anionic, negatively charged chromophore

• acidic dyes

• basic dyes

• positive staining

• negative staining

cationic, positively charged chromophore

• acidic dyes

• basic dyes

• positive staining

• negative staining

surfaces of microbes are negatively charged and attract basic dyes

• negative staining

• positive staining

• basic dyes

• acidic dyes

microbe repels dye, the dye stains the background

• acidic dyes

• basic dyes

• positive staining

• negative staining

one stain is used; it reveals shape, size, and arrangement

reveal certain cell parts not revealed by conventional methods: capsule and flagellar stains.

use a primary stain and a counterstain to distinguish cell types or parts (examples: Gram stain, acid-fast stain, and endospore stain).

Simple or negative stain?

Simple or negative stain?

During gram staining, purple cells are

• Gram negative

• gram positive