Currently, it is separated into four evolutionary groups which are likely to change as we discover more about these microscopic organisms. The four current clades of archaea are Korarchaeotes, Euryarchaeotes, Crenarchaeotes, and Nanoarchaeotes. Euryarchaeotes are one of the best-known groups of archaea.
It includes a range of extreme halophiles lovers of salt and all methanogens. Some of these extreme halophiles are used in commercial salt production to help speed up the evaporation of saltwater ponds. Some euryarchaeotes have a unique way of using light energy to produce food. Instead of using the well-known pigments, such as chlorophyll a , some euryarchaeotes use a combination of a protein and a pigment called retinal to trap light energy.
Retinal is also a key molecule involved in vision for animals. Crenarchaeotes and euryarchaeotes are the two best-known groups of archaea. This group includes the majority of the known thermophiles lovers of heat. They most commonly live in hot or acidic environments.
The first korarchaeotes were discovered in a hot spring in in Yellowstone National Park. They have since been discovered around the world but so far only in hot springs and deep sea hydrothermal vents. Nanoarchaeotes are the most recently discovered archaea.
They were first discovered in in Iceland. They are parasites that grow attached to a crenarchaeote cell.
Since , they have been discovered in various places around the world including Siberia, Yellowstone National Park and deep in the Pacific Ocean. Learn about animals, plants, evolution, the tree of life, ecology, cells, genetics, fields of biology and more. A confirmation email has been sent to the email address that you just provided.
Check your emails and make sure you click the link to get started on our 6-week course. Basic Biology: An Introduction.
Also available from Amazon , Book Depository and all other good bookstores. Know the answer? Why not test yourself with our quick 20 question quiz. Archaea Archaea is a vast group of little-known microorganisms. Structure of archaea Archaea are structurally very diverse and there are exceptions to most of the general cell features that I describe here. Where are archaea found? Methanogens Methanogens are a group of archaea that produce methane gas as a part of their metabolism.
Different groups of archaea Very little is known about the evolutionary tree of the Domain Archaea. The size and complexity of the archaeal genome makes it difficult to classify. Most taxonomists agree that within the Archaea, there are currently five major phyla: Crenarchaeota , Euryarchaeota , Korarchaeota , Nanoarchaeota , and Thaumarchaeota. There are likely many other archaeal groups that have not yet been systematically studied and classified.
With few exceptions, archaea are not present in the human microbiota, and none are currently known to be associated with infectious diseases in humans, animals, plants, or microorganisms.
However, many play important roles in the environment and may thus have an indirect impact on human health. Crenarchaeota is a class of Archaea that is extremely diverse, containing genera and species that differ vastly in their morphology and requirements for growth. All Crenarchaeota are aquatic organisms, and they are thought to be the most abundant microorganisms in the oceans. Figure 1. Sulfolobus , an archaeon of the class Crenarchaeota, oxidizes sulfur and stores sulfuric acid in its granules.
In the presence of oxygen, Sulfolobus spp. In anaerobic environments, they oxidize sulfur to produce sulfuric acid, which is stored in granules. Sulfolobus spp. They have flagella and, therefore, are motile. Thermoproteus has a cellular membrane in which lipids form a monolayer rather than a bilayer, which is typical for archaea. Its metabolism is autotrophic. To synthesize ATP, Thermoproteus spp. The phylum Euryarchaeota includes several distinct classes. Species in the classes Methanobacteria, Methanococci, and Methanomicrobia represent Archaea that can be generally described as methanogens.
Methanogens are unique in that they can reduce carbon dioxide in the presence of hydrogen, producing methane. They can live in the most extreme environments and can reproduce at temperatures varying from below freezing to boiling.
Methanogens have been found in hot springs as well as deep under ice in Greenland. Some scientists have even hypothesized that methanogens may inhabit the planet Mars because the mixture of gases produced by methanogens resembles the makeup of the Martian atmosphere. Some genera of methanogens, notably Methanosarcina , can grow and produce methane in the presence of oxygen, although the vast majority are strict anaerobes.
Halobacteria require a very high concentrations of sodium chloride in their aquatic environment. One remarkable feature of these organisms is that they perform photosynthesis using the protein bacteriorhodopsin , which gives them, and the bodies of water they inhabit, a beautiful purple color Figure 2.
Archaea can also generate energy differently and have unique ecological roles to play, such as being responsible for producing biological methane—something no eukaryotes or bacteria can do. These differences may not seem like a big deal to most people—why, then, are they in different groups? By comparing the genomes of different organisms and studying the rate at which genetic changes occur over time, scientists can trace the evolutionary histories of living things and estimate when each group formed a new branch of the tree of life.
The molecular and genetic differences between archaea and other living things are profound and ancient enough to warrant an entirely separate domain.
Archaea are famous for their love of living in extreme environments. However, scientists are slowly learning more, helped by new techniques and technologies that make it easier to discover these species in the first place. Methods such as metagenomics allow for the study of genetic material without the need to grow cultures of a particular species in a lab, allowing researchers to study the genetic blueprints of more microbes than ever before.
Archaea are generally pretty friendly. A lot of archaea live in mutualistic relationships with other living things, meaning they provide some kind of benefit to another species and get something good in return. For example, the vast numbers of methanogens archaea that produce methane as a by-product that live in the human digestive system help to get rid of excess hydrogen by utilising it to produce energy.
0コメント