Studies on the metabolism of the protozoa. 9. Comparative metabolism of blood-stream and culture forms of Trypanosoma rhodesiense

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Abstract
The motility and respiration of the blood-stream and culture forms of Trypanosoma rhodesiense depend on a supply of extracellular substrate; both can utilize glycerol, glucose, fructose and mannose, whereas the culture forms can also utilize some tricarboxylic acid cycle intermediates, especially under acid conditions. Culture forms oxidize glucose or glycerol with a high R.Q., mainly to carbon dioxide with small amounts of acetic acid and succinic acid; under anaerobic conditions they convert them into succinic acid and acetic with a net assimilation of carbon dioxide, which is essential for anaerobic metabolism. Blood-stream forms convert glucose or glycerol mainly into pyruvic acid and the R.Q. is low; in addition glycerol is formed from glucose under anaerobic conditions. The respiration of culture forms is sensitive to cyanide, though that of blood-stream forms is not; cytochrome pigments have been detected spectroscopically in culture but not blood-stream forms. Cell-free preparations of both forms show hexokinase, glycerol kinase, [alpha]-glycerophosphate dehydrogenase, aldolase, lactic dehydrogenase, oxaloacetic decarboxylase, malic dehydrogenase (NAD-linked), malic enzyme (NADP-linked), isocitricdehydrogenase and glucose 6-phosphate dehydrogenase activity; both contain fumarase and aconitase, although aconitase activity is particularly low in the blood-stream form. Culture trypanosomes show pyruvic-oxidase activity, whereas blood-stream forms do not. Attempts to demonstrate transhydrogenases have been inconclusive.
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