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19 Cards in this Set
- Front
- Back
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Why do you avoid turning the petri dish lid upside down when you remove the lid from the petri dish?
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This will keep other microbes from contaminating the media.
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Why do you incubate the plate inverted?
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This keeps water from running onto the culture and contaminating our culture.
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What is the Gram reaction of dead cells?
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The cell will appear to be gram - because the degrading cell all can not retain the primary stain and it wil appear to be red.
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Is the capsule stain a differential stain? If so, what is the decolorizing agent?
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Yes, Copper Sulfate is the decolorizing agent
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What are the 2 most obvious visual observations that indicate that you do not have a pure culture?
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1. The culture looks different than the other organisms (different morphology)
2. The culture will not be on the streak line. |
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On an isolation streak plate, what might account for differences in colony size of a pure culture?
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1. Availability of nutrients
2. Time of incubation |
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In an acid-fast stain, what color are non-acid fast organisms?
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Blue (Ziehl-Neelsen) or blue-green (Kenyon)
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What role do capsule play in the disease process?
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Capsuls protect bacteria from phagocytosis
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Are there any water wash steps in the Anthony's capsule stain?Explain?
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No, because the stain is water soluble and because some slime layers/capsules are water soluble.
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As the resolution increases does the resolution increase or decrease?
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Resolution distance decreases
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What function does the oil serve when using the oil immersion lens?
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Oil allows you to view higher resolution images in higher magnifications.
It prevents scattering of light. |
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Should the stage be lower to prevent objective lens from hitting the slide when you change to the next higher power objective? Explain?
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No you shouldn't have to move the objective because no lenses are par focal.
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Describe the structure of the cell wall of Gram + bacteria:
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Thick layer of peptidoglycan and acid. (does not have an outer cell membrane)
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Describe the structure of the cell wall of a Gram - bacteria:
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Thin layer of peptidoglycan without acids.(has an outer membrane)
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What are two examples of diseases that are caused by spore forming bacteria?
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1. Bacillus anthracis
(causes anthrax) 2. Bacillus cereus (causes 2 types of food poisoning) |
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What are 2 examples of acid-fast pathogens and what disease they cause?
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1. Micobacterium leprae
(causes leprosy) 2. Micobacterium tuberculosis (causes TB) |
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Describe 2 different bacteria that play a role in tooth decay:
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1. Streptococcus mutans-metabolize sucrose and lactic acid
2. Lactobacillus- cause existing lesions to progress. |
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Why are there no stains or decolorizing reagents containing organic solvents or heat fixing steps used in negative stains?
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To prevent shrinkage and distortion of the cells.
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What are 2 examples of diseases that are caused by bacteria with capsules?
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1. Kiebsiella pneumoniae- causes pneumonia found in the soil, water act.
2. Salmonella typhi- causes Typhoid Fever |
