Abstract
Chloroflexus aurantiacus OK-70 fl was grown photoautotrophically with hydrogen as electron source. The cultures were subjected to long term labelling experments with 13C-labelled acetate or alanine in the presence of sodium fluoroacetate. The presence of fluoroacetate caused the cells to accumulate large amounts of polyglucose which was hydrolysed and analysed by NMR. The labelling patterns of glucose were symmetric and in agreement with carbohydrate synthesis from acetate and CO2 via pyruvate synthase. The content of carbon derived from added acetate was highest in C2 and C5 of glucose, at least 20% higher than in C1 and C6. About one third of the glucose carbon was derived from added acetate, the rest being from CO2. Contrary to expectations, in glucose formed in the presence of C1-labelled acetate C1 and C6 contained more label than C2 and C5, and with C2-labelled acetate as the tracer glucose was mainly labelled in C2 and C5. Labelled CO2 was formed from acetate labelled at either position. The labelling data indicate a new metabolic pathway in C. aurantiacus. It is suggested that the cells form C1-labelled acetyl-CoA from C2-labelled acetyl-CoA and vice versa by a cyclic mechanism involving concomitant CO2 fixation and that this cycle is the part of the autotrophic CO2 fixation pathways in C. aurantiacus in which acetyl-CoA is formed from CO2.
The polyglucose of C. aurantiacus appears to have predominantly α(1–4)-linked structure with about 10% α(1–6)-linkages as revealed by 13C-NMR.
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Holo, H., Grace, D. Polyglucose synthesis in Chloroflexus aurantiacus studied by 13C-NMR. Arch. Microbiol. 148, 292–297 (1987). https://doi.org/10.1007/BF00456707
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DOI: https://doi.org/10.1007/BF00456707