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Tiny Organisms, Giant Potential ; Diatoms May Hold Answers for Technological Advances

Posted on: Friday, 3 September 2004, 06:00 CDT

Churning and drifting through the world's oceans - indeed in any place where there is water - are diatoms: single-celled, planktonic algae that are easily overlooked and generally unremarked upon until you actually see one through a microscope.

Then, they become small wonders, possessors of a singular kind of crystalline beauty. Each diatom species - worldwide estimates range from 100,000 to 1 million - boasts its own distinct shape. Some resemble pillboxes, others look like barrels, pincushions, flowers, flagpoles, spoked wheels, splashing raindrops, ladders or stars.

For centuries, diatomists focused their microscopes primarily upon the task of finding and describing these variegated species. There was a certain thrill in that, but lately something has been happening. Others are taking note of diatoms: engineers, chemists and materials scientists who admire them not only for their biological beauty, but also for the potential of their microscopic architecture.

"You show a picture of a diatom to scientists," said David Wright, a professor of chemistry at Vanderbilt University, "and you've immediately got your audience. The structure of these organisms is so amazing, so varied. There's nothing in modern science to match it."

Which got some people thinking small.

"The goal of nanotechnology is to synthesize incredibly tiny structures (on scales of millionths of a meter) that can be used for all sorts of things in medicine, research, engineering and industry," said Mark Hildebrand, a professor of biology and diatomist at the Scripps Institution of Oceanography. "But we're never going to be able to build structures like diatoms in a test tube, at least not anytime soon, so why not find ways to use or make diatoms that will do what we want them to do on the nano-scale?"

Nanotechnologies are mightily constrained by cost, time and difficulty. To create three-dimensional objects with features smaller than the width of a hair requires adding layer upon layer of material until the final shape is achieved. More exotic nano- objects like tubes built of carbon molecules or cage-like fullerenes are even harder to build, and most remain largely in the province of scientific curiosities.

Yet the promise of nanotechnology is indisputably compelling. If researchers could design and build structures at the scale of single molecules or atoms, the world of possibilities would be metaphorically huge: drug factories the size of pinheads, computers in the brain to aid memory, robots moving through the bloodstream to repair internal injury or disease.

One look at diatoms and it's obvious that nature has already figured out how to build small and cheap. "In the lab, you can grow billions of diatoms in a week for just a few dollars," Hildebrand said.

But growing them is the easy part. Exploiting their nanotechnological potential will require that scientists intimately understand how diatoms become what they are. And that, at the moment, is a big and largely unanswered question.

The basic biology is broadly known. Diatoms are found in every body of water on Earth, an abundance and ubiquity that is essential to life on this planet. Diatoms form the base of the food chain, the main meal of most zooplankton. They represent the primary source of energy in the ocean. Though comprising just 1 percent of the planet's biomass, diatoms generate about half of the Earth's photosynthesis - the conversion of carbon dioxide, nutrients and light into consumable sugars - and produce roughly a quarter of the planet's atmospheric oxygen.

But nanotech's interest in diatoms is strictly superficial. Every diatom is encased in an intricate shell - or frustule - made of silica, the stuff of glass. Diatoms make these frustules quickly, at room temperature and pressure, in ordinary water, without requiring or producing toxic chemicals. But how diatoms build themselves at all remains incompletely explained.

Much research is ahead before any practical applications can be realized. As Hildebrand said, "We're at the beginning of a long road."

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