enzymes were inducible and were produced in significant levels only in the presence of the specific substrate, hydrogen or carbon dioxide. M. gordonae exhibited increased growth rates and yields, indicating mixotrophic growth, in the presence of a number of single organic substrates, including acetate, pyruvate, glucose, fructose, and glycerol. In contrast to other aerobic hydrogen autotrophs, the presence of either acetate or pyruvate did not repress ribulose diphosphate carboxylase, and mixotrophic growth was rapid with these substrates. In the absence of carbon dioxide, growth in glycerol medium under an atmosphere of hydrogen and oxygen was severely inhibited, even with cells preadapted to heterotrophic growth on glycerol. Cyclic adenosine monophosphate was not effective in inducing hydrogenase or carboxylase in heterotrophic, mixotrophic, or hydrogen-inhibited cultures.

Molecular Hydrogen Metabolism: a Widespread Trait of Pathogenic Bacteria and Protists

“…However, there is growing evidence that some pathogens can grow chemolithoautotrophically by using electrons derived from H 2 to support carbon fixation. A subset of mycobacteria containing ribulose 1,5bisphosphate carboxylase (RuBisCO), including M. gordonae (68,285), can grow chemolithoautotrophically and mixotrophically on H 2 /CO 2 under oxic conditions. Among anaerobes, preliminary evidence suggests the colonic bacteria Eggerthella lenta (family Coriobacteriaceae) (286,287) and C. difficile (family Peptostreptococcaceae) (70) are capable of hydrogenotrophic acetogenesis through the Wood-Ljungdahl pathway.…”