Mixotrophy in Protists: from Model Systems to Mathematical Models

Mixotrophy, the combination of phagotrophy and photosynthesis within a single organism, is found across the eukaryotic tree of life and is a widely encountered phenomenon in marine microbial food webs. Mixotrophy includes a broad array of nutritional modes that vary in the relative importance of heterotrophic and phototrophic metabolisms and encompasses a wide variety of ecological niches. At its broadest level of classification, mixotrophs can be lumped into two categories: constitutive mixotrophs, those organisms that possess permanent plastids but sometimes eat, or non-constitutive mixotrophs, organisms that lack plastids but either steal them from algal prey or host endosymbiotic algae. Although it is often viewed as a specialized mode of survival, mixotrophs are widespread and abundant in all sunlit ecosystems. While in temperate near-shore environments there is seasonal variability in when mixotrophy is important, it is fundamental and omnipresent among microbial eukaryotes in oligotrophic gyres. From an organismal perspective of nutrient acquisition and energy metabolism, to the role of mixotrophy in community interactions and complexity, to an ecosystem view of nutrient cycling and biogeochemistry, themes of mixotrophic research have greatly expanded in recent years. This Research Topic seeks to engage scientists from a broad array of backgrounds and who use diverse approaches to mixotrophy research, including model culture systems, field studies, and mathematical modeling. By highlighting recent developments in empirical and theoretical research, we hope to further stimulate community interest in mixotrophy research and the need for new collaborations and interdisciplinary studies.