Proteobacteria is a large group that contains many different styles of bacteria. There are photoautotrophs, chemoautotrophs, and heterotrophs. Photoautotrophs gain energy from the sunlight. Chemoautotrophs gain energy through chemicals. Heterotrophs feed on organic matter in other organisms. Some do not need oxygen to live, while others do. These bacteria are broken down into these groups: Alpha, Beta, Gamma, Delta, Epsilon.