Examples of Autotrophs

The following are some of the examples of autotrophs;

a. Green plants

• Green plants are the most important example of autotrophs as they are responsible for almost all the biomass on the planet.
• Green plants are photoautotrophs that capture solar energy in order to reduce carbon dioxide into glucose.
• Green plants contain chlorophyll in their cells which are the photosynthetic center of these organisms. The chlorophyll captures rays of different wavelengths and uses the energy to move electrons to the water molecule.
• These plants are called producers, and these provide food to other plants as well as heterotrophs. These from the primary trophic level in the food chain.
• The food is prepared in the green parts of the plant, which is then transferred to other parts via plant tissues.
• Green plants are found in most ecosystems where these are the primary source of food and energy for all other living organisms.

b. Green Sulfur Bacteria

• Green sulfur bacteria are microorganisms that are strictly anaerobic, photoautotrophs that assemble carbon compounds by utilizing sulfur compounds as electron donors.
• The photosynthetic center of these bacteria is similar in structure and function to the photosystem of plants and cyanobacteria.
• The light-induced electron transfer in green sulfur bacteria is non-cyclic which results in the generation of NADPH.
• The green sulfur bacteria live in sulfur-rich environments with low-light intensities. In order to capture enough light, these have an extensive antenna system so as to capture all available photons.
• Unlike photosynthesis in green plants, photosynthesis in green sulfur bacteria doesn’t produce oxygen.

c. Methanogens

• Methanogens are a group of bacteria that produce methane and other organic compounds by utilizing the electrons found in hydrogen gas.
• These bacteria occur in underground areas like the bottom of the sea, deep-sea trenches, and vents where they produce large bubbles of methane gas.
• Most methanogens utilize acetate as the primary carbon source, resulting in the production of acetyl-CoA during autotrophic CO₂ fixation.
• The process of production of methane by these bacteria is known as methanogenesis, and the process is driven by energy obtained via different chemical reactions.
• The biological production of methane is not as effective as the industrial processes; however, the methane produced by these organisms has a higher tolerance against impurities.
• Some of the examples of methanogenic bacteria include Methanococcales, Methanobacteriales, Methanosarcina, etc.

d. Nitrogen-fixing bacteria

• Nitrogen-fixing bacteria are a group of bacteria that are involved in the conversion of molecular nitrogen into the organic form. The organic form of nitrogen can then be taken up by plants as a nutrient.
• These bacteria are chemoautotrophic bacteria that utilize the energy obtained from the chemical reaction for the transfer of electrons from the donor to the receiver.
• The molecular nitrogen in the environment is converted to nitrate by these bacteria, which is then taken by plants for the production of amino acids.
• Nitrogen fixation is an important process in the nitrogen cycle as well as in plants as plants depend on the process for their need for nitrogen.
• Some of these bacteria occur in a symbiotic relationship with different plants, which enables the transformation of unusable inorganic nitrogen into the usable organic form.
• Some examples of nitrogen-fixing bacteria include Azotobacterium, Azospirillum, Rhizobium, etc.