Archaea is a domain of microorganisms that are mostly extremophiles, meaning they live in environments with extreme temperatures. Archaea are found often in geysers, such as those in Yellowstone National Park, and in the deep basins of the ocean. Some members of Archaea, however, live in normal climates such as swamps, ponds, and even people. Archaea are being found to be more and more profitable in the science community on a regular basis. Their unique talents are utilized for things such as food processing, sewage treatment, DNA cloning, and antibiotic production.
Archaea are microorganisms that have characteristics distinct from the other two domains, Bacteria and Eukarya. Species from Archaea 1) lack peptidoglycan, a polymer composed of sugars and amino acids that form a mesh-like layer outside the plasma membrane, 2) can have branched carbon chains in their membrane lipids of the phospholipid bilayer and 3) contain a different type of RNA polymerase, an enzyme that produces RNA. They are single-celled organisms with no nucleus, making them prokaryotic. One of the most unusual characteristics of Archaea is that they do not possess packaging proteins, but instead have proteins similar to histones, the chief protein components of chromatin. Archaea usually have a single cellular chromosome which may be as large as 5,751,492 base pairs, two nucleotides on opposite complementary DNA of RNA strands that are connected by hydrogen bonds. Archaea have only one type of RNA polymerase, closest to eukaryotes RNA polymerase II. Organisms from Archaea are very diversified and come in a wide variety of shapes, such as flat or square. Some Archaea have flagella and use thermotaxis which means that they are drawn toward extreme temperatures. There are three main types of Archaea which are classified as kingdoms, crenarchaeota: characterized by their ability to tolerate extreme temperatures in acidity, euryarchaeota: which includes methane-producers and salt-lovers, and korarchaeota: a diverse and widely encompassing group of which little is known.
Archaea reproduce asexually by binary or multiple fission, fragmentation, or budding. Meiosis does not occur within organisms from the domain Archaea. So, if a species of Archaea exists in more than one form, they will all have the same genetic material. Cell division, in Archaea, is controlled in a cell cycle; this is a cycle where, after the cell’s chromosome is replicated and the two daughter cells separate, the cell divides. No known Archaea produce spores, though they are commonly formed in other bacteria and eukaryotes. Some species experience phenotypic switching where they grow several different types of cells, including thick-walled structures that are resistant to osmotic shock; this allows the Archaea to survive in water at low concentrations of salt, but they are not reproductive structures and may instead help them disperse to new habitats.
Most Archaea are extremophiles, which means they live in extreme environments and temperatures. Some extremophiles love the heat; they live in boiling water such as that in the geysers at Yellowstone National Park. Archaea are known to survive high temperatures, often above 100 °C. One Archaea, Methanopyrus kandleri thrives at 122°C, the highest recorded temperature at which any organism will grow. Other extremophiles, called halophiles, live in hypersaline environments, meaning that they are very salty. Archaea are also commonly found in cold oceanic environments, such as the polar seas. Not all Archaea, however, are extremophiles, some live in marshland, sewage, oceans, soils, and even inside people. The Archaea found in the world’s oceans in the plankton community are believed to assist in the all-essential oceanic nitrogen cycle.
Archaea contribute up to 20% of the Earth’s total biomass and are part of the earth’s natural recycling process; they recycle elements such as carbon, nitrogen, and sulfur. However, they can also contribute to changes that humans have made in the environment, and even cause pollution. Archaea do not need sunlight or oxygen, instead they absorb carbon dioxide (CO2), nitrogen (N2), or hydrogen sulfide (H2S), and give off methane gas.
Archaea have formed symbiosis with many other organisms on earth. Interactions between Archaea and other organisms are either mutualism, where each individual derives a fitness benefit, or commensal, where one benefits and the other is not significantly harmed or benefited. Protozoa are a famous example of the Archaea mutualism with another organism; protozoa break down cellulose from a plant to obtain energy. This process will eventually release hydrogen, which will be converted to methane, which will give off even more energy. Some Archaea live in the human gut and aid in food digestion.
Archaea in Technology
Archaea have been found to be a source of enzymes. With their unusual resistance to heat and extreme acidity, the enzymes have proven to be very durable. A thermal stable DNA polymerase called TAQ polymerase has revolutionized molecular biology by allowing the polymerase chain reaction to be used as an easy and swift technique for cloning DNA.
In the food industry, a species called Pyrococcus functions at over 100 °C, allowing food processing at high temperatures, such as the production of low lactose milk and whey. The enzymes also tend to be used in environmentally friendly processes in green chemistry that synthesize organic compounds. Some Archaea are vital in sewage treatment, while others are part of anaerobic digestion, or aid in mineral processing. New classes of potential antibiotics have been found in Archaea, and many more with hidden potential are believed to exist.
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