You probably have never heard of them before, but without cyanobacteria none of us would be here. Cyanobacteria helped “fix” nitrogen into nitrates, nitrites, and ammnonia. They increased the oxygen level. High levels of oxygen eventually created an extinction event that forced organisms to adapt. The second part why Cyanobacteria are amazing is because they appear to have become chloroplasts. How can we now such things? First, they have their own DNA (and so do mitochondria). They also share many genetic and physical characteristics. This is actually what happened with mitochondria too. The oxygen we breath, the nitrogen we need, all living organisms that require oxygen would not be here if it wasn’t for cyanobacteria.
When people complain about human pollution, I like to point out that humans are neither the first not the best polluters of the planet. Cyanobacteria were so successful and invasive that they poisoned the entire planet with their own waste byproduct: oxygen, changing the composition of the entire atmosphere forever. And in doing so, virtually wiped themselves off the planet. Humans are rank amateurs in the Pollution Olympics. Please Register or Log in to view the hidden image!
When I was a biology undergraduate (in paleolithic times), 'cyanobacteria' were known as 'blue-green algae'. Of course we knew that they were prokaryotes, but we didn't classify them as bacteria. It might have been in the process of changing at that time, since we knew that they were very similar to and most closely related to bacteria, and were called 'algae' for historical rather than biological reasons. An interesting conclusion that can perhaps be drawn from their huge effects on the environment is that ecological changes aren't always bad, simply by definition. 'Ecology' isn't always about preserving things exactly the way they currently are (or were, before human beings appeared). Today 'ecology' means 'environmentalism' which often seems to veer awfully close to 'nature worship'. Like everything else in contemporary society, it's been thoroughly moralized. When cyanobacteria produced large amounts of oxygen in the ancient oceans, that radically changed the Earth's ecological environment. It led to a mass extinction event among the then-prevailing anaerobes (who no doubt would have labeled it 'bad', had they been able to think), but it opened the door to aerobic respiration. I think that when it comes to ecology there isn't really any 'good' or 'bad', there are just 'changes'. Changes might doom many species specialized for ecological niches that cease to exist, but they open up a host of new evolutionary possibilities as well. Life always seems to adapt to these things. It's one of the things that drives evolution.
