In a petri dish in Salzburg, Austria, scientists have cracked a puzzle that has confounded biologists since the early 1800s. Maximilian Ganser and his colleagues at the University of Salzburg have discovered that the intricate shells of tintinnids—microscopic planktonic organisms found in oceans and freshwater lakes worldwide—are built from self-assembling proteins, a finding that rewrites our understanding of biological materials.
For more than two centuries, researchers had marveled at these tiny architects. Tintinnids construct their transparent, vase-like shells from material they secrete directly into the surrounding water, and the structures form autonomously within minutes. The shells are remarkably durable, standing up to high temperatures and harsh chemicals that would destroy most biological materials. Yet nobody knew what they were actually made of.
The answer, it turns out, lies in a family of proteins the team has named "Tintinnidorin"—proteins that exist only in tintinnids and possess an unusual combination of properties. They are extraordinarily stable, adhesive, and resistant even in moist, salty environments where most materials break down. Unlike spider silk or silkworm fibers, which are spun into fixed shapes, these proteins can form a remarkable variety of structures, opening doors that were previously closed to materials scientists.
"All previously known protein biomaterials that serve as models for bioinspired materials originate from animals," Ganser said. "Our study demonstrates for the first time that eukaryotic single-celled organisms produce biological materials with equal potential."
This matters because tintinnids offer researchers something spiders and silkworms cannot: simplicity. While spiders require complex spinning organs to produce their silk, tintinnids simply secrete their shell material into water and let physics do the rest. That accessibility could accelerate research into new biomaterials with applications ranging from medical implants to protective coatings.
With roughly 1,000 known tintinnid species, the team suspects this is only the beginning. "The remarkable diversity suggests that many more variants of tintinnidorin remain to be discovered," said Sabine Agatha, who led the research group. The findings, published in Nature Communications, position tintinnids as a new model system for developing advanced materials—and a reminder that answers to old questions are sometimes swimming right in front of us.