Sea sponges use protein filament to pattern silica deposition and build intricate glass spicules | The American Ceramic Society

Sea sponges use protein filament to pattern silica deposition and build intricate glass spicules

This vibrant yellow glass sponge (Bolosoma sp.) was observed at a depth of 2,479 meters while exploring Sibelius Seamount.

[Image above] A yellow glass sponge (Bolosoma sp.) on the Sibelius Seamount in the Pacific. Credit: NOAA Ocean Exploration & Research; Flickr CC BY-SA 2.0

I am still completely fascinated by the fact that sea sponges make their own glass skeletons.

Sea sponges are ancient, incredibly simple marine organisms that somehow survive with no nervous, digestive, or circulatory systems—and yet (some species of) these creatures come equipped with the ability to build internal glass structural supports called spicules.

Of course, we know that just because it’s made of glass doesn’t mean it’s fragile. I’ve written before about research that has analyzed how sponges make these glass spicules so strong—including the spicules’ engineered concentric layers and optimized structural shape.

Ultimately, glass spicules afford sponges with the flexibility and strength to maintain their shape and stay securely put on the sea floor. It’s absolutely fascinating.

But in the absence of the high-temperatures that we humans use to shape glass, how is it that sponges can build such intricate structures out of silica?

Sure, sponges can extract silica from seawater to biofabricate their glass houses, but those silica spicules come in a wide variety of intricate shapes, from pointy spears to spiky orbs—so what gives for the bio-architectural design of these glass abodes?

New research shows that sea sponges use an internal protein filament to determine and guide the shape of their uniquely structured silica spicules.

With the help of synchrotron X-rays, researchers have peered inside at the internal organization of sponge spicules. Despite examining spicules of different shapes from different sponge species, the researchers saw the same basic protein structure.

A closer look revealed that individual sponge species take this basic protein structure and then make it their own—they diversify their individual spicule design by varying the structure of their internal axial protein filaments.

Because these filaments catalyze silica biomineralization, they serve as a scaffold for the spicules design and ultimately determine the spicules’ final silica shape.

Credit: Science Magazine; YouTube

This process is actually quite similar to what happens during crystallization processes. “We find it fascinating that nature and mankind independently converged to a similar route of forming highly regular 3-D architectures,” the authors write in a Science Advances paper detailing the research.

And because experimental technologies that use similar growth principles are now being explored to manufacture solar cells and electronics, for example, the authors suggest that such understanding of how nature fabricates intricate and complex shapes may help us humans do the same.

“Using the crystalline axial filament, nature has mastered the fabrication of extremely complex glass structures at low temperatures—a capacity that is far beyond the reach of current human technology.”

And with this discovery, perhaps we humans can advance that technology.

The open-access paper, published in Science Advances, is “Shaping highly regular glass architectures: A lesson from nature” (DOI: 10.1126/sciadv.aao2047).

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