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micro lab 3

exercise 2/3

QuestionAnswer
you stain/ dye to make bacteria more visible
positive stains specimen
negative stains background
simple staining is 1 stain
differential staining is 2 or more stains
we use gram stain so that we can distinguish between 2 different groups of bacteria
color retention is directly related to the cell wall
positive is purple
negative is pink
give 2 reasons why a slide must be heat fixed kill organism fix organism to slide
what would happen if no heat fixing were done organism would move, no clear structures, wash away during staining process
why would an inoculating loop be used to prepare a smear from broth? to hold microbes
why would an inoculating wire be used with solidgar? to retrieve colonies
E. coli is pink- negative
S. epidermidis is purple- positive
B. subtilis is purple- positive
Primary stain crystal violet- stains bacteria cell wall
mordant stain iodine- forms large complex with crystal violet and remains trapped
decolorization removes traces of primary stain and mordant. resolves all lipids on outter membrane
counterstain safarfance- to revel/ show if its positive/ negative. show detail
how would the age of the culture affect gram staining? could give false negative results
how could the thickness of a smear affect gram staining? unable to distinguish bacterial structures (clumping)
what advantage does a gram stain have over a simple stain? GS- can distinguish whether negative or positive Simple- only one color
what is the most critical step in the outcome of the gram stain? decolorizer
Chemical Gram-Positive Gram negative Chart Chemical Gram-Positive Gram- Negative Crystal purple purple Iodine purple purple Decolorizer purple clear Safarfance purple pink
Spores are formed by some genera of bacteria as a survival mechanism
for spores you use a _____ to penetrate the spore, ____ is a counterstain fir the vegetative portion of the cell. malachite green, safranin
the capsule is an external covering on some bacteria
Flagella are external structures that provide motility to some bacteria
do bacterial endospores stain using the gram stain yes but not easily
Name the 2 stains used in a sport stain 1. malachite green 2. safranin
Why are 2 stains used in a spore stain? 1. one penetrates the bacteria 2. safranin as counterstain
why are capsules difficult to stain? polysaccharide and/or protein repels stain
what type of stain is used to demonstrate capsules? nigrosin or congo red
why is a mordant used in flagella staining? increases diameter of flagella
what is a negative or acid stain? stain the background
Created by: xokitty17xo