Analyses of amino acid transport systems in Japanese Paramecium symbiont F36-ZK were performed using 14C -amino acids. Kinetic analyses of amino acid uptake and competitive experiments revealed three transport systems; a basic amino acid transport system, which catalyzed transport of L-Arg and L-Lys, a general amino acid transport system, which had broad specificity for 19 amino acids (but not L-Arg), and an alanine transport system. These three systems were considered to be capable of active transport. Amino acid-proton symport was indicated by the following data: decreases in pH of the medium observed during L-Ser and L-Ala uptake, and uptake of L-Arg, L-Ser and L-Ala being inhibited by carbonyl cyanide m-chlorophenylhydrazone, sodium azide and vanadate. The optimal pH for uptake of neutral amino acids and L-Arg was around 5 and 5 to 6.5, respectively. Uptake of L-Asp and L-Glu was very sensitive to pH and little uptake of L-Asp was measured above pH 6.0. Amino acid uptake was not inhibited by nitrate or ammonium, and cultured cells with ammonium also possessed constitutive uptake systems.
Keywords:Paramecium bursaria, Chlorella, amino acid transport Japanese P. bursaria F36 (Kamako et al., 2005). The symbiont released maltose the similar to other Paramecium symbionts; however, it could not utilize nitrate due to lack of nitrate reductase. These findings suggest that F36-ZK was more adapted to its host than hosts associated with European and American symbionts. Japanese symbiont F36-ZK multiplied in the presence of amino acids rather than ammonium (Kamako et al., 2005;Kato et a!., 2006). In addition, preliminary study indicated that F36-ZK could transport more kinds of amino acids than the American Paramecium symbiont, which could import a few amino acids (McAuley, 1986;1989), and the free-living C. vulgaris, which was phylogenetically close to F36-ZK