Staining Techniques

A bacterium is rod-shaped. What's the morphology?

bacillus

A bacterium is sphere-shaped. What's the morphology?

coccus

A bacterium is spiral-shaped. What's the morphology?

spirillum

Bacterial cells in pairs have this arrangement:

diplo

Bacterial cells in chains have this arrangement:

strepto

Bacterial cells in clusters have this arrangement:

staphylo

A basic stain has a ______________ charge.

positive

An acidic stain has a ______________ charge.

negative

What is the purpose of a simple stain?

To determine size, shape and arrangements of bacteria.

What is the chemical stain used in negative stain?

Nigrosin (India Ink)

What is the function of the capsule?

support, water storage, protection (evade host's immune system)

What is the decolorizer used in capsule staining?

copper sulfate

How does the capsule appear on a staining technique?

halos around stained cells

What is a Gram stain used for?

classify bacteria by cell wall composition

Gram-positive bacteria

Bacteria that have a thick peptidoglycan cell wall, and no outer membrane. They stain very darkly (purple) in Gram stain.

Gram-negative bacteria

Bacteria that have a thin peptidoglycan cell wall covered by an outer plasma membrane. They stain very lightly (pink) in Gram stain. Gram-negative bacteria are typically more resistant to antibiotics than Gram-positive bacteria.

What are the steps of a Gram stain?

1. primary stain - crystal violet

2. mordant - iodine

3. decolorizer - acetone-alcohol

4. counter stain - safranin

What are the results of Gram stain?

Gram positive will be purple

Gram negative will be pink

What is the function of an acid-fast stain?

To distinguish bacteria that have mycolic acid in their cell wall

Which genus of bacteria is acid-fast positive?

Mycobacterium

What is the primary stain of acid-fast staining?

carbol fuchsin

What is the decolorizer of acid-fast staining?

acid alcohol

What is the counterstain of acid-fast staining?

methylene blue

What is the purpose of the endospore stain?

to stain and visualize endospores and differentiate spore forming cells from non-spore forming cells (a differential stain)

What is the primary stain in endospore staining?

malachite green

What is the counterstain in endospore staining?

safranin