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Microbiology LECTURE > Chapter 6 MICROBIAL GROWTH > Flashcards

Chapter 6 MICROBIAL GROWTH Flashcards

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1
Q

Factors affecting bacterial growth

A
  1. Physical

2. Biochemical/Nutritional

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2
Q

What are the physical factors that affect bacterial growth

A

pH, temperature, oxygen concentration, moisture, hydrostatic pressure, osmotic pressure and radiation

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3
Q

What are the nutritional factors that affect bacterial growth

A

Availability of carbon, nitrogen, sulfur, phosphorus, trace elements and in some cases vitamins

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4
Q

What are the 3 groups of microorganisms based on preferred range of temperature

A
  1. Psychrophiles
  2. Mesophiles
  3. Thermophiles
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5
Q

How many groups of psychrophiles are there

A

2

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6
Q

Psychotrophs

A

Is the other group of psychrophiles that can grow at 0°C with an optimal growth at 20-30°C. These cause low temperature food spoilage in the fridge

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7
Q

Psychrophiles

A

1st group has a strict hroth at 0°C with an optimal growth at 15°C. Found in oceans or polar regions.

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8
Q

Can psychotrophs survive subfreezing temperatures

A

Yes, they might become dormant and gradually decrease in numbers.

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9
Q

What are signs of food spoilage by psychotrophs

A

They slowly degrade food. Mold mycelium growth occurs, slime on food surfaces or off tastes or colors.

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10
Q

Mesophiles

A

Moderate temperature loving organisms. Optimum for growth at temperatures that humans favor; 25 to 40ﾟC ( 37ﾟC for pathogenic bacteria). Most common organism. These are the most common spoilage and disease causing organisms.

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11
Q

Thermophiles

A

Heat loving organisms capable of growing at high temperatures, with optimal growth at 50 to 60ﾟC. These temperatures are found in hot tap water, sunlit soil, thermal water such as Hot Springs. They cannot grow at 45ﾟC or lower.

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12
Q

Which microbes form and endospores and where are they usually found? Are they considered a public threat?

A

Thermophiles. They are heat resistant and may survive heat Tx of canned goods, spoiling food. Not considered a public threat.

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13
Q

What important role do thermophiles play in daily life

A

They play a role in organic compost piles where temperatures can rise rapidly to 50-60°C

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14
Q

Extreme thermophiles

A

These are made up of archaea microbes. Also known as hyperthermophiles. Their optimal growth is at 80°C or higher. They live in hot springs or volcanic sediment rich in sulfur.

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15
Q

Which microorganisms require nutrients rich in sulfar

A

Hyperthermophiles

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16
Q

What is the normal pH range for bacterial growth

A

6.5 to 7.5, few with pH of 4

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17
Q

What bacteria that can live in of pH 4 and what are they used for in daily life

A

Acidophiles. Food preserved from spoilage with bacterial fermentation such as sauerkraut, pickles and cheese.

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18
Q

What is the optimal pH for mold and yeast growth

A

pH 5 to 6

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19
Q

What type of pH inhibits microbial growth and is it used for food preservation

A

Alkalinic. Its rarely used to preserve foods.

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20
Q

What problem do bacteria cultured in the lab come across as far as pH is concerned? How is this addressed?

A

Bacteria often produce acids which interfere with their own growth. Chemical buffers are used such as phosphate salts which are non toxic and provide phosphorus which is an essential nutrient, and pep tones and amino acids are also used as buffers.

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21
Q

Where do microbes obtain most of their nutrients from

A

From solution of surrounding water. They require 80 to 90% for growth

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22
Q

How does high osmotic pressure affect bacterial cells

A

It can remove the necessary water from cell leading to plasmolysis. The cell growth is inhibited as plasma membrane pulls away from cell wall

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23
Q

What is plasmolysis

A

Shrinkage of cells cytoplasm

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24
Q

How is osmotic pressure used to persevere food

A

High salt and sugar draw water out leading to plasmolysis of microbial cells that are present and inhibiting growth. This is used for salted fish, honey, and condensed milk.

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25
Q

Extreme halophiles

A

Adapted to high salt concentrations required for growth. They are obligate halophiles, some able to live in concentrations as high as 30% salt.

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26
Q

Facultative halophiles

A

Do not require high salt concentrations. They are able to grow in up to 2% salt concentrations. These concentrations inhibit the growth of other organisms. Some can tolerate up to 15% salt concentration.

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27
Q

Most organisms require a medium that is mostly ______________

A

Water

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28
Q

What nutritional needs do carbon provide for bacteria

A

Structural backbone of living matter

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29
Q

What nutritional needs do nitrogen provide for bacteria

A

Synthesis of DNA, RNA, Proteins: amino acids

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30
Q

Where is nitrogen sources from

A

from decomposition, nitrates, atmosphere, and soil

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31
Q

What nutritional needs do sulfur provide for bacteria

A

Amino acids and vitamins

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32
Q

What nutritional needs do phosphorus provide for bacteria

A

ATP, nucleic acids

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33
Q

What nutritional needs do vitamins K, Mg, and Ca provide for bacteria

A

Cofactors

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34
Q

What are trace elements

A

Minerals that can be found naturally in tap water.They include iron, copper, zinc, cobalt and molybdenum.

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35
Q

What nutritional function do trace elements play in bacteria

A

They function with enzymes as cofactors

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36
Q

What other vitamins do bacteria use

A

Folic acid, Vit B12, Vit K

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37
Q

How are microbes that use molecular oxygen more efficient than those that don’t

A

Those that use molecular oxygen extract more energy from nutrients than those that don’t

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38
Q

Obligate aerobes

A

Require oxygen to live (oxygen is poorly soluble in water)

39
Q

Facultative aerobes

A

Use oxygen when present otherwise use fermentation

40
Q

What happens to the production of energy when anaerobic respiration is used

A

There is a decreased efficiency in energy production

41
Q

What substitute for oxygen can be used in respiration

A

Nitrates

42
Q

What are examples of facultative aerobes

A

E.coli and yeasts

43
Q

Obligate anaerobes

A

Bacteria unable to use molecular oxygen for energy yielding reaction. They are usually harmed by 02. Cannot use 02 in cellular materials. Get it from water.

44
Q

Example of obligate anaerobe

A

Clostridium

45
Q

Toxic forms of 02

A
  1. Singlet 02
  2. Superoxide radicals
  3. Peroxide anion
  4. Hydroxyl radical
46
Q

Singlet 02

A

Normal molecular oxygen. It is boosted into higher energy state. It is extremely reactive

47
Q

Superoxide radicals

A

▪︎AKA superoxide anions
▪︎Formed in small quantities during normal respiration of orgs that use 02 as FEA,forming water
▪︎Toxicity is caused by instability that leads to stealing electrons from neighboring molecule–>radical

48
Q

Radicals…..

A

Steal electrons

49
Q

What enzyme must organisms attempting to grow in atmospheric oxygen produce? Why?

A

Superoxide dismutase (SOD)–> to neutralize superoxide radicals because they are toxic to cellular components

50
Q

Which type of bacteria produce SOD

A

Aerobic bacteria, facultative anaerobes growing aerobically, aerotolerant anaerobes

51
Q

Do obligate anaerobes form superoxide radicals

A

Yes, some form in the presence of oxygen

52
Q

What does SOD convert superoxide radicals to

A

Molecular oxygen and hydrogen peroxide

53
Q

Is hydrogen peroxide toxic

A

Yes because it contains peroxide anion

54
Q

When is hydrogen peroxide formed

A

During normal aerobic respiration

55
Q

What enzyme have microbes produced to neutralize hydrogen peroxide

A

Catalase or peroxidase

56
Q

What reaction does Catalase have with bacterial cells in comparison to peroxidase

A

Catalase produces oxygen bubbles and peroxidase does not produce oxygen

57
Q

Hydroxyl radical

A

An intermediate form of 02 and probably the most reactive. It is formed in the cytoplasm by ionizing radiation. Most aerobic respiration produces traces of this, but it is transient.

58
Q

What is an essential component of the body’s most important defenses against pathogens

A

The toxic forms of 02. In phagocytosis, ingested pathogens are killed by exposure to singlet 02, superoxide radicals, peroxide anions of hydrogen peroxide, and hydroxyl radicals and other oxidative compounds

59
Q

Aerotolerant anaerobes

A

Cannot use 02 for growth. Tolerate 02 fairly well. Will grow on surface of medium without special technique. Characteristically ferment carbohydrates to lactic acid.

60
Q

Lactic acid accumulation on medium inhibits the growth of

A

Aerobic competitors

61
Q

Example of Aerotolerant anaerobes

A

Lactobacilli

62
Q

Why can aerotolerant bacteria tolerate oxygen

A

Because they produce SOD,which neutralizes toxic forms of 02

63
Q

Microaerophiles

A

They are aerobic and require 02. Require 02 concentrations lower than those in air

64
Q

Where do microaerophiles grow

A

▪︎In solid medium at depth where small amounts of 02 diffused into medium
▪︎Do not grow near 02 rich surface or below narrow zone of adequate 02

65
Q

Why can’t microaerophiles live in 02 rich environments

A

They produce lethal concentrations of superoxide radicals and peroxides

66
Q

Example of microaerophiles

A

Helicobacter pylori

67
Q

Example of obligate aerobe

A

Bacillus subtilis and pseudomonas

68
Q

What is an essential organic compound an organism is unable to synthesize

A

Organic growth factors are directly obtained from environment

69
Q

Can humans or bacteria synthesizer their own vitamin

A

Humans get their vitamins from the environment and some bacteria can synthesize their own vitamins

70
Q

What are examples of growth factors for bacteria

A

Organic growth factors are amino acids, purines, pyrimidines, and vitamins for those that lack the enzymes to synthesize certain vitamins

71
Q

Biofilm

A

Microbial communities that live and a matrix made up of polysaccharides, DNA, and proteins

72
Q

Biofilms form

A

Slime or hydrogels

73
Q

Quorum sensing

A

Cell to cell chemical communication between single species or diverse group of microorganisms. These microorganisms form a biological system that coordinates all activities and group together for beneficial reasons

74
Q

Where do biofilms attach to

A

To surfaces such as rock,pond, human tooth, mucous membranes

75
Q

What benefits do microrganisms in biofilm have

A

Sharing of nutrients, they’re sheltered from harmful environments, their close proximity allows sharing of genetic material

76
Q

Why do microorganisms in a biofilm avoid a thick uniform monolayer

A

This is to avoid toxic waste accumulation and crowding and competition of nutrients

77
Q

What % and what is a common nosocomial infection that affects humans as a result of biofilm

A

70%–> most are catheters and other are indwelling medical devices

78
Q

What’s substance abundant in human secretions inhibits biofilm formation and how

A

Lactoferrin binds with iron and inhibits surface motility essential for aggregation of bacterial biofilms

79
Q

Is candida a biofilm

A

Yes

80
Q

Culture medium

A

Nutrient material prepared for growth of micro organisms in lab

81
Q

Inoculum

A

Microbes introduced into a culture media to initiate grow

82
Q

Culture

A

Microbe that grow and multiply in a culture medium

83
Q

Criteria for growth

A

Right nutrients, Sufficient moisture, Properly adjusted PH, Suitable level of oxygen or none, Must initially be sterile with no living micro organisms, Incubation at proper temperature

84
Q

Agar

A

Solidifying agent made up of complex polysaccharide, Added to medium to grow bacteria

85
Q

Why is agar used for growth of microbes

A

Few microbes can degrade Agar, it remaines solid

86
Q

At what temperature does Agar liquefy and what benefit does this have

A

100°C, useful for thermophilic bacteria

87
Q

At what temperature does our agar solidify

A

40ﾟC at sea level

88
Q

Sterile

A

Complete absence of life forms and formers, including viruses, pathogenic and non pathogenic microbes

89
Q

Agar is used for what 3 culture medias

A

Slants,petri plates, and deeps

90
Q

What are 2 problems that culturing bacteria in the lab present

A
  1. A pure culture of a single species is needed to study an organism’s characteristics
  2. A medium must be found that will support growth of the desired organism
91
Q

What is a pure culture

A

A culture that contains only a single species of organism

92
Q

Chemically defined media

A

Exact chemical composition is known

93
Q

Complex media

A

Extracts and digets of yeast, meat, or plants varies by composition,

94
Q

What are 2 types of complex media

A

Nutrient broth and nutrient agar

Microbiology LECTURE (13 decks)

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