The Enzymes of Carbon Metabolism in the Thermotolerant Bacillar Strain K1

Abstract

To determine enzymatic activities in the thermotolerant strain K1 (formerly “Sulfobacillus thermosulfidooxidans subsp. thermotolerans”), it was grown in a mineral medium with (1) thiosulfate and Fe2+ or pyrite (autotrophic conditions), (2) Fe2+, thiosulfate, and yeast extract or glucose (mixotrophic conditions), and (3) yeast extract (heterotrophic conditions). Cells grown mixo-, hetero-, and autotrophically were found to contain enzymes of the tricarboxylic acid (TCA) cycle, as well as malate synthase, an enzyme of the glyoxylate cycle. Cells grown organotrophically in a medium with yeast extract exhibited the activity of the key enzymes of the Embden–Meyerhof–Parnas and Entner–Doudoroff pathways. The increased content of carbon dioxide (up to 5 vol %) in the auto- and mixotrophic media enhanced the activity of the enzymes involved in the terminal reactions of the TCA cycle and the enzymes of the pentose phosphate pathway. Carbon dioxide is fixed in the Calvin cycle. The highest activity of ribulose bisphosphate carboxylase was detected in cells grown autotrophically at the atmospheric content of CO2 in the air used for aeration of the growth medium. The activities of pyruvate carboxylase, phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase, and phospho-enolpyruvate carboxytransphosphorylase decreased with increasing content of CO2 in the medium.