The first two types of bacteria are archaebacteria and eubacteria. Both groups have common ancestors dating to more than 3 billion years ago. Archaebacteria live in environments where, because of the high temperature, no other life can grow. These environments include hot springs and areas of volcanic activity. They contain lipids but lack certain chemicals in their cell wall.
Eubacteria are all other bacteria.
Most of them are phototrophic, i.e. they use the sun's energy as food through the process of photosynthesis. Another classification of bacteria is according to their need of oxygen to live. Those who do require oxygen to live are considered aerobes. The bacteria who don't use oxygen to live are known as anaerobes. The shape of specific bacteria provides for the next step in the identification process.