Date Published: October 12, 2004
Publisher: Public Library of Science
Author(s): Jane Bradbury
Abstract: Diatoms are unicellular algae with ornate silica shells. Their dazzling ability to build tiny structures could inspire applications in the semiconductor industry, drug delivery, and engineering.
Partial Text: Diatoms, unicellular algae with ornate silica shells, have fascinated amateur and professional biologists ever since the invention of the microscope. But these days, diatoms and their exquisite shells are also attracting the attention of nanotechnologists who hope that diatoms will teach them how to make minute structures currently beyond the capabilities of materials scientists. And now these nanotechnologists, together with ecologists interested in the global carbon cycle—in which diatoms play a central role—have a genomic blueprint to help them in their studies: the annotated genome sequence of Thalassiosira pseudonana (http://genome.jgi-psf.org/diatom/).
Diatoms, microalgae that are found in all aquatic and moist environments, first appeared more than 180 million years ago. Since then, diatom diversity has literally exploded; no one is sure how many living species there are—probably about 100,000—or why there are so many different types. Plant molecular biologist Chris Bowler (Ecole Normale Supérieure, Paris, France and Stazione Zoologica, Napoli, Italy) explains that molecular phylogeny and morphological studies suggest that diatoms originated ‘probably as the result of a eukaryote being invaded or engulfed by a photosynthetic eukaryote, most probably a red alga’.
Richard Gordon, Professor of Radiology at the University of Manitoba in Winnipeg, Canada, somewhat accidentally laid the foundations of ‘diatom nanotechnology’ in 1988 when he was invited to give a lecture at an engineering conference. ‘I’m not an engineer’, explains Gordon, ‘but I knew engineers were interested in what was then called microfabrication so I told them about diatoms because they are so good at making small things’. Gordon, a keen diatom hobbyist, explained to his audience how diatoms could make a three-dimensional micro- or nanoscale structure for them without them lifting a finger. By contrast, says Gordon, ‘nanotechnology techniques then and now are tedious, involving painstakingly building three-dimensional structures up layer by layer’.
Daniel Rokhsar, Department Head for Computational Genomics at JGI, explains why his institute undertook the sequencing and computer annotation of the genome of T. pseudonana, a marine centric diatom ‘We believe that knowing this genome will help us to figure out how to mimic the processes that diatoms use to construct their very precise structures, and that we can then learn how to create similarly precise structures ourselves’. Also, he adds, diatoms are extremely important on an ecological level.
‘One of the striking things about the T. pseudonana genome is that we can figure out quite a bit from it about how this diatom deals with organic materials, but it is hard to figure out what it is doing with silicon’, admits Rokhsar. ‘The only way we can really figure out what a gene is doing is by comparing it with known genes in other organisms, but because diatoms are so unique in their use of silicon, we don’t have that option. We literally just have the parts list’.