Microbiology Lab Tests Review

Flashcards for microbiology lab tests, including media, metabolic activity, key ingredients, and interpretation of results.

Gram Stain

Differentiates bacteria based on cell wall structure using crystal violet, iodine, alcohol, and safranin; purple cells are Gram-positive, pink/red cells are Gram-negative.

Catalase Test

Tests for the presence of the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen; bubbles indicate a positive result.

Oxidase Test

Tests for the presence of cytochrome c oxidase using oxidase reagent; purple color indicates a positive result.

Dextrose (Glucose) Fermentation

Tests for the ability to ferment glucose using Phenol Red Broth with glucose; yellow broth indicates fermentation (acid production), gas may also be present.

Lactose Fermentation

Tests for the ability to ferment lactose using Phenol Red Broth with lactose; yellow broth indicates fermentation (acid production), gas may also be present.

Mannitol Fermentation

Tests for the ability to ferment mannitol using Phenol Red Broth with mannitol; yellow broth indicates fermentation (acid production), gas may also be present.

Methyl Red Test

Tests for mixed acid fermentation using MR-VP Broth and methyl red; red color indicates a positive result (acidic pH).

Voges-Proskauer Test

Tests for the production of acetoin from fermentation using MR-VP Broth and Barritt’s Reagents; red color indicates a positive result (acetoin produced).

Hydrogen Sulfide (H2S) Production

Tests for the ability to reduce sulfur using SIM Agar or TSI Agar; black precipitate indicates H2S production (positive).

Citrate Utilization

Tests for the ability to use citrate as a carbon source using Citrate Agar; blue color indicates citrate utilized (positive).

Litmus Milk Test

Tests for lactose fermentation, litmus reduction, and acid/gas production using Litmus Milk Agar; pink=acid, blue=alkaline, white=reduction, curdling=coagulation, gas bubble=gas production.

Starch Hydrolysis

Tests for the ability to break down starch using Starch Agar Plate and iodine; a clear zone around growth indicates starch hydrolysis (positive).

Phenylethyl Alcohol (PEA) Agar

Selective medium that inhibits Gram-negative bacteria using PEA Agar; growth indicates Gram-positive bacteria.

Mannitol Salt Agar (MSA)

Selective and differential medium testing mannitol fermentation and salt tolerance using MSA Agar; yellow agar indicates mannitol fermentation, growth indicates salt tolerance.

MacConkey's Agar

Selective and differential medium testing lactose fermentation and bile salt tolerance using MacConkey Agar; pink colonies indicate lactose fermentation, growth indicates bile salt tolerance.

Dichotomous Key

Tool to identify bacteria based on test results, using a series of yes/no questions to narrow down possibilities.

ELISA Test - Sample

Contains the target molecule (antigen or antibody) for detection.

ELISA Test - Primary Antibody

Specifically binds to the target molecule in the sample.

ELISA Test - Secondary Antibody

Binds to the primary antibody and is linked to an enzyme for detection.

ELISA Test - Enzyme Substrate

Reacts with the enzyme linked to the secondary antibody, producing a color change or signal.

ELISA Test - Wash Buffer

Removes unbound antibodies or proteins, preventing false results.

ELISA Test - Positive Result

Color change or detectable signal indicates the presence of the target antigen or antibody.

ELISA Test - Negative Result

No color change indicates the absence of the target antigen or antibody.