Bacteria knowledge
The first organisms
Bacteria have been the very first organisms to live on Earth. They made their appearance 3 billion years ago in the waters of the first oceans. At first, there were only anaerobic heterotrophic bacteria (the primordial atmosphere was virtually oxygen-free). The first autotrophic bacteria, very similar to the current cyanobacteria, appeared approximately 2 billion years ago. Photosynthesis occurred in these organisms and this is how the atmosphere was enriched with precious oxygen. Cyanobacteria or blue algae made the primitive atmosphere breathable and allowed life to colonise the lands above sea level. Man has just recently become aware of the existence of bacteria because they were too small to be observed or studied before the microscope was invented.
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