Their fossils have been found in rocks that are about 2500 million years old. They are still with us. Indeed, blue-green algal blooms are becoming increasingly evident in Australia's rivers and lakes as human activities create conditions in which they thrive. Cyanobacteria, and bacteria in general, are prokaryotic life-forms. This simply means that their cells do not have distinct nuclei - their genetic material mixes it with the rest of the cell.
Bacteria are hardy creatures.
They can survive in hot, cold, salty, acidic and alkaline environments in which eukaryotes would perish. Yet, without them we may not be here at all. Most scientists believe that bacteria were the earliest life-forms, simple creatures that fed on carbon compounds that were accumulating in Earth's early oceans. In the harsh conditions that were present then, no other organism could have survived. Slowly, other bacteria evolved that could use the sun's energy to manufacture their own food.