Engineers Envy Diatoms Glass-Sculpturing Prowess
What is it? An ornate crown? A crystal serving dish cover? A work of art? The photo on the cover of the July 17 Science News, labeled “silicon jewels,” is a microphotograph of a diatom, a one-celled organism that lives in the sea and builds itself a glass house too small to see with the naked eye. There are thousands of species of diatoms, each with a unique shell design. The article has more diatom photos: one that looks something like a bent sombrero made out of a collander with two goblets sticking out, another that looks for all the world like an Indian tom-tom, complete with stitching, and another that looks like a sunflower head complete with Fibonacci spirals (see 11/20/2003 headline). Others look like sieves, gears, triangles, stars, and many other shapes both common and extraordinary.
Scientists dreaming of nanotechnology can’t get over the skill of diatoms in glass manufacturing (see 03/19/2002 headline). Diatoms are inspiring world-wide efforts to probe their secrets, so that engineers can mass-produce useful molecular devices like photonic crystals and lenses (see 01/29/2003 headline), gas sensors, miniature reaction tubes and other microscopic structures of high tensile strength (see 02/19/2003 headline). Though focused on scientists imitating nature, author Alexandra Goho shares some amazing facts in passing about diatoms:
- Ecology: Scientists have long prized diatoms… because they remove large amounts of a greenhouse gas—carbon dioxide—from the atmosphere.
- Glass: The cell wall of this unicellular organism is made entirely of glass. More precisely, diatom shells consist of silica, or silicon dioxide, the primary constituent of glass.
- Art: Many shells are ornately patterned with features just tens of nanometers in size.
- Efficiency: Joanna Aizenberg of Lucent Technologies’ Bell Laboratories in Murray Hill, N.J., says, “We can think of diatoms as living silicon chips.” Semiconductor-chip manufacturers carve micro- and nanoscale features out of blocks of electronic and optical materials—a costly and time-consuming endeavor. Diatoms build structures out of silicon much more efficiently.
- Throughput: Once researchers figure out how to engineer useful devices out of diatom shells, they could enlist the reproductive capabilities of diatoms to generate trillions of silica structures in a matter of weeks. Some species of diatoms can replicate up to eight times a day. Sandhage says, “For a fairly small number of reproductions, you could get incredibly large numbers of the exact-same three-dimensional structure.”
- Flexibility: Diatoms can make just about any structure you can imagine.
- Technique: It begins when the algal cell divides, forcing it to split its shell into two halves. The new cells, each now bearing only half a shell, begin to reconstruct their missing halves by taking up silicic acid—a simple compound of silicon, oxygen, and hydrogen—from the surrounding water. Each new organism deposits the silicic acid in a compartment called the silica-deposition vesicle. There, the chemical is converted into silica particles, each measuring about 50 nm in diameter. These then aggregate to form larger blocks of material. Researchers speculate that a set of special proteins guides the formation of the silica particles and their subsequent assembly into larger structures. Hildebrand says that other cellular proteins outside of the vesicle stretch and mold the compartment to shape the silica inside. Once the half shell is complete, the vesicle merges into the cell’s membrane, exposing the newly created structure.
- Genome: Scientists are searching for the protein-coding genes among the diatom’s approximately 11,000 genes….
- Programming: Diatoms of the same species consistently form shells with exactly the same pattern, suggesting that the designs are genetically programmed.
- Catalysis: Nils Kröger, a diatom biologist at the University of Regensberg in Germany, was the first to identify the silica-forming proteins in diatoms. The molecules of this class, which he calls silaffins, are unusual among proteins in that many of them have long side chains of organic molecules known as polyamines. The proteins are also decked out with an assortment of other molecules, including sugars and phosphates.
When Kröger and his colleagues added silaffins to a test tube containing silicic acid, tiny silica spheres formed in a matter of minutes. In contrast, a solution of silicic acid without any proteins “can take hours or even days to form hard silica,” says Kröger…. “we don’t completely understand how it works.”
- Individuality: Each protein does something different: One produces spheres, one makes porous shapes, and the third forms platelike structures.
Moving beyond these simple shapes will require a greater understanding of the diatom’s molecular machinery. What’s more, dozens or even hundreds of proteins may govern the shell-formation process. Mapping the myriad interactions among all the components could be a daunting task.
- Green and Clean: Fabrication of silicon chips and other electronic devices currently requires harsh chemicals and generates much waste. Diatoms and sponges [see 08/20/2003 headline] know how to produce materials under ambient conditions without these harsh chemicals,” says Aizenberg. “And yet the end result is the same.”
Goho’s article is seasoned with high praise for the abilities of these miniature factories. “We’re just scratching the surface” to understand them, says one, and another wants to “harness the power of biological materials.” But they stand humbled at the creative power of these little organisms:
“It will be impossible to reproduce this process in a test tube because it’s such a complicated cellular process,” says [Mark] Hildebrand [of Scripps Institute].
[Joanna] Aizenberg [of Bell Labs] adds, “The question is, ‘Will we be able to bridge the gap between what goes on in nature and what we can do in the lab?’”
So how did these tiny one-celled organisms achieve “manufacturing prowess” that makes our best engineers stand in awe? “Nature has been building things on the nanoscale for a long time,” says materials scientist Ken Sandhage of the Georgia Institute of Technology in Atlanta. Alexandra Goho ends, “Materials scientists are only beginning to uncover the secrets of this aquatic community of glass-sculpture artists produced over millions of years of evolution.”
1Alexandra Goho, “Diatom Menagerie,” Science News, Week of July 17, 2004; Vol. 166, No. 3 , p. 42
Gag! Choke! This is like watching a spectacular stage show then being expected to bow to a fat Charlie image at the end. We were all set to applaud and praise this well-written glimpse into another wonder of nature, a wonder that shouts intelligent design, and then Goho has the gall to say evolution over millions of years produced “glass-sculpture artists” with 11,000 genes, hundreds of which work together in coordinated fashion to build unique, exquisite, precision structures out of glass without pollution or waste of energy. Unbelievable. Did any of the scientists present any evidence that evolution could do such a thing?* No; in line with the stinking habit of the Darwin Party, they merely assumed evolution did it, because they have committed their lives, their fortunes, and their sacrilegious honor to the philosophical belief that there is no God, no Creator, no intelligent Designer. Their faith forces them to believe the absurd, in spite of the evidence. This one example should be enough to make any clear-thinking scientist toss Charlie’s figurehead overboard, but thumb through a few more “Amazing” Chain Links below and ask yourself how many other wonders of nature we are asked to believe happened by mindless, chance processes. Phooey; a wonderful science story was ruined by the last sentence. So instead of praising this article unequivocally to the tune of This Is My Father’s World, it saddens us to have to sound the Bronx cheer as we hand out another Stupid Evolution Quote of the Week award.
Enough of that. Just marvel for a minute at the manufacturing skill of these tiny robotic factories. God could have made the earth so boring. He could have provided just enough design to permit survival. There could be brown sky, brown scum, brown water, and we could all subsist on mud. He could have fashioned little amorphous sponges to soak up the carbon dioxide and keep Earth from overheating. Instead, He gave us a superabundance of “useless beauty,” exquisite crystal jewelry filling the seas, a wonder to silently lay undiscovered till the invention of the microscope. Considering the thickness of diatomaceous earth beds (see 02/02/2004 headline), trying to count the number of intricate glass sculptures that have reproduced themselves by the elaborate preprogrammed process described above would be like trying to count the snowflakes or the stars. As the Moody Science Classic film Hidden Treasures teaches, diatoms are miniature marvels that should remind us God cares for each one of us.