Exercise 13 - Enumeration Of Bacteria Flashcards Preview

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Flashcards in Exercise 13 - Enumeration Of Bacteria Deck (11)
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0
Q

Dilution factors of bottle B’s 1ml and .1ml plates

A

1ml = 10^4

.1ml = 10^5

1
Q

Serial dilution procedure

A

Take 1ml from the culture and transfer to bottle A

Transfer 1ml from bottle A to bottle B

Transfer .1 ml to a petri, as well as 1ml to another Petri from bottle B

Transfer 1ml from bottle B to bottle C

Transfer .1ml to a petri, as well as 1ml to another petri from bottle C

2
Q

Dilution factors of bottle A’s 1ml and .1ml plates

A

1ml = 10^6

.1ml = 10^7

3
Q

What is the correct plate to count

A

30 - 300 colonies

4
Q

Direct counting methods advantages and disadvantages

A

Advant - count only live cells (viable)

Disadvantages - requires incubation time

5
Q

Be able to calculate number of organisms per ml in original culture from the appropriate plate

A

(The # of organisms in correct plate) x 10^7

Then convert to scientific notation

Ex. 45 x 10^7 = 4.5 x 10^8 cfu/ml

6
Q

Turbidity

A

Cloudiness, measured as Optical Density OD

7
Q

Advantages and disadvantages of indirect counting method

A

Advant- quick, no incubation time

Disadvant- counts live + dead cells

8
Q

OD =

A

OD = 2-log%T

9
Q

Steps for calibrating spec 20, and measuring % transmittance

A

Set the wavelength to 686

Select transmittance mode

Zero it out

Insert calibrating cuvette

Adjust transmittance to 100%

Remove calibrating cuvette

Insert bacterial cuvette, read % transmittance

10
Q

High % transmittance =

A

Low growth