Graham Smith
Bio 205
Final Project
Archaea
“Archaea” are a diverse group of “bacteria-like” (prokaryotes/no nucleus) and are
often considered a major group unto themselves. This group is called the Archaea (from
Greek, ‘old’) for short and to distinguish them from the other prokaryotes, all other
bacteria are then called Eubacteria.” source:
http://www.bacteriamuseum.org/niches/evolution/evolution.shtml
one classification system as dsiplayed on:
http://honeybee.helsinki.fi/users/gjurgens/Archaea/archaea.htm
According to the above diagram, the Archaeans are not bacteria at all, but exist in an
entirely exclusive domain composed of halophiles(salt-loving Archaeans) and
thermophiles (Archeans that habitate environments of extreme temperature).
Ecology
Archaeans are often discovered in “extreme” environments. Many archaeans live in
extremely acidic or alkaline conditions. Others inhabit deep sea rift vents where
temperatures are in excess of 100 degrees Centigrade. Recently, Archaean icrobes were
discovered here in Northern Indiana. Contaminated groundwater created from years of
steel slag dumping provided an extremely alkaline environment in which these particular
Archaeans have probably been thriving for years.
“ ’Just how the unusual bacteria got to the slag dumps is currently a
mystery,’ says Roadcap. ‘ I’d hate to hazard a guess,’ he said, regarding their origins.
One possibility is that local bacteria adapted to the extreme environment over the last
century. Another possibility is that they somehow got imported. As for whether the
unexpected microbial community has any effect on the extensive groundwater
archaeans are often called “nature’s
extremists”because of the oustandingly dynamic environments they inhabit such as the hotspring shown above.
http://calvin.st-andrews.ac.uk/external_relations/down_loads/archaea-brilliant_but_small.jpg
contamination problem in the slag dumps, ‘ We have not come to any conclusion about
that,’ says Roadcap. Among the possible harmful things microbes could do is collect and
distribute hazardous materials to nearby lakes and wetlands. But so far that has not been
documented.” (Department of Geology – UIUC.
http://www.geology.uiuc.edu/news_info/RoadcapAlkaline.html )
“Although many archaea are extremophiles, direct rDNA amplification from
environmental samples has made it clear that the archaea are widespread also in
non-extreme biotopes. Thus, they have ecological significance for large-scale
circulation of energy, nutrients and biomass, as well as for the greenhouse effect,
since all biologically released methane (several hundred million tons annually) is
produced by archaea.” http://artedi.ebc.uu.se/molev/resarch/archaea.html
Human beings have had a tremendous effect on the domain Archaea and have
even created some of their many habitats. As discussed above, slag dumping in “the
region” (NW Indiana/Chicago/Lake Michigan area) has resulted in extremely
contaminated groundwater which serves as a supportive ecosystem for a few different
Archaeans.
Reproduction
Archaeans reproduce asexually. Binary fission (simple cell division) is utilized.
Molecular and Cellular Information
There is much debate over how to classify Archaeabacteria, or the “Archaeans.”
Because these organisms are prokaryotic, many scientists wish to call them bacteria.
However, other professionals maintain that Archaeans are as different from bacteria as
humans are when it comes to biochemistry and genetics. I will use both terms when
referring to the organisms in question in this project. Archaeans have no nucleus as
implied by the frequent prokaryotic classification. They resemble other bacteria in many
ways, but there also exist critical differences.
Archaeans “are more similar to Eukaryotes than to bacteria in several ways: their
cell-wall does not contain peptidoglycan (a component of each bacterial cell)...)
http://www.bacteriamuseum.org/niches/evolution/evolution.shtml
The Archaea are predominantly unicellular. The cell does not(like other
prokaryotes) contain a nucleus. It also does not contain membrane-bound organelles.
Archaean cells are capable of growth at temperatures exceeding 80 degrees Celcius.
Histone proteins and gas vesicles are present. An Archaean cell is capable of
Denitrification, Nitrogen fixation, and Chemolithotrophy.
Genetics/Evolution
In Archaeans, DNA occurs in circular form. Operons( gene clusters under common
control in bacteria.) are also present. pewagbiotech.org/resources/glossary/ . Archaeans have no
nucleus and DNA is stored free-floating within the cell membrane. According to
scientists Archeans have been on the scene since the dawn of time.
“ In the universal phylogenetic tree, all the shortest and deepest branches consist of
hyperthermophiles. This suggests that the last common ancestor of all life on Earth was a
hyperthermophile, and most hyperthermophiles are archaea. Thus, by studying the
archaea, it may be possible to deduce properties of the earliest cellular organisms. It has
also been suggested that the eukaryotic lineage originated from a series of cellular fusions
between different bacteria and archaea. Archaea therefore provide insights into the origin
of the eukaryotes, and provide simple model systems for complex eukaryal processes, in
particular for the transcription and replication machineries.”
http://artedi.ebc.uu.se/molev/resarch/archaea.html
ebiomedia.com/ prod/images/Tree2.jpg
Most scientists maintain that as the Earth changed over the years, Archaeans were
by far one of the most adaptable groups of unicelluar organisms on the planet. This
accounts for their extreme adaptibility to extreme environments. The question is raised,
however, as to whether the Archaens are an invasive species in such environments as the
slag dumps mentioned above. Archaeans most definitely affect other organisms, but the
effects are largely indirect due to the fact that these “Slag-Archaeans” were found deep in
the ground. The real invasive species in this instance would be human beings. It was,
indeed, humans that polluted the groundwater.
Closing
The domain Archaea was not recognized until recently. In previous times
scientists classified organisms as either plants or animals. With the development of the
domains “Bacteria” and “Eukaryota” scientists were forced to place the Archaeans in one
of these categories. However, this task was not so easy as it was found that the Archaens
shared characteristics with both bacteria and eukaryotes. Thus, the domain “Archaea”
was born. The archaens are unique in that they inhabit such extreme environments.
Research is still uncovering new information about these fascinating organisms and much
speculation continues as to why Archaens choose such “strange” circumstances in which
to exist.