The β-hemolytic colonies are created by colonies of Streptococcus pyogenes and a zone of alpha-hemolysis is created by colonies of Streptococcus pneumoniae on blood agar.
Beta-hemolysis also called complete hemolysis, is the complete lysis of red blood cells in the surrounding and underlying medium of a colony. The area appears bright yellow and transparent. The exotoxin, streptolysin, is an enzyme produced by bacteria that causes complete lysis of red blood cells.
Alpha-hemolysis is the reduction of erythrocyte hemoglobin to methemoglobin in the medium surrounding the colony. This will turn the media green or brown. Color is synonymous with cell bruises.
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