Quiz #4 Week 10

Question 1

Purpose of this lab was to determine the number of ______ ________ in a culture or in _______, _______ or soil

Answer 1

viable bacteria, food, water,

Question 2

The procedure preparing a standard plate count of viable bacteria in a sample comprises of ___ stages

Answer 2

3

Question 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

Answer 3

c. prepare a serial dilution of the sample

Question 4

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

Answer 4

c. mix and aliquot of dilution with melted agar that is then poured in a plate, cooled, and incubated

Question 5

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

Answer 5

a. count the number of colonies embedded within and on the agar and us the number from the plate

Question 6

What concentration of NaCl was used?

Answer 6

0.85%

Question 7

In Lammert - agar tubes are liquefied and cooled to what temperatures?

Answer 7

48-50C

Question 8

For the 10 fold serial dilution - How many dilution tubes were used and what were the concentrations?

Answer 8

7, 10to the -1 to 10to the -7

Question 9

In Lammert - How many plates are used and what concentrations

Answer 9

5, 10to the -4 to 10 to the -8

Question 10

How much is transfered to make 10 to the -1 dilution tube

Answer 10

1.0ml or 1000microL

Question 11

How long were the cultures grown at what temp?

Answer 11

Overnight @ 37 degrees C

Question 12

What is the purpose of adding the sterile broth to the first well?

Answer 12

To document the baseline response of the environment-instrument-sample system

Question 13

What wavelength is used for the spectrophotometer?

Answer 13

600nm

Question 14

For the two-fold serial dilution, what are the dilution concentrations? Culture to dilution 7

Answer 14

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

Question 15

How many wells were in the plate provided?

Answer 15

96

Question 16

Mix the contents of the tube vigorously by rolling between your open palms - how many times?

Answer 16

25

Question 17

Spread the melted agar over the bottom of the plate by ?

Answer 17

Gently swirling - avoid splashing over the edge or onto the lid

Question 18

In Lammert when transferring the dilution tubes to the agar tubes what direction does the transfer take place?

Answer 18

10 to the -8 to 10 to the -1 - no need to change tips.

Question 19

How long and at what temp are the agar plates incubated at and for?

Answer 19

35 degrees C and 24 hours

Question 20

What plates are used to calculate the colony forming units?

Answer 20

> 30 to <300 CFU

Question 21

What is the equation used to calculate concentration of viable cells in the sample (CFU/mL)

Answer 21

CFU/mL=number of colonies on plate/dilution of sample that was plated.

Question 22

If 187 colonies were counted on the 10 to the -5 plate what is the concentration of viable cells?

Answer 22

1.9 x 10 to the 7

Question 23

Why does the final value only have 2 sig figs?

Answer 23

The margin of error is at least 10%

Question 24

make sure agar remains liquid to prevent what 2 things?

Answer 24

premature gelling and unwanted bacterial death

Question 25

when solidified agar becomes______

Answer 25

more translucent and lighter

Question 26

cfu refers to a single cell and a

Answer 26

clump cells that serve as the founder of a colony

Question 27

In triplicates use average

Answer 27

just know

Question 28

At what concentration does a broth appear turbid?

Answer 28

10 to the 7 cells/mL

Question 29

A spectrophotometer measures the lowered ______ of light or the increased __________

Answer 29

transmittance, absorbance

Question 30

absorbance is directly proportional to

Answer 30

cell density

Question 31

Are live and dead cells distiguished with spectrophotometry?

Answer 31

no

Question 32

Turn the power knob to the _____ until the transmittance reads 0%

Answer 32

left

Question 33

Turn the power knob to the _____ until the transmittance reads 100% absorbance is 0

Answer 33

right

Question 34

the mark to align the cuvette is at the ______ of the holder

Answer 34

front

Question 35

determine the undiluted cell concentration by perfoming a direct count with either the __________ counting chamber or a standard ____________

Answer 35

Petroff-Hausser, plate count

Question 36

cell concentration is plotted on the __ axis and absorbance is plotted on the ___ axis

Answer 36

X,Y

Question 37

Keep the cover on the cuvett cover closed when taking the reading. Extraneous light that _____ in will cause ______ results

Answer 37

leaks, spurious

Question 38

Shake tube so that bacteria are ________ dispersed

Answer 38

uniformly

Question 39

spectrophotometer is only an estimate including live and dead cells

Answer 39

just know

Question 40

recalibrate spectrophotometer to avoid ______

Answer 40

drift

Question 41

if using an analog spec read absorbance value when the needle is superimposed over it’s image in the mirror in the background

Answer 41

just know

Question 42

if using digital spec be sure to set reading of absorbance with the mode select button

Answer 42

just know