In the 60s, Lynn Margulis, an American researcher, demonstrated that ex-bacteria live inside the cells of all animals and plants. What initially seemed a daring and unrealistic idea quickly became an account of one of the most fascinating feats in the evolution of life on Earth.
Over the years, evidence has accumulated and today there seems to be little doubt that some 1,5 billion years ago, some bacteria, perhaps looking for shelter, found their ideal partner, forever changing course. of the history of life on Earth.
The most spectacular thing about this partnership is that bacteria are not just parasites exploiting their hosts. On the contrary, they are the reason for your life. Today we call them mitochondria (existing in practically all eukaryotic cells, with cellular nucleus and organelles) and chloroplasts (existing in eukaryotic cells that carry out photosynthesis).
What could have justified this union? Why would a pre-eukaryotic cell (precursor of modern cells) accept being parasitized by a bacterium? Apparently, they were mere economistic interests…
The ancestors of chloroplasts were incredibly innovative beings. As they transformed solar energy into chemical energy, they broke the water molecule, releasing oxygen into the atmosphere, which, when accumulating, contributed to the formation of the ozone layer.
At the same time, they transformed carbon dioxide (CO2), a very abundant substance on Earth, into organic compounds. Unlike CO2, which until then had little value for living beings, organic compounds were precious to many forms of life and immediately began to be used to nourish and form new cells. This sophisticated way of using light, water and CO2 to generate energy and organic compounds has given rise to a veritable explosion of life.
The ancestors of mitochondria were also revolutionary beings for their time, as they could carburete oxygen and, therefore, generate much more energy than other living beings.
On a cellular scale, success is measured by the ability to generate energy. More energy can mean greater speed of reproduction and adaptation to the medium and the possibility to develop sophisticated functions. The symbiosis of pre-eukaryotic cells with the bacteria that gave rise to mitochondria and chloroplasts allowed living beings to become larger, more complex and sophisticated, conquering new habitats.
But the contributions of microbes to energy production do not stop there. They were also key players in the formation of reserves that humanity has been exploring. Three good examples are coal, oil and natural gas.
In the first case, the digestive action of some anaerobic microbes (they live in the absence of oxygen) on the dead vegetation would have been decisive in transforming it into peat, later converted into charcoal.
Oil is also thought to have originated from the decomposition of marine living beings, promoted by microbes.
In these decomposition processes there was always the involvement of methane-producing microbes, the main constituent of natural gas. Biologically derived methane is also the main constituent of biogas, the production of which may be associated with the recovery of waste, for example in animal production or in sewage treatment.
Fuel alcohol or hydrogen are just two more examples of the use of microbes in the generation of alternative energy. Let there be imagination, which skilled microbes do not seem to be lacking.
Author Célia Manaia is a professor and researcher at the School of Biotechnology at the Catholic University of Porto
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