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micro lab 3
exercise 2/3
Question | Answer |
---|---|
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 |