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

The Domain Archaea “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

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

Methanogens They release methane (CH 4 ) 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!

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 (H 2 S) and other dissolved minerals (rotten egg smell)

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. Black Smokers

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

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, ,400 gallons of boiling water, and reaches heights of 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 light- driven 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 。

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