title: L-Proline uptake in Crithidia deanei is influenced by its endosymbiont bacterium.
abstract: Crithidia deanei, a monoxenic trypanosomatid, presents an endosymbiotic bacterium in its cytoplasm. Both the protozoan and the bacterium maintain intensive metabolic exchange, resulting in an interesting model to study the coevolution of metabolisms. The relevance of l-proline for the growth of C. deanei and its transport into these cells was studied. Both the endosymbiont-containing (wild) and the endosymbiont-free protozoa (aposymbiont or cured) strains, when grown in medium supplemented with l-proline, reached higher cell densities than those grown in unsupplemented media. We biochemically characterized the uptake of l-proline in both the wild (K(m)=0.153+/-0.022 mM, V(max)=0.239+/-0.011 nmol min(-1) per 4 x 10(7) cells) and the aposymbiont strains (K(m)=0.177+/-0.049 mM, V(max)=0.132+/-0.012 nmol min(-1) per 4 x 10(7) cells). These data suggest a single type of proline transporter whose activity is upregulated by the presence of the symbiotic bacterium. Proline transport was further characterized and was found to be insensitive to the extracellular concentration of Na+, but sensitive to K+ and pH. The abolition of proline uptake by respiratory chain inhibitors and valinomycin indicates that the proline transport in C. deanei is dependent on the plasma membrane K+ gradient.
authors.affiliation: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brasil.
authors.forename: Robert Leonardo
authors.initials: RL
authors.lastname: Galvez Rojas
authors.forename: Mariana Lins
authors.initials: ML
authors.lastname: Frossard
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Machado Motta
authors.forename: Ariel Mariano
authors.initials: AM
authors.lastname: Silber
mesh_terms: D000818:Animals; D000968:Antimycin A / Q000031:analogs & derivatives / Q000494:pharmacology; D001419:Bacteria / Q000378:metabolism; D003421:Crithidia / Q000378:metabolism* / Q000382:microbiology*; D003470:Culture Media; D004269:DNA, Bacterial / Q000032:analysis; D003864:Depression, Chemical; D006863:Hydrogen-Ion Concentration; D008985:Monensin / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011392:Proline / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D012402:Rotenone / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D013559:Symbiosis; D013696:Temperature; D013997:Time Factors; D015854:Up-Regulation; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D003470:Culture Media; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012402:Rotenone; C032456:antimycin; D014634:Valinomycin; D000968:Antimycin A; D008985:Monensin; D011392:Proline; D012964:Sodium; D011188:Potassium