Chemoautotroph Examples
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Autotroph and Heterotroph

Definition & Chemoautotroph Examples


Autotrophs are organisms that can produce their own food with the help of sunlight, water, and minerals. Those that make their food by using chemicals found in their environment are called chemoautotrophs. Chemosynthesis is the process by which chemoautotrophs feed on chemicals like ammonia and sulfides.

This is often because it uses inorganic compounds as sources of electrons and carbon. This allows it to harness energy for the production of new biomass from inorganic compounds.  These organisms are often found in dark places like deep-sea hydrothermal vents, or in low oxygen environments like swamps.

A chemoautotroph is an organism that uses inorganic compounds as its energy and carbon source and converts them to organic form by reducing CO2 with hydrogen. Chemosynthesis is the process of obtaining chemical energy from carbon dioxide, hydrogen, and inorganic compounds.

Organisms that obtain energy from this method are chemoautotrophs. This knowledge about the chemical process is very helpful in finding organisms on earth and other planets because this process allows us to find organisms with different energy cycles.

Chemoautotrophic Nutrition

Chemoautotrophic nutrition is an energy source sustained by the oxidation of organic compounds, such as glucose or acetate, by inorganic substances. It is the process of obtaining nutrients from inorganic compounds, such as ammonium (NH4+), nitrite (NO2-), and sulfur (S).

These organisms can also use inorganic carbon, such as carbon dioxide (CO2). This process is different from the process of heterotrophic nutrition. Chemotrophs use inorganic compounds to produce energy and organic compounds for growth. It is common in bacteria and can be found in deep ocean trenches.

This type of nutrition is beneficial to organisms that live in deep ocean trenches because levels of light decrease at depths greater than three kilometres, making it difficult to use photosynthesis. This type of energy source is also common in bacteria because they thrive in oxygen-free environments.

Chemoautotroph Examples

Chemoautotroph Bacteria

Chemoautotroph bacteria are examples of microbes that use inorganic molecules to obtain energy. In order to survive, chemoautotroph bacteria need an environment with little to no light and with a sufficient concentration of available inorganic molecules.

They are typically found in deep ocean trenches, in the absence of light, and below the surface layer of soil and sediment. One example of chemoautotrophic bacteria is Desulfovibrio sp.

Although some bacteria can capture the energy and use it to maintain their cellular functions, such as photosynthesis, chemoorganosynthesis is the process by which certain bacteria use the natural oxidation-reduction reactions of organic substances in their environment to produce organic matter.

As chemoorganotrophs, these bacteria can be grouped into categories relating to their energy source, whether the bacteria use H2, H2S or CO2 as their electron acceptor.

The most common chemoautotrophs are bacteria and archaea. Archaea can live in extreme places with little or no oxygen, such as in groundwater, sewage, and oil wells. They obtain their energy from inorganic compounds such as hydrogen, sulfur, and carbohydrates through the process of chemosynthesis.

These organisms have different structures but they all carry out the same two main processes: carbon fixation and energy conservation.

They do this using the electron transport chain which is also located in the mitochondria of eukaryotic cells. This electron transport chain will accept electrons from NADH and H2O to form NAD+ which is then transferred to the respiratory chain.

This is the second major process that these organisms rely on. It transfers electrons from the respiratory chain to molecular oxygen. The final process in their cycle is releasing energy as ATP molecules, which can then be used to perform a chemical reaction or build new molecules.

These organisms are also known as chemosynthetic bacteria and archaea. The first organism that showed this was “Sulfolobus acidocaldarius”. This organism was discovered in 1981 by Yoshihiro Kilias, a Japanese biochemist.

It was found from deep-sea hydrothermal vents in the Mariana Trench which are located near Guam. It is also known as a hyperthermophile which means that it thrives in high temperatures. This organism is able to grow at 100 °C, which is very impressive due to the boiling point of water being 100 °C.

Other chemosynthetic bacteria and archaea are not as tolerant of their high-temperature environment as “Sulfolobus”. “Thermus aquaticus” can only withstand temperatures from 30 to 70 °C. “Deinococcus” are able to withstand temperatures from 60 to 85 °C, whereas “Korarchaeum maricopense” can survive up to 180 °C. The lower temperature limits for these organisms are not known because most of them live in the deep sea.

To find out more about chemosynthesis, scientists performed chemical reactions on bacteria and archaea. The results showed that these organisms produced ATP molecules from organic compounds and inorganic molecules. The cells then used these ATP molecules to produce proteins and other organic chemicals. Some of the reactions were done on “Sulfolobus acidocaldarius”.

This organism was mixed with different metal ions, hydrogen-sulfide, sulfite, and carbonyl sulfide. The results showed that the organism utilized hydrogen as an electron donor when reacted with dissolved carbon dioxide, which was then transferred to pyruvic acid. A similar reaction was done on “Thermus aquaticus”, but the organism used dissolved carbon dioxide instead.

These reactions are far from complete and scientists are still trying to better understand the process of chemosynthesis.

“Sulfolobus acidocaldarius” is a chemoautotroph that obtains its energy from inorganic compounds such as hydrogen, sulfur, and carbonyl sulfide. It is also an extreme thermophile which allows it to survive in extremely high temperatures.

The methyl-accepting chemolithoautotroph “Deinococcus radiodurans” also thrives in extremely high temperatures. It uses hydrogen as an electron donor to obtain electrons and then passes the electrons through the electron transport chain to produce molecular oxygen as a byproduct. After passing the electrons through this chain, it forms sulfide which is then used as a source of energy or carbon for growth.

In addition to using hydrogen, it uses organic compounds that include methane and formaldehyde. This organism also lives in extremely high temperatures so it is difficult to slow down or interrupt its chemical reactions because of the extreme temperatures.

“Deinococcus suberi” thrives in high temperatures as well. It also utilizes hydrogen to obtain electrons instead of carbon dioxide for energy which is then passed through the electron transport chain and oxidized by molecular oxygen as a byproduct. It can also use organic compounds such as methanol and formaldehyde.

“Thermococcus litoralis” is very similar to “Deinococcus radiodurans” in the way that it uses hydrogen, organic compounds, and molecular oxygen. The difference between them is that “Thermococcus litoralis” can only grow in colder temperatures and not as high as “Deinococcus radiodurans”.

“Korarchaeum maricopense” is another extreme thermophile that grows very well in high temperatures. It can also use other organic compounds besides methane and formaldehyde. The organism uses hydrogen, carbon dioxide, and ethanol to obtain the electrons for the electron transport chain.

Chemosynthesis is more common in the deep sea because there are fewer organisms housing a complete set of enzymes required for aerobic respiration. However, chemosynthesis is not limited to the deep sea. It is also important in hydrothermal vents and cold seeps.

There are many organisms that thrive in high temperatures which facilitate chemosynthesis. For example, it allows the organisms to live in hydrothermal vents where there are basic geochemical reactions being driven by steam at extreme temperatures.

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