How does archaea obtain energy

Archaea and viruses likely had a relationship as early as 2 billion years before present day, some researchers positing that co-evolution may have been occurring between these groups at such an early time. It has been further suggested that the last common ancestor of the bacteria and archaea was a thermophile, raising the likelihood that low temperatures are really the extreme environments viewed from an ancestral archaea point of view, and organisms that can tolerate cold conditions appeared only later in evolutionary time.

It was not until that archaea were recognized as a separate domain of prokaryotes through the work of Woese and Fox. Until the chief techniques of distinguishing microorganisms were use of morphology and metabolic functions. Woese and Fox culminated a research direction begun by a number of researchers started in the early s, in which gene coding of DNA material was viewed as a more fundamental technique for organism relatedness.

By the close of the 20th century, an enhanced understanding of the significance and ubiquity of archaea arose by using the polymerase chain reaction to detect prokaryotes in samples of water or soil based solely upon their nucleic acid. The greatest remaining puzzle is whether to acknowledge species within the domain of archaea. While morphological and DNA findings support the recognition of species, it is not clear that significant gene transfer is prohibited, thereby annihilating the validity of species.

In any case, in the present treatment we shall allow the attribution of species, if for no other reason than to follow published research designations and for simplicity of naming. Archaea and bacteria are superficially similar in size and shape, although some archaea species have remarkable geometric shapes, such as the flat and square-shaped cells of some genus Haloquadra members.

Despite this visual similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes: notably the enzymes involved in gene transcription and translation. Other aspects of archaean biochemistry are unique, such as the occurrence on ether lipids within their cell membranes.

As with bacteria, archaea have no interior membranes or organelles. Cell membranes are typically bounded by a cell wall and motility is achieved using one or more flagellar tail structures. Archaea most resemble gram-positive bacteria. Most archaea exhibit a single plasma membrane and cell wall, lacking a periplasmic space; however, Ignicoccus manifests a notably large periplasm with membrane-bound vesicles , enclosed by an outer membrane. Certain archaea aggregate to yield filaments of cells as long as nanometers—such forms are prominent in biofilms.

Thermococcus coalescens, on the other hand, have cells that can fuse in culturing to produce monster single cells. Genus Pyrodictium archaea form an elaborate multicell colony manifesting arrays of slender elongated hollow tubes termed cannulae that protrude from the cellular surface and connect into a dense agglomeration; this protruding form appears to encourage connection or nutrient exchange with neighboring cells of the same genus.

Crenarchaeota exhibit a diverse set of geometries: irregularly shaped lobed cells, needle-like filaments that are less than nanometers in cross-section and amazing rectangular rods. These odd morphologies are likely produced both by their cell walls as well as a prokaryotic cytoskeleton. Proteins associated with cytoskeleton elements of other organisms exist in archaea.

Archaeal flagella function like their bacterial counterparts, with elongated stalks driven by rotatory motors at the base. The motors themselves are powered by the electrochemical gradient across the membrane.

However, archaeal and bacterial flagella came from different ancestors. The bacterial flagellum is hollow and is assembled by subunits moving up the central pore to the tip of the flagella, while archaeal flagella are constructed from addition of subunits at the base. The membranes of Archaea are constructed from molecules unlike those in other life forms; this morphology demonstrates the ancestral distance from bacteria and eukaryotes.

For every organism, cell membranes are made of phospholipid molecules. These phospholipids exhibit a polar part that dissolves in water a phosphate head , and a hydrophobic non-polar part a lipid tail that is water insoluble. These dissimilar ends are connected by a glycerol group. In water, phospholipids aggregate, with heads facing the water and tails facing the opposite direction. The principal structure in cell membranes is a dual layer of phospholipids, often termed a lipid bilayer.

In the case of bacteria and eukaryotes, membranes consist chiefly of glycol-ester lipids, but archaea have membranes made of glycerol-ether lipids. Ether bonds are chemically more stable than ester bonds, assisting archaea in survival at extreme temperatures and extreme pH environments. Some archaea, called lithotrophs, obtain energy from inorganic compounds such as sulfur or ammonia. Other examples include nitrifiers, methanogens, and anaerobic methane oxidizers.

One compound acts as an electron donor and one as an electron acceptor. The energy released generates adenosine triphosphate ATP through chemiosmosis in the same basic process that happens in the mitochondrion of eukaryotic cells. Many basic metabolic pathways are shared between all forms of life. For example, archaea use a modified form of glycolysis the Entner—Doudoroff pathway and either a complete or partial citric acid cycle. These similarities to other organisms probably reflect both early origins in the history of life and their high level of efficiency.

Some Euryarchaeota are methanogens living in anaerobic environments such as swamps. This form of metabolism evolved early, and it is possible that the first free-living organism was a methanogen. A common reaction in methanogens involves the use of carbon dioxide as an electron acceptor to oxidize hydrogen.

Methanogenesis uses a range of coenzymes that are unique to these archaea, such as coenzyme M and methanofuran. Some archaea, called lithotrophs, obtain energy from inorganic compounds such as sulfur or ammonia.

Other examples include nitrifiers, methanogens, and anaerobic methane oxidizers. One compound acts as an electron donor and one as an electron acceptor. The energy released generates adenosine triphosphate ATP through chemiosmosis in the same basic process that happens in the mitochondrion of eukaryotic cells. Archaea in an Extreme Environment : Archaea can live in extreme environments and live off autotrophic sources.

Here archaea were found living under highly acidic conditions, in the runoff from an iron mine. Many basic metabolic pathways are shared between all forms of life. For example, archaea use a modified form of glycolysis the Entner—Doudoroff pathway and either a complete or partial citric acid cycle.

These similarities to other organisms probably reflect both early origins in the history of life and their high level of efficiency. Some Euryarchaeota are methanogens living in anaerobic environments such as swamps. This form of metabolism evolved early, and it is possible that the first free-living organism was a methanogen.

A common reaction in methanogens involves the use of carbon dioxide as an electron acceptor to oxidize hydrogen. Methanogenesis uses a range of coenzymes that are unique to these archaea, such as coenzyme M and methanofuran. Other organic compounds such as alcohols, acetic acid, or formic acid are used as alternative electron acceptors by methanogens.

These reactions are common in gut-dwelling archaea. Acetotrophic archaea also break down acetic acid into methane and carbon dioxide directly. These acetotrophs are archaea in the order Methanosarcinales, and are a major part of the communities of microorganisms that produce biogas.

Other archaea, called autotrophs, use CO 2 in the atmosphere as a source of carbon, in a process called carbon fixation. In addition, the Crenarchaeota use the reverse Krebs cycle while the Euryarchaeota use the reductive acetyl-CoA pathway.

Carbon—fixation is powered by inorganic energy sources. Phototrophic archaea use sunlight as a source of energy; however, oxygen—generating photosynthesis does not occur in any archaea.