The uncultured majority of marine heterotrophic microeukaryotes

Abstract

Microorganisms are central in the evolution of life and play fundamental roles in all ecosystems, where they constitute main reservoirs of genetic and metabolic diversity. Marine microbes are very challenging to grow in culture, so their study typically requires molecular tools. Significant progress has been obtained in marine prokaryotes and photosynthetic microbial eukaryotes (microeukaryotes), but the unpigmented microeukaryotes, known as heterotrophic flagellates, have received much less attention. Yet, these account for ~20% of eukaryotes in the oceans, are main actors in herbivory and bacterial mortality, and are pivotal in marine food webs. Not a single cultured species exists that represents the dominant microbial grazers in the oceans, therefore heterotrophic flagellates are the uncultured majority of microeukaryotes, constituting one of the last frontiers in the exploration of marine life