Acquired Phototrophy in Ciliate Plankton Communities

Ciliate plankton display remarkable trophic flexibility through acquired phototrophy, a process by which heterotrophic protists obtain photosynthetic capacity by sequestering algal organelles or entire endosymbionts. This capability transforms primary consumers into mixotrophs, combining phagotrophic ingestion of prey with autotrophic carbon fixation. Kleptoplastidy—the retention of functional chloroplasts—and in some cases retention of prey nuclei, extends photosynthetic activity beyond ingestion. Such interactions not only shape food-web dynamics but also influence nutrient cycling, bloom formation and resilience to environmental stressors. Genetic and transcriptomic analyses reveal that hosts regulate sequestered plastids via both inherited and horizontally acquired gene functions. Ecologically, acquired phototrophy underpins periodic red tides and can modulate community structure under shifting pH, temperature and light regimes. The global significance of this mode of nutrition lies in its role in marine primary production, biogeochemical feedbacks and the evolutionary transition towards permanent symbiosis.

Research from Nature Portfolio

Recent studies have outlined evolutionary constraints on the integration of photosynthetic endosymbionts into heterotrophic hosts. Work on eukaryotes engaging in acquired phototrophy demonstrates that pre-existing mechanisms for oxidative stress management, originally evolved to cope with mitochondrial respiration, are extended to handle photosynthetic reactive oxygen species. Host cells regulate chloroplast light absorption, repair or digest damaged plastids and adjust phagocytic rates under illumination. Seminal investigations into unicellular predators feeding on photosynthetic prey reveal conserved transcriptomic responses across distant lineages, including upregulation of chlorophyll-detoxification enzymes and accelerated digestion of ingested algal cells. Those findings emphasise common strategies that likely prefigured the establishment of permanent photosynthetic organelles.

Acquired Phototrophy in Ciliate Plankton Communities publication trend

The graph below shows the total number of articles in acquired phototrophy in ciliate plankton communities across all publications each year (not limited to Nature Index journals).

Technical terms

Acquired phototrophy: The process by which a heterotrophic organism obtains photosynthetic function by sequestering chloroplasts or algal cells.

Mixotrophy: A nutritional strategy combining heterotrophic ingestion of prey with autotrophic carbon fixation.

Kleptoplastidy: The retention and functional maintenance of ingested algal chloroplasts within a non-photosynthetic host.

Phagotrophy: The feeding mode involving engulfment and digestion of particulate prey items.

Endosymbiosis: A stable, intracellular association in which one organism resides within the cells of another, often leading to metabolic integration.

Oxidative stress: Cellular damage resulting from accumulation of reactive oxygen species, commonly produced during photosynthesis and respiration.

References

1. Cellular interactions and evolutionary origins of endosymbiotic relationships with ciliates. The ISME Journal: Multidisciplinary Journal of Microbial Ecology (2024).
2. Taming the perils of photosynthesis by eukaryotes: constraints on endosymbiotic evolution in aquatic ecosystems. Communications Biology (2023).
3. Responses of unicellular predators to cope with the phototoxicity of photosynthetic prey. Nature Communications (2019).
4. The combined effect of pH and dissolved inorganic carbon concentrations on the physiology of plastidic ciliate Mesodinium rubrum and its cryptophyte prey. Harmful Algae (2023).
5. The Genetic Diversity of Mesodinium and Associated Cryptophytes. Frontiers in Microbiology (2016).