Analysis of functional and taxonomic diversity of symbionts among euglenozoan protists (SYMBIOZOANS)

Symbiosis is a phenomenon of close and often long-term interactions between organisms of different species. Symbioses of multicellular organisms have fascinated scientists for centuries. However, microorganisms are also involved in spectacular symbioses, such as those corals and unicellular algae or fungal consortia with algae known as lichens.

Symbioses have played an essential role in the evolution of eukaryotic organisms, exemplified by the mitochondria and chloroplasts having descended from prokaryotic symbionts. Numerous more recent endosymbionts continue to play a significant role in the evolution of eukaryotes, expanding their metabolic potential and diversifying ecological niches by providing various nutrients, removing toxic host waste, digesting complex nutrient substrates, and defending against bacterial infections and predation. Symbioses with prokaryotes (bacteria and archaea) are especially common among unicellular eukaryotes (also known as protists). Although protists account for most eukaryotic diversity, a limited number of symbioses have been documented for most protist lineages.

The knowledge of symbiont frequency and diversity remains very limited and superficial for most protist groups. To close this gap, I will study one of the overlooked groups – euglenozoan protists. Euglenozoans are split into three major clades – Kinteoplastida, Euglenida and Diplonemida. Diplonemida has recently been shown to be one of the most diversified heterotrophic plankton in the oceans. Free-living kinetoplastids thrive in marine and freshwater environments, and Euglenids are common photosynthetic algae in highly eutrophic freshwaters. Despite being exceptionally taxonomically diverse, abundant, and dominant in many freshwater and marine environments, euglenozoans are among the least studied groups in terms of their symbioses with prokaryotes.

The project’s primary goal is to expand our understanding of endosymbiosis among euglenozoan protists. I will study the cultures and single cells of those protists to identify their symbionts and reveal their functions. I will use microscopic and high-throughput sequencing techniques to identify and validate symbionts’ presence and understand their possible role in the symbiont-host interaction.

Completing this project will allow me to close the gap in our knowledge of euglenozoan symbionts. I will also develop a new approach for the effective screening of symbionts in protists, which could be applied to other groups of microbial eukaryotes. Finally, an in-depth study of the euglenozoan protists’ interactions with their symbionts is crucial for understanding their evolution and functioning in the environment.