Alpha hemolysis (α-hemolysis): Alpha hemolysis is the incomplete lysis of the red blood cells around and under the colonies on a blood agar plate. This area appears dark and greenish. Streptococcus pneumoniae and a group of streptococci (Streptococcus viridans or viridans streptococci) found in oral flora display alpha hemolysis.

Beta hemolysis (β-hemolysis): Beta hemolysis is the complete lysis of the red blood cells around and under the colonies on a blood agar plate. This area appears transparent. Streptococcus pyogenes displays beta hemolysis and is often called Group A beta-hemolytic strep (GABHS).

Catalase test: The catalase test is used to differentiate some bacterial species. The test is done by placing a drop of hydrogen peroxide on a microscope slide. Using an applicator stick, a small portion of a colony is then added to a drop of hydrogen peroxide drop.

• If bubbles or froth forms, the organism is said to be catalase-positive.
  Staphylococci and micrococci are catalase-positive
• If no bubbles form, the organism is catalase-negative. Streptococci and Enterococci are catalase-negative

Gram stain: The Gram stain, is a laboratory staining technique that distinguishes between two groups of bacteria that have differences in the structure of their cell walls. Standard bacterial taxonomy makes a distinction between Gram-negative bacteria, which stain red/pink and the Gram-positive bacteria, which stain blue/purple. Different antimicrobial agents are directed specifically at gram-positive bacteria and gram-negative bacteria.