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.

Comparison of closely related, uncultivated Coxiella tick endosymbiont population genomes reveals clues about the mechanisms of symbiosis

“…In tsetse flies, removal of its essential symbiont, Wigglesworthia glossinidae, leads to hypoprolinemia due to the symbiont involvement in the pathway of proline metabolism, and ultimately decreased fecundity (Michalkova et al, 2014;Rio et al, 2016). In the trypanosomatid Crithidia deanei, proline was shown to be a growth promoter (as for tick cell culture), and the incorporation of proline was higher in cells bearing an endosymbiont (Galvez Rojas et al, 2008).…”

Diversidade e filogenia de tripanossomatídeos parasitas de dípteros.

“…Tripanossomatídeos que contêm endossimbiontes bacterianos não exigem adição de ornitina, arginina e citrulina no meio de cultura, intermediários do ciclo da uréia que são supridos pelo endossimbionte (Galinari e Camargo, 1978 Freymuller, 1977). Os endossimbiontes também influenciam na síntese de fosfatidilcolina (de Azevedo-Martins et al, 2007), ajudam na captação de prolina (Galvez Rojas et al, 2008) e sintetizam treonina-desaminase, primeira enzima da via biossintética de isoleucina, leucina e valina, envolvida na conversão de treonina em alfa-cetobutirato. Assim, espécies com endossimbiontes sobrevivem na ausência desses aminoácidos, o que não ocorre com C. fasciculata, cujo desenvolvimento é bastante prejudicado (Alfieri e Camargo, 1982).…”