Quiz #4 Week 10 Flashcards
20/20
Purpose of this lab was to determine the number of ______ ________ in a culture or in _______, _______ or soil
viable bacteria, food, water,
The procedure preparing a standard plate count of viable bacteria in a sample comprises of ___ stages
3
First stage of standard plate count of viable bacteria is:
a. count the number of colonies embedded within and on the agar and us the number from the plate
b. mix and aliquot of dilution with melted agar that is then poured in a plate, cooled, and incubated
c. prepare a serial dilution of the sample
c. prepare a serial dilution of the sample
Second stage of standard plate count of viable bacteria is:
a. count the number of colonies embedded within and on the agar and us the number from the plate
b. prepare a serial dilution of the sample
c. mix and aliquot of dilution with melted agar that is then poured in a plate, cooled, and incubated
c. mix and aliquot of dilution with melted agar that is then poured in a plate, cooled, and incubated
Third stage of standard plate count of viable bacteria is:
a. count the number of colonies embedded within and on the agar and us the number from the plate
b. prepare a serial dilution of the sample
c. mix and aliquot of dilution with melted agar that is then poured in a plate, cooled, and incubated
a. count the number of colonies embedded within and on the agar and us the number from the plate
What concentration of NaCl was used?
0.85%
In Lammert - agar tubes are liquefied and cooled to what temperatures?
48-50C
For the 10 fold serial dilution - How many dilution tubes were used and what were the concentrations?
7, 10to the -1 to 10to the -7
In Lammert - How many plates are used and what concentrations
5, 10to the -4 to 10 to the -8
How much is transfered to make 10 to the -1 dilution tube
1.0ml or 1000microL
How long were the cultures grown at what temp?
Overnight @ 37 degrees C
What is the purpose of adding the sterile broth to the first well?
To document the baseline response of the environment-instrument-sample system
What wavelength is used for the spectrophotometer?
600nm
For the two-fold serial dilution, what are the dilution concentrations? Culture to dilution 7
Culture - 1 Dilution 1 - 1/2 Dilution 2 - 1/4 Dilution 3 - 1/8 Dilution 4 - 1/16 Dilution 5 - 1/32 Dilution 6 - 1/64 Dilution 7 - 1/128
How many wells were in the plate provided?
96
Mix the contents of the tube vigorously by rolling between your open palms - how many times?
25
Spread the melted agar over the bottom of the plate by ?
Gently swirling - avoid splashing over the edge or onto the lid
In Lammert when transferring the dilution tubes to the agar tubes what direction does the transfer take place?
10 to the -8 to 10 to the -1 - no need to change tips.
How long and at what temp are the agar plates incubated at and for?
35 degrees C and 24 hours
What plates are used to calculate the colony forming units?
> 30 to <300 CFU
What is the equation used to calculate concentration of viable cells in the sample (CFU/mL)
CFU/mL=number of colonies on plate/dilution of sample that was plated.
If 187 colonies were counted on the 10 to the -5 plate what is the concentration of viable cells?
1.9 x 10 to the 7
Why does the final value only have 2 sig figs?
The margin of error is at least 10%
make sure agar remains liquid to prevent what 2 things?
premature gelling and unwanted bacterial death
