Busy. Please wait.

show password
Forgot Password?

Don't have an account?  Sign up 

Username is available taken
show password


Make sure to remember your password. If you forget it there is no way for StudyStack to send you a reset link. You would need to create a new account.

By signing up, I agree to StudyStack's Terms of Service and Privacy Policy.

Already a StudyStack user? Log In

Reset Password
Enter the associated with your account, and we'll email you a link to reset your password.

Remove ads
Don't know
remaining cards
To flip the current card, click it or press the Spacebar key.  To move the current card to one of the three colored boxes, click on the box.  You may also press the UP ARROW key to move the card to the "Know" box, the DOWN ARROW key to move the card to the "Don't know" box, or the RIGHT ARROW key to move the card to the Remaining box.  You may also click on the card displayed in any of the three boxes to bring that card back to the center.

Pass complete!

"Know" box contains:
Time elapsed:
restart all cards

Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.

  Normal Size     Small Size show me how


Micro 6.2

What are the two common methods of preserving bacterial cultures for long periods? Deep-freezing and lyophilization
What is deep-freezing? method where a pure culture of microbes is placed in suspending liquid and quick-frozen.
What's the range of temperatures for deep-freezing? -50 to -95 degrees Celsius.
After deep-freezing, how long is the microbe preserved? For several years.
What is lyophilization? Freeze-drying.
What happens during lyophilization? A suspension of microbes is quickly frozen and the water is removed by a high vacuum.
What is the temperature range for lyophilization? -54 to -72 degrees Celsius.
lyophilization: what's done to the container while the water is removed by the vacuum? The container is sealed by melting the glass with a high temperature torch.
How do the organisms remain after the deep-freezing process? After lyophilization? Deep-freezing leaves a block of ice. Lyophilization leaves organisms in a powder-like residue.
How long can the microbes be stored after lyophilization? How are they revived? Decades. Can be revived by hydration with a suitable liquid nutrient medium.
What's the definition of generation time? The length of time it takes for a cell to divide and for its populations to double. (on multiple choice as well! Answer on there is written as simply "The length of time it takes for a cell to divide")
What are the 4 DIRECT methods of measuring microbial growth Plate count, filtration, the most probable number (MPN) method, and direct microscopic count.
What does a plate count reflect? the # of viable microbes. Assumes that each bacterium grows into a single colony.
How are plate counts reported? as colony-forming units (CFU)
What are the 2 methods of doing a plate count? 1. pour plate method 2. streak plate method
What happens during filtration? bacteria are retained on the surface of a membrane filter and are then transferred to a culture medium to grow and subsequently be counted.
What is the most probably number (MPN)? What kind of microbes can it be used for? It's a statistical estimation that can be used for microbes that will grow in a liquid medium.
How are microbes counted in a direct microscopic count? the microbes in a measured volume of a bacterial suspension are counted with the use of a specially designed slide.
What are the 3 INDIRECT methods of measuring microbial growth? Turbidity, metabolic activity, dry weight.
What's used to determine turbidity? How does it work? A spectrophotometer. Measures the amount of light that passes through a suspension of cells.
What does the metabolic activity method assume? That the amount of metabolic product (like acid, or CO2) is in direct proportion to the # of bacteria present. (there's only as much poop as there are people, after all)
What do you do during the dry weight method? Extract, filter extra material, & dry it in a desiccator. Weigh.
Created by: 100001455498513