Biological carbon fixation
[2] Understanding biological carbon fixation is essential for comprehending ecosystem dynamics, climate regulation, and the sustainability of life on Earth.
It is estimated that approximately 250 billion tons of carbon dioxide are converted by photosynthesis annually.
The gross amount of carbon dioxide fixed is much larger since approximately 40% is consumed by respiration following photosynthesis.
[6][7] Historically, it is estimated that approximately 2×1011 billion tons of carbon has been fixed since the origin of life.
The organisms the Calvin cycle is found in are plants, algae, cyanobacteria, aerobic proteobacteria, and purple bacteria.
Consuming adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADPH), the Calvin cycle in plants accounts for the predominance of carbon fixation on land.
It was discovered by Evans, Buchanan and Arnon in 1966 working with the photosynthetic green sulfur bacterium Chlorobium limicola.
[16] The key steps of the reverse Krebs cycle are: This pathway is cyclic due to the regeneration of the oxaloacetate.
The Carbon Monoxide Dehydrogenase/Acetyl-CoA Synthase is the oxygen-sensitive enzyme that permits the reduction of CO2 to CO and the synthesis of acetyl-CoA in several reactions.
This key enzyme is also the catalyst for the formation of acetyl-CoA starting from the products of the previous reactions, the methyl and the carbonyl residues.
[25] An important characteristic of this cycle is that it allows the co-assimilation of numerous compounds, making it suitable for the mixotrophic organisms.
[25] A variant of the 3-hydroxypropionate cycle was found to operate in the aerobic extreme thermoacidophile archaeon Metallosphaera sedula.
In addition to photosynthetic and chemosynthetic processes, biological carbon fixation occurs in soil through the activity of microorganisms, such as bacteria and fungi.
[3] In soil environments, organic matter derived from dead plant and animal material undergoes decomposition, a process carried out by a diverse community of microorganisms.
Bacteria and fungi assimilate carbon from decomposed organic matter into their cellular structures as they grow and reproduce.
[35] These substances help bind together soil particles,[36] forming aggregates that protect organic carbon from microbial decomposition and physical erosion.
The sequestration of carbon in soil not only helps mitigate the accumulation of atmospheric CO2 and mitigate climate change but also enhances soil fertility, water retention, and nutrient cycling, thereby supporting plant growth and ecosystem productivity.
Biological carbon fixation is a fundamental process that sustains life on Earth by regulating atmospheric CO2 levels, supporting the growth of plants and other photosynthetic organisms, and maintaining ecological balance.
