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Microbial World > Week 7 > Flashcards

Week 7 Flashcards

1
Q

Is bacterial reproduction sexual or asexual?

A

Asexual

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2
Q

How many stages does binary fission have?

A

4

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3
Q

By what process do bacteria grow?

A

Binary fission

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4
Q

What are the 4 stages of binary fission?

A
  1. The cell elongates and the DNA is duplicated.
  2. Cell and plasma membrane begin to divide.
  3. Septum completes.
  4. Daughter cells separate
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5
Q

What is the approximate generation time of E.Coli?

A

20 minutes

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6
Q

What is the generation time for most bacterial species?

A

1-3 hours

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7
Q

What is the generation time of Mycobacterium Tuberculosis?

A

24 hours

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8
Q

What are the 4 phases of bacterial growth (as part of a graph)?

A

Lag
Log
Stationary
Death

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9
Q

What happens in the lag phase of bacterial growth.

A

There is no overall increase in cells but there is intense metabolic activity.

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10
Q

What happens during the log phase of bacterial growth?

A

The maximum possible growth rate for that given environment is maintained.

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11
Q

During what phase of bacterial growth should rate of growth be measured?

A

The exponential log phase.

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12
Q

What happens during the stationary phase of bacterial growth?

A

There is a balance between cellular division and cellular deaths.
The cells still remain metabolically active.

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13
Q

What are the possible causes of the stationary phase of bacterial growth?

A

Exhaustion of nutrients, accumulation of waster, harmful changes in pH, oxygen depletion, spore formation.

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14
Q

What device is used for bacterial continuous culture

A

Chemostat

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15
Q

What is bacterial continuous culture ?

A

A device called a chemostat is used to maintain bacterial population at a constant density which is similar to bacterial growth in a natural environment.

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16
Q

What are the advantages of using continuous culture to grow bacteria?

A

Continuous log phase of growth.
Not limited by nutrient availability.
Closed system makes it easy to control conditions for maximum growth.

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17
Q

Define sterilisation

A

The killing or removal of all living organisms and their viruses

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18
Q

Define disinfection

A

Elimination of microorganisms from inanimate objects

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19
Q

Define antibiotic

A

A chemical substance produced by a microorganism that kills or inhibits the growth of another microorganism

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20
Q

What are the features of a good microbial growth control agent?

A

Inexpensive
Fast acting
Stable during storage
Control all microbial growth whilst being harmless to humans, animals and objects.

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21
Q

What are the substances needed for bacterial growth?

A 
Water 
Optimum temperature
Food source
Oxygen 
Correct pH
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22
Q

What is the overall purpose of food preservation?

A

To prevent microbial growth on foods to avoid spoilage and increase food shelf life.

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23
Q

How does keeping food in low temperature areas help preservation?

A

It reduces metabolic activity and enzyme catalysed reactions which microbes carry out.

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24
Q

How does refrigeration alter the effects of microbes on foods?

A

It reduce enzymic and metabolic activity.

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25
Q

How does freeing alter the effects of microbes on foods?

A

Decreases water activity, slows microbial activity

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26
Q

What is pasteurisation of a food or drink?

A

The partial sterilisation of a product to make it safe for consumption.

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27
Q

Describe the relative strengths of pasteurisation and and sterilisation

A

Pasteurisation is weaker

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28
Q

What type of substances is pasteurisation usually used to preserve?

A

Heat sensitive liquids

29
Q

What method is frequently used to preserve heat sensitive liquids?

A

Pasteurisation

30
Q

How does pasteurisation prevent food/ liquid spoilage?

A

It retards the growth of spoilage microorganisms.

31
Q

What type of food is easiest to can?

A

Acidic

32
Q

What is ‘canning’ of food?

A

Sealed food is heated to kill or inhibit microbial growth.

33
Q

What type of microorganisms can spoil canned food?

A

Anaerobes

34
Q

What are the issues that can occur with canned food?

A

Anaerobic molecules can spoil the food, releasing gases as they do so. This increases pressure in the can and can often lead to bursting.

35
Q

What is asepsis in terms of food preparation?

A

Avoidance of contamination

36
Q

What methods can be used to remove water from foods?

A

Lyophiliation

Spray Drying

37
Q

What methods can be used to reduce water availability of foods?

A

Adding solutes

38
Q

Is gamma radiation ionising or not?

A

Yes

39
Q

Is U.V. radiation ionising or not?

A

No

40
Q

What is water activity ?

A

The measurement of availability of water that a microorganism can use.

41
Q

How do you calculate water availability to a microorganism?

A

(Relative humidity of the product)/ (Relative humidity of pure water)

42
Q

What water availability can most bacteria not grow below?

A

0.85

43
Q

What water availability can most yeast and mould not grow below?

A

0.65

44
Q

How can water become unavailable for microorganisms?

A

If it becomes bound to food.

45
Q

By what methods can water be removed from foods?

A

Evaporation
Sublimation
Adding solutes to the food

46
Q

What are the effects of reduced water activity in microbes?

A

Reduced metabolism and growth

47
Q

What is fermentation?

A

A process used to presence and enhance foods.

48
Q

What factors can affect the process of fermentation?

A

Water availability
pH
Presence of fermentative organisms

49
Q

What is irradiation?

A

The use of gamma rays to kill organisms within a food

50
Q

What is the term used to describe the use of gamma rays to kill organisms in food?

A

Irradiation

51
Q

What are autoclaves and what do they do?

A

Sealed chambers which use a high temperature to create a higher temperature than boiling water. This is used to kill microorganisms.

52
Q

On average, how long do autoclaves take to achieve sterility?

A

60 minutes

53
Q

How does ‘dry heat’ kill microorganisms?

A

Incinerates them

54
Q

Describe the relative Times taken to kill microorganisms using autoclave and dry heat methods.

A

Autoclave is quicker

55
Q

What type of substances is filtration used to remove microbes from?

A

Liquids that heating would damage

56
Q

What method can be used to sterilise liquids that would be damaged by heating?

A

Filtratin

57
Q

Describe the wavelength used when radiating microbes and why this is used

A

Short wavelength use to give greater energy and penetrative force

58
Q

What type of substances are disinfectants used to disinfect?

A

Non-living

59
Q

What type of substances are antiseptics used to disinfect?

A

Living tissues

60
Q

What are the uses of ‘phenols’ as controllers of microbial growth?

A

Surgical antiseptics

Used in health care and in labs

61
Q

What type of microbes can alcohols kill?

A

Bacteria and fungi but not spores or viruses

62
Q

How do alcohols kill bacteria and fungi overall?

A

Protein denaturation or membrane disruption.

63
Q

Give a use of alcohol as a microbial killer

A

Used on the skin before injections

64
Q

How is chlorine halogen used as a microbial killer?

A

To treat drinking water and swimming pools

65
Q

How is Hypochlorite halogen used as a microbial killer?

A

Used for cleaning babies bottles and surfaces

66
Q

How is iodine halogen used as a microbial killer?

A

Antiseptic for wounds

67
Q

How is hydrogen peroxide used as a microbial killer?

A

Disinfect and sterilise surfaces of objects

68
Q

How do surfactants have biocidal action?

A

They assist in the removal of microorganisms by scrubbing.

Microbial World (10 decks)

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