The main characteristic of archaebacteria and eubacteria are that they are unicellular, or single-celled. Archaebacteria are only found in hot boiling water or other types of extreme environments, while eubacteria are found all over.
Archaebacteria were found originally in Yellowstone National Park. This type of bacteria also was found under the Pacific Ocean, deep in a spot in which the molten rock and hot gases formed the interior of the Earth. They live in conditions where no oxygen is, or in highly acidic environments.
Eubacteria may be single-celled organisms, but they are complex. The majority of bacteria fall under this category. They have been placed in their own category because of their unique chemical makeup. Some of the eubacteria are beneficial, creating food such as yogurt. However, there are some which cause people to become ill, like Streptococci.