ABSTRACT
Prokaryotes can be classified by relation to oxygen and generation of biological energy. The periodic table of prokaryotic evolution and classification was proposed to clarify the physiological and evolutionary connections between the microbial groups, and to give a logical basis on which students can understand microbial diversity. The three major types of biological energy generation are the results of the evolution of Earth’s atmosphere from an anaerobic to an aerobic one. Therefore, microbial physiological diversity can be shown as being created in three evolutionary periods that are related to the origin and existence of fermenting, anaerobically respiring, and aerobically respiring groups of microorganisms. These groups exist in all three parallel phylogenetic lines: (1) organisms of aquatic origin; (2) organisms of terrestrial origin; (3) organisms originated from extreme, isolated environments. Prokaryotes of aquatic, terrestrial, and extreme environments are in the following lines: (1) Gram-negative bacteria (Gracilicutes), cells with thin walls that originated from environments with stable osmotic pressure (water, tissues of macroorganisms); (2) Gram-positive bacteria (Firmicutes), cells with a rigid cell wall that originated from environments with changeable osmotic pressure (soil); (3) Archaea (Mendosicutes), cells without the conventional peptidoglycan that originated from environments with some extreme conditions, usually high temperature or negative oxidation–reduction potential. A quiz bank is added to this chapter.
