The CO2 assimilation via the reductive tricarboxylic acid cycle in an obligately autotrophic, aerobic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus
The incorporation of 14CO2 by the cell suspensions of an extremely thermophilic, aerobic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus was studied. After short time incubation of the cell suspensions with 14CO2, the radiactivity was initially present in aspartate, glutamate, succinate, phosphorylated compounds, citrate, malate and fumarate. All of these compounds except phosphorylated compounds were related to the members of the tricarboxylic acid cycle. The proportion of labelled aspartate onglutamate in total radioactivity on each chromatogram decreased with incubation time, while the percentage of the radioactivity incorporated in phosphorylated compounds increased with time up to 10 s. These indicated that aspartate and glutamate is derived from primary products of CO2 fixation.
In cell-free extracts of Hydrogenobacter thermophilus, the two key enzymes in the Calvin cycle, ribulose-1,5-bisphosphate carboxylase and phosphoribulokinase could not be detected. The key enzymes of the reductive tricarboxylic acid cycle, fumarate reductase and ATP citrate lyase were present. Activities of phosphoenolpyruvate synthetase and pyruvate carboxylase were also detected. The referse reactions (dehydrogenase reactions) of α-ketoglutarate synthase and pyruvate synthase could be detected by using methyl viologen as an electron acceptor.
These findings strongly suggested that a new type of the reductive tricarboxylic acid cycle operated as the CO2 fixation pathway in Hydrogenobacter thermophilus.
Key wordsHydrogenobacter thermophilus Autotrophic CO2 assimilation The reductive tricarboxylic acid cycle Pyruvate carboxylase Phosphoenolpyruvate synthetase ATP citrate lyase Fumarate reductase Pyruvate synthase α-Ketoglutarate synthase
Unable to display preview. Download preview PDF.
- Bassham JA, Calvin M (1957) The path of carbon in photosynthesis. Prentice-Hall Inc, Englewood Cliffs, NJGoogle Scholar
- Cooper RA, Kornberg HL (1974) Phosphoenolpyruvate synthetase and pyruvate, phosphate dikinase. In: Boyer PD (ed) The enzymes, 3rd edn, vol 10. Academic Press, New York, pp 631–649Google Scholar
- Eden G, Fuchs G (1982) Total synthesis of acetyl coenzyme A involved in autotrophic CO2 fixation in Acetobacterium woodii. Arch Microbiol 133:66–74Google Scholar
- Eden G, Fuchs G (1983) Autotrophic CO2 fixation in Acetobacterium woodii. II. Demonstration of enzymes involved. Arch Microbiol 135:68–73Google Scholar
- Eyzaguirre J, Jansen K, Fuchs G (1982) Phosphoenolpyruvate synthetase in Methanobacterium thermoautotrophicum. Arch Microbiol 132:67–74Google Scholar
- Fuchs G, Stupperich E (1980) Acetyl CoA, a central intermediate of autotrophic CO2 fixation in Methanobacterium thermoautotrophicum. Arch Microbiol 127:267–272Google Scholar
- Fuchs G, Stupperich E (1982) Autotrophic CO2 fixation pathway in Methanobacterium thermoautotrophicum. Zbl Bakt Hyg, 1 Abt Orig C 3:277–288Google Scholar
- Fuchs G, Stupperich E (1983) CO2 fixation pathway in bacteria. Physiol Veg 21:845–854Google Scholar
- Fuchs G, Stupperich E, Thauer RK (1978) Acetate assimilation and the synthesis of alanine, aspartate and glutamate in Methanobacterium thermoautotrophicum. Arch Microbiol 117:61–66Google Scholar
- Fuchs G, Stupperich E, Jaenchen R (1980a) Autotrophic CO2 fixation in Chlorobium limicola. Evidence against the operation of the Calvin cycle in growing cells. Arch Microbiol 128:56–63Google Scholar
- Fuchs G, Stupperich E, Eden G (1980b) Autotrophic CO2 fixation in Chlorobium limicola. Evidence for the operation of a reductive tricarboxylic acid cycle in growing cells. Arch Microbiol 128:64–71Google Scholar
- Fuchs G, Winter H, Steiner I, Stupperich E (1983) Enzymes of gluconeogenesis in the autotroph Methanobacterium thermoautotrophicum. Arch Microbiol 136:160–162Google Scholar
- Ishii M, Kawasumi T, Igarashi Y, Kodama T, Minoda Y (1983) 2-Methylthio-1,4-naphthoquinone, a new quinone from an extremely thermophilic hydrogen bacterium. Agric Biol Chem 47:167–169Google Scholar
- Ivanovsky RN, Sintsov NV, Kondratieva EN (1980) ATP-linked citrate lyase activity in the green sulfur bacterium Chorobium limicola forma thiosulfatophilum. Arch Microbiol 128:239–241Google Scholar
- Jansen K, Stupperich E, Fuchs G (1982) Carbohydrate synthesis from acetyl CoA in the autotroph Methanobacterium thermoautotrophicum. Arch Microbiol 132:355–364Google Scholar
- Kandler O, Stetter KO (1981) Evidence for autotrophic CO2 assimilation in Sulfolobus brierleyi via a reductive carboxylic acid pathway. Zbl Bakt Hyg, I Abt Orig C 2:111–121Google Scholar
- Kawasumi T, Igarashi Y, Kodama T, Minoda Y (1980) Isolation of strictly thermophilic and obligately autotrophic hydrogen bacteria. Agric Biol Chem 44:1985–1986Google Scholar
- Kawasumi T, Igarashi Y, Kodama T, Minoda Y (1984) Hydrogenobacter thermophilus gen. nov., sp. nov., an extremely thermophilic, aerobic, hydrogen-oxidizing bacterium. Int J Syst Bacteriol 34:5–10Google Scholar
- Myers WF, Huang KY (1969) Thin-layer chromatography of citric acid cycle compounds. In: Lowenstein JM (ed) Methods in enzymology, vol 13. Academic Press, New York, pp 431–434Google Scholar
- Shiba H, Kawasumi T, Igarashi Y, Kodama T, Minoda Y (1982) The deficient carbohydrate metabolic pathways and the incomplete tricarboxylic acid cycle in an obligately autotrophic hydrogen-oxidizing bacterium. Agric Biol Chem 46:2341–2345Google Scholar
- Shiba H, Kawasumi T, Igarashi Y, Kodama T, Minoda Y (1984) Effect of organic compounds on the growth of an obligately autotrophic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6. Agric Biol Chem 48:2809–2813Google Scholar
- Stupperich E, Fuchs G (1981) Products of CO2 fixation and 14C labelling pattern of alanine in Methanobacterium thermoautotrophicum pulse-labelled with 14CO2. Arch Microbiol 136:294–300Google Scholar
- Takeda Y, Suzuki F, Inoue H (1969) ATP citrate lyase (citrate-cleavage enzyme). In: Lowenstein JM (ed) Methods in enzymology, vol. 13. Academic Press, New York, pp 153–160Google Scholar
- Zeikus JG (1983) Metabolism of one-carbon compounds by chemotrophic anaerobes. Adv Microbial Physiol 24:215–299Google Scholar