Term
The Letal Effect of Ultraviolet
Light on Microbial Growth |
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Definition
- Medium: Tripticase Soy Agar
- UV-C is bactericidal
- Shorter the wavelength the more energy
- UV rays are commonly used to disinfect laboratory work surfaces.
Steralize vs. Dissenfect vs. Decontaminate
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Term
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Definition
- Application: Differentiate members of Enterobacteriaceae and to distinguish them from other Gram negative rods
- Medium: Phenol Red Broth (Base)
- Phenol Red - pH indicator that turns yellow below 6.8 (sugar fermentation) and magenta about 7.4 (peptones are deaminated creating NH3)
- Glucose, Xylose, Lactose
- Adjusted to 7.3 during preparation
- Durham tube to determine gas production
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Term
Methyl Red
Voges-Proskauer Test
MRVP |
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Definition
- Application: a component of IMViC battery of tests
- Used to distinguish between members of the family Enterobacteriaceae and differentiate them from other Gram-negative rods
- Medium: MRVP Broth
- Peptone (provide protein), Glucose (provides fermentable CHO), and a Phosphate Buffer
- Reagents
- Methyl Red Indicator - Red at 4.4 (mixed acid fermentation) and Yellow at 6.2 (no fermentation)
- Voges-Proskauer - Reacts with the acetoin formed during glucose fermentation and turns red. Can take up to 60 minutes to read (basic) red top layer?
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Term
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Definition
- Application: used to differentiate members of the catalase-postive Micrococcaceae from the catalase-negative Streptococcaceae.
- We add H2O2 to a sample of our bacteria for the presence of Catalase, which indicates that the organism has the carrier molecule flavoprotein and is able to bypass the next carrier in the chain.
- Positive - Bubbles
2H2O2 -----> 2H2O + O2↑ |
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Term
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Definition
- Application: Identification of oxidase-positive Neisseria. It also can be useful in differnetiating oxidase-negative Enterobacteriaceae from the oxidase-postive Pseudomonadaceae.
- Chromogenic Reducing reagent is saturated onto a solid testing media, bacterial sample is added, if cytochrome c oxidase is present the tetrmethyl-p-pheylenediamine changes purple (postive).
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