Autotrophic bacteria are bacteria that synthesize their own food. The energy they consume is derived from either light or chemical reactions.
This can be done by utilizing inorganic compounds such as carbon dioxide, hydrogen sulfide, and water to transform them into organic compounds such as proteins and carbohydrates to get their required energy.
Types Of Autotrophic Bacteria
There are two types of autotrophic bacteria. Both types require a carbon source to synthesize their food.
These two types, however, have different sources of their energy, and are referred to as photoautotrophic bacteria and chemoautotrophic bacteria.
Photoautotrophic bacteria derive their energy from sunlight and then require a carbon source to synthesize their food.
However, chemoautotrophic bacteria derive their energy from chemical energy combined with carbon dioxide and other compounds.
Examples Of Photoautotrophic Bacteria
Photoautotrophic bacteria convert the light that they’ve trapped into chemical energy, and so create their own food in a similar manner to plants.
They may either perform anoxygenic photosynthesis or oxygenic photosynthesis. These bacteria may be used as biofertilizers, bioremediation, wastewater treatment, and for the purification of polluted water.
Down below are a series of types of photoautotrophic bacteria and examples of the different types.
Anoxygenic Photosynthetic Bacteria
Most photosynthetic bacteria are anoxygenic and don’t utilize water as an electron donor. Instead, they use chemicals such as thiosulphate as a reducing agent and sources of hydrogen.
They have a photosynthetic pigment called bacteriochlorophyll, which is similar to chlorophylls found in plants. Examples of anoxygenic photosynthetic bacteria have been listed below.
Green sulfur bacteria are generally non-motile and can be found in deep ocean waters with low light and near thermal vents.
Their electron donors are hydrogen, sulfide, or ferrous ions. They commence carbon fixation by reversing the RTCA cycle. They contain bacteriochlorophyll c d and e, alongside a.
Pigments can be found in their chlorosomes and plasma membranes.
Purple sulfur bacteria are found both in hot springs and stagnant water, thriving in anaerobic or environments with poor oxygen. PSB utilized hydrogen sulfide as a reducing agent and release sulfur.
Their main pigments are bacteriochlorophyll a and b, which are located in the plasma membrane.
There are two types of these bacteria, chromatiaceae which have intercellular sulfur granules, and ectothiorhodospiraceae, which have extracellular granules.
However, purple non-sulfur bacteria mostly use hydrogen as their reducing agent. These bacteria are vital as they produce multiple beneficial substances that are used as growth-promoting substances for plants.
These increase the plant’s growth and resistance to environmental stress and improve its biomass.
They can also be used in the bioremediation of heavy metals and can reduce greenhouse gas emissions.
Oxygenic Photosynthetic Bacteria
An example of oxygenic photosynthetic bacteria is cyanobacteria. They use water as an electron donor and then produce oxygen.
While they don’t have chloroplasts, photosynthetic pigments such as chlorophyll-a are present in the systole. As cyanobacteria are colonial or filamentous, so they also can perform nitrogen fixation as well.
Examples Of Chemoautotrophic Bacteria
Chemosynthetic autotrophs are reliant on chemical compounds to get their energy.
They perform chemosynthesis, which allows them to utilize chemical energy as it is produced from the oxidation of inorganic compounds.
If they combine carbon sources, they can produce the oxidation of ammonia, carbon monoxide, iron salts, methane, and more.
The energy is then liberated from the oxidation trapped in ATP for the organic synthesis.
Chemoautotrophic bacteria can be either aerobic or anaerobic. From wherever they derive energy, they may be categorized into a variety of types of bacteria, which you can see examples of below.
They also play a vital role in recycling nutrients.
Hydrogen bacteria oxidize molecular hydrogen. Aerobic variations use oxygen as an electron acceptor, while anaerobic variations use nitrogen dioxide or sulfate as electron acceptors.
Iron bacteria oxidize ferrous ions into ferric ions. They can be found in iron-rich environments, including lava beds and hydrothermal vents.
Methanotrophs use methane as their carbon source to get energy. Aerobic variations oxidize methane into formaldehyde which is utilized in multiple pathways to make organic compounds.
Anaerobic variations utilize other compounds as electron acceptors and assimilate formaldehyde through the RuMP pathway.
These produce food for animals. Some variations assimilate formaldehyde via the serine pathway.
Nitrogen bacteria convert ammonia into nitrite, which in turn becomes nitrate. In the oxidation process, energy is released, and nitrate is then utilized by the plants.
Sulfur bacterias oxidize hydrogen sulfide or thiosulphates to molecular sulfur.
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