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
when solidified agar becomes______
more translucent and lighter
cfu refers to a single cell and a
clump cells that serve as the founder of a colony
In triplicates use average
just know
At what concentration does a broth appear turbid?
10 to the 7 cells/mL
A spectrophotometer measures the lowered ______ of light or the increased __________
transmittance, absorbance
absorbance is directly proportional to
cell density
Are live and dead cells distiguished with spectrophotometry?
no
Turn the power knob to the _____ until the transmittance reads 0%
left
Turn the power knob to the _____ until the transmittance reads 100% absorbance is 0
right
the mark to align the cuvette is at the ______ of the holder
front
determine the undiluted cell concentration by perfoming a direct count with either the __________ counting chamber or a standard ____________
Petroff-Hausser, plate count
cell concentration is plotted on the __ axis and absorbance is plotted on the ___ axis
X,Y
Keep the cover on the cuvett cover closed when taking the reading. Extraneous light that _____ in will cause ______ results
leaks, spurious
Shake tube so that bacteria are ________ dispersed
uniformly
spectrophotometer is only an estimate including live and dead cells
just know
recalibrate spectrophotometer to avoid ______
drift
if using an analog spec read absorbance value when the needle is superimposed over it’s image in the mirror in the background
just know
if using digital spec be sure to set reading of absorbance with the mode select button
just know
