Nanoorganisms

A new study notes the discovery of what may be the smallest living organisms on Earth:

"For 11 years, Jill Banfield at the University of California, Berkeley, has collected and studied the microbes that slime the floors of mines and convert iron to acid, a common source of stream pollution around the world.
"Imagine her surprise, then, when research scientist Brett Baker discovered three new microbes living amidst the bacteria she thought she knew well. All three were so small - the size of large viruses - as to be virtually invisible under a microscope, and belonged to a totally new phylum of Archaea, microorganisms that have been around for billions of years.
"What made Baker's find possible was shotgun sequencing, a technique developed and made famous by Celera Corp., which used it to sequence the human genome in record time." ...
"Banfield, Baker and their UC Berkeley and University of Queensland, Australia, colleagues report their findings in the Dec. 22 issue of Science." ...
"The organisms in the mine drainage, which live in a pink slick on pools of acidic green water, obtain energy by oxidizing iron - that is, generating rust -- and in the process create sulfuric acid and dissolve pyrite (iron sulfide or fool's gold) to release more iron and sulfur. This self-sustaining process creates the acidic drainage that pollutes creeks and rivers, including those around the researchers' study site, the Richmond Mine at Iron Mountain, Calif. The mine is one of the largest Superfund sites in the country.
"Banfield has been trying to understand how the extremophiles - microbes that live in extreme environments - live together and generate the acid drainage that makes such mines toxic hazards. The green runoff from the mine, captured and treated by the Environmental Protection Agency, is a hot 108 degrees Fahrenheit, as acidic as battery acid, and loaded with toxic metals - zinc, iron, copper and arsenic.
"In 2004, Banfield collaborated with the Department of Energy's Joint Genome Institute to shotgun sequence a drop of the slime. This type of sequencing involves homogenizing the organisms in the sample, isolating the combined DNA and breaking it into lots of random strands. Each strand is then sequenced, and a powerful computer is used to find overlaps so that the pieces can be properly reordered.
"This process identified five separate genomes that corresponded to five bacteria and Archaea - four of them uncultivated at that time, though closely related to known microbes.
"Baker probed the gene fragments more thoroughly to turn up three Archaea from a totally unknown group, probably representing a new phylum among the several dozen known phyla of Archaea. They fall within a large class of microbes known as thermophiles, which are Archaea that live in warm and even scalding conditions. Many of these thermophiles have been recovered from hydrothermal vents in the deep mid-ocean ridges, where lava boils up between continental plates.
"Once Baker had found gene segments (ribosomal RNA) from three Archaea, he was able to fish the microbes out of the slime soup and found that they were extremely small, around 200 nanometers in diameter, the size of large viruses. Bacteria average about five times this diameter.
"These therefore could be the smallest organisms ever found, though Baker needs to culture them before confirming this. Because they're so small, however, they may not be free-living." ...
"Baker now is trying to find the right conditions for these Archaea to thrive in a culture dish. For now, he has dubbed them ARMAN-1, -2 and -3, for Archaeal Richmond Mine Acidophilic Nanoorganisms."