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MBIO 1010 > Lecture 5: The Effects of Physical/Chemical Conditions on Microbial Growth > Flashcards

Lecture 5: The Effects of Physical/Chemical Conditions on Microbial Growth Flashcards

1
Q

______ is a major environmental factor controlling microbial
growth

A

Temperature

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2
Q

_______: the minimum, optimum, and maximum
temperatures at which an organism grows

A

Cardinal temperatures

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3
Q

T/F: cardinal temperatures are characteristic of each different organism

A

true

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4
Q

Microorganisms can be classified into groups by their growth temperature optima, what are these four groups?

A

Psychrophile

Mesophile

Thermophile

Hyperthermophile

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5
Q

______: low temperature

A

Psychrophile

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6
Q

_______: midrange temperature

A

Mesophile

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7
Q

________: high temperature

A

Thermophile

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8
Q

______: very high temperature

A

Hyperthermophile

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9
Q

what types of animals/environments are mesophiles in?

A

Warm-blooded animals

Terrestrial and aquatic environments

Temperate and tropical latitudes

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10
Q

________: organisms that grow under very hot or very cold conditions

A

extremophiles

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11
Q

_______:
* Organisms that can grow at 0ºC but
have optima of 20ºC to 40ºC

  • More widely distributed in nature than
    true psychrophiles
A

Psychrotolerant

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12
Q

what molecular adaptations that support psychophily?

A

production of enzymes that function optimally in the cold
modified membranes (high unsaturated fatty acids!!)

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13
Q

T/F: Above ~65ºC, only prokaryotic life forms exist

A

true! high prokaryotic diversity! both archaea and bacteria represented

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14
Q

T/F: No phototrophy above approx. 70C

A

true

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15
Q

_________:
* Organisms with cold temperature optima (<20C)
* Inhabit permanently cold environments
* Deep ocean, Arctic and Antarctic environment

A

Psychrophiles

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16
Q

________: organisms with growth temperature optima between
45ºC and 80ºC
* Terrestrial hot springs, very active compost

A

Thermophiles

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17
Q

_______: organisms with optima greater than 80ºC
* Inhabit hot environments, including boiling hot springs and seafloor
hydrothermal vents that can experience temperatures in excess of 100ºC

A

Hyperthermophiles

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18
Q

T/F: Current temperature maximum record is held by an archaeon, Methanopyrus
kandleri, which can grow at 122C

A

true!

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19
Q

what are the molecular adaptations to thermophily?

A

specific modifications provide thermal stability to enzymes and proteins
modifications in cytoplasmic membranes

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20
Q

T/F: Hyperthermophiles produce enzymes widely used in industrial
microbiology

A

true!

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21
Q

T/F: Enzymes of thermophiles are more stable and tend to have lower activity than their mesophilic counterparts

A

false!

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22
Q

What are the upper temperature
limits for life?

A

Laboratory experiments with
biomolecules suggest 140–150°C

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23
Q

T/F: New species of thermophiles and
hyperthermophiles are still being discovered

A

true!

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24
Q

T/F: Hyperthermophiles may be the closest descendants of ancient microbes

A

true!
The oxidation of H2 is common to many hyperthermophiles (early Earth atmosphere had no carbon, need to be very simple to live off H2!)

May have been the first energy-yielding metabolism

25
Q

T/F: the pH of an environment greatly affects
microbial growth

A

true!

26
Q

Most organisms grow best between pH
6 and 8, what are they called?

A

neutrophiles

27
Q

______: Organisms that grow best at low pH (<6)

A

acidophiles

28
Q

_______: Organisms that grow best at high pH (>9)

A

alkaliphiles

29
Q

what homeostatic effects MUST stay the same?

A

cytoplasmic membrane maintains its integrity at growth pH

internal pH must stay 7, close to neutral

30
Q

what do we include in microbial media cultures to maintain homeostasis inside the cell?

A

buffers to maintain constant pH

Some bacteria produce acids
* Acetic, lactic, sulfuric acid = decreases the pH

Some bacteria grow on amino acids
* Releases ammonia = increases the pH

31
Q

________ (aw): water availability; expressed in physical terms

A

Water activity

32
Q

________: is defined as the ratio of vapor pressure of air in equilibrium with a
substance or solution to the vapor pressure of pure water

Reflects the amount of water that is interacting with ions and polar compounds in solution

A

water activity

33
Q

T/F: Typically, the cytoplasm has a higher solute concentration than the
surrounding environment

A

true! water will want to move into the cell, creates turgor pressure

34
Q

______: grow best at reduced water potential;
have a specific requirement for NaCl

A

Halophiles

  • Many marine microbes
35
Q

________: Require high levels of NaCl for growth

A

Extreme halophiles
* 15 – 30%
* Ex) Microbes from Great Salt lake or the Dead Sea

36
Q

______: can tolerate some reduction in
water activity of environment but generally grow
best at lower solute concentrations

A

Halotolerant
ex: s aureus, lives on human skin (sweat causes low concentrations of NaCl in env.)

37
Q

________: Organisms that grow with high sugar as solute

A

Osmophiles

38
Q

_______: Organisms able to grow in very dry environments

A

Xerophiles

39
Q

T/F: Honey, jams and jellies do not have many organisms growing in them

A

true! very low moisture contents make it difficult to sustain life/growth, high solute concentration kills bacteria!

40
Q

T/F: High osmolarity created with NaCl is not used to select for acid producing
microorganisms

A

false!
Used for sauerkraut and pickle fermentation

Combination of high salt and low pH prevents the growth of most pathogens
in the completed product

41
Q

how do cells combat low water activity in surrounding environment?

A

Pumping inorganic ions from environment into cell

Synthesizing or concentrating organic solutes

42
Q

________: compounds used by cell to counteract low water activity in surrounding environment

A

Compatible solutes

43
Q

_______: require oxygen to live

A

Obligate aerobes

44
Q

_____: do not require oxygen and may even be killed by
exposure

A

Strict anaerobes

45
Q

______: can live with or without oxygen, they use oxygen when it is available

A

Facultative aerobes

46
Q

______: can tolerate oxygen and grow in its presence
even though they cannot use it

A

Aerotolerant anaerobes

47
Q

_____: can use oxygen only when it is present at levels
reduced from that in air

A

Microaerophiles

48
Q

how can we distinguish differences in oxygen use/tolerance?

A

using thioglycolate broth

49
Q

_______: Complex medium that separates microbes based on oxygen requirements

A

thioglycolate broth

50
Q

how does thioglycolate work?

A

Thioglycolate reacts with oxygen creating an anaerobic environment
* Oxygen can penetrate only the top of the tube
* Contains an oxygen responsive dye that turns pink in the presence of oxygen and colorless when the oxygen is low or absent

51
Q

what will an obligate aerobe do in Thioglycolate broth?

A

grows only in the oxic zone at the top of the tube

52
Q

what will a strict anaerobe do in Thioglycolate broth?

A

grows only in the anoxic zone at the bottom of the tube

53
Q

what will a falcultative anaerobe do in Thioglycolate broth?

A

grows throughout the tube

Better growth occurs in the oxic zone, where it can generate energy by aerobic
respiration

54
Q

what will a microaerophile do in Thioglycolate broth?

A

grows in a narrow band between the oxic and anoxic zones

  • Needs O2 for aerobic respiration
  • Killed by atmospheric O2 levels
55
Q

what will a aerotolerant anaerobe do in Thioglycolate broth?

A

grows well
throughout the tube
* Doesn’t use O2
* Not harmed by O2

56
Q

what needs to happen to grow anaerobic microbes? what special techniques are used?

A

Reducing agents may be added to culture media to reduce oxygen
* Thioglycolate, cysteine, H2S and other sulfur containing compounds

Removal of air, and replacement with an inert gas
* Ex) nitrogen or argon

57
Q

what are the three toxic forms of oxygen that can form spontaneously in the cell?

A

Superoxide anion
Hydrogen peroxide
Hydroxyl radical

58
Q

what 4 enzymes are present inside the cell to neutralize toxic oxygen forms?

A

Catalase
Peroxidase
Superoxide dismutase
Superoxide reductase

59
Q

why can’t obligate anaerobes combat oxidative stress? neutralize these toxic forms of oxygen?

A

they lack some or all of the enzymes that neutralize toxic oxygen!

MBIO 1010 (12 decks)

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