Question

1. Explain how the type of hemolysis can be used to tell apart two species that would look the same under the microscope. Give a specific example and describe the results for each.

Answer 1

hemolysis

• Hemolysis is the destruction of the red blood cells causes the release of hemoglobin from the red blood cells to the blood plasma.

• Several specific types of bacteria produce an enzyme called hemolysin that catalyzes the breakdown of red blood cells.

• Hemolysis is in three types;

• alpha hemolysis, beta hemolysis, and gamma hemolysis.

• In alpha hemolysis, red blood cells are partially broken down

• In beta hemolysis, red blood cells are completely broken down by the bacterial enzymes.

Alpha Hemolysis

• incomplete hemolysis.
• It is catalyzed by the bacterial hemolytic enzyme called alpha-hemolysin.
• examples are  Streptococcus pneumoniae, Streptococcus mitis, Streptococcus mutans, and Streptococcus salivarius.

Blood agar medium

• When these bacteria are grown in blood agar medium, around their colonies greenish colour develops due to the incomplete destruction of red blood cells.
• The greenish colour is due to the presence of biliverdin, and this compound is a by-product of hemoglobin breakdown.

Beta Hemolysis

• complete hemolysis
• Beta hemolysis occurs due to the bacterial enzyme called beta-hemolysin.
• common species are Streptococcus pyogenes and Streptococcus agalactiae.

Blood agar medium

• When these bacteria are grown in blood agar medium, they release beta-hemolysin into the medium.
• Beta hemolysins break down the red blood cells completely.
• Hence, clear zones are produced around the bacterial colonies.
• Beta hemolysis is identified by the clear zones produced around the bacterial colonies.