Eubacteria fall into four primary categories, which are gram-positive eubacteria, proteobacteria, cyanobacteria and spirochetes. Eubacteria are much more common than archaebacteria, which are closely related members of the prokaryote division. Eubacteria live in many areas around the world, including some of the most extreme and inhospitable environments.
Many eubacteria are distinguishable only at the most complex cellular level. Gram-positive eubacteria are identified and classified based on a technique called gram staining. This method involves detecting the volume of peptidoglycan that exists in the cell walls of these organisms. If this substance is present, special dyes refer that information back to researchers, who can then classify the organism as gram-positive. These bacteria are malicious but not deadly. In humans, they cause illnesses such as strep throat and respiratory infections. Proteobacteria include the most prevalent and active eubacteria. One type of proteobacteria is the enteric bacteria, which includes the species E. coli. This bacterial group includes organisms that fix nitrogen by converting the gas into substances then used to create amino acids and nucleic acids. Cyanobacteria include organisms that produce oxygen and undergo the task of photosynthesis. These bacteria are commonly referred to as blue-green algae, and they appear in lakes, streams and other bodies of water. Lastly, spirochetes are spiral-shaped eubacteria that exist in aerobic and anaerobic forms.