The long story of the algae – Part 1

Algae are known by most people just as a gelatinous covering on the damp stairs of a cellar, or as “floating mucilage” in the pond of the garden. On the contrary, the fact we don’t recognize them as single algae but rather as a mass just depends on the tiny dimensions. By observing them under a microscope is it possible to recognize very aesthetic architectural shapes with a really evident realization project. Many would be surprised to discover the nice shapes they realize. An equal interest is raised by the scientifically recognized definition of the algae, since they are called “oxidative-photosynthetic organisms without embryo”. An embryo is only found among the mosses, which develop from the egg cells fertilized on the mother plant. The product obtained by the photosynthesis of the algae is oxygen, as opposed to the sulfur metabolism, which represents the oldest earthly story of metabolism form and nowadays is only exploited by the anaerobic bacteria. As an example of this circumstance reference can be made to the hydrothermal springs that reach temperatures up to 350°C, founded at depths up to 3.600 meters in the Atlantic Ocean. The original atmosphere, after the cooling, had such a mortal composition for the present organisms, as it only contained oxygen traces; at its place, instead, there was a carbon dioxide content of around ten percent. When life developed on earth, unknown predecessors gave birth to the first bacteria, which were able to live in these anaerobic conditions. These organisms oxidized the sulfur thus obtaining energy. At that time life exclusively fed on energies, which in the true sense of the word could be considered as the “primords”.

The calcareous alga Peysonnelia squammaria forms red-brown encrustations.

The calcareous alga Peysonnelia squammaria forms red-brown encrustations.

A new form of metabolism was generated: the photosynthesis

At a certain point there was a development of bacteria capable of exploiting even the “non-earthly” energy. According to the current knowledge, the primordial atmosphere contained around seven percent of hydrogen sulphide, and it is supposed that these bacteria were able to break down this compound with the help of the solar energy and to use the obtained hydrogen for their metabolism. A following step was the water dissociation that provided more energy. The photosynthesis, as well as it exists nowadays in every plant, was generated. The bacteria used the increasingly available hydrogen together with the abundant carbon dioxide, synthesizing the sugars with which the solar energy could be stored. The oxygen was released as a waste product, which in turn could be reused to burn sugars. Initially, however, this was only possible in a very slow way, since the oxygen was available in extremely small quantities. The greatest profit, at that time, consisted in the fermentation, which equally released energy, even though in the same but minimized way. This constituted an advantage for those bacteria that were able to carry out the photosynthesis, compared to all the others, and therefore a great breeding potential. What is particularly interesting is that these photosynthesizing bacteria, still today, live even in our marine aquaria. They are defined as cyanobacteria or blue algae, and their quite rapid breeding capacity is well known by the marine aquarist. As a consequence of the strong occupation of the planet by these photosynthesizing blue algae, there was the first significant supply of oxygen to the hearth’s atmosphere. A huge part of the biomass of that time, however, sank through the sedimentation in the depths of the Oceans, thus ending in anaerobic (low-oxygen) areas, where an oxidative degradation was no longer possible. Therefore part of the oxygen produced could not be consumed, slowly leading to the creation of an atmosphere containing oxygen, which promoted the further evolution and development of the species.

Part 2 Follows