Utilization of Glucose and the Effect of Organic Compounds on the Chemolithotroph Thiobacillus ferrooxidans

Abstract

The utilization of glucose by the chemolithotroph Thiobacillus ferrooxidans results in a repression of the ability to oxidize iron, the substrate for autotrophic growth. An assay with resting cells was used to measure iron oxidation rates. Concomitant with the decreased iron oxidation rates, the enzyme responsible for carbon dioxide fixation, ribulose diphosphate (RuDP) carboxylase, was also repressed. Maximum iron oxidation rates precede peak RuDP carboxylase levels, consistent with the role of these processes in autotrophic metabolism in nonrepressed cells. The degree of iron oxidation repression depends on the organic substrate supplied, as does the level of RuDP carboxylase. The uptake of glucose parallels an increase in synthesis of glucose-6-phosphate dehydrogenase and the accumulation in cells of poly-β-hydroxybutyrate. The organism is also capable of growing on glucose and other organic supplements in the absence of its inorganic energy source; growth rates depend on the organic substrate supplied.