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Bacte Lab (Finals > Water microbiology Part 2 > Flashcards

Water microbiology Part 2 Flashcards

1
Q

Heterotrophic plate count is formerly known as?

A

Standard plate count

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2
Q

A procedure for estimating the number of LIVE heterotrophic bacteria

A

Heterotrophic plate count

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3
Q

What is the unit for heterotrophic plate count?

A

Colony forming Units (CFU)

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4
Q

Causes no heat shock
Colonies are ON the agar (Easy transfer and distinguish)

A

Spread Plate method

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5
Q

What is the amount of sample for Spread plate method?

A

0.1 - 0.5 mL

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6
Q

Simple to perform
Colonies are small and compact
Less tendency to encroach

Slow grower and difficult to transfer
Thermostatically controlled water bath (Heat shock)

A

Pour plate

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7
Q

What is the amount of sample can be use in pour plate?

A

0.1 - 2mL

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8
Q

No heat shock

Expensive (Filter and vacuum pump)
Small display area
Possible damage to cells due to vacuum

A

Membrane filtration technique

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9
Q

What is the amount of sample for Membrane filtration technique?

A

100mL

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10
Q

Size of pore in filtration?

A

0.2 or 0.4 mm

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11
Q

Procedure for HPC spread plate?

A
  1. Label Plates
  2. Mixed the bottle (Invert)
  3. aseptic
  4. Transfer by using serological pipette (0.1mL)
  5. Place it on the middle
  6. Spread using glass spreader or metal spreader
    6.1. Aseptic by putting it on ethanol and flame it
  7. Spread it evenly
  8. w8 15 mins to dry out
  9. invert it for incubation
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12
Q

Procedure for HPC pour plate

A
  1. Label
  2. Mix water sample
  3. Aseptic the bottle
  4. Transfer 1 mL on empty petri dish
  5. Add molten plate count agar
  6. Swirl it to mix and let the cover open
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13
Q

What is the temp for molten agar?

A

44 -46C

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14
Q

For pour plate what is the first thing to do?

A

Prepare dilution water

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15
Q

What is the water used in dilution water?

A

Buffered water / Peptone water

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16
Q

How to prepare Stock phosphate buffer solution?

A

Dissolve 34g potassium dihydrogen phosphate in 500mL reagent grade water (Deionized water)

pH 7.2 +- 0.5 with 1N sodium hydroxide

Dilute to 1L with reagent grade water

17
Q

2nd steps on creating dilution water?

A

1.25 mL Phosphate buffer solution
+
5.0 mL of Magnesium chloride (81.1g / L)
+
Dilute it till 1L using reagent grade water

18
Q

How to prepare peptone water?

A

10% solution = 10g / 100mL
0.1% solution = 1g / 1000mL

Final pH: 6.8

19
Q

How many minutes can bacteria die that is suspended in a dilution water?

A

30 mins at room temp

20
Q

2nd step in preparing pour plate?

A

Prepare molten plate count agar?

21
Q

What is the pH required for molten plate count agar?

A

7.0+- 0.2

22
Q

Temp for maintaining the molten plate count agar?

A

44 and 46C

23
Q

How many hours should Molten plate agar be used?

A

Not longer than 3 hours

24
Q

Size of Standard sterile glass?

A

65cm^2

25
Q

Size of pre-sterilized disposable plastic petri dishes?

A

57 cm^2

26
Q

Amount of PCA to be poured in a petri dish?

A

10-12 mL

27
Q

Incubation for Pour plate?

A

35+- 0.5 for 48 hours with humidity

28
Q

Average colonies to count?

A

30-300

29
Q

What is the appearance of colonies in pour plate?

A

Small banana shape colonies

30
Q

What is the reporting for “No colonies”?

A

<1.0 CFU/mL

31
Q

What is the reporting for “Less than 300 colonies per plate”?

A

_Count_est. CFU/mL (39 est. CFU/mL)

32
Q

How to report “If colonies exceed 300, and if there are fewer than 10 colonies/cm^2”?

A

Glass plate
- Count in 13 squares in colony counter
- Add
- Multiply it by 5

Plastic plate
- Count in 19 squares
- Add
- Multiple it by 3

_Count_est. CFU/mL (39 est. CFU/mL)

33
Q

How to report “If colonies exceed 300, and if there are greater than 100 colonies/cm^2”?

A

Glass plate
- Reported as >6500 CFU/mL

Plastic plate
- Reported as >5700 CFU/mL

34
Q

What is the value that is satisfactory enough to drink?

A

<500

35
Q

What happens if the value for CFU is >500?

A

Unsatisfactory

Bacte Lab (Finals (13 decks)

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