Microbiology Lab Tests: Hemolysis, Fermentation, Catalase & Coagulase

Vocabulary flashcards covering key terms from BIOL-107 Week 8 lab lecture on hemolysis, fermentation, catalase, and coagulase tests.

Hemolysis

The breakdown of red blood cells (RBCs) by bacterial enzymes on blood agar.

Hemolysins

Bacterial exotoxins that lyse red blood cells, producing hemolysis on blood agar.

Sheep Blood Agar (SBA)

Differential medium used to observe hemolysis patterns produced by bacteria.

Alpha (α) Hemolysis

Partial RBC lysis on SBA, giving a greenish discoloration around colonies.

Beta (β) Hemolysis

Complete RBC lysis on SBA, creating a clear zone surrounding bacterial growth.

Gamma (γ) Hemolysis

No RBC lysis on SBA; agar remains red and unchanged around colonies.

Phenol Red Fermentation (PRF) Broth

Broth that differentiates bacteria based on their ability to ferment specific carbohydrates and produce acid or gas.

Phenol Red Indicator

pH indicator in PRF broth that turns yellow in acid (fermentation) and fuchsia in alkaline conditions.

Durham Tube

Inverted vial placed in PRF broth to trap gas produced during carbohydrate fermentation.

Coagulase

Enzyme that causes clotting of plasma fibrin, allowing bacteria to form a protective shield from phagocytosis.

Agglutination

Visible clumping reaction indicating a positive coagulase test.

Catalase

Enzyme that decomposes hydrogen peroxide into water and oxygen, protecting bacteria from reactive oxygen species.

Hydrogen Peroxide (H₂O₂)

Substrate used in the catalase test; bubbles indicate its breakdown by catalase.

Exotoxin

Heat-labile, secreted bacterial protein (such as hemolysin) that acts on host cells at a distance.