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Photosynthesis is the main means by which plants, algae and many bacteria produce organic compounds and oxygen from carbon dioxide and water (green arrow). An autotroph is an organism that can convert abiotic sources of energy into energy stored in organic compounds, which can be used by other organisms.
Winogradsky column showing Photoautotrophs in purple and green. Photoautotrophs are organisms that can utilize light energy from sunlight and elements (such as carbon) from inorganic compounds to produce organic materials needed to sustain their own metabolism (i.e. autotrophy).
For example, cyanobacteria and many purple sulfur bacteria can be photolithoautotrophic, using light for energy, H 2 O or sulfide as electron/hydrogen donors, and CO 2 as carbon source, whereas green non-sulfur bacteria can be photoorganoheterotrophic, using organic molecules as both electron/hydrogen donors and carbon sources.
For example, the speed with which Phormidium autumnale glides increases linearly with the incident light intensity. [174] [26] Phototactic microorganisms move according to the direction of the light within the environment, such that positively phototactic species will tend to move roughly parallel to the light and towards the light source.
Purple sulfur bacteria can be found in different ecosystems with enough sulfate and light, for example shallow lagoons polluted by sewage or deep waters of lakes, in which they could even bloom. They can also be found in microbial mats where the lower layer decomposes and sulfate reduction occurs.
Nitrifying bacteria are chemolithotrophic organisms that include species of genera such as Nitrosomonas, Nitrosococcus, Nitrobacter, Nitrospina, Nitrospira and Nitrococcus. These bacteria get their energy from the oxidation of inorganic nitrogen compounds . [ 1 ]
A lithoautotroph is an organism that derives energy from reactions of reduced compounds of mineral (inorganic) origin. [1] Two types of lithoautotrophs are distinguished by their energy source; photolithoautotrophs derive their energy from light, while chemolithoautotrophs (chemolithotrophs or chemoautotrophs) derive their energy from chemical reactions. [1]
Trichodesmium is an example of cyanobacteria that is capable of fixing nitrogen through an alternative photosynthetic pathway. [10] Other photosynthetic bacterioplankton, including purple and green bacteria, undergo anoxygenic photosynthesis in anaerobic conditions. The pigments synthesized in these organisms are sensitive to oxygen.