CO-limited chemostat cultures of excreted 13·5; nmol glycollate min (mg protein). This confirmed the earlier finding that glycollate excretion by is dependent on the CO/O ratio applied in the chemostat and thus is probably due to the oxygenase activity of -ribulose-1,5-bisphosphate (RuBP) carboxylase. RuBP-dependent oxygen uptake and activity of phosphoglycollate phosphatase were demonstrated in cell-free extracts of

was able to metabolize exogenous glycollate only to a limited extent. The proportion of dry weight that was derived from [1-C]glycollate by both CO and thiosulphate-limited chemostat cultures was only 0·7;% of the total. Short-term labelling experiments with [1-C]glycollate and enzyme studies indicated that can metabolize glycollate via two pathways. The enzymes of the glycine-serine pathway were demonstrated in cell-free extracts, but on the basis of kinetic experiments it was concluded that this pathway does not play a major role in glycollate metabolism. Malate was the major primary labelling product. Glyoxylate, formed from glycollate, may be incorporated into malate via malate synthase, which was detected in cell-free extracts of

The activities of the enzymes needed for the metabolism of glycollate were independent of growth conditions applied in the chemostat. The results are discussed in relation to the possible causes of obligate chemolithotrophy.


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