African trypanosomes cause human sleeping sickness and livestock trypanosomiasis in sub-Saharan Africa. We present the sequence and analysis of the 11 megabase-sized chromosomes of Trypanosoma brucei . The 26-megabase genome contains 9068 predicted genes, including ∼900 pseudogenes and ∼1700 T. brucei –specific genes. Large subtelomeric arrays contain an archive of 806 variant surface glycoprotein (VSG) genes used by the parasite to evade the mammalian immune system. Most VSG genes are pseudogenes, which may be used to generate expressed mosaic genes by ectopic recombination. Comparisons of the cytoskeleton and endocytic trafficking systems with those of humans and other eukaryotic organisms reveal major differences. A comparison of metabolic pathways encoded by the genomes of T. brucei, T. cruzi , and Leishmania major reveals the least overall metabolic capability in T. brucei and the greatest in L. major . Horizontal transfer of genes of bacterial origin has contributed to some of the metabolic differences in these parasites, and a number of novel potential drug targets have been identified.

To complement the sequencing of the three kinetoplastid genomes reported in this issue, we have undertaken a whole-organism, proteomic analysis of the four life-cycle stages of Trypanosoma cruzi . Peptides mapping to 2784 proteins in 1168 protein groups from the annotated T. cruzi genome were identified across the four life-cycle stages. Protein products were identified from >1000 genes annotated as “hypothetical” in the sequenced genome, including members of a newly defined gene family annotated as mucin-associated surface proteins. The four parasite stages appear to use distinct energy sources, including histidine for stages present in the insect vectors and fatty acids by intracellular amastigotes.

To survive extremely different environments, intracellular parasites require highly adaptable physiological and metabolic systems. Leishmania donovani extracellular promastigotes reside in a glucose‐rich, slightly alkaline environment in the sand fly vector alimentary tract. On entry into human macrophage phagolysosomes, promastigotes differentiate into intra‐cellular amastigotes. These cope with an acidic milieu, where glucose is scarce while amino acids are abundant. Here, we use an axenic differentiation model and a novel high‐coverage, comparative proteomic methodology to analyze in detail protein expression changes throughout the differentiation process. The analysis identified and quantified 21% of the parasite proteome across 7 time points during differentiation. The data reveal a delayed increase in gluconeogenesis enzymes, coinciding with a decrease in glycolytic capacity. At the same time, β‐oxidation, amino acid catabolism, tricarboxylic acid cycle, mitochondrial respiration chain, and oxidative phosphorylation capacities are all up‐regu‐lated. The results indicate that the differentiating parasite shifts from glucose to fatty acids and amino acids as its main energy source. Furthermore, glycerol and amino acids are used as precursors for sugar synthesis, compensating for lack of exogenous sugars. These changes occur while promastigotes undergo morphological transformation. Our findings provide new insight into changes occurring in single‐cell organisms during a developmental process.—Rosenzweig D., Smith, D., Opperdoes, F., Stern, S., Olafson, R. W., Zilberstein D. Retooling Leishmania metabolism: from sand fly gut to human macrophage. FASEB J. 22, 590–602 (2008)