Autotroph

An autotroph or producer, is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) from simple substances present in its surroundings, generally using energy from light (photosynthesis) or inorganic chemical reactions (chemosynthesis).[1] They are the producers in a food chain, such as plants on land or algae in water (in contrast to heterotrophs as consumers of autotrophs). They do not need a living source of energy or organic carbon. Autotrophs can reduce carbon dioxide to make organic compounds for biosynthesis and also create a store of chemical energy. Most autotrophs use water as the reducing agent, but some can use other hydrogen compounds such as hydrogen sulfide. Some autotrophs, such as green plants and algae, are phototrophs, meaning that they convert electromagnetic energy from sunlight into chemical energy in the form of reduced carbon.

Autotrophs can be photoautotrophs or chemoautotrophs. Phototrophs use light as an energy source, while chemotrophs use electron donors as a source of energy, whether from organic or inorganic sources; however in the case of autotrophs, these electron donors come from inorganic chemical sources. Such chemotrophs are lithotrophs. Lithotrophs use inorganic compounds, such as hydrogen sulfide, elemental sulfur, ammonium and ferrous iron, as reducing agents for biosynthesis and chemical energy storage. Photoautotrophs and lithoautotrophs use a portion of the ATP produced during photosynthesis or the oxidation of inorganic compounds to reduce NADP+ to NADPH to form organic compounds.[2]

Auto-and heterotrophs
Overview of cycle between autotrophs and heterotrophs. Photosynthesis is the main means by which plants, algae and many bacteria produce organic compounds and oxygen from carbon dioxide and water (green arrow).

History

The Greek term autotroph was coined by the German botanist Albert Bernhard Frank in 1892.[3] It stems from the ancient Greek word τροφή (trophḗ), meaning "nourishment" or "food".

Variants

Some organisms rely on organic compounds as a source of carbon, but are able to use light or inorganic compounds as a source of energy. Such organisms are not defined as autotrophic, but rather as heterotrophic. An organism that obtains carbon from organic compounds but obtains energy from light is called a photoheterotroph, while an organism that obtains carbon from organic compounds but obtains energy from the oxidation of inorganic compounds is termed a chemoheterotroph, chemolithoheterotroph, or lithoheterotroph.

Evidence suggests that some fungi may also obtain energy from radiation. Such radiotrophic fungi were found growing inside a reactor of the Chernobyl nuclear power plant.[4]

AutoHeteroTrophs flowchart
Flowchart to determine if a species is autotroph, heterotroph, or a subtype

Ecology

Colpfl27a
Green fronds of a maidenhair fern, a photoautotroph

Autotrophs are fundamental to the food chains of all ecosystems in the world. They take energy from the environment in the form of sunlight or inorganic chemicals and use it to create energy-rich molecules such as carbohydrates. This mechanism is called primary production. Other organisms, called heterotrophs, take in autotrophs as food to carry out functions necessary for their life. Thus, heterotrophs — all animals, almost all fungi, as well as most bacteria and protozoa — depend on autotrophs, or primary producers, for the energy and raw materials they need. Heterotrophs obtain energy by breaking down organic molecules (carbohydrates, fats, and proteins) obtained in food. Carnivorous organisms rely on autotrophs indirectly, as the nutrients obtained from their heterotroph prey come from autotrophs they have consumed.

Most ecosystems are supported by the autotrophic primary production of plants that capture photons initially released by the sun. Plants can only use a fraction of this energy for photosynthesis, approximately 1% is used by autotrophs.[5] The process of photosynthesis splits a water molecule (H2O), releasing oxygen (O2) into the atmosphere, and reducing carbon dioxide (CO2) to release the hydrogen atoms that fuel the metabolic process of primary production. Plants convert and store the energy of the photon into the chemical bonds of simple sugars during photosynthesis. These plant sugars are polymerized for storage as long-chain carbohydrates, including other sugars, starch, and cellulose; glucose is also used to make fats and proteins. When autotrophs are eaten by heterotrophs, i.e., consumers such as animals, the carbohydrates, fats, and proteins contained in them become energy sources for the heterotrophs.[6] Proteins can be made using nitrates, sulfates, and phosphates in the soil.[7][8]

See also

References

  1. ^ Chang, Kenneth (12 September 2016). "Visions of Life on Mars in Earth's Depths". The New York Times. Retrieved 12 September 2016.
  2. ^ Mauseth, James D. (2008). Botany: An Introduction to Plant Biology (4 ed.). Jones & Bartlett Publishers. p. 252. ISBN 978-0-7637-5345-0.
  3. ^ Frank, A.B. Lehrbuch der Botanik. W. Engelmann, Leipzig 1892-93, [1].
  4. ^ Melville, Kate (23 May 2007). "Chernobyl Fungus Feeds On Radiation". Archived from the original on 4 February 2009. Retrieved 18 February 2009.
  5. ^ H., Schurr, Sam. Energy, economic growth, and the environment. New York. ISBN 9781617260209. OCLC 868970980.
  6. ^ Beckett, Brian S. (1981). Illustrated Human and Social Biology. Oxford University Press. p. 38. ISBN 978-0-19-914065-7.
  7. ^ Odum, E. P.; Barrett, G. W. (2005). Fundamentals of ecology. Brooks Cole. p. 598. ISBN 978-0-534-42066-6.
  8. ^ Smith, Gilbert M. (2007). A Textbook of General Botany. READ BOOKS. p. 148. ISBN 978-1-4067-7315-6.
Chemosynthesis

In biochemistry, chemosynthesis is the biological conversion of one or more carbon-containing molecules (usually carbon dioxide or methane) and nutrients into organic matter using the oxidation of inorganic compounds (e.g., hydrogen gas, hydrogen sulfide) or methane as a source of energy, rather than sunlight, as in photosynthesis. Chemoautotrophs, organisms that obtain carbon through chemosynthesis, are phylogenetically diverse, but also groups that include conspicuous or biogeochemically-important taxa include the sulfur-oxidizing gamma and epsilon proteobacteria, the Aquificae, the methanogenic archaea and the neutrophilic iron-oxidizing bacteria.

Many microorganisms in dark regions of the oceans use chemosynthesis to produce biomass from single carbon molecules. Two categories can be distinguished. In the rare sites at which hydrogen molecules (H2) are available, the energy available from the reaction between CO2 and H2 (leading to production of methane, CH4) can be large enough to drive the production of biomass. Alternatively, in most oceanic environments, energy for chemosynthesis derives from reactions in which substances such as hydrogen sulfide or ammonia are oxidized. This may occur with or without the presence of oxygen.

Many chemosynthetic microorganisms are consumed by other organisms in the ocean, and symbiotic associations between chemosynthesizers and respiring heterotrophs are quite common. Large populations of animals can be supported by chemosynthetic secondary production at hydrothermal vents, methane clathrates, cold seeps, whale falls, and isolated cave water.

It has been hypothesized that chemosynthesis may support life below the surface of Mars, Jupiter's moon Europa, and other planets. Chemosynthesis may have also been the first type of metabolism that evolved on Earth, leading the way for cellular respiration and photosynthesis to develop later.

Chemotroph

Chemotrophs are organisms that obtain energy by the oxidation of electron donors in their environments. These molecules can be organic (chemoorganotrophs) or inorganic (chemolithotrophs). The chemotroph designation is in contrast to phototrophs, which use solar energy. Chemotrophs can be either autotrophic or heterotrophic. Chemotrophs are found in ocean floors where sunlight cannot reach them because they are not dependent on solar energy. Ocean floors often contain underwater volcanos that can provide heat as a substitute for sunlight's warmth.

Chlorella autotrophica

Chlorella autotrophica, or Chlorella sp. (580), is a euryhaline, unicellular microalgae found in brackish waters first isolated in 1956 by Ralph A. Lewin. The species is defined by its inability to use organic carbon as a food source, making the species an obligate autotroph. It is sometimes considered a variety of Chlorella vulgaris.

Consumer (food chain)

Consumers are organisms that eat organisms from a different population. These organisms are formally referred to as heterotrophs, which include animals, some bacteria and fungi. Such organisms may consume by various means, they are called primary consumers.

Dinophysis acuminata

Dinophysis acuminata is a marine plankton species of dinoflagellates that is found in coastal waters of the north Atlantic and Pacific oceans. The Dinophysis genus includes both phototrophic and heterotrophic species. D. acuminata is one of several phototrophic species of Dinophysis classed as toxic, as they produce okadaic acid which can cause diarrhetic shellfish poisoning (DSP). Okadiac acid is taken up by shellfish and has been found in the soft tissue of mussels and the liver of flounder species. When contaminated animals are consumed, they cause severe diarrhoea. D. acuminata blooms are constant threat to and indication of diarrhoeatic shellfish poisoning outbreaks.Dinophysis acuminata is a photosynthesising Dinophysis species by acquiring secondary plastids from consuming the ciliate Myrionecta rubra, which in turn had ingested them from the alga Teleaulax amphioxeia. Thus, D. acuminata is a mixotroph, primarily a heterotroph, but autotroph once it acquires plastids. This is also an example of cell organelle stealing, the concept called kleptoplasty, and endosymbiosis. Dinophysis acuminata reproduces sexually and asexually.

Ditylum brightwellii

Ditylum brightwelli is a species of cosmopolitan marine centric diatoms. It is a unicellular photosynthetic autotroph that has the ability to divide rapidly and contribute to spring phytoplankton blooms.

Endolith

An endolith is an organism (archaeon, bacterium, fungus, lichen, algae or amoeba) that lives inside rock, coral, animal shells, or in the pores between mineral grains of a rock. Many are extremophiles, living in places long imagined inhospitable to life. They are of particular interest to astrobiologists, who theorize that endolithic environments on Mars and other planets constitute potential refugia for extraterrestrial microbial communities.

Heterotroph

A heterotroph (; Ancient Greek ἕτερος héteros = "other" plus trophe = "nutrition") is an organism that cannot produce its own food, relying instead on the intake of nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but not producers. Ninety-five percent or more of all types of living organisms are heterotrophic, including all animals and fungi and some bacteria and protists. The term heterotroph arose in microbiology in 1946 as part of a classification of microorganisms based on their type of nutrition. The term is now used in many fields, such as ecology in describing the food chain.

Heterotrophs may be subdivided according to their energy source. If the heterotroph uses chemical energy, it is a chemoheterotroph (e.g., humans and mushrooms). If it uses light for energy, then it is a photoheterotroph (e.g., green non-sulfur bacteria).

Heterotrophs represent one of the two mechanisms of nutrition (trophic levels), the other being autotrophs (auto = self, troph = nutrition). Autotrophs use energy from sunlight (photoautotrophs) or inorganic compounds (lithoautotrophs) to convert inorganic carbon dioxide to organic carbon compounds and energy to sustain their life. Comparing the two in layman's terms, heterotrophs (such as animals) eat either autotrophs (such as plants) or other heterotrophs, or both.

Detritivores are heterotrophs which obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). Saprotrophs (also called lysotrophs) are chemoheterotrophs that use extracellular digestion in processing decayed organic matter. It is a term most often associated with fungi. The process is most often facilitated through the active transport of such materials through endocytosis within the internal mycelium and its constituent hyphae.

Mesodinium chamaeleon

Mesodinium chamaeleon is a ciliate of the genus Mesodinium. It is known for being able to consume and maintain algae endosymbiotically for days before digesting the algae. It has the ability to eat red and green algae, and afterwards using the chlorophyll granules from the algae to generate energy, turning itself from being a heterotroph into an autotroph. The species was discovered in January 2012 outside the coast of Nivå, Denmark by professor Øjvind Moestrup.

In contrast to certain other species of the genus, Mesodinium chamaeleon can be maintained in culture for short periods only. It captures and ingests flagellates including cryptomonads. The prey is ingested very rapidly into a food vacuole without the cryptomonad flagella being shed and the trichocysts being discharged. The individual food vacuoles subsequently serve as photosynthetic units, each containing the cryptomonad chloroplast, a nucleus, and some mitochondria. The ingested cells are eventually digested. This type of symbiosis differs from other plastid-bearing Mesodinium spp. in retaining ingested cryptomonad cells almost intact. The food strategy of the new species appears to be intermediate between heterotrophic species, such as Mesodinium pulex and Mesodinium pupula, and species with red cryptomonad endosymbionts, such as Mesodinium rubrum.

Organotroph

An organotroph is an organism that obtains hydrogen or electrons from organic substrates. This term is used in microbiology to classify and describe organisms based on how they obtain electrons for their respiration processes. Some organotrophs such as animals and many bacteria, are also heterotrophs. Organotrophs can be either anaerobic or aerobic.

Antonym: Lithotroph, Adjective: Organotrophic.

Photoheterotroph

Photoheterotrophs (Gk: photo = light, hetero = (an)other, troph = nourishment) are heterotrophic phototrophs—that is, they are organisms that use light for energy, but cannot use carbon dioxide as their sole carbon source. Consequently, they use organic compounds from the environment to satisfy their carbon requirements; these compounds include carbohydrates, fatty acids, and alcohols. Examples of photoheterotrophic organisms include purple non-sulfur bacteria, green non-sulfur bacteria, and heliobacteria. Recent research has indicated that the oriental hornet and some aphids may be able to use light to supplement their energy supply.

Phototroph

Phototrophs (Gr: φῶς, φωτός = light, τροϕή = nourishment) are the organisms that carry out photon capture to acquire energy. They use the energy from light to carry out various cellular metabolic processes. It is a common misconception that phototrophs are obligatorily photosynthetic. Many, but not all, phototrophs often photosynthesize: they anabolically convert carbon dioxide into organic material to be utilized structurally, functionally, or as a source for later catabolic processes (e.g. in the form of starches, sugars and fats). All phototrophs either use electron transport chains or direct proton pumping to establish an electro-chemical gradient which is utilized by ATP synthase, to provide the molecular energy currency for the cell. Phototrophs can be either autotrophs or heterotrophs. As their electron and hydrogen donors are inorganic compounds [Na2S2O3 (PSB) and H2S (GSB)] they can be also called as lithotrophs, and so, some photoautotrophs are also called photolithoautotrophs. Examples of phototroph organisms: Rhodobacter capsulatus, Chromatium, Chlorobium etc.

Primary nutritional groups

Primary nutritional groups are groups of organisms, divided in relation to the nutrition mode according to the sources of energy and carbon, needed for living, growth and reproduction. The sources of energy can be light and organic or inorganic compounds; the sources of carbon can be of organic or inorganic origin.

The terms aerobic respiration, anaerobic respiration and fermentation do not refer to primary nutritional groups, but simply reflect the different use of possible electron acceptors in particular organisms, such as O2 in aerobic respiration, or nitrate (NO3−), sulfate (SO42−) or fumarate in anaerobic respiration, or various metabolic intermediates in fermentation. Because all ATP-generating steps in fermentation involve modifications of metabolic intermediates instead of the use of an electron transport chain fermentation is often referred to as substrate-level phosphorylation.

Primary production

In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are known as primary producers or autotrophs, and form the base of the food chain. In terrestrial ecoregions, these are mainly plants, while in aquatic ecoregions algae predominate in this role. Ecologists distinguish primary production as either net or gross, the former accounting for losses to processes such as cellular respiration, the latter not.

Producer

Producer or producers may refer to something that produce its own food. Some examples...

Sedimentary organic matter

Sedimentary organic matter includes the organic carbon component of sediments and sedimentary rocks. The organic matter is usually a component of sedimentary material even if it is present in low abundance (usually lower than 1%). Petroleum (or oil) and natural gas are particular examples of sedimentary organic matter. Coals and bitumen shales are examples of sedimentary rocks rich in sedimentary organic matter.

Sulfolobus solfataricus

Saccharolobus solfataricus is a species of thermophilic archaeon. It was transferred from the genus Sulfolobus to the new genus Saccharolobus with the description of Saccharolobus caldissimus in 2018.

It was first isolated and discovered in the Solfatara volcano which it was subsequently named after. However, these organisms are not isolated to volcanoes but are found all over the world in places such as hot springs. The species grows best in temperatures around 80° Celsius, a pH level between 2 and 4, and enough sulfur for solfataricus to metabolize in order to gain energy. These conditions qualify it as an extremophile and it is specifically known as a thermoacidophile because of its preference to high temperatures and low pH levels. It usually has a spherical cell shape and it makes frequent lobes. Being an autotroph it receives energy from growing on sulfur or even a variety of organic compounds.Currently, it is the most widely studied organism that is within the Crenarchaeota branch. Solfataricus are researched for their methods of DNA replication, cell cycle, chromosomal integration, transcription, RNA processing, and translation. All the data points to the organism having a large percent of archaeal-specific genes, which showcases the differences between the three types of microbes: archaea, bacteria, and eukarya.

Thermithiobacillus tepidarius

Thermithiobacillus tepidarius (from the Latin tepidarium; a warm bath fed by natural thermal water) is a member of the Acidithiobacillia isolated from the thermal groundwaters of the Roman Baths at Bath, Avon, United Kingdom. It was previously placed in the genus Thiobacillus.

The organism is a moderate thermophile, 43–45 °C (109–113 °F), and an obligate aerobic chemolithotrophic autotroph. Despite having an optimum pH of 6.0–7.5, growth can continue to an acid medium of pH 4.8. Growth can only occur on reduced inorganic sulfur compounds (thiosulfate, polythionates from trithionate to octathionate pace pentathionate, sulfide) and elementary sulfur, but unlike some species in other genus of the same family, Acidithiobacillus, Thermithiobacillus spp. are unable to oxidise ferrous iron or iron-containing minerals.The genome sequence was completed in 2016.

Trophic mutualism

Trophic mutualism is a key type of ecological mutualism. Specifically, "trophic mutualism" refers to the transfer of energy and nutrients between two species. This is also sometimes known as resource-to-resource mutualism. Trophic mutualism often occurs between an autotroph and a heterotroph. Although there are many examples of trophic mutualisms, the heterotroph is generally a fungus or bacteria. This mutualism can be both obligate and opportunistic.

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