2025-10-30 国立遺伝学研究所
<関連情報>
- https://www.nig.ac.jp/nig/ja/2025/10/research-highlights_ja/rh20251030.html
- https://www.science.org/doi/10.1126/sciadv.adz0004
ゾウリムシ–クロレラにおける閉鎖型栄養循環システム光共生は貧栄養条件下での生存に寄与する The closed nutrient recycling system in the Paramecium–Chlorella photosymbiosis contributes to survival under oligotrophic conditions
Kaoru Okada, Takayuki Fujiwara, Shunsuke Hirooka, Yusuke Kobayashi, […] , and Shin-ya Miyagishima
Science Advances published:29 Oct 2025
DOI:https://doi.org/10.1126/sciadv.adz0004
Abstract
Endosymbiotic relationships between a heterotrophic host and a unicellular algal endosymbiont are observed across many eukaryotic lineages. Although these relationships are prevalent in oligotrophic environments, how they function and provide an advantage under such conditions remains largely unknown. To address these issues, we examined the behavior of the ciliate Paramecium bursaria hosting Chlorella endosymbionts under nitrogen- and prey-depleted conditions. The Paramecium host survived for up to 5 weeks while maintaining the number of Chlorella endosymbionts, whereas aposymbiotic Paramecium and free-living Chlorella either died or bleached, respectively, under the same conditions. In the symbiotic state, the host continuously fed on the endosymbionts without excreting nitrogenous waste into the medium, while the remaining endosymbionts continued to proliferate using heterotrophic metabolites from the host and light energy. Thus, the cyclical farming of endosymbionts by the host maintains a high concentration of nutrients within the closed system, providing a selective advantage in oligotrophic environments.
