staining

Staining

coloring microorganisms with a dye that empathizes certain structures

Smear

• a thin film of material containing microorganisms spread over a slide

Fixing

smear must precede staining:

Attaches microorganisms to the slide

Kills the microbes

Basic dyes

chromophore cation

Crystal violet, methylene blue, safranin

what charge do bacteria have

Bacteria have negative charges so basic, so dyes adhere to them 

what dye is used for simple staining

Crystal violet

Safrain

methylene blue

Mordant

used to hold the stain or coat the specimen to enlarge

what is simple staining used for

Use to high the cell for visual shapes and structure 

Differential stain used for

• Distinguish between bacterial/cells 

Differential stain used to detect

presence or absence of structures: special stain

endospores , flagella, capsules

what does Gram Stain do

detect bacteria in clinical specimens, Often the first step used to id bacteria, Can be used valuable for treatment, Bacteria need to young a actively growing 

Gram-positive: bacteria

• Thick peptidoglycan cells walls 

Gram-negative: bacteria

Thin peptidoglycan cell walls and an outer membrane of lipopolysaccharides and phospholipids

Acid-fast stain 

• Binds to bacteria that are waxy in their cell walls which is not decolorized acid alcohol

Acid-fast stain is used to id

Mycobacterium

Nocardia

what are the Special stain

• Capsule stain 

• Endospore stain 

• Flagella stain

Capsules

are a gelatinous cover DOES NOT ACCEPT MOST DYES 

Capsules stain process

1. India ink or nigrosin contrast the background with the capsule

2. Cells stained with simple stain 

3. Capsules appears as a halo around the bacterial cell

Endospore

are resistant, dormant structures that cannot be stained by ordinary methods  

Schaeffer-Fulton endospore stain

1) malachite green, usually

with heat to help dye penetrate the

Endospore

2)Decolorize: water

3) Counterstain: safranin

what color are the spores appear in endospore stain

green

what color are the cells appear in endospore stain

red or pink

Flagella

structures of movement

Flagella have to be stained becuase

• Too slender r and cannot be viewed with a light microscope unless stained

Flagella process

1. Flagellar stain uses a mordant and carbolfuchsin to thicken appearance of flagella, making them visible under the light microscope

2. Enables determination of the number and arrangement of flagella