Test 1-Quiz 4 Flashcards
Purpose of the gram stain
differential procedure, uses 2 basic dyes and a decolorization step to differentiate between 2 classes of bacteria based on their cell wall composition
Gram positive bacteria
- cell wall
- color when stained
- diseases caused
- thick layer of peptidoglycan
- Purple due to crystal violet
- scarlet fever, pneumonia, gas gangrene
Gram negative bacteria
- cell wall
- color when stained
- diseases caused
- thin layer of peptidoglycan
- pink due to Safranin
- dysentry, typhoid fever, bubonic plague
Basic Dye primary stain
Crystal Violet
Mordant
Gram’s Iodine
Decolorizing Agent
95% Ethanol or H20 (endospore stain)
Counterstain (secondary stain)
Safranin O
Crystal Violet soaks into the cell wall of
any bacteria present, gram positive or negative
Gram’s Iodine is a ____ that ____ the dye to the cells
mordant, fixes
95% Ethanol is used to
rinse the Gram’s Iodine off the slide.
The gram ____ are decolorized due to the dissolution of the lipid layer in the cell wall and the thinner layer of peptidoglycan
negative
The final process after the gram negative bacteria has been decolorized is to apply the secondary stain _______, which will cause that bacteria to turn pink
Safranin O
The ___ is a differential staining technique used to detect the presence and location of spores in bacterial cells
endospore
Characteristics of endospores (3)
- one cell can make one spore
- Resistant to heat, chemicals, radiation
- do not take up conventional dyes
Purpose of the endospore
increases chance for survival
Bacteria that produce endospores
Bacillus-anthrax
Clostridium-Tetanus, Botulism, Gas Gangrene
_____ is a differential stain used to detect cells that are capable of retaining a primary stain when treated with acid alcohol.
Acid-Fast
The main acid-fast organisms are members of the genus ______
Mycobacterium
Characteristics of Mycobacterium (3)
- cell wall contains mycolic acid (waxy lipid) that causes bacterium to resist staining
- heat drives stain into cell walls and makes it resistant to decolorization
- leprosy and tuberculosis
T or F: Mycobacterium produces endospores
False
What is the primary stain used during the gram stain
Crystal Violet
Microscope slides must be steamed over boiling water during which staining procedures
Acid Fast and Spore stains
What genus is detected by performing acid-fast stain
Mycobacterium
Gram negative is ___ and gram positive is ___
pink, purple
