Bacterial kingdoms are part of the classification scheme that fits bacteria into appropriate groupings based on certain criteria. The kingdom is the broadest classification category.

There are two kingdoms of prokaryotes. These are the bacteria (or eubacteria) and the archaebacteria (or the Archaea). The members of these two kingdoms appear similar in shape and appearance, even under the extreme magnification of the electron microscope. However, they are very different from each other in a number of molecular and biochemical aspects. It is these differences that have resulted in the microorganisms being grouped into separate kingdoms.

For example, eubacteria contain the rigid, stress-bearing network known as the peptidoglycan. The only exceptions are the bacteria from the genera Mycoplasma and Chlamydia. Archaebacteria do not contain peptidoglycan. Instead, they contain a different structure that is called pseudomurein.

Another major difference in the prokaryotic kingdoms is in the sequence of...