Expansion Microscopy Unlocks Unprecedented View of Plankton Architecture

Researchers have successfully adapted expansion microscopy to visualize the intricate internal structures of critical ocean plankton species with significantly enhanced clarity. This methodological breakthrough physically magnifies biological samples by up to sixteenfold, overcoming the inherent resolution limits of conventional optical microscopy. The technique centers on transforming the sample matrix itself, providing a clearer look into the cellular realities of these foundational marine organisms.

Scientists from the European Molecular Biology Laboratory (EMBL) and the Swiss Federal Institute of Technology Lausanne (EPFL) spearheaded this application, focusing on challenging marine protists like Ichthyosporea. These organisms possess robust cell walls that typically impede detailed internal probing. By physically expanding the sample, the technique enables sharper imaging of internal components, mapping the fundamental building blocks within the ocean's smallest inhabitants.

This pioneering work gained traction following the Traversing European Coastlines (TREC) expedition. During this extensive mapping effort, the team used the advanced imaging capabilities to delineate cytoskeleton structures, including the delicate microtubule network, across more than 200 distinct eukaryotic plankton species. The samples for this analysis were collected near Roscoff, France, offering a geographically relevant snapshot of biodiversity.

The results, published in the journal Cell, laid the foundation for creating a global plankton atlas, designed to reveal the hidden structural diversity of microscopic ocean inhabitants. The insights derived from this novel visualization technique are proving invaluable for understanding the cellular organization and evolutionary development of these organisms, which are central to marine ecosystems. The ability to observe these foundational architects at high resolution positions scientists to better model global biogeochemical cycles, given plankton's vital role in carbon sequestration and oxygen production.

Expansion microscopy, first introduced in 2015, represents a paradigm shift by decoupling resolution from the wavelength of light used for imaging. The method chemically anchors biomolecules to a swellable polymer network, which is then uniformly expanded. This success has already prompted further investment, with the team securing additional resources as part of the PlanExM (Plankton Expansion Microscopy) project to investigate the evolutionary pathways of mitosis and the emergence of multicellularity within the planktonic realm.

The technique's broad utility is evident as it has also been transformative in fields like neuroscience for mapping neural circuits at nanoscale resolution. Seeing these ocean organisms at such a high resolution deepens appreciation for the complexity woven into ocean life and supports efforts to understand the planet's overall equilibrium.