mixotrophen

Mixotrophy refers to metabolic strategies in which an organism combines autotrophic and heterotrophic nutrition. Mixotrophs can perform photosynthesis to fix carbon and energy while also obtaining energy or nutrients by ingesting prey or absorbing dissolved organic matter. This flexibility allows them to rely on multiple sources of carbon and energy, depending on environmental conditions. The term mixotrophen is used in German to refer to the same concept.

Mixotrophy is common among protists in marine and freshwater ecosystems, as well as in soils. Groups include certain dinoflagellates, chrysophytes, ciliates, and euglenoids. Some species acquire plastids from prey through a process called kleptoplasty, enabling photosynthesis even when their own plastids are insufficient.

Mechanisms vary: phototrophy provides carbon and energy via photosynthesis; phagotrophy or osmotrophy supplies additional carbon, nitrogen, vitamins, or energy. Some mixotrophs are obligate, requiring both modes for growth, while others are facultative and switch modes according to light, prey availability, or nutrient status. The balance between autotrophy and heterotrophy can differ among species and environments.

Ecologically, mixotrophs influence carbon cycling and food webs by contributing to primary production while also recycling nutrients through predation. Their flexibility can confer advantages in nutrient-poor or fluctuating conditions and in stratified waters. In ecological modeling, mixotrophy can blur the distinction between autotrophic and heterotrophic productivity, affecting estimates of ecosystem respiration and carbon flow.

Research on mixotrophy combines organismal physiology, molecular biology, and stable isotope techniques to quantify the relative contribution of autotrophic and heterotrophic processes. Ongoing work aims to clarify phylogenetic distribution, ecological roles, and the response of mixotroph communities to environmental change.