Bacteria are one of the most interesting microorganisms within all those that are studied from microbiology. The investigations that have these microscopic and unicellular beings as protagonists, generally have a direct impact on various areas of interest to science and all kinds of human activities, from medicine to agriculture.
If we consider the nutrition of prokaryotes, we find all the possibilities present in living beings. Not surprisingly, bacteria are the first organisms present on Earth and in the billions of years that they have evolved, they have adapted to all possible means and forms of nutrition.
Heterotrophs, most prokaryotic cells are heterotrophic. That is, they obtain their food by incorporating organic matter formed by other living beings. Of these, most are saprophytes, which means that they feed on dead organic matter and thus contribute to recycling the matter in ecosystems.
They can perform aerobic catabolisms -with the use of oxygen- and anaerobic, through fermentations, many of which are useful for our industries.
There are heterotrophic bacteria that live associated with other organisms, with mutual benefit, so they would be symbiotic. A clear example is Escherichia coli, a bacterium that lives in the human intestinal tract. Many herbivores can take advantage of cellulose thanks to the microbial flora in their digestive tubes that contain the enzyme cellulase. Another symbiosis is that of some plants with bacteria that fix atmospheric nitrogen (Rhizobium) in which the plant takes advantage of part of the nitrogen fixed by the bacteria which, in turn, takes advantage of a part of the plant's sugars.
Many others are parasites, they take advantage of the organic matter of that other living being causing it a loss; This is the case for all pathogenic bacteria that cause disease. Some pathogens (chlamydia, rickets and some mycoplasmas) have simplified their structure and can only reproduce within another cell: they are obligate parasites.
Within the exotic group of myxobacteria, a type of slippery bacteria that have the ability to aggregate several cells to form structures that allow them to migrate, they include some that are predators of other bacteria.
Bacteria feed on these resources and, as we have noted, their survival strategies are very varied. Without a doubt, they are all an example of evolutionary adaptation throughout history and they continue to be so to this day, having a fundamental role in the nature and life cycles of our planet.
