Effect of Japanese Paramecium bursaria Extract on Photosynthetic Carbon Fixation of Symbiotic Algae

Abstract

To investigate the relationship between the Japanese Paramecium bursaria host and its symbiont, we studied the effect of a host cell-free extract on carbon fixation and photosynthate release of the symbiont. The host extract enhanced symbiotic algal carbon fixation about 3-fold at an increased concentration; however, release of photosynthate hardly changed. Since the enhancing effect was not affected by elimination of carbon dioxide from the host extract, the existence of a host factor that stimulates algal carbon fixation was made clear. The host factor is a heat-stable, low molecular weight substance. In relation to the pH dependence, the extract improved carbon fixation at acidic and neutral pH and showed almost no effect at pH 9.0. Therefore, the stimulation of carbon fixation by the host factor is unlikely to be caused by intracellular pH change. The extract also improved carbon fixation of several Chlorella species, symbiotic and free-living, and apparently exhibited no species specificity. Therefore, the host seems to regulate the photosynthesis of the symbiont via a specific compound.

Did the peridinin plastid evolve through tertiary endosymbiosis? A hypothesis

“…the endosymbiosis between the chlorophyte Chlorella and the coelenterate Hydra; Habetha & Bosch, 2005) and an alga with a secondary plastid (e.g. the endosymbiosis between the heterokont Vaucheria and the mollusc Elysia; Rumpho et al, 2001; see also Raven, 2002;Okamoto & Inouye, 2005;Foster et al, 2006;Kamako & Imamura, 2006). Given the results of recent analyses of P. chromatophora, it could be supposed that some of these less well-characterized endosymbionts already represent at least partially integrated organelles with their host cells.…”

Forced symbiosis betweenSynechocystisspp. PCC 6803 and apo-symbioticParamecium bursariaas an experimental model for evolutionary emergence of primitive photosynthetic eukaryotes

“…2,3 This organism has attracted the attention of cell biologists, biochemists and ecologists since P. bursaria serves as an excellent experimental model for studying the nature of endo-symbiosis in which one species propagates inside the cells of other species under the precise control through the chemical communications between the host and symbiont cells, and knowledge on the recognition of the symbiotic partners, exchange of chemicals and regulation of metabolic processes have been documented. [4][5][6] It is well known that synchronization on the algal cell division is imposed by the hosting paramecia possibly through chemical communication between the partners. 7 In our recent study focusing on the impacts of the host's cell cycle and growth status on the life cycle in endo-symbiotic algae, flow-cytometric analysis has revealed that the life cycle of symbiotic algae is largely affected by the growth status of the hosting cells.…”

Metabolic co-dependence drives the evolutionarily ancient Hydra–Chlorella symbiosis

“…Despite these similarities, however, there are also conspicuous differences among symbiotic cnidarians in particular with respect to the nutrients provided by the symbiont to the host. For example, symbiotic Chlorella algae in green hydra, Paramecium and fresh water sponges provide their photosynthetic products in form of maltose and glucose (Figure 8B) (Brown and Nielsen, 1974; Wilkinson, 1980; Kamako and Imamura, 2006). In contrast, Symbiodinium provides glucose, glycerol, organic acids, amino acids as well as lipids to its marine hosts (Figure 8C) (Muscatine and Cernichiari, 1969; Lewis and Smith, 1971; Trench, 1971; Kellogg and Patton, 1983).…”