Proliferating bloodstream-form Trypanosoma brucei use a negligible part of consumed glucose for anabolic processes

Our quantitative knowledge of carbon fluxes in the long slender bloodstream form (BSF) Trypanosoma brucei is mainly based on non-proliferating parasites, isolated from laboratory animals and kept in buffers. In this paper we present a carbon balance for exponentially growing bloodstream form trypanosomes. The cells grew with a doubling time of 5.3 h, contained 46 μmol of carbon (108 cells)−1 and had a glucose consumption flux of 160 nmol min−1 (108 cells)−1. The molar ratio of pyruvate excreted versus glucose consumed was 2.1. Furthermore, analysis of the 13C label distribution in pyruvate in 13C-glucose incubations of exponentially growing trypanosomes showed that glucose was the sole substrate for pyruvate production. We conclude that the glucose metabolised in glycolysis was hardly, if at all, used for biosynthetic processes. Carbon flux through glycolysis in exponentially growing trypanosomes was 10 times higher than the incorporation of carbon into biomass. This biosynthetic carbon is derived from other precursors present in the nutrient rich growth medium. Furthermore, we found that the glycolytic flux was unaltered when the culture went into stationary phase, suggesting that most of the ATP produced in glycolysis is used for processes other than growth.

Figure optionsDownload high-quality image (59 K)Download as PowerPoint slideHighlights
► A carbon balance for exponentially growing bloodstream form (BSF) Trypanosoma brucei was made.
► Glucose consumption flux of BSF trypanosomes is 160 nmol min−1 (108 cells)−1.
► Carbon requirement of BSF trypanosomes is one-tenth of glycolytic flux.
► All glucose carbon ends up in pyruvate and is hardly used for biosynthetic processes.
► Most of the ATP synthesised in glycolysis is for processes other than growth.