ARCHAEA
AND
EUBACTERIA
KINGDOMS
By: jacorey williamson
biology
vocabulary
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autotroph an organism that can make its own food
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binary fission
of bacteria
asexual reproduction in which a single cell divides into two with no exchange of genetic material; reproduction method
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commensalism
species
a symbiotic relationship between two organisms in which one species benefits and no effect is apparent to the other
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eukaryote a cell that has a membrane-bound nucleus and/or organelles as its major characteristic
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heterotroph
an organism that relies on eating other organisms for energy or food
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microbiology
the study of organisms that are too small to be seen with the naked eye
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mutualism
a symbiotic relationship between two organisms in which both species receive some type of benefit
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pathogen a disease-causing organism; a germ
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prokaryote
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protist
a cell whose nucleus is not bound by a membrane
a one- or few-celled organism with chromosomes; may have characteristics of both animals and plants
ARCHAEA AND BACTERIA DOMAINS
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The Archaea and Bacteria domains encompass relatives of the oldest organisms on Earth. They
are highly diverse because of all the time they have had to evolve and differentiate. These
organisms are everywhere. They are on everything you touch and ingest. In fact, there are
billions of bacteria in your intestines right now!
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The members of both Archaea and Bacteria have several similarities. For one, they are all
prokaryotes. This means, they are all one-celled and are absent of a true nucleus. Their DNA
is contained in a single, twisted chromosome that stays in a nucleoid region or is simply
floating free in the cytoplasm. They generally lack organelles, though some exceptions have
ribosomes. All have relatively thick cell walls to hold them together
Reproduction occurs principally by binary fission, in which the
cell divides into two equal halves.
ARCHAEA VS. EUBACTERIA
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Prokaryotes were originally under one domain: Bacteria. They originally
were categorized under the Monera kingdom. However, in 1977, Carl
Woese, a microbiologist and physicist discovered significant differences
between some of the prokaryotes. These differences were so significant
that the prokaryotes were separated into two separate domains:
Archaea and Bacteria, and hence two kingdoms: Archaea and
Eubacteria. Some texts still refer to the Archaea kingdom as the
Archaebacteria kingdom; however, this term has recently been
abandoned because they are not bacteria; they are archaea
ARCHAEA VS. EUBACTERIA (2)
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What makes these two groups of organisms so different is
their genetic make-up, primarily the gene sequences of
ribosomal RNA (rRNA). Woese found that archaean
biochemistry was more similar to that of eukaryotes—
multi-celled organisms—than that of eubacteria. In
particular, there were similarities with the enzymes
involved with transcription and translation of DNA and
with several metabolic pathways. The cell membrane of
archaea is also unique from that of eubacteria,
possessing unusual lipids. Amongst this significant
genetic difference, there are many other differences
between these two groups of organisms
ARCHAEA CHARACTERISTICS
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Archaea ("ancient") microbes are believed to be the ancestors of the
protists and the first eukaryotes, due to their genetic make-up. They
obtain most of their energy from sulfur, salt, hydrogen, and carbon
dioxide. They tend to be more tolerant of extreme environmental
conditions and are often found where most other life is unable to exist—
such as at the bottom of the sea or in volcanoes.
ARCHAEA CHARACTERISTICS
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There are three main types of archaea. The methanogens are anaerobic,
meaning they are intolerant of oxygenated areas and produce methane
gas. They thrive in swamps, mud, carcasses of animals, and even your
intestines! Halophiles ("salt lovers") live in high salt concentrations of
water, like the Dead Sea in the Middle East or the Great Salt Lake in Utah.
Bacteria can't normally survive in salty environments, but these archaea
thrive in it. Then there are thermoacidophiles ("heat lovers"), which live
in hot, acidic, sulfuric, areas. Thermoacidophiles can survive
temperatures as high as 230 degrees Fahrenheit and pH levels below 2
(hydrochloric acid has a pH of 1). The ability of archaea to survive in
extreme environments gave them the name extremophiles.
ARCHAEA CHARACTERISTICS
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Recent studies have also found archaea in a broader range of habitats,
including soils, oceans, and marshlands. They play an important role as
decomposers, helping in the carbon, sulfur, and nitrogen cycles.
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Some archaea have been known to have symbiotic relationships like that of
mutualism—a partnership between two organisms, in which both organisms
benefit from each other—and commensalism—when one organism benefits
and the other organism receives neither harm nor gain. As mentioned, archaea
are also helpful in biogeochemical cycles, recycling vital elements like nitrogen,
carbon, and sulfur. In biotechnology efforts, archaea produce biogas for the
treatment of sewage. Archaea also contribute to pollution and global warming.
Methane gas is a main source of greenhouse gases, and methanogens are the
number one producers of it.
EUBACTERIA CHARACTERISTICS
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Eubacteria are probably more commonly known because they thrive in a
wider variety of environments. These are bacteria you will most likely
find in your body, in your food, or in your home. Most eubacteria live as
decomposers and heterotrophs—dependent on others for food. Most
decomposers provide an ecological service, as they break down
nutrients in dead carcasses, releasing nutrients back into the soil.
Cyanobacteria are a type of eubacteria that you may have heard about. It
grew in the oceans over 3 billion years ago and was responsible for
adding oxygen into our developing atmosphere. So, similar to archaea,
eubacteria are also part of biogeochemical cycles. They also help in
biotechnology efforts with the treatment of sewage and production of
yogurt and cheese.
EUBACTERIA CHARACTERISTICS
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Clostridium botulina are decomposers that act fast on some food items,
releasing a powerful poison. If you ingest these bacteria, you are most likely to
get food poisoning. Some heterotrophic eubacteria are pathogens, or diseasecausing germs that harm other organisms. In humans, pathogens cause
infectious diseases like cholera, syphilis, and tuberculosis—a fatal disease.
Some other eubacteria are mutualistic. For example, Escherichia coli, or E. coli,
are a type of eubacteria that live inside our colon. They help absorb water and
break down vitamins. In return, these bacteria are provided with a comfortable
environment and a consistent supply of nutrients by us.
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Other common groups of eubacteria are autotrophs—bacteria that can make
their own food through photosynthesis. They have a chain-like structure and
are commonly found in moist areas like lakes and ponds. Autotrophs indicate
that eubacteria are ancestors of plants. There are also chemoautotrophs—
bacteria that get their energy from chemical compounds.
EUBACTERIA CHARACTERISTICS
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When the environment isn't supportive, some eubacteria have the ability
to form spores and "hibernate"—in other words, they become
metabolically inactive until conditions improve. As lightweight spores,
they are able to float in the air and move all over. Within their specific
environments, some are immobile while others have flagella that move
them along
IDENTIFICATION
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Besides classifying archaea and eubacteria by habitat and means of
existence, they are also identified by other means. Identifying an
organism as an archaean is mainly done by studying its genetic make-up.
Differences in rRNA remain the main classification characteristic. But
other characteristics are also considered
IDENTIFICATION
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Archaea and eubacteria also have different ways of moving—by a
corkscrew motion, gliding, or propelling with flagella. All of these
characteristics, including habitat and means of existence, are ways to
help identify the thousands of species that exist in the Archaea and
Eubacteria kingdoms. Although we can't see most of them with the
naked eye, they do exist and are important to life and earth functions