![]() How could tiny cyanobacteria be the harbingers of a change of such magnitude? Among all the biochemical inventions that life could conceive, the ability of cyanobacteria to utilize water as fuel for oxygen generation must rank as one of the most ingenious. Stromatolites are large, layered structures built up by mats of cyanobacteria. ![]() More significantly, the by-product of photosynthesis happened to be oxygen. Cyanobacteria possessed the machinery to utilize water as a fuel source by oxidizing it. ![]() These microbes possessed the remarkable ability to perform photosynthesis, (i.e., they could generate energy from sunlight). Phylogenetic analyses based on 16S and 23s rRNA, genome reconstructions and fossil evidence have been used to understand the evolutionary characteristics of these early living organisms. However, around 2.7 billion years ago, a peculiar group of microbes, known as cyanobacteria, evolved. Since oxygen was projected to be absent from the earth at that time, metabolism in living organisms would have been anaerobic, involving the use of minerals present in the ocean to generate energy. Enter CyanobacteriaĪccording to the noted biochemist Leslie Orgel, who pioneered research on the origins of life, the earliest onset of life on our planet occurred around 3.8 billion years ago. That mysterious entity happened to be a microbe: Cyanobacteria. A silent, mysterious force worked to release oxygen steadily, until the very composition of the atmosphere changed. Though sunlight split the water vapor in the atmosphere into oxygen and hydrogen, the oxygen quickly reacted with methane and got locked into the earth’s crust, barely leaving any traces in the atmosphere. At that time, the earth had a reducing atmosphere, consisting of carbon dioxide, methane and water vapor, as opposed to the present-day atmosphere that consists primarily of nitrogen and oxygen. When the earth was formed around 4.5 billion years ago, it had vastly different conditions. However, oxygen was absent from the earth’s atmosphere for close to half of its lifespan. We are so acclimatized to the presence of oxygen on our planet Earth, that we take it for granted. Illustration of Cyanobacteria, Prochlorococcus spp.
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