Energetics of mixotrophic and autotrophic C1-metabolism by Thiobacillus acidophilus

Jack Pronk, P. de Bruijn, J.P. van Dijken, P. Bos, J.G. Kuenen

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)

Abstract

Although the facultatively autotrophic acidophile Thiobacillus acidophilus is unable to grow on formate and formaldehyde in batch cultures, cells from glucose-limited chemostat cultures exhibited substrate-dependent oxygen uptake with these C1-compounds. Oxidation of formate and formaldehyde was uncoupler-sensitive, suggesting that active transport was involved in the metabolism of these compounds. Formate- and formaldehyde-dependent oxygen uptake was strongly inhibited at substrate concentrations above 150 and 400 μM, respectively. However, autotrophic formate-limited chemostat cultures were obtained by carefully increasing the formate to glucose ratio in the reservoir medium of mixotrophic chemostat cultures. The molar growth yield on formate (Y=2.5 g ·mol-1 at a dilution rate of 0.05 h-1) and RuBPCase activities in cell-free extracts suggested that T. acidophilus employs the Calvin cycle for carbon assimilation during growth on formate. T. acidophilus was unable to utilize the C1-compounds methanol and methylamine. Formate-dependent oxygen uptake was expressed constitutively under a variety of growth conditions. Cell-free extracts contained both dye-linked and NAD-dependent formate dehydrogenase activities. NAD-dependent oxidation of formaldehyde required reduced glutathione. In addition, cell-free extracts contained a dye-linked formaldehyde dehydrogenase activity. Mixotrophic growth yields were higher than the sum of the heterotrophic and autotrophic yields. A quantitative analysis of the mixotrophic growth studies revealed that formaldehyde was a more effective energy source than formate.
Original languageEnglish
Pages (from-to)576-583
JournalArchives of Microbiology
Volume154
Issue number6
DOIs
Publication statusPublished - 1990

Keywords

  • Thiobacillus acidophilus
  • Acidophiles
  • Mixotrophic growth
  • Chemostat cultures
  • Formate metabolism
  • Formaldehyde metabolism

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