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1. Microbiology > Bacterial Growth Requirements > Flashcards

Bacterial Growth Requirements Flashcards

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Biology 101 flashcards
1
Q

What is bacterial growth?

A

An increase in the number of bacterial cells

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2
Q

How do bacteria grow?

A

Asexually through binary fission

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3
Q

Briefly explain how binary fission works.

4

A

Bacteria replicate its DNA

Cell elongates

Copy of DNA goes to each side of cell

Cell splits off into two daughter bacterial cells

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4
Q

How often does binary fission happen?

A

Every 20 minutes

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5
Q

What is a batch culture?

A

Bacteria inoculated in a flask containing a fixed amount of nutrient medium

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6
Q

How many phases are there to bacterial growth of a batch culture?

A

Four

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7
Q

What are the four phases of bacterial growth in a batch culture called?

A

Lag phase

Log phase

Stationary phase

Death phase

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8
Q

What happens during the lag phase of microbial growth?

3

A

Microbes are adjusting to environment

Microbes not yet reproducing

Cells are synthesising DNA, ribosomes and enzymes to breakdown nutrients and synthesize macromolecules

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9
Q

What do bacteria cells synthesize during the lag phase?

3

A

DNA

Ribosomes

Enzymes

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10
Q

Why do bacterial cells synthesize DNA, ribosomes and enzymes during the lag phase?

A

To breakdown nutrients and synthesize macromolecules

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11
Q

What is the log phase also called?

A

The exponential phase

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12
Q

What happens during the log phase?

3

A

Cells have the optimum conditions for growth

Exponential growth occurs

This rate of growth is influenced by environmental conditions and genetic characteristics of the bacteria

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13
Q

What influences the rate of growth in the log phase?

2

A

Environmental conditions

Genetic characteristics

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14
Q

What happens during the stationary phase of bacterial growth?
(2)

A

Death occurs due to reduced nutrients, pH changes, toxic waste and reduced oxygen

No net increase or decrease in cell number

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15
Q

Why does death occur in the stationary phase?

A

In a batch culture exponential growth cannot occur indefinitely

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16
Q

What causes death in the stationary phase?

4

A

Reduced nutrients

pH changes

Toxic waste

Reduced oxygen

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17
Q

What is the death phase also called?

A

Decline phase

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18
Q

What happens during the death phase?

2

A

Cells die at an exponential rate

Death occurs due to accumulation of wastes, loss of cell’s ability to detoxify toxins etc

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19
Q

How do bacterial cells die in the death phase?

A

Their cytoplasmic membrane collapses and cell lysis occurs

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20
Q

What are the nutritional requirements for bacteria?

3

A

Energy

Nutrients

Growth factors

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21
Q

What are the environmental requirements for bacteria?

4

A

Oxygen gas concentration

Temperature

pH

Water availability

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22
Q

Through what three ways can energy by obtained in nature.

A

Organic chemicals

Inorganic chemicals

Light

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23
Q

What are chemoorganotrophs?

A

Organisms that obtain their energy from organic compounds

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24
Q

What is the name given to organisms that obtain their energy from organic compounds?

A

Chemoorganotrophs

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25
Q

Explain how chemoorganotrophs get their energy.

2

A

They oxidise an organic compound to get energy

This energy is stored as adenosine triphosphate (ATP)

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26
Q

What are aerobes?

A

Chemoorganotrophs that can extract energy from compounds in the presence of oxygen

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27
Q

What are anaerobes?

A

Chemoorganotrophs that can extract energy from compounds in the absence of oxygen

28
Q

What are chemolithotrophs?

A

Organisms that can trap the energy available in inorganic compounds

29
Q

What is the name given to organisms that can trap the energy available in inorganic compounds?

A

Chemolithotrophs

30
Q

Chemolithotrophs are only found in what kingdom?

A

Prokaryotes

31
Q

What are the benefits of being a chemolithotroph?

3

A

Only few bacteria are chemolithotrophs

There is no competition for inorganic substrates

Many inorganic compounds are waste products of chemoorganotrophs

32
Q

What are phototrophs?

A

Organisms that can contain pigments that allow them to use light as an energy source - cells are coloured e.g. purple bacteria

33
Q

What is the name given to organisms that use light as an energy source?

A

Phototrophs

34
Q

How do phototrophs work?

A

ATP is made from the energy of sunlight

35
Q

What elements are needed for bacterial growth?

6

A

Hydrogen

Oxygen

Carbon

Nitrogen

Phosphorus

Sulphur

36
Q

What are heterotrophs?

A

Organisms that require one or more organic compound as their carbon source

e.g. heterotrophs

37
Q

What are autotrophs?

A

Organisms that use CO2 as their carbon source

e.g. nearly all phototrophs and most chemolithotrophs

38
Q

Name the two places nitrogen can be gotten for bacteria.

A

Inorganic sources

Organic sources

39
Q

List four inorganic sources of nitrogen.

A

Nitrogen gas (N2)

Nitrate (NO3)

Nitrite (NO2)

Ammonia (NH3)

40
Q

Give an example of an organic source of nitrogen.

A

Nitrogen can be gotten from the breaking down of proteins into amino acids

41
Q

What are growth factors?

A

Essential compounds that an organisms in unable to synthesize from available nutrients

42
Q

What are fastidious organisms?

A

Organisms that need growth factors

43
Q

What are the three categories of growth factors?

A

Purines and pyrimidines

Amino acids

Vitamins

44
Q

What are purines and pyrimidines needed for?

A

Required for synthesis of nucleic acids (DNA and RNA)

45
Q

What are amino acids needed for?

A

Required for the synthesis of proteins

46
Q

What are vitamins needed for?

A

Needed as coenzymes and functional groups of certain enzymes

47
Q

What are extremophiles?

A

Organisms that inhabit extreme environments

48
Q

Why does temperature have such a profound effect on microorganisms?

A

Because enzyme-catalyzed reactions are sensitive to temperature

49
Q

What is optimal growth temperature?

A

The temperature range at which the highest rate of reproduction occurs

50
Q

How are bacteria grouped according to their optimal growth temperature?

A

Psychrophiles

Mesophiles

Thermophiles

Hyperthermophiles

51
Q

At what temperature do psychrophiles grow best?

A

Between 0 and 30 degrees

52
Q

At what temperature do mesophiles grow best?

A

15-40 degrees

53
Q

At what temperature do thermophiles grow best?

A

Between 40 and 70 degrees

54
Q

At what temperature do hyperthermophiles grow best?

A

Above 80 degrees and up to 115 degrees

55
Q

How are bacteria grouped according to their need for oxygen?

3

A

Obligate aerobes

Obligate anaerobes

Facultative anaerobes

56
Q

What are obligate aerobes?

A

Organisms that need oxygen gas to grow

57
Q

What are obligate anaerobes?

3

A

Organisms that cannot grow in the presence of oxygen

They do not need oxygen for growth

Oxygen either kills or inhibits them

58
Q

What are facultative anaerobes?

3

A

Organisms that can switch between aerobic and anaerobic types of metabolism

Fermentation/anaerobic respiration without oxygen

Aerobic respiration with oxygen

59
Q

How are bacteria grouped based on their preferred pH?

A

Acidophiles

Neutrophiles

Alkaliphiles

60
Q

What are acidophiles?

A

Organisms which grow at an optimum pH well below neutrality

e.g. most fungi

61
Q

What are neutrophiles?

A

Organisms which grow best at neutral pH

62
Q

What are alkaliphiles?

A

Organisms which grow best under alkaline conditions

63
Q

What is relative humidity?

A

Presence of water in the atmosphere

64
Q

What is water activity?

A

Presence of water in solution

65
Q

What affects water activity?

A

The presence of solutes such as salts or sugars, that are dissolved in the water

66
Q

What are halophiles?

2

A

Organisms that require some NaCl for growth

Grouped into mild, moderate and extreme halophiles

1. Microbiology (12 decks)

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