28 terms

Micro Lab Pour Plate

The pour plate differs from the streak plate in that the agar medium is inoculated while it is still liquid , but cooled to 45 degrees Celsius, and colonies develop throughout the medium, not just on the _____.
The idea is to make successive _____ of the cells and then on at least one of the poured plate colonies will be separated well enough to see them as isolated.
Move quickly; because..
If the medium ____ in the tube, remelting kills the organisms and re inoculation is required.
pure culture
grow from well isolated colony (no contaminants)
mixed culture
will show different types of colonies
pour, spread, quadrant streak
Name the three ways to isolate colonies.
1) _____ plate
2) ____ plate
3) ____ ____
serial dilutions
several dilutions of same volume in a row
quantitative dilutions
Serial dilutions AKA....
Pour plate:
Add inoculum to plate then pour agar on top and gently _____ plate.
Pour Plate:
Inoculum must be ____ culture
skill, separation
Pour Plate Advantages:
- Less ____ than streak methods
- May provide greater _____
reculturing, concentration, seen
Pour Plate Disadvantages:
1) most colonies grow below surface;
- difficult to access for _____
2) surface growth appears different than subsurface growth
3) difficult to get the right ______ of cells/plate for counting (30-300)
-Which means do multiple plates (different concentrations)
4) species with low numbers of colonies may not be _____
Exercise Protocol:
Work in groups of 2-3 to complete the procedure
Very important to follow directions and work _____
- Read protocol carefully
- Do not write directly on bottles
*label w/ tape & remove when done
plates, flame
Exercise Protocol:
- Prepare everything ahead of time
* Label everything and put inoculum in ____ before getting agar out of the water bath
- Wipe water and condensation off of agar tubes (even under lid), then ___ tube rim before pouring
* Make sure there is nothing growing in the tube
- Swirl gently to mix; leave on bench until solid
- Incubate 37°C
Pipets should only be used _____ at a time.
multiples, bench top
Pipets should NEVER:
1) Be removed in _____
2) Placed on a ____ ____ before or after use
direct method
plate count from pour plate
indirect method
count with spectrophotometry
The direct method always involves ___.
Surface growth appears different than subsurface growth
- So be sure to count ____colonies
colony forming units
CFU stands for
A measure of viable cells in which a colony represents an aggregate of cells derived from a single progenitor cell.
estimated, original
- CFU is an ____ measurement
- Correlation of number of colonies to the number of bacteria in _____ culture
average, 30, 300
Count colonies on each of duplicate plates and _____
-choose dilution w/ ___-____ colonies
Quebec colony counter
If too many colonies to easily count, use ____ ____ ___;
-Petri plate is 56cm2
-count 4 squares (1cm2)
-average the counts from 4 squares
-multiply by 56 to get total for plate (56 cm2)
-Take colony count X _____ of dilution factor for the plate that was counted
Ex. 238 colonies counted from plate with 1 ml of 10-8
238x108 CFU/ml
2.38x1010 CFU/ml
The measure of the amount of light absorbed by a suspension of bacterial cells or a solution of an organic molecule with the use of a colorimeter or spectrophotometer.
surface, subsurface
The streak plate method involves streaking the culture across a sterile agar gel surface. In the pour plate method, agar in a molten state is poured over the sample, and the plate is then inverted. The streak plate therefore produces only _____ colonies, whereas the poured plate shows those colonies AND _____colonies both on and within the agar layer.