Small life forms are true rulers of Earth
oldest stromatolites are found in Western Australia.
Cyanobacteria are primary producers, making complex carbon molecules like proteins from carbon dioxide and water using the energy supplied by sunlight.
The process that achieves this is called photosynthesis and is way beyond the capability of human biology.
Humans are exploiters, acquiring carbon in a state suitable for making complex molecules by consuming primary producers.
Photosynthesis is an enormously complex process, much of it carried out in the world of sub-atomic particles and quantum physics. That’s not the only chemical trick cyanobacteria perform – they can also extract nitrogen from the atmosphere to make nucleic acids.
Plants and algae use cell machinery called chloroplasts to harvest sunlight for photosynthesis, but in a sign of their early evolutionary history, cyanobacteria don’t have chloroplasts. Instead they capture sunlight in structures located in the external folds of their cellular membrane. Unlike more complex life forms, cyanobacteria don’t have a cell nucleus.
When it comes to the ability to adapt to changing environments coupled with toughness, cyanobacteria are hard to beat. Different species are found in oceans, freshwater, hyper-saline water, hot springs and even living in damp rocks. They are also present in habitats at all latitudes from the Arctic tundra to rice paddies to the ice of Antarctica.
Ancestral cyanobacteria were the first photosynthetic microbes on Earth and produced a waste product that was to change the evolutionary development of life – molecular oxygen.
Initially a relatively small quantity of oxygen was produced on Earth and entered the atmosphere, but oxygen is highly reactive and was quickly removed when it reacted with rocks and minerals. Iron, the fourth most common element in the Earth’s crust, reacts with oxygen to give red iron oxide.
But when oceanic cyanobacteria began to take hold, the oxygenation of the planet really took off and this oxygen quickly poisoned any organisms present because, at that time, life was substantially adapted to surviving in oxygen-free (anaerobic) conditions.
Cyanobacteria initiated the mass extinction of most of the anaerobic life on Earth. The path was then open for the highly genetically adaptable, tough cyanobacteria to rule the planet, which they did.
Vast populations turned the oceans a blue-green colour and produced so much oxygen that all of the elements, such as iron, that could easily react with oxygen, did so. The excess oxygen was free to enter the atmosphere as oxygen gas. The huge injection of free oxygen into the atmosphere is referred to as the Great Oxygenation Event.
The free oxygen liberated life on Earth from the bottleneck imposed by having to generate energy in anaerobic conditions. The set of life-sustaining chemical reactions within a cell is called metabolism. Metabolic reactions with oxygen are 15 times more efficient than without oxygen.
The energy bonanza delivered by the availability of oxygen released by cyanobacteria allowed a huge increase in biodiversity to take place and gave a boost to evolution. About 1.8 billion years ago, the first cells with a cell nucleus appeared; 800 million years ago the first multi-celled organism, 225 million years ago the earliest dinosaurs and on until the first anatomically modern humans, about 250,000 years ago.
To this day cyanobacteria play a major role in the Earth’s ecology. For example, more than half the photosynthesis in the world’s oceans is due to the tiny marine cyanobacteria species, Prochloroccocus.
Cyanobacteria truly are the champion life form on this planet.