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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 |
Created by:
xokitty17xo
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