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Microb 230 Labs 2 > Microbial Growth > Flashcards

Microbial Growth Flashcards

1
Q

Name the environmental factors to which microbes may adapt.

A

temperature,
pH,
osmotic pressure,
atmospheric gases, and
the availability of nutrients.

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2
Q

Regarding metabolism, what determines how environmental factors affect microbial growth.

A

Enzyme systems

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3
Q

Identify a way in which environmental factors may prevent enzymes from functioning.

A

ruin the structure of enzymes making them unable to function

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4
Q

What are the three key temperatures we use to describe the range in which a microbe can survive.

A

Also called cardinal temperatures.
* minimum
* maximum
* optimum

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5
Q

Briefly describe the minimum temperature of a microbe.

A

A minimum temperature is necessary for metabolic functions to continue. Below that temperature the cell may not die but will certainly cease to grow.

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6
Q

Describe the consequences for a microbe when the temperature exceeds its maximum.

A

Temperatures can only increase so much before key enzymes break down and cease to function. The cell cannot survive.

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7
Q

The name or phrase for the break down of enzymes. Briefly describe its consequences for a microbe.

A

This is called denaturation and leads to loss of function, which the cell cannot survive.

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8
Q

Briefly describe the optimum temperature for a microbe.

A

Most organisms have a preferred optimum temperature at which metabolism and growth proceed at the highest level possible.

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9
Q

List the names of classification for organisms according to their temperature range.

A
  • Psychrophiles grow best at cold temperatures
  • Mesophiles prefer moderate temperatures
  • Thermophiles require very warm temperatures
  • Extreme thermophiles grow best in extremely high temperatures
  • Psychrotrophs, have a very wide tolerance to temperature. They grow best at room temperature.
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10
Q

Give an example used in the labs for a human pathogen that thrives at body temperature but can survive and grow even in refrigerated conditions.

A

Staphylococcus aureus

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11
Q

Give two examples from the labs for beneficial use of temperature with microbes.

A

This understanding can be used, for example, to preserve certain foods or to treat infections.

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12
Q

Give two examples from the labs for use of temperature in experiments with microbes.

A

The growth of microorganisms can be controlled in the laboratory by placing them in preferred growing conditions (e.g., an incubator) or by restricting their growth (e.g., placing them in a refrigerated cooler).

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13
Q

Identify one way to measure the growth of bacteria in a broth culture.

A

One way to measure growth is by turbidity measurements. When bacteria multiply in a broth culture they turn the clear solution cloudy, or turbid.

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14
Q

Briefly define turbid and turbidity.

A
  • muddy, cloudy
  • how cloudy a liquid is
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15
Q

What is the use of an instrument called a spectrophotometer?

A

This instrument quantitatively measures the amount of light that is absorbed or transmitted by molecules in solution.

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16
Q

How is a spectrophotometer used to identify the presence of specific bacteria?

A

Different cells and culture media absorb best at a specific, known, wavelength. In this case the amount of light transmission is related to the number of bacteria present.

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17
Q

Briefly define Optical Density

A

is the value given to the measurement of turbidity.

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18
Q

What is the turbidity measurement with no bacterial growth?

A

Tubes with no bacterial growth will show zero turbidity.

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19
Q

When measuring turbidity, how does the reading indicate growth?

A

The more growth present, the higher the reading will be.

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20
Q

In the labs, what did we learn by sampling turbidity at various temperature levels?

A

turbidity indicates bacterial growth at various temperature levels, reveals the range and optimal temperature for the growth of the sampled organism.

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21
Q

Identify the optically clear container for holding liquid samples in a spectrophotometer.

A

A spectrophotometer uses a cuvette, which is a straight-sided, clear container for holding liquid samples.

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22
Q

The name or phrase for visual changes temperature variation can cause (other than growth rates).

A

phenotypic changes

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23
Q

Name and describe the example given in the labs for a bacteria with phenotypic changes.

A

The organism Serratia marcescens will appear reddish on a slant culture due to pigment production at room temperature (25℃). The same organism incubated at body temperature (38℃) will not exhibit this red coloring on a slant.

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24
Q

Briefly describe the oxygen requirements for microbial organisms.

A

Some organisms require oxygen for metabolism, while others find oxygen to be toxic. Some can use oxygen if present but do not require it for survival.

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25
Q

Identify the toxic byproducts of oxygen in microbes.

A

Oxygen creates the following toxic byproducts that must be neutralized:
* Superoxide ion
* Peroxide
* Hydroxyl radicals

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26
Q

Identify the enzymes that allow organisms to degrade the byproducts of oxygen.

A

include:
* Catalase
* Superoxide dismutase
* Peroxidase

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27
Q

Regarding oxygen metabolism, describe obligate aerobe.

A
  • oxygen REQUIRED
  • CAN detoxify oxygen byproducts
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28
Q

Regarding oxygen metabolism, describe microaerophile

A
  • oxygen REQUIRED (in small amounts)
  • CANNOT detoxify oxygen byproducts
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29
Q

Regarding oxygen metabolism, describe facultative anaerobe.

A
  • CAPABLE of oxygen use buy not required
  • CAN detoxify oxygen byproducts
30
Q

Regarding oxygen metabolism, describe aerotolerant anaerobe.

A
  • CANNOT use oxygen
  • CAN detoxify oxygen byproducts
31
Q

Regarding oxygen metabolism, describe obligate anaerobe.

A
  • CANNOT use oxygen
  • CANNOT detoxify oxygen byproducts
32
Q

Briefly describe how microbe growth can be controlled according to their preferences for oxygen.

A

Growth can also be controlled by placing microbes in an environment with oxygen or in a special growth chamber that contains very little, or even zero, oxygen.

33
Q

What was the medium used in the lab exposing 3 bacteria to variable oxygen concentrations. What is the chief reason it was used?

A
  • a fluid thioglycolate medium,
  • it can support the growth of both aerobic and anaerobic organisms.
34
Q

Describe the colors present in the fluid thioglycolate medium and what they indicate.

A
  • The top of the fluid in the tube is slightly red, indicating the presence of oxygen.
  • The middle and bottom of the tube are yellowish in color, indicating low to no oxygen present.
35
Q

What is the purpose of agar in the fluid thioglycolate medium?

A

contains a small amount of agar to localize organisms in place

36
Q

What does growth in the fluid thioglycolate medium help show us?

A

Bacterial organisms will grow in specific locations in the tube where the oxygen concentration is most favorable for growth.

37
Q

What classification of organism will grow at the top in an FTM tube?

A

obligate aerobe

38
Q

What classification of organism will not grow at the top but only near the top in an FTM tube?

A

microaerophile

39
Q

What classification of organism will grow all throughout an FTM tube?

A

facultative anaerobe

40
Q

What classification of organism will grow at the bottom in an FTM tube?

A

obligate anaerobe

41
Q

Briefly describe the environment required to grow obligate anaerobes.

A

oxygen-free

42
Q

Name and describe the device used to create an anaerobic environment.

A

Anaerobic jars are used to create an anaerobic environment by using a chemical envelope that, when activated, catalyzes a reaction to remove free oxygen from the container.

43
Q

How do we verify the environment inside an anaerobic jar?

A

An indicator strip is used to verify the anaerobic conditions inside the jar.

44
Q

Regarding oxygen metabolism, which microbes will only grow when incubated under normal atmospheric conditions?

A

obligate aerobes

45
Q

Regarding oxygen metabolism, which microbes will only grow on the plate incubated in the anaerobic jar?

A

obligate anaerobes

46
Q

Regarding oxygen metabolism, which microbes will be able to grow in either type of oxygen-containing environment and will be present on both plates?

A

facultative organisms

47
Q

What happens to Microorganisms exposed to pH levels outside of their survival range?

A

will experience protein denaturation, ultimately leading to cell death.

48
Q

Describe the range of the pH scale.

A

The pH scale numbers from 0-14. In the middle, pH7 is neutral,so anything less than 7 is acidic and anything above 7 is basic or alkaline.

49
Q

List the Organism Classifications Based on pH Preferences.

A
  • Acidophile
  • Neutrophile
  • Alkalinophile
50
Q

What is the pH range of an acidophile?

A

optimum below 5.5

51
Q

What is the pH range of an neutrophile?

A

optimum near 7

52
Q

What is the pH range of an alkalinophile?

A

optimum above 8.0

53
Q

Briefly define Osmosis

A

– movement of water across the cell membrane due to unbalanced solute concentrations.

54
Q

Briefly define Isotonic solution and its effect on a cell.

A

– equal solute concentrations inside and outside the cell, resulting in no net change in cell volume.

55
Q

Briefly define Hypotonic solution and its effect on a cell.

A

– lower solute concentration, resulting in water moving into the cell causing it to increase in volume.

56
Q

Briefly define Hypertonic solution and its effect on a cell.

A

– higher solute concentration, resulting in water moving out of the cell causing it to decrease in volume.

57
Q

Briefly describe the effect of a hypotonic environment on a bacteria.

A

Since bacteria have a cell wall, the effect is not harmful and the cells can survive and reproduce. An example would be freshwater ponds and streams.

58
Q

Briefly describe the effect of a hypertonic environment on a bacteria.

A

In a hypertonic environment, there is a net movement of water out of the cell causing shrinkage and irreversible damage to the cell wall and metabolic machinery. An example would be salt water or cured and salted meats or fruit jam.

59
Q

Describe the solute concentrations that most bacteria prefer.

A

most bacteria prefer environments where solute concentrations are near 1% (isotonic)

60
Q

List the classifications of organisms by salt tolerance.

A
  • halotolerant
  • halophile
  • osmophile
61
Q

Briefly describe halotolerant organisms.

A

Halotolerant organisms, like Staphylococcus, can grow in salt concentrations as high as 13%.

62
Q

Briefly describe halophile organisms.

A

Halophiles actually require high salt concentrations of at least 13% to survive and grow best at 25% salt concentration.

63
Q

Briefly describe osmophile organisms.

A

Osmophiles can grow in high sugar concentrations. Certain yeasts can grow and contaminate fruit juices and even honey.

64
Q

Name two beneficial applications of osmotic pressure with microbes.

A

This understanding can be used, for example, to preserve certain foods or to treat and prevent infections.

65
Q

What were the 4 salt concentrations used to test the effects of osmotic pressure on three microbes?

A

There are 4 plates with the following salt concentrations: 1%, 6.5%, 10% and 25%.

66
Q

What were the 3 microorganisms used to test the effects of osmotic pressure.

A
  • E. coli
  • S. aureus
  • H. salinarium
67
Q

What is the salt tolerance of E. coli?

A

Does not tolerate

68
Q

What is the salt tolerance of S. aureus?

A

Halotolerant

69
Q

What is the salt tolerance of H. salinarium?

A

Obligate halophile

70
Q

A hypertonic solution is prepared by the addition of sucrose. What will happen to bacteria placed in this solution?

A

The bacterial cells will shrink and undergo irreversible damage.

Microb 230 Labs 2 (4 decks)

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