Chapter 1 Lecture 9/14

Question 1

Media Type by function (specialized media)

Answer 1

General growth media
Enriched media
Selective media
Differential media

Question 2

Enriched media

Answer 2

can be used to increase a particular population of microbes with a specific property from a mixture of cell types

Question 3

Selective media

Answer 3

allows for isolation of microbes with specific properties

Question 4

Differential media

Answer 4

allows certain microbes to be recognized based on visual reactions in the medium

Question 5

Notes to obtaining a pure culture

Answer 5

One of the benefits of a solid medium is that cells are held in place on the surface and can be isolated.
This can lead to separating a mixture of cells into a pure population.
There are 3 methods for separating cells on a plate.

Question 6

3 methods for separating cells on a plate

Answer 6

Streak plate method
Spread plate method
Pour plate method

Question 7

Nitrogen

Answer 7

amino acids, purines, pyrimidines, some carbohydrates, lipids, enzyme cofactors etc.

supplied in numerous ways
-Metabolism of amino acids, nitrates, ammonia, from atmosphere
-Nitrogen Fixation

Question 8

Phosphorus

Answer 8

nucleic acids, phospholipids, coenzymes, some proteins, etc.

Common phosphorous sources
Inorganic phosphate
Organic molecules containing a phosphoryl group

Question 9

Sulfur

Answer 9

amino acids, coenzymes

Obtained from 2 sources
Amino acids cysteine and methonine

Sulfate
-assimilatory sulfate reduction
sulfatesulfitehydrogen sulfide

Question 10

Growth factors

Answer 10

organic compounds that cannot be synthesized by an organism but are essential for growth

Question 11

3 classes of growth factors

Answer 11

1) amino acids -protein synthesis

2) purines/pyrmidines -nucleic acid synthesis

3) vitamins- enzyme cofactors, needed in very small amounts

Question 12

Nutrient concentration

Answer 12

Growth rate –dependent on amounts of nutrients in environment

One key nutrient, available in the lowest amount, will dictate how much growth can occur over time

Question 13

Aerobes

Answer 13

Aerobes grow in the presence of oxygen.

Obligate aerobes REQUIRE oxygen.

Microaerophiles grow best when there is less oxygen than normal.

Question 14

Anaerobic growth

Answer 14

Anaerobic growth occurs without oxygen.

Aerotolerant anaerobes aren’t harmed by oxygen but don’t use it, either.

Obligate anaerobes cannot grow when oxygen is present.

Facultative anaerobes CAN use oxygen but can also grow in the absence of oxygen.

Question 15

Thioglycolate Broth

Answer 15

Reducing compound which shows gradient of compound

Less oxygen at bottom than at top

Question 16

Obligate aerobe

Question 17

Facultative anerobe

Question 18

Aerotolerant anaerobe

Question 19

Strict anaerobe

Question 20

Microaerophile

Question 21

Factors affecting microbial growth

Answer 21

Effects of oxygen on microbial growth

Often determined by what defenses are available against oxygen’s negative effects in the cell

Question 22

Reactive Oxygen Species

Answer 22

oxygen easily reduced to toxic reactive oxygen species (ROS)

O2 + e- –> O2- (superoxide radical)

O2- + e- + 2H+ –> H2O2 (hydrogen peroxide)

H2O2 + e- + H+ –> H2O + OH (hydroxyl radical)

Question 23

Enzymes that protect against toxic O2 products

Answer 23

Aerobes produce protective enzymes

2O2- + 2H+ –(superoxide dismutase)–> O2 + H2O2

2H2O2 –(catalase)–> 2H2O + O2

H2O2 + NADH + H+ –(peroxidase)–> 2H2O + NAD+

Question 24

Strict Anaerobic Microbes

Answer 24

*Strict anaerobic microorganisms lack

• Superoxide dismutase
• Catalase

*These microbes cannot tolerate O2

*Anaerobes must be grown without O2

• work station with incubator
• gaspak anaerobic system

Question 25

An Anaerobic Workstation

Answer 25

Incubator Airlock Gloves

Question 26

The GasPak Anaerobic System

Answer 26

Catalyst chamber Gas generator envelope Lid Lockscrew Clamp Rubber gasket seal Anaerobic indicator strip

Question 27

pH

Answer 27

Effects of pH on microbial growth Microbes have an optimal pH range for growth. Acidophiles = pH < 5.5 Neutrophiles = pH 5.5 to 8.5 Alkalophiles = pH > 8.5

Question 28

hypotonic solution

Answer 28

(higher osmotic concentration outside) - water enters the cell - cell swells may burst

Question 29

hypertonic

Answer 29

(lower osmotic concentration outside) - water leaves the cell - membrane shrinks from the cell wall (plasmolysis) may occur

Question 30

halophiles

Answer 30

grow optimally in the presence of NaCl or other salts at a concentration above about 0.2M

Question 31

extreme halophiles

Answer 31

require salt concentrations of 2M and 6.2M

Question 32

Compatible solutes

Answer 32

molecules that can be kept at high internal concentration

Question 33

Solutes and Water Activity

Answer 33

water activity (aw) amount of water available to organisms Aw of distilled water is 1.0 Aw of milk is 0.97 Aw of dried fruits is 0.5

Question 34

Osmotolerant microbes

Answer 34

Osmotolerant microbes can grow over wide ranges of water activity (e.g., Staphylococcus aureus 3M NaCl)

Question 35

Temperature

Answer 35

Effects of temperature on microbial growth Different microbes have different optimal temperature growth ranges.

Question 36

Cardinal Growth Temperatures

Answer 36

Minimal Maximal Optimal

Question 37

psychrophiles

Answer 37

0 to 20 C

Question 38

psychrotrophs

Answer 38

0 to 35 C

Question 39

mesophiles

Answer 39

20 to 45 C

Question 40

thermophiles

Answer 40

55 to 85 C

Question 41

hyperthermophiles

Answer 41

85 to 113 C

Question 42

Resistance to heat denaturation in cells

Answer 42

for DNA, more GC will help DNA maintain Hydrogen bonds and prevent some denaturation

Question 43

Cell resistance to extreme cold

Answer 43

Everything slows down Saturation to prevent Ice formation: H2O in cell freezes into crystals and cuts everything, unless you saturate cells (mix with glycerol) to prevent ice formation, you can prevent death by ice Structural adaptations

Question 44

Adaptations of Thermophiles

Answer 44

protein structure stabilized by a variety of means histone-like proteins stabilize DNA membrane stabilized by variety of means e.g., ether linkages (archaeal membranes)