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

Question 1

______ is a major environmental factor controlling microbial
growth

Answer 1

Temperature

Question 2

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

Answer 2

Cardinal temperatures

Question 3

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

Answer 3

true

Question 4

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

Answer 4

Psychrophile

Mesophile

Thermophile

Hyperthermophile

Question 5

______: low temperature

Answer 5

Psychrophile

Question 6

_______: midrange temperature

Answer 6

Mesophile

Question 7

________: high temperature

Answer 7

Thermophile

Question 8

______: very high temperature

Answer 8

Hyperthermophile

Question 9

what types of animals/environments are mesophiles in?

Answer 9

Warm-blooded animals

Terrestrial and aquatic environments

Temperate and tropical latitudes

Question 10

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

Answer 10

extremophiles

Question 11

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

• More widely distributed in nature than
  true psychrophiles

Answer 11

Psychrotolerant

Question 12

what molecular adaptations that support psychophily?

Answer 12

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

Question 13

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

Answer 13

true! high prokaryotic diversity! both archaea and bacteria represented

Question 14

T/F: No phototrophy above approx. 70C

Answer 14

true

Question 15

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

Answer 15

Psychrophiles

Question 16

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

Answer 16

Thermophiles

Question 17

_______: 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

Answer 17

Hyperthermophiles

Question 18

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

Answer 18

true!

Question 19

what are the molecular adaptations to thermophily?

Answer 19

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

Question 20

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

Answer 20

true!

Question 21

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

Answer 21

false!

Question 22

What are the upper temperature
limits for life?

Answer 22

Laboratory experiments with
biomolecules suggest 140–150°C

Question 23

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

Answer 23

true!

Question 24

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

Answer 24

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

Question 25

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

Answer 25

true!

Question 26

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

Answer 26

neutrophiles

Question 27

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

Answer 27

acidophiles

Question 28

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

Answer 28

alkaliphiles

Question 29

what homeostatic effects MUST stay the same?

Answer 29

cytoplasmic membrane maintains its integrity at growth pH internal pH must stay 7, close to neutral

Question 30

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

Answer 30

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

Question 31

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

Answer 31

Water activity

Question 32

________: 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

Answer 32

water activity

Question 33

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

Answer 33

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

Question 34

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

Answer 34

Halophiles * Many marine microbes

Question 35

________: Require high levels of NaCl for growth

Answer 35

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

Question 36

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

Answer 36

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

Question 37

________: Organisms that grow with high sugar as solute

Answer 37

Osmophiles

Question 38

_______: Organisms able to grow in very dry environments

Answer 38

Xerophiles

Question 39

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

Answer 39

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

Question 40

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

Answer 40

false! Used for sauerkraut and pickle fermentation Combination of high salt and low pH prevents the growth of most pathogens in the completed product

Question 41

how do cells combat low water activity in surrounding environment?

Answer 41

Pumping inorganic ions from environment into cell Synthesizing or concentrating organic solutes

Question 42

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

Answer 42

Compatible solutes

Question 43

_______: require oxygen to live

Answer 43

Obligate aerobes

Question 44

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

Answer 44

Strict anaerobes

Question 45

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

Answer 45

Facultative aerobes

Question 46

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

Answer 46

Aerotolerant anaerobes

Question 47

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

Answer 47

Microaerophiles

Question 48

how can we distinguish differences in oxygen use/tolerance?

Answer 48

using thioglycolate broth

Question 49

_______: Complex medium that separates microbes based on oxygen requirements

Answer 49

thioglycolate broth

Question 50

how does thioglycolate work?

Answer 50

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

Question 51

what will an obligate aerobe do in Thioglycolate broth?

Answer 51

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

Question 52

what will a strict anaerobe do in Thioglycolate broth?

Answer 52

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

Question 53

what will a falcultative anaerobe do in Thioglycolate broth?

Answer 53

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

Question 54

what will a microaerophile do in Thioglycolate broth?

Answer 54

grows in a narrow band between the oxic and anoxic zones * Needs O2 for aerobic respiration * Killed by atmospheric O2 levels

Question 55

what will a aerotolerant anaerobe do in Thioglycolate broth?

Answer 55

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

Question 56

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

Answer 56

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

Question 57

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

Answer 57

Superoxide anion Hydrogen peroxide Hydroxyl radical

Question 58

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

Answer 58

Catalase Peroxidase Superoxide dismutase Superoxide reductase

Question 59

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

Answer 59

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