Imagine a world where the tiniest creatures hold the key to life as we know it. These microscopic powerhouses, hidden in plain sight, are the unsung heroes of our planet's survival. But here's where it gets fascinating: a groundbreaking microscopy technique is finally pulling back the curtain on this invisible realm, revealing secrets that could reshape our understanding of life on Earth.
Plankton, often overlooked, are the silent architects of our ecosystem. These minuscule organisms generate a staggering portion of the world’s oxygen and form the foundation of the ocean’s food web. Their diversity is mind-boggling—tens of thousands of species have been identified, with countless more awaiting discovery. Among them, protists—single-celled organisms with immense evolutionary significance—stand out. For years, scientists could only study them through genetic data, as traditional imaging methods failed to capture their intricate internal structures.
But here’s where it gets controversial: What if the limitations of our tools have kept us from fully grasping the complexity of life’s building blocks? A pandemic-era collaboration between researchers at EMBL and EPFL is changing that. During the COVID-19 lockdown, a Zoom call between Gautam Dey and Omaya Dudin sparked a revolution. Dudin had just adapted a cutting-edge imaging method, expansion microscopy, to visualize the inner workings of Ichthyosporea, a marine protist with tough cell walls that had long stumped scientists.
This technique, originally developed at MIT and refined by Paul Guichard and Virginie Hamel at the University of Geneva, makes cell walls permeable, allowing researchers to observe internal structures in unprecedented detail. And this is the part most people miss: By physically expanding biological samples up to 16 times their original size, expansion microscopy bypasses the limitations of traditional light microscopy, revealing structures too small to be seen otherwise.
Motivated by this breakthrough, the team embarked on a three-year collaboration that has yielded a treasure trove of knowledge about hundreds of protist species. Their work lays the foundation for a “planetary atlas” of plankton, mapping the hidden diversity of these microscopic organisms. The EMBL-led Traversing European Coastlines (TREC) expedition provided the perfect opportunity to explore further. Published in Cell, their findings offer detailed insights into the cellular structures of over 200 plankton species, particularly eukaryotes—organisms with membrane-bound nuclei.
At Roscoff, France, one of TREC’s sampling sites, the team gained access to Europe’s most comprehensive collection of marine microorganisms. Expecting a few dozen samples, they were stunned to receive over 200 species. “We spent three days and nights just fixing those samples,” recalled Felix Mikus, a co-first author of the study. “It was a once-in-a-lifetime opportunity we couldn’t pass up.”
Using expansion microscopy, the team conducted one of the most comprehensive studies ever of the cytoskeleton—the filament network that gives eukaryotic cells their shape and organization. They focused on microtubules and centrins, proteins crucial for cell division, movement, and structure. Here’s a thought-provoking question: Could mapping these structures across diverse species unlock the secrets of evolution itself?
Hiral Shah, another co-first author, explained, “The scale of this study allows us to make evolutionary predictions. For example, we mapped tubulin and centrin structures in dinoflagellates, one of the ocean’s most diverse groups, revealing patterns that hint at their evolutionary history.”
Armando Rubio Ramos, a postdoctoral fellow, added, “Expansion microscopy is bridging the gap between molecular data and the physical organization of life. It’s transforming how we study protists and their evolutionary journey.”
This research not only illuminates the inner workings of eukaryotic cells but also offers clues about how their structures evolved. It demonstrates the power of expansion microscopy to analyze complex environmental samples directly from the ocean.
Looking ahead, the team envisions a planetary atlas of microscopic life, linking cellular physiology with genomic data across the tree of life. With a CHF 2 million grant from the Moore Foundation, they’re diving deeper into specific species to answer questions about mitosis, multicellularity, and evolutionary transitions.
But here’s the real question: As we uncover the secrets of these microscopic powerhouses, how will it change our understanding of life’s origins and our role in preserving it? Share your thoughts in the comments—let’s spark a conversation about the invisible forces that shape our world.
