Exercise 3: Staining Methods--->Gram Stain

Differential stain detects what with how many dyes?

detects differences between organisms through the use of many dyes and reagents

An example of a differential stain is:

a gram stain

a structural stain confirms:

structural characteristics of cells

Who developed the gram stain?

Hans Christian Gram (mid 1800s)

The gram stain was initially used to differentiate what bacteria?

bacteria causing pneumonia from lung tissue in deceased patients

The gram stain differentiates bacteria into two groups. What are they?

-gram positive

-gram negative

Gram positive has a ___ layer of peptidoglycan?

thick

Gram negative has a ____ layer of peptidoglycan

thin

In gram negative, the peptidoglycan is surrounded by:

the outer membrane

What material are used for a gram stain (in order)

-crystal violet

-grams iodine

-95% ethanol

-safranin

primary dye=?; what does it stain?

primary dye; stains all cells

mordant=

grams iodine

decolorizer=

95% ethanol

secondary dye=?; what does it do/stain?

safranin; it is a counterstain, so it will stain those that are not purple after the ethanol step

What specifically in the gram method makes it a differential procedure?

the safranin dye

If you do not decolorize, all the cells would be what color?

purple (crystal violet dye)

When starting with crystal violet, you leave it on for how long? What do you use to rinse it off?

1 minute; distilled water

When using grams iodine, you leave it long for how long? What do you use to rinse it off?

1 minute; distilled water

When using ethanol, what is the process? How long do you keep on? What do you use to rinse it off?

apply ethanol onto the slide at a 45 degree angle and allow to drip for 10-12 seconds; distilled water immediately after the 10-12 seconds

When using safranin, you leave it long for how long? What do you use to rinse it off?

1 minute; distilled water

What color are gram positive cells? Gram negative?

purple= gram +

red/pink= gram -

a gram stain that produce both gram + and - is called:

a mixed gram reaction slide