Gram Staining Flashcards

Vocabulary flashcards based on the Gram staining lecture notes.

Gram stain

A differential stain that divides bacteria into Gram positives and Gram negatives based on cell wall structure.

Differential staining

A staining process that uses more than one chemical stain to distinguish between different types of bacteria.

Gram positive bacteria

Bacteria with a thick layer of peptidoglycan in their cell wall, stain purple/dark blue in Gram staining.

Gram negative bacteria

Bacteria with a thin layer of peptidoglycan and an outer membrane of lipids, stain red/pink in Gram staining.

Peptidoglycan

A macromolecule that provides strength and complexity to the bacterial cell wall.

Crystal violet

The primary stain used in Gram staining, penetrates the cell walls of both Gram positive and Gram negative bacteria, making them appear purple

Iodine

Acts as a mordant in Gram staining, binds to the crystal violet to form a large complex.

Decolorizing alcohol

Used in Gram staining to dissolve the outer membrane of Gram-negative cells, allowing the crystal violet/iodine complexes to wash away.

Safranin

The counterstain used in Gram staining, stains all bacterial cells red, but only visible in Gram-negative bacteria.

Acid-fast staining

A differential stain that distinguishes microbes with mycolic acid in their cell walls from those without.

Mycolic acid

A component of the cell wall in acid-fast positive microbes.

Carbol fuschin

Primary staining agent in acid-fast staining, binds tightly to mycolic acid molecules.

Methylene blue

Counterstain in acid-fast staining, stains acid-fast negative organisms a blue color.