The Earth, from what scientists have been able to determine, is about 4.6 billion years old. It was a volcanically active, inhospitable place. That was until around 3.6 - 2.8 billion years ago, when the first cyanobacteria (blue-green algae) evolved. Cyanobacteria were some of the first organisms capable of performing true photosynthesis: the ability to use water, carbon dioxide, and sunlight in order to produce energy for themselves. The chemical equation works like this : CO2 + H20 + sunlight = glucose and O2. In this process of photosynthesis, cyanobacteria were able to create sugars that they were in turn able to feed upon. The other biproduct of this process is our handy dandy friend, oxygen. Currently, about 21% of our atmosphere is made up of oxygen and it without cyanobacteria, this would never have been possible. They were able to take massive amounts of CO2 out of the early atmosphere and convert it into oxygen. This allowed for organisms that had once been confined to obtaining oxygen from the sea, to be able to move onto land and use the oxygen that was now present in the atmosphere. While this was indeed a slow process, it would not have been possible without cyanobacteria. However this is not the end of the story.
Cyanobacteria were also amongst the Earth's first nitrogen fixers. In layman's terms, this means that they are able to convert inorganic nitrogen (N2) into organic ammonia (NH3). To think about this a different way, the Earth's atmosphere is about 78% N2 which you and I breath in and out each day. While we need this element to allow our cells to perform the various functions they need, our bodies cannot process nitrogen in it's inorganic (N2) form. Therefore, we and all other organisms rely on nitrogen fixers to turn N2 into NH3. So again, every organism that needs oxygen to breath and nitrogen to stay alive, owes its life to cyanobacteria.
Now despite this whole making the Earth a fit place to live for us mouth breathers thing, how else have they helped us? Well there are these awesome things called photosynthetic plants (trees, grass, whatever) that would never have been able to become photosynthetic without cyanobacteria. The process of evolution is one that has become ever more complex the more we learn about the world around us and the way it developed. We are all aware of cases of symbiotic relationships, two or more organisms working together to mutually benefit the other. Fish that clean the teeth of sharks, birds that peck at rhinos, the list goes on and on. Millions of years ago, there was a relationship that involved cyanobacteria and the early ancestors of what would become photosynthetic plants. Cyanobacteria had already developed the ability to harness energy from the sun and other critters wanted to get in on the action. Some of these organisms paired with cyanobacteria and over millions of years, helped to develop what are known today as chloroplasts. Chloroplasts are the organelles (organs like your stomach or lungs but on the cellular level) where photosynthesis takes place in the cells of plants. These are basically the power plants of plants. When scientists examined the DNA of these chloroplasts, they discovered that in fact these chloroplasts shared a lot of genetic similarities to cyanobacteria. Meaning that over the course of millions of years, the mutualism that once existed between certain genuses of cyanobacteria and the ancient ancestors of plants, had developed into one organism, or organelle. This organelle, the chloroplast, is the basis of photosynthesis in plants and would not have developed without the one and only, already photosynthetic, cyanobacteria.
While this is all well and good for those damn organisms in the past, but what has cyanobacteria done for you lately? Well despite the whole providing oxygen and nitrogen for us (kind of a big deal still) and helping to develop into chloroplasts, they provide food for literally the entire world. Cyanobacteria that grow in the oceans provide food for many organisms in the oceans and today, they provide food to millions of people worldwide. The Aztecs were the first known people to cultivate cyanobacteria as a food source. They would harvest it, dry it, and use the powdered form to turn into a "flour like" substance which was than baked and consumed. Today, cyanobacteria provide food to people all over the planet and the United Nations is using it to help combat hunger across the world. This is because it is relatively easy to produce and contains many essential vitamins. Its main appeal however is that 70% of its weight is in proteins, exactly what people need to help keep them alive. It helps sick people get better and put on weight. It is literally being used to combat global hunger, check out IIMSAM, the Intergovernmental Institution for the use of Micro-algae Spirulina Against Malnutrition. As if this all weren't enough, cyanobacteria are being used in experiments to help combat AIDS, chemotherapy induced heart damage, stroke recovery, age-related declines in memory, diabetes, and in combating hay fever.
Seriously, next time you take a walk outside, breath in some of that fresh air and thank those microscopic little guys. The ones that we all owe our lives too, cyanobacteria.
Link to IIMSAM home page -http://iimsam.org/
Link to a company that produces Spirulina as a dietary supplement -http://www.spirulina.com/
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