What are the three types of hemolysis?

The three types of hemolysis are referred to as alpha hemolysis, beta hemolysis and gamma hemolysis, according to the American Society for Microbiology. These terms describe how red blood cells are reacting when exposed to various bacteria on blood agar plates.

Observing hemolytic reactions consists of holding the blood agar plate up to a source of light, explains the ASM. In alpha hemolysis, the cell wall remains intact, and a brown or green discoloring forms around the colony. In beta hemolysis, a true or complete lysis occurs, and a transparent zone surrounds the colony. Gamma hemolysis indicates a lack of hemolysis, and as such, there is no reaction in the medium.