Lab Exam 1 Flashcards
Homogenization
Cell walls of the bacteria are broken down
Purpose of EDTA
Disrupts the cell membrane
Purpose of proteinase K
Degrades the proteins
Purpose of phenol/chloroform
Denatures proteins and separates them from the DNA
Precipitation
DNA is concentrated by removing it from the aqueous layer
Purpose of sodium acetate
Neutralizes the charge of the sugar-phosphate backbone making the DNA less hydrophilic
Deproteinization
Proteins in the cells are removed
Non-fastidious bacteria
Do not require additional nutrients for growth
Fastidious bacteria
Requires CHNOPS and additional nutrients for growth
Defined media
Exact chemical composition is known
Growth of non-fastidious bacteria
Complex media
Contains sources for CHNOPS but exact composition not known
Enriched media
Contains sources of CHNOPS plus additional nutrients
Ex) Blood Agar
Differential media
Appearance of bacteria depends on their ability to us a specific substrate or produces a specific enzyme
Ex) Blood agar
Basic dyes
Have a positive charge and stain the microbial cells
Acidic dyes
Have a negative charge and stain the background
Gram positive cells stain what color?
Blue/violet
Gram negative cells stain what color?
Pink
Crystal violet dye
Basic dye; stains all bacteria blue/violet
Gram’s Iodine
Forms a complex with the crystal violet w/in the peptidoglycan of gram positive cell walls
Ethanol Stain
Decolorizer; solubilizes the outer membrane of gram negative cells and removes the crystal violet. Gram positive cells resist decolorization.
