Ex 4 gram stain
1 / 20

Ex. 4: Gram Stain - PowerPoint PPT Presentation

  • Uploaded on

Ex. 4: Gram Stain. Chromophores Basic vs. acidic dyes. Primary stain (stains all cells on slide) Decolorizing step (removes stain from certain types of cells) Counterstain (stains the decolorized cells). Differential Stain. Strongly advised:.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Ex. 4: Gram Stain' - pier

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Ex 4 gram stain
Ex. 4: Gram Stain

  • Chromophores

  • Basic vs. acidic dyes

Differential stain

Primary stain (stains all cells on slide)

Decolorizing step (removes stain from certain types of cells)

Counterstain (stains the decolorized cells)

Differential Stain

Strongly advised
Strongly advised:

When doing any of the microbiology labs, make sure to carefully follow the procedure outlined in the Materials and Methods section . . . And any advice given by your instructor!

From now on: read the labs before coming to class!

Have fun!

How to label a slide
How to label a slide

Circles on back

Other info on front

Smear preparation
Smear Preparation

From Liquid Medium

From Solid


Transfer one loopful of H2O into circle area of slide.

Using loop, suspend very small quantity of colony of interest in that drop of water and spread the suspension evenly. It should only appear slightly milky. Do NOT use too many bacteria

Air-dry and heat-fix

  • Suspend bacterial sediment in culture tube by gently tapping on it.

  • Transfer one loopful of the bacterial suspension to slide and spread out (You may exceed the limits of the circle)

  • Air-dry and heat-fix

Gram stain is
Gram Stain is ….

…the most important bacterial stain!


Memorize steps as soon as possible

Ex 4 gram stain

Gram Staining Reagents

Decolorizing agent

Primary stain



Gram stain mechanism slide from lecture
Gram Stain Mechanism(slide from lecture)

  • Crystal violet-iodine crystals form in cell.

  • Gram-positive

    • Alcohol dehydrates peptidoglycan

    • CV-I crystals do not leave

  • Gram-negative

    • Alcohol dissolves outer membrane and leaves holes in peptidoglycan.

    • CV-I washes out

Gram stain animations
Gram Stain Animations

ASM Microbe Library

YouTube presentation

MacGraw Hill Animation


Precipitated crystal violet stain may resemble cocci. Clues: dense clumping, small size of the gram-positive dots. Paucity of organisms elsewhere in the field.