Us
and Them and Them: The Amazing Archaea
 |
Hot
tail, cool head. Alvinella pompejana, or the Pompeii
worm, survives the highly variable temperatures of its
habitat with the help of the furry coat of bacteria
growing along its back.
(Photo courtesy of University of Delaware, Graduate
College of Marine Studies) |
Thirty years
ago, if you'd ask biologists to tell you something about
archaea, they'd have looked at you quite blankly. Thirty
years ago, no one knew they existed. At that time, it was
widely held that there were, at the most basic level, two
domains of life: the eukarya - organisms like humans, that
have cells with nuclei - and the bacteria (prokarya) - whose
simple cells contain no nuclei.
This was the
widely accepted paradigm of life in the late 1970s, when
Dr. Carl Woese and his colleagues at the University of Illinois
set about studying the relationships among prokaryotes using
DNA sequencing - something that had never been done before.
It was then that they discovered the completely distinct
group of organisms that have come to be known as archaea.
Since most archaea don't look different from bacteria under
a microscope, new technology was key to the discovery: molecular
biology made it possible to see the genetic differences
that lie beneath the surface. And, genetically and biochemically,
archaea are as different from bacteria as they are from
hummingbirds, horses, or humans. While some archael genes
have similar counterparts in bacteria, others are shared
with the eukarya. A large portion of archaea genes, however,
are unique, establishing them as a distinct group of organisms.
 |
| New
kid on the block. The archaea
branch of evolution wasn't added to the evolutionary
tree of all of Earth's life-forms until the late 1970s.
Though they resemble bacteria under a microscope, archaea
are as genetically and biochemically different from
bacteria as they are from hummingbirds, horses, or humans.
(Phylogenetic tree graphic courtesy of Ed DeLong) |
In any case,
they are an interesting bunch, living in the harshest, and
most bizarre environments imaginable.In the harsh category
are acidic boiling pools, alkaline lakes, and salt marshes,
while the bizarre includes, among others, the digestive
tract of cows and termites, the mud at the bottom of the
ocean floor, and oil deposits deep below the Earth.
While there are
plenty of these extremists in the archael family tree, researchers
have been surprised by recent findings of large "mainstream"
populations in the plankton of the open sea, indicating
that the archaea - creatures we didn't know existed thirty
year ago - may be among the most abundant microorganisms
on the planet.
Makes you wonder
what other little surprises Nature has in store for us.
