Biosynthesis of vitamins and cofactors in bacterium-harbouring trypanosomatids depends on the symbiotic association as revealed by genomic analyses.

Some non-pathogenic trypanosomatids maintain a mutualistic relationship with a betaproteobacterium of the Alcaligenaceae family. Intensive nutritional exchanges have been reported between the two partners, indicating that these protozoa are excellent biological models to study metabolic co-evolution. We previously sequenced and herein investigate the entire genomes of five trypanosomatids which harbor a symbiotic bacterium (SHTs for Symbiont-Haboring Trypanosomatids) and the respective bacteria (TPEs for Trypanosomatid Proteobacterial Endosymbiont), as well as two trypanosomatids without symbionts (RTs for Regular Trypanosomatids), for the presence of genes of the classical pathways for vitamin biosynthesis. Our data show that genes for the biosynthetic pathways of thiamine, biotin, and nicotinic acid are absent from all trypanosomatid genomes. This is in agreement with the absolute growth requirement for these vitamins in all protozoa of the family. Also absent from the genomes of RTs are the genes for the synthesis of pantothenic acid, folic acid, riboflavin, and vitamin B6. This is also in agreement with the available data showing that RTs are auxotrophic for these essential vitamins. On the other hand, SHTs are autotrophic for such vitamins. Indeed, all the genes of the corresponding biosynthetic pathways were identified, most of them in the symbiont genomes, while a few genes, mostly of eukaryotic origin, were found in the host genomes. The only exceptions to the latter are: the gene coding for the enzyme ketopantoate reductase (EC:1.1.1.169) which is related instead to the Firmicutes bacteria; and two other genes, one involved in the salvage pathway of pantothenic acid and the other in the synthesis of ubiquinone, that are related to Gammaproteobacteria. Their presence in trypanosomatids may result from lateral gene transfer. Taken together, our results reinforce the idea that the low nutritional requirement of SHTs is associated with the presence of the symbiotic bacterium, which contains most genes for vitamin production.

Estudios sobre Trypanosoma rangeli Tejera, 1920 XI-ensayo de protección en ratas "Wistar" y proechymis sp. / Studies on Trypanosoma rangeli Tejera, 1920 XI-protection trials in \"Wistar\" rats and proechymis sp

El seguimiento sistemático del curso de la infección primaria y la respuesta a sucesivas reinfecciones por Trypanosoma rangeli en ratas "Wistar" y Proechymis sp., reveló un comportamiento similar del parásito en ambos modelos vertebrados, observándose durante la primo-infección una parasitemia relativamente baja y de corta duración en todos los animales. Se observa una protección activa contra T.rangeli en ambos modelos a partir de la segunda reinfección con el parásito, evidenciada por ausencia de parásitos sanguícolas y detección de anticuerpos circulantes. Se discuten aspectos epidemiológicos sobre estos hallazgos. Ensayos de protección pasiva por transferencia de suero inmune y células esplénicas como factores inmunológicos en ratas "Wistar" demostró un muy corto período de protección sólo en los animales que recibieron simultáneamente suero inmune y células esplénicas. Se especulan las posibles causas de esta efímera protección