Category: Evolution
Posted on: December 23, 2006 2:02 AM, by John S. Wilkins
My mate Marc Buhler noticed this one:
This week's issue of Science magazine has an article that is the subject of a story (pasted below the fold) from the NY Times.
"From Scum, Perhaps the Tiniest Form of Life" by William J. Broad - Dec. 23, 2006 The smallest form of life known to science just got smaller.What's interesting about this is that it changes how we visualise metabolic processes in very small spaces. A while back, in 1998, Phillipa Uwins, then of the University of Queensland where I work, announced the existence of "nanobes", which were a little smaller than these beasties (20-150nm), and which were treated skeptically because they were too small for biological processes. I wonder, as a complete amateur, if there are chemical processes that are possible in small spaces that we have hitherto overlooked because we were focusing on the prototypical processes of much larger organisms. Carol Cleland, of the Center for Astrobiology at the University of Colorado,
Four million of a newly discovered microbe - assuming the discovery, reported yesterday in the journal Science, is confirmed - could fit into the period at the end of this sentence.
Scientists found the microbes living in a remarkably inhospitable environment, drainage water as caustic as battery acid from a mine in Northern California. The microbes, members of an ancient family of organisms known as archaea, formed a pink scum on green pools of hot mine water laden with toxic metals, including arsenic.
"It was amazing," said Jillian F. Banfield of the University of California, Berkeley, a member of the discovery team. "These were totally new." In their paper, the scientists call the microbes "smaller than any other known cellular life form."
Scientists say the discovery could bear on estimates of the pervasiveness of exotic microbial life, which some experts suspect forms a hidden biosphere extending down miles whose total mass may exceed that of all surface life.
It may also influence the search for microscopic life forms elsewhere in the solar system, a discovery that would prove that life in the universe is not unique to Earth but an inherent property of matter.
The tiny microbes came from an abandoned mine at Iron Mountain in Shasta County, Calif., which produced gold, silver, iron and copper before closing in 1963.
Today, rain and surface water run over exposed minerals, producing sulfuric acid. The mine is one of the largest Superfund cleanup sites.
Starting in 2002, the scientists obtained drops of the acidic slime and searched for genetic signs of novel microbes. "We were essentially looking for new stuff," one of the scientists, Brett J. Baker, said in statement from Berkeley, "and we found it."
The microbes are about 200 nanometers wide - the size of large viruses, which scientists consider lifeless because they cannot reproduce on their own. Bacteria average about five times that size.
The scientists must do further tests to confirm that the organisms are the smallest ever found, and that they can reproduce. If those analyses hold up, they said in their Science paper, "it may be necessary to reconsider existing paradigms for the minimum requirements for life."
has an argument that there may be kinds of life we do not know about because they fall through our assays, which were designed to deal with "ordinary" life. Watch this space.
These organisms are "pleomorphic", a lovely term that means they have no fixed morphology at the cell shape level. Folding their membranes gives them a lot more surface area to react upon.
Transmission electron microscope images of four cells inferred to belong to the ARMAN group. (A) A large area showing many cells of the ARMAN type, a subset of which are indicated by arrows. Also present are rounded objects, membrane debris, and a small number of Leptospirillum group II cells (LII). (B) Most cells exhibit one or two folded membrane-bounded protrusions.... (C) Most cells appear to be surrounded by an S-layer with periodicity in the cell surface. The dark internal contrast is consistent with densely packed ribosomes. (D) Some cells have very dark inclusions (arrow). [From the paper]
These cells are much smaller than the previously identified members of the Archae called Nanoarchaeota. They have been called "Archaeal Richmond Mine Acidophilic Nanoorganisms" (ARMAN).
