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Archaea
古若筠 章存祈 朱福華崔麗娜
Archaebacteria
• The Archaea constitute a domain of
single-celled microorganisms. These
microbes have no cell nucleus or
any other membrane-bound
organelles within their cells.
Some recent findings…
•
In 1996, scientists decided to split Monera into
two groups of bacteria:
Archaebacteria and Eubacteria
• Because these two groups of bacteria were
different in many ways scientists created a
new level of classification called a DOMAIN.
• Now we have 3 domains
1. Bacteria
2. Archaea
3. Eukarya
• “ancient” bacteria
• Some of the first
archaebacteria
were discovered
in Yellowstone
National Park’s
hot springs and
geysers.
• Prokaryotes are
structurally simple,
but biochemically
complex
The Domain
Archaea
Basic Facts
• They live in extreme environments (like
hot springs or salty lakes) and normal
environments (like soil and ocean
water).
• All are unicellular (each individual is
only one cell).
• No peptidoglycan in their cell wall.
• Some have a flagella that aids in their
locomotion.
Some weird things about this
Archaea…
• Most don’t need oxygen to survive
• They can produce ATP (energy) from
sunlight
• They can survive enormous temperature
extremes
• They can survive high doses of radiation
(radioactivity)
• They can survive under rocks and in ocean
floor vents deep below the ocean’s surface
• They can tolerate huge pressure differences
3 Main Types
Methanogens
Thermoacidophiles
Halophiles
• They release methane
(CH4) as a waste product
• Many live in mud at the
bottom of lakes and
swamps because it lacks
oxygen
• Some live in the intestinal
tracts of animals to help
break down food
• Others like to hang out in
the stomach
• Your intestinal gas is a
waste product caused by
bacteria in the body
breaking down the food
you eat—that’s why farts
don’t smell sweet!
Methanogens
Significance of methanogens
• They could play a role in
garbage/sewage cleanup
by having methanogens
eat garbage.
– The methane waste the
bacteria produce after
eating the garbage or
sewage could be used
as fuel to heat homes.
• Some landfills already
employ this method—the
only problem is that it’s
expensive.
Thermoacidophiles
• Live in the dark
• Live without oxygen
• Like to live in superheated water with
temperatures reaching 750 deg F
• Prefer environments that are very acidic
(between pH of 1-3)
• Live in a chemical soup of hydrogen sulfide
(H2S) and other dissolved minerals (rotten
egg smell)
Black Smokers
The interior layers of the Earth are
made up of many different types of
metals (iron, copper). The black color is
caused by a chemical reaction of the
metals with the ocean water. In
extreme temperatures and pressures,
this is where some thermoacidophiles
like to live.
Other thermoacidophiles like to live in hot springs or
geysers. Hot springs are pools of hot water that have
moved toward earth's surface. The source of their
heat is the hot magma beneath and they can reach
temperatures as high as 400 degrees Fahrenheit
http://www.nps.gov/archive/yell/oldfaithfulcam.htm
Old Faithful erupts more
frequently than any of the other
big geysers. Its average interval
between eruptions is about 91
minutes. An eruption lasts 1 1/2
to 5 minutes, expels 3,700 - 8,400
gallons of boiling water, and
reaches heights of 106 - 184 feet.
Halophiles
• Can live in water
with salt
concentrations
exceeding 15%
• The ocean’s
concentration is
roughly 4%
The Great Salt Lake in Utah
Halobacterium salinarum
• Halobacterium salinarum is an extremely
halophilic marine Gram-negative obligate
aerobic archaeon. his microorganism is
not a bacterium, but rather a member of
the domain Archaea. It is found in salted
fish, hides, hypersaline lakes, and
salterns. As these salterns reach the
minimum salinity limits for extreme
halophiles, their waters
• become purple or reddish color due to the
high densities of halophilic Archaea.[1] H.
salinarum has also been found in high-salt
food such as salt pork, marine fish, and
sausages. The ability of H. salinarum to
survive at such high salt concentrations
has led to its classification as an
extremophile.
Adaptation to extreme
conditions
High salt
• To survive in extremely salty
environments, this archaeon—as with
other halophilic Archaeal species—utilizes
compatible solutes (in particular potassium
chloride) to reduce osmotic stress.[5]
Potassium levels are not at equilibrium
with the environment, so H. salinarum
expresses multiple active transporters
which pump potassium into the cell.[2] At
• extremely high salt concentrations protein
precipitation will occur. To prevent the
salting out of proteins, H. salinarum
encodes mainly acidic proteins. These
highly acidic proteins are overwhelmingly
negative in charge and are able to remain
in solution even at high salt
concentrations.
Low oxygen and photosynthesis
• H. salinarum can grow to such densities in
salt ponds that oxygen is quickly depleted.
Though it is an obligate aerobe, it is able
to survive in low-oxygen conditions by
utilizing light-energy. H. salinarum express
the membrane protein
bacteriorhodopsin[8] which acts as a lightdriven proton pump. It consists of two
parts, the 7-transmembrane protein,
bacterioopsin, and the light-sensitive
• cofactor, retinal. Upon absorption of a
photon, retinal changes conformation,
causing a conformational change in the
bacterioopsin protein which drives proton
transport.[9] The proton gradient which is
formed can then be used to generate
chemical energy by ATP synthase.
• To obtain more oxygen H. salinarum
produce gas vesicles, which allow them to
float to the surface where oxygen levels
are higher and more light is available.
These vesicles are complex structures
made of proteins encoded by at least 14
genes. Gas vesicles were first discovered
in H. salinarum in 1967.
UV protection
There is little protection from the Sun in salt
ponds, so H. salinarum are often exposed to
high amounts of UV radiation. To
compensate, they have evolved a
sophisticated DNA repair mechanism. The
genome encodes DNA repair enzymes
homologous to those in both bacteria and
eukaryotes. This allows H. salinarum to
repair damage to DNA faster and more
• efficiently than other organisms and allows
them to be much more UV tolerant.
• H. salinarum is responsible for the bright
pink or red appearance of the Dead Sea
and other bodies of salt water. This red
color is due primarily to the presence of
bacterioruberin, a 50 carbon carotenoid
pigment present within the membrane of
• H. salinarum. The primary role of
bacterioruberin in the cell is to protect
against DNA damage incurred by UV
light.[13] This protection is not, however,
due to the ability of bacterioruberin to
absorb UV light. Bacterioruberin protects
the DNA by acting as an antioxidant,
rather than directly blocking UV light。
資料來源
• http://plantphys.info/organismal/lechtml/arc
haea.shtml
• http://en.wikipedia.org/wiki/Halobacterium_
salinarum
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