摘要：

Chlorofluexus aurantiacus OK-70 fl was grown photoautotrophically with hydrogen as the electron source. The lowest doubling time observed was 26 h.The mechanism of CO 2 fixation in autotrophically grown cells was studied. The presence of ribulose-1,5-bis-phosphate carboxylase and phosphoribulokinase could not be demonstrated. Carbon isotope fractionation (δ 13 C) was small, and alanine and aspartate but not 3-phosphoglycerate were the major labelled compounds in short term 14 CO 2 labelling. Thus CO 2 is not fixed by the Calvin cycle.Fluoroacetate (FAc) completely inhibited protein synthesis in cultures and caused a slight citrate accumulation. However, CO 2 fixation continued and increased polyglucose formation occurred. Under these conditions added acetate was metabolized to polyglucose, as were glycine, serine, glyoxylate and succinate, but to a lesser extent; little or no formate or CO was utilised.Glyoxylate inhibited CO 2 fixation in vivo, indicating that pyruvate is formed from acetyl-CoA and CO 2 by pyruvate synthase. Two key enzymes of the reductive TCA cycle, citrate lyase and α-ketoglutarate synthase were not detected in cell free extracts, but pyruvate synthase and phosphoenolpyruvate carboxylase were demonstrated. It is concluded that acetyl-CoA is a central intermediate in the CO 2 fixation process, but the mechanism of its synthesis is not clear.

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