Lab 4, pt. 2: Differential Stains II

Gram Staining, Endospore Staining, Acid Fast Staining

What is the point of differential stains?

To identify a specific property of certain cells in a complex sample

What is gram staining?

differential staining technique that provides an easy differentiation of bacteria into one of two groups

Name some characteristics in **gram-positive cell walls**

* **Thick** peptidoglycan
* 90% peptidoglycan
* teichoic acids
* 1 layer
* not many polysaccharides

Name some characteristics in **gram-negative cell walls**

* **Thin** peptidoglycan
* 5-10% peptidoglycan
* No teichoic acids
* 3 layers
* Outer membrane has lipids, polysaccharides

What does ethanol do in the gram-staining procedure?

Removes stain from **Gram Negatives** but not **Gram Positives**

What are the 4 conditions to be followed for a Gram staining procedure?

* young cultures (18-24hrs old)
* thin smear
* fresh reagents (of proper strength)
* control cultures

Gram stained slides of…

Neisseria

Gram stained slides of…

Streptococcus

Gram stained slides of…

Pseudomona

What kind of staining is this?

Endospore staining

What is an **endospore**? What do they germinate into?

* Dormant and highly resistant cell which contains a copy of the cellular DNA
* Endospores germinate into **vegetative cells** when nutrients are around

What kind of stain is this?

* Acid-fast Stain
* Mycobacteria

Name some characteristics of the acid-fast bacterial cell wall

* Thick cell walls
* 60% lipids - little peptidoglycan
* Doesn’t stain well

What bacteria is used for acid-fast stains?

Mycobacterium

What kind of colonies are these?

Mycobacterium tuberculosis colonies

What example of acid-fast staining is this?

Mycobacterium tuberculosis

What example of acid-fast staining is this?

Mycobacterium leprae

What example of acid-fast staining is this?

Mycobacterium marinum

What colors do spores stain?

Green

What color does vegetative cells stain?

Red/pink