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Microbiology > Lecture #5 > Flashcards

Lecture #5 Flashcards

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1
Q

What are the 3 physical requirements needed for microbial growth?

A
  1. Temperature
  2. pH
  3. Osmotic pressure
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2
Q

What is a psychorophile? What temperature do they grow at?

A

A bacteria that loves the cold.

-5 to 15 degree celsius

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3
Q

Where are psychorophiles found?

A

Deep ocean and polar environments

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4
Q

What are pschrotrophs? What temperature do they grow at?

A

Bacteria with a very broad temperature range. Grow 0-35 (optimal 15-30)

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5
Q

Which of the 5 microbial temperature groups will cause food spoilage?

A

Psychrotrophs

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6
Q

What are mesophiles? What temperature do they grow at?

A

Moderate temperature loving bacteria. 10-45 degrees celsius

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7
Q

Which of the 5 microbial temperature groups is most common?

A

Mesophiles

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8
Q

What are thermophils optimal temperature growth? What is their growth range?

A

60, 45-70 degrees celsius

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9
Q

Can thermophils cause disease in the human body?

A

No

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10
Q

What are hyperthermophiles temperature range?

A

65-110

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11
Q

Why are hyperthermophiles so limited to places they live on earth?

A

Because they live in the few places where water reaches that high of temperatures

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12
Q

What two things are needed to control bacterial populations in food growth?

A

Both hot and cold temperatures

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13
Q

What is used to kill mesophiles and psychrotrophs living in food products?

A

Heat

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14
Q

What is cold temperatures used to do regarding food safety?

A

Slow the growth of microorganisms

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15
Q

Which of the 5 temperature groups of microbial growth is able to grow in the fridge?

A

psychrotrophs

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16
Q

What is pH?

A

The measurement of the acidity or alkalinity of a substance

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17
Q

If a substance is below 7 pH, what is it called?

A

Acidic

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18
Q

If is a substance pH is 7, what is it called?

A

Neutral

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19
Q

At a pH of 7, what happens to proteins? Why?

A

Allows proteins to fold because charges attract

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20
Q

If a substance is above 7pH what is it called?

A

Alkaline

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21
Q

What pH do most bacteria grow at?

A

7

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22
Q

Bacteria the grow at a low pH, it is called?

A

Acidophile

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23
Q

What is a alkalophile?

A

Bacteria that grow at a very high pH

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24
Q

What is a neutrophil?

A

Bacteria that grow at a pH between 5 and 8

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25
Q

What is osmosis?

A

the movement of solvent molecules across a membrane or a barrier of some sort

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26
Q

Water always moves from a area of ______ concentration to an area of _______ high concentration

A

Low to high (up the concentration gradient)

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27
Q

What is a hypertonic solution?

A

Solution very concentrated with solute

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28
Q

What happens to a cell when placed in a hypertonic solution

A

Water wil rush out of cell (cell shrivels)

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29
Q

What is a hypotonic solution?

A

Low concentration of solute

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30
Q

What happens to cell when placed in a hypotonic solution

A

Water rushes into the cell (cell can burst)

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31
Q

What is an isotonic solution?

A

When two solutions are of = concentration

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32
Q

What is a halophile?

A

A bacteria that can survive in very high salt concentrations

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33
Q

Why can’t microorganisms grow in blood?

A

Salt concentration is too low

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34
Q

What are the 4 chemical requirements for micro bacterial growth

A
  1. Carbon
  2. Nitrogen, sulfur, phosphorus and iron
  3. Trace elements
  4. oxygen
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35
Q

What is the backbone for all living matter

A

Carbon

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36
Q

How do heterotrophs obtain their carbon?

A

From organic material (sugars, proteins and lipids)

37
Q

How do autotrophs obtain their carbon?

A

From inorganic matter (CO2)

38
Q

Are nitrogen, sulfur, phosphorus and iron required more or less than carbon?

A

Less

39
Q

What are nitrogen, sulfur, phosphorus and iron used for in micro bacterial growth?

A

Synthesis of cellular material, enzyme function, etc

40
Q

What are trace elements used for in a micro bacteria?

A

Essential for the function of certain enzymes

41
Q

Is oxygen required for all micro bacteria?

A

No

42
Q

What are the 5 classes of microorganisms based on oxygen tolerance?

A
  1. Obligate Aerobes
  2. Facultative anaerobes
  3. Obligate anaerobes
  4. Microaerophiles
  5. Aerotoleran Anaerobes
43
Q

What is culture

A

microbes that are continuously growing and multiplying

44
Q

What are microbes called that are induced into a culture?

A

Inoculum

45
Q

Obligated aerobes use does or does not require oxygen?

A

Does require oxygen

46
Q

Facultative anaerobes do or do not need oxygen to grow?

A

Grows best with oxygen but can also grow without

47
Q

Obligated Anaerobes can or cannot grow with O2?

A

Cannot

48
Q

Microaerophiles do or do not grow with oxygen?

A

Grow only if small amounts are available

49
Q

Aertolerant anaerobes do or do not use oxygen to grow?

A

They grow equally fine with or without oxygen

50
Q

What is batch culture?

A

Liquid media

51
Q

Do batch cultures need nutrients added along the way?

A

No, once started they do not require additions

52
Q

What happens in batch culture when nutrients get used up?

A

Bacteria begin to die

53
Q

What is the limiting component of batch culture?

A

The amount of nutrients

54
Q

What is continuous culture?

A

When nutrients are continually added to the culture and wastes are continually removed

55
Q

How long can batch culture grow? Continuous culture?

A

Batch- until nutrients are used up

Continuous- indefinitely

56
Q

What is solid media?

A

Densely packed groups of cells

57
Q

What does solid media allow for?

A

Growth of colonies and isolation of pure cultures

58
Q

Does solid media need nutrients added?

A

No, it contains all the nutrients required by the cell

59
Q

What is solid media that is the solidifying agent?

A

Agar

60
Q

What is culture medium?

A

Nutrients prepared for microbial growth

61
Q

What does culture medium allow for?

A

Allows us to grow pure bacterial culture in a lab

62
Q

Medium can be chemically ______ or chemically _______

A

defined or undefined

63
Q

What is the difference between chemically defined and chemically undefined media?

A

Undefined- contains unknown components

Defined- All the media components are known

64
Q

What is selective media used for?

A

To suppress the growth of unwanted organisms

65
Q

How does selective media suppress growth of unwanted organisms?

A

Promotes the growth of desired bacteria

66
Q

What is an example of selective media and how does it work?

A

Bismuth Sulfite Agar- inhibits the growth of gram positive and most other gram negative bacteria

67
Q

What is differential media used for?

A

To distinguish in between different types of media

68
Q

How does differential media work?

A

All types of bacteria are able to grow but colonies of certain bacteria look different on plate

69
Q

What type of agar is both selective and differential media?

A

McConkey Agar

70
Q

Most bacteria reproduce by? How does it work?

A

Binary fission- cell elongates and duplicates chromosome, the cell with two chromosome continue to grow and forms a wall between the two chromosome then separate

71
Q

What is generation time?

A

The time it takes for a bacterial population to double in size

72
Q

Generation time varies between..?

A

Different bacteria

73
Q

E.coli is fast or slow in generation time? Why?

A

It is very fast because it is rich in media

74
Q

How long is the generation time of M.tuberculosis?

A

Very slow, 24 hours

75
Q

Why do we use log when showing growth time of bacteria?

A

Because it is easier to show on graph since numbers are smaller

76
Q

What are the 4 stages in the bacterial growth curve?

A
  1. Lag phase
  2. Exponential Phase
  3. Stationary phase
  4. Death phase
77
Q

What occurs in the lag phase

A

Cells adjust to new media and prepare for growth

78
Q

What occurs in the exponential phase (log phase)

A

Cells are increasing exponentially

79
Q

Which phase is used to calculate the growth rate? Which period has maximal reproduction?

A

Exponential phase

80
Q

What occurs in the stationary phase?

A

Nutrients have been depleted and cells have reached max population density

81
Q

Which phase is at the peak of cell growth?

A

Stationary growth stage

82
Q

What occurs in the death stage?

A

All nutrients have been exhausted, toxic waste has accumulated and death rates exceed growth rate

83
Q

What are the two primary ways bacteria can be counted?

A

Direct count and Viable count

84
Q

How are cells counted with the direct count method?

A

Using a light microscope

85
Q

Why is the direct counting method very inaccurate?

A

It counts both dead and alive cells

86
Q

How does viable counting method work?

A

A liquid culture is diluted, dilutions are plated onto agar plates and plies are incubated until the colonies grow

Each cell from its original dilutions develop a single colony

87
Q

In viable counting method, what form are the counts expressed in?

A

Colony forming units/ mL (cfg/mL)

88
Q

Why is viable count more accurate?

A

It only counts live cells

Microbiology (16 decks)

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