Lab 4 Quiz Microbiology

Primary Stain

imparts color to all cells

Mordant

Intensifies color of primary stain

Decolorizing agent

may remove primary stain or from certain cell structures based on the chemical composition of the components

Counterstain

Contrasting color to the primary stain. Any cells or structures that were de-stained will appear the color of the counterstain

Who discovered that certain stains were retained by some bacterial cells, but removed from others?

Hans Christian Gram

How is gram staining valuable?

It is a diagnostic tool for identifying and categorizing bacteria.

Differential Stain

cells or structures within cells display dissimilar staining reactions that can be distinguished by different dyes

What does gram stain differentiate?

Between gram-positive and gram negative

What dye does gram-positive retain?

purple dye

What dye does gram-negative retain?

They are decolorized and counterstained with a red dye

What is the primary stain?

crystal violet

What does gram’s iodine form when added to the smear?

forms an insoluble complex with crystal violet in Gm+ cells

What does decolorization remove?

Removes purple stain from Gm- cells but not Gm+

What is applied as a counterstain?

Safranin, which colors Gm- cells red/pink

What 3 gram stains were performed?

E.coli, S. aureus, and a mixture of the two bacteria

What does E.Coli stain as?

red or pink

What does S. aureus stain as?

purple