Quiz 3 Flashcards
What is the importance of bacterial plate counts?
We can use this to test the quality of food, milk, and water
Why are dilutions important for bacterial cultures?
because our original sample is too concentrated. In order to reduce concentration, we will dilute the specimen (aliquot) with a diluent.
What is the valid range for bacterial plate counts?
30-300
What is CFU?
Colony forming units: a unit used to estimate the number of viable bacteria in a sample.
What is a diluent?
the fluid we use to dilute a sample
What is an aliquot?
the smaller volume we obtain from the concentrated sample
What is dilution factor?
A ratio from the initial sample to the diluted sample
What is hypertonic?
When the outside concentration is greater than the inside (cell shrivels up because water leaves)
What is hypotonic?
When the outside concentration is less than the inside
cell swells up because water enters
What is isotonic?
When the outside concentration is equal to the inside concentration of the cell
what affects bacterial growth
- osmotic pressure
- oxygen
- pH
- temperature
what is a strict aerobe?
An organism that relies on oxygen to live and grow
What is a strict anaerobe?
An organism that cannot live with oxygen (it is toxic to them)
What is a facultative anaerobe?
An organism that can live with or without oxygen (doesn’t affect them)
What is an aerotolerant anaerobe?
An organism that does not need oxygen but can use it to grow
What is a microaerophile?
An organism that can grow with low oxygen levels and higher carbon dioxide
How does thioglycollate medium work?
This medium is a differntial media that allows us to detect qnd determine an organisms ability to use oxygen. We can add resazurin which is an agent that turns pink in the presence of oxygen
What are examples of strict aerobes?
Bacillus subtilis, Mycobacterium tuberculosis, Mycobacterium leprae.
What are examples of facultative anaerobes?
Staphylococcus, Corynebacterium, Klebsiella, and Bacillus anthracis
What is an example of aerotolerant aerobes?
Clostridium sporogenes.
What is an example of a strict anaerobe?
Clostridium perfringens
What is a soluble pigment?
A pigment that diffuses into the media/agar