Bacteria are classified into two kingdoms: Eubacteria and Archaebacteria.

Eubacteria are your more common bacteria that live all around us and at times can make us sick.These are your typical "bug" that you may take antibiotics for; such as Strep Throat (streptococcus pharyngitis) or a skin infection (Staphylococcus aureus).

Archaebacteria are the extremists of bacteria. They live in extreme conditions. Some live in places such as the Dead Sea where it has a high salinity concentration(halophiles) and no other organisms can survive. Others live in thermal vents in the oceans or hot springs--love extreme heat(thermophiles). Acidophiles live in environments where the pH can be below 2 like in the acid mud pods of Yellowstone National Park.

Below is a diagram of a typical prokaryotic cell.