Breakthroughs in Marine Protist Research During the COVID-19 Pandemic

Amid the COVID-19 pandemic, a collaborative journey among scientists led to remarkable discoveries in the world of microbiology. It all began with a Zoom call between Gautam Dey, a group leader at EMBL, and Umaya Dudin, who was leading a research group at EPFL. This partnership resulted in the development of a new technique to visualize the internal organization of a type of marine protist, an unprecedented achievement.

The Beginning: Expansion Microscopy Technique

The expansion microscopy technique was developed at MIT and later enhanced into super-structural expansion microscopy by Paul Guichard and Virginie Hamel at the University of Geneva. These improvements allowed the cell walls of protists to become permeable, giving scientists a clear view of their internal structure for the first time.

These successes prompted Dudin, Dey, Guichard, and Hamel to establish a long-term partnership that resulted in a wealth of information about hundreds of protist species, paving the way for the creation of a planetary atlas of plankton.

Unprecedented Exploration of Marine Plankton

The TREC expedition, led by EMBL, provided an ideal opportunity to delve deeper into these marine organisms. The team’s findings were recently published in the journal Cell, offering detailed insights into the cellular structures of over 200 species of plankton, particularly eukaryotes.

At the Roscoff Biological Station in France, one of Europe’s most comprehensive marine organism collection sites, the team gained access to over 200 species instead of the few expected samples. Felix Mikos, one of the lead authors, described these samples as a treasure not to be overlooked.

How Expansion Microscopy Works

Expansion microscopy physically enlarges biological samples. The sample is embedded in a transparent gel that absorbs water and expands, yet the internal structures of the cells remain intact and proportionally extended. This allows researchers to magnify the sample up to 16 times without the need for high-power lenses.

When combined with standard light microscopy techniques, expansion microscopy enables scientists to overcome the usual wave barriers that limit the resolution of structures seen with light microscopy.

Mapping the Cellular Structure of Life

Using samples from Roscoff and a second set from Bilbao, the team conducted one of the most comprehensive studies ever on the cellular structural network. They focused on microtubules and centriolar proteins that play a role in organizing these tubules.

Hiral Shah, a postdoctoral fellow in the Dey and Schwab groups at EMBL, explained that the study allowed for mapping the features of microtubule organization across different groups of eukaryotes, opening the door to potential evolutionary predictions.

Conclusion

The super-structural expansion microscopy technique is revolutionizing the exploration of the superstructure of protists. By integrating this technique with high-throughput imaging and comparative analyses, it is possible to begin decoding how cellular structures have diversified through evolution. The results not only illuminate how eukaryotic cells are organized but also provide clues about the internal evolution of their structures.

With Thomas Richards from the University of Oxford joining the collaboration, Dey and Dudin secured a grant of 2 million Swiss francs from the Moore Foundation to continue expanding their research. The next step is to look deeper into specific types within this vast group to answer specific questions about how cell division and multicellularity evolved.