Image: Dr Roberto Anitori
Cyanobacteria: The mothers of our atmosphere?
Cyanobacteria are a versatile, usually single-celled, organisms that are highly conserved – meaning throughout their billions of years of existence on Earth, they have not changed much. They have a significant role in splitting water molecules and releasing oxygen during photosynthesis long before plants and trees evolved to continue that process.
Cyanbacteria are otherwise known as ‘blue-green algae’ but it is now known cyanobacteria are prokaryotes and belong in the bacteria kingdom of the tree of life.
They are probably one of the best known and easily recognisable bacteria on the planet, with a history that stretches back at least 2.8 billion years, and probably longer. They grow in a wide range of habitats from the sea and freshwater to bare rocks and the soil.
They are autotrophic, which means they manufactures their own food as opposed to hetrotrophrophic where the organism eats other organisms or carbon-bearing molecules for survival. They need sunlight and carbon dioxide to grow.The process continues to be the dominant form of taking carbon dioxide out of the atmosphere and replacing it with oxygen.
Unlike many bacteria they have no flagella (whip like tail) for locomotion, but some can readily slide from place to place.
One of the things they do well is to form mats with other microbes, and these mats trap and precipitate sediment, eventually becoming rock.
Because plants, animals and algae have invaded virtually every viable niche, cyanobacteria are more readily found where eukaryotes do not thrive – in extreme environments like hypersaline, acid and alkaline lakes, dry desert crusts, bare Antarctic rocks, and hot springs.
It is not known whether cyanobacteria were part of the microbial mat-making communities that seem to have been present to build the 3.5 billion year old stromatolite structures, though it is often suggested. There is no evidence of cyanobacterial microfossils within or associated with stromatolites in the early Archaean. However, they played a major part in ancient stromatolites at 2.8 billion years old and younger, and still do today in modern environments.
See the Stromatolite Explorer for an animated movie that explores the construction of modern day microbial mats.