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1. Microbiology > Bacterial Growth Requirements > Flashcards

Bacterial Growth Requirements Flashcards

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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
Explain how chemoorganotrophs get their energy. | 2
They oxidise an organic compound to get energy This energy is stored as adenosine triphosphate (ATP)
26
What are aerobes?
Chemoorganotrophs that can extract energy from compounds in the presence of oxygen
27
What are anaerobes?
Chemoorganotrophs that can extract energy from compounds in the absence of oxygen
28
What are chemolithotrophs?
Organisms that can trap the energy available in inorganic compounds
29
What is the name given to organisms that can trap the energy available in inorganic compounds?
Chemolithotrophs
30
Chemolithotrophs are only found in what kingdom?
Prokaryotes
31
What are the benefits of being a chemolithotroph? | 3
Only few bacteria are chemolithotrophs There is no competition for inorganic substrates Many inorganic compounds are waste products of chemoorganotrophs
32
What are phototrophs?
Organisms that can contain pigments that allow them to use light as an energy source - cells are coloured e.g. purple bacteria
33
What is the name given to organisms that use light as an energy source?
Phototrophs
34
How do phototrophs work?
ATP is made from the energy of sunlight
35
What elements are needed for bacterial growth? | 6
Hydrogen Oxygen Carbon Nitrogen Phosphorus Sulphur
36
What are heterotrophs?
Organisms that require one or more organic compound as their carbon source e.g. heterotrophs
37
What are autotrophs?
Organisms that use CO2 as their carbon source e.g. nearly all phototrophs and most chemolithotrophs
38
Name the two places nitrogen can be gotten for bacteria.
Inorganic sources Organic sources
39
List four inorganic sources of nitrogen.
Nitrogen gas (N2) Nitrate (NO3) Nitrite (NO2) Ammonia (NH3)
40
Give an example of an organic source of nitrogen.
Nitrogen can be gotten from the breaking down of proteins into amino acids
41
What are growth factors?
Essential compounds that an organisms in unable to synthesize from available nutrients
42
What are fastidious organisms?
Organisms that need growth factors
43
What are the three categories of growth factors?
Purines and pyrimidines Amino acids Vitamins
44
What are purines and pyrimidines needed for?
Required for synthesis of nucleic acids (DNA and RNA)
45
What are amino acids needed for?
Required for the synthesis of proteins
46
What are vitamins needed for?
Needed as coenzymes and functional groups of certain enzymes
47
What are extremophiles?
Organisms that inhabit extreme environments
48
Why does temperature have such a profound effect on microorganisms?
Because enzyme-catalyzed reactions are sensitive to temperature
49
What is optimal growth temperature?
The temperature range at which the highest rate of reproduction occurs
50
How are bacteria grouped according to their optimal growth temperature?
Psychrophiles Mesophiles Thermophiles Hyperthermophiles
51
At what temperature do psychrophiles grow best?
Between 0 and 30 degrees
52
At what temperature do mesophiles grow best?
15-40 degrees
53
At what temperature do thermophiles grow best?
Between 40 and 70 degrees
54
At what temperature do hyperthermophiles grow best?
Above 80 degrees and up to 115 degrees
55
How are bacteria grouped according to their need for oxygen? | 3
Obligate aerobes Obligate anaerobes Facultative anaerobes
56
What are obligate aerobes?
Organisms that need oxygen gas to grow
57
What are obligate anaerobes? | 3
Organisms that cannot grow in the presence of oxygen They do not need oxygen for growth Oxygen either kills or inhibits them
58
What are facultative anaerobes? | 3
Organisms that can switch between aerobic and anaerobic types of metabolism Fermentation/anaerobic respiration without oxygen Aerobic respiration with oxygen
59
How are bacteria grouped based on their preferred pH?
Acidophiles Neutrophiles Alkaliphiles
60
What are acidophiles?
Organisms which grow at an optimum pH well below neutrality e.g. most fungi
61
What are neutrophiles?
Organisms which grow best at neutral pH
62
What are alkaliphiles?
Organisms which grow best under alkaline conditions
63
What is relative humidity?
Presence of water in the atmosphere
64
What is water activity?
Presence of water in solution
65
What affects water activity?
The presence of solutes such as salts or sugars, that are dissolved in the water
66
What are halophiles? | 2
Organisms that require some NaCl for growth Grouped into mild, moderate and extreme halophiles

1. Microbiology (12 decks)

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