Amino acid transport systems of JapaneseParamecium symbiont F36-ZK

Abstract

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

Characterization of the RNA-interference pathway as a tool for reverse genetic analysis in the nascent phototrophic endosymbiosis, Paramecium bursaria

“…Paramecium bursaria is a ciliate protist which harbours several hundred cells of the green algae, Chlorella spp., in a nascent and facultative photoendosymbiosis [8][9][10][11][12]. The algae provide sugar and oxygen derived from photosynthesis, in exchange for amino acids, CO 2 , divalent cations and protection from viruses and other predators [5,6,[13][14][15][16][17][18][19]. While the interaction is heritable, the P. bursaria-Chlorella spp.…”

Metabolic Symbiosis Facilitates Species Coexistence and Generates Light-Dependent Priority Effects

“…This facilitative priority effect of P. bursaria on Colpidium is absent in direct competition (Hsu et al, unpublished) and is unlikely due to free-living endosymbiotic algae Chlorella. Although Chlorella can escape host cells and grow independent of P. bursaria (Lowe et al, 2016), there was no significant increase in chlorophyll-a from free-living Chlorella across light levels (Supplementary Figure S2) perhaps due to the presence of Chlorella viruses in our cultures or lack of regulatory factors to survive on its own (Kato and Imamura, 2009;Johnson, 2011). Facilitative priority effects are often explained by niche modification, in which the early arriving species alters the type of niches available in the local environment, consequently shaping the species that are capable of colonization (Fukami, 2015).…”

Emergent RNA-RNA interactions can promote stability in a nascent phototrophic endosymbiosis

“…The algae provide sugar and oxygen derived from photosynthesis, in exchange for amino acids, CO2, divalent cations, and protection from viruses and a range of predators 6,[21][22][23][24][25][26][27] . While the interaction is heritable, the P. bursaria -Chlorella system is described as a 'nascent' or 'facultative' endosymbiosis as both host and endosymbiont can typically survive independently 18,[28][29][30][31] .…”

“…However, we know little about how enforcement mechanisms can emerge in a nascent endosymbiotic interaction.The ciliate protist, Paramecium bursaria, and its intracellular green algae, Chlorella spp., represents a model phototrophic endosymbiosis 10,17 . Hundreds of alga cells, many of which are clonal 11,18,19 , are harboured within modified host phagosomes called perialgal vacuoles 20 .The algae provide sugar and oxygen derived from photosynthesis, in exchange for amino acids, CO2, divalent cations, and protection from viruses and a range of predators 6,[21][22][23][24][25][26][27] . While the interaction is heritable, the P. bursaria -Chlorella system is described as a 'nascent' or 'facultative' endosymbiosis as both host and endosymbiont can typically survive independently 18,[28][29][30][31] .…”