Flashcards in Lecture 9 Deck (48):
How is growth measured for bacteria
Increase in the number of individuals
What is binary fission?
When one cell splits into two cells
How often doe binary fission happen?
Once every 20 minutes
T of F- The growth curve is not logarithmic
False, it is logarithmic
T or F- The growth curve count all cells
False, it only counts viable cells
What are the major phases of the growth curve?
1. Lag Phase
2. Log Growth Phase
3. Stationary Phase
4. Death Phase
Define the lag phase
It is the time that it takes for the organism to get used to its environment, has an increase in metabolism, and little to no cell division
Define the log growth phase
It is the point where the population actually starts doubling
When is a culture a young culture?
During the log growth phase
Define the stationary phase
Carrying capacity of the enviroment, with an equal number of cells dying as are dividing
When is a culture a mature culture?
In the stationary phase
Define the log death phase
Large number of individuals dying
When is a culture mature?
During the log death phase
What does cultural enumeration mean?
it means that you are growing out the colony
What is the CFU?
The colony forming unit, which is a single cell that will grow out into a colony
What is the name for the single cell that grows out into a colony?
The colony forming unit (CFU)
What are the direct plating methods?
1. Colony Count Plating Method
3. Membrane Filter Method
Explain the colony count plating method
A serial dilution wherein you take 1mL of sample and dilute it into 9mL of water/saline. You repeat this process until the number of colonies on a plate is between 25-250
What does TNTC mean and when is it used?
'Too numerous to count', used where there are more than 250 colonies on a plate
Why is load important?
Load is important because the higher load you have (more bacteria) the more medication you need to give to the patient
Why do we do serial dilutions?
To find out the load of the bacteria, which in turn tells us how much medication the patient needs
What is the difference between the enumeration method and the colony count plating method?
The enumeration method only takes .1mL from the flask to determine the growth factor of the colony. CCP uses 1mL
Define Membrane filter method
Used mostly for water samples that you would not expect much bacteria in. A filter membrane with small holes is placed to catch remaining bacteria
How large are the holes in the filter of the membrane filter method?
About .2um, which results in clogging with highly contaminated samples
Is the membrane filter method a direct or indirect method?
What are the indirect methods for cultural enumeration?
1. Most probable number
Describe the Most Probable Method process
Get a major sample of bacteria and place 10mL in 5 tubes, 1mL in 5 tubes, and .1mL in 5 tubes. Inside each tube is a secondary tube that will trap the gasesm allowing you to calculate the number of bacteria in the original sample
Do you count the individual colonies in the Most Probable method?
How many tubes total are used in MPN method?
15, 5 with 10mL, 5 with 1mL, and 5 with .1mL
Why do you use to many tubes in the MPN method?
To ensure accuracy
What is the MPN method most comonly used for?
used to test for coliforms, such as e.coli, in water
What test would you use to test for coliforms?
The Most Probable Number test (MPD)
Name the non-cultural enumeration methods
2. Coulter counter
1. Total volume
What are the direct noncultural enumeration methods?
2. Coulter counter
Is the MPN method direct or indirect?
Name the direct non-cultural enumeration methods
1. Total volume
Describe the cytometer count method
It is the gold standard for non-enumeration, and use you a gridded slide and count the number of bacteria that grow on it. It need to be standardized before use, and repeated if any of the count differ by 10% from other counts
Cytometer is best used for what kind of samples?
Describe the Coulter count method
A long electronic beam passes through a tube and is broken every time a bacteria passes through it. This needs to be standarized before use using the cytometer count method
What method do you use to standardize the coulter count method?
The cytometer count method
Describe the total volume method
You place the sample in a centrifuge, which results in the solids sitting at the bottom of the tube, can be done in 5 minutes, and need to be standardized using the colony count plate method
What do you use to standardize the total volume method?
The colony count plate method
What is the total volume method commonly used for?
How long does a total volume method normally take?
About 5 minutes
Describe the turbometric method
You shine a light through your sample and measure how much is absorbed. The more that is absorbed, the more bacteria there is. This needs to be standardized
You are using the turbometric method, and find that a lot of light shines through your sample. What does this mean?
It means you don't have a lot of bacteria in that sample
The the total volume method a cultural enumeration method or a noncultural enumeration method?
noncultural enumeration method