Lab 6: Environmental Factors that Effect Microbial Growth and Introduction to Special Media

Question 1

Three environmental factors that affect growth:

Answer 1

• Oxygen
• pH
• Temperature

Question 2

Obligate Aerobes

Answer 2

Only grow aerobically
* In the presence of oxygen (aerobically)

Question 3

Obligate Anaerobes

Answer 3

Only grow anaerobically
* Are unable to use oxygen and are harmed by it

Question 4

Facultative Anaerobes

Answer 4

Grow aerobically or anaerobically
* Can grow with or without oxygen

Question 5

Aerotolerant Anaerobes

Answer 5

Grow in the presence of oxygen because these microorganisms can tolerate it
* Cannot use oxygen for metabolic purposes

Question 6

Microaerophiles

Answer 6

Grow only aerobically
* Differ from obligate aerobes because concentrations of oxygen lower than air are required for growth

Question 7

Answer 7

Obligate Aerobes

Question 8

Answer 8

Obligate Anaerobes

Question 9

Answer 9

Facultative Anaerobes

Question 10

Answer 10

Aerotolerant Anaerobes

Question 11

Answer 11

Microaerophiles

Question 12

Answer 12

Aerotolerate Anaerobe

Question 13

Answer 13

Facultative Anaerobe

Question 14

notice the pink media at the top of the test tube indicating the presence of O2

Answer 14

Obligate/Strict Anaerobe

Question 15

Answer 15

Obligate/Strict Aerobe

Question 16

notice the pink media at the top of the test tube indicating the presence of O2

Answer 16

Microaerophile

Question 17

Resazurin

Answer 17

Turns media pink indicating presence of O2

Question 18

Answer 18

O2 has been reduced

colorless

Question 19

Answer 19

Presence of O2

media turns pink

Question 20

Identify A:

Answer 20

Facultative Anaerobe

since it grew in both aerobic and anaerobic conditions

Question 21

Identify B:

Answer 21

Obligate Anaerobe

because only grew in anaerobic jar

Question 22

Identify C:

Answer 22

Obligate Aerobe

because only grew in aerobic conditions

Question 23

Identify D:

Answer 23

Facultative Anaerobe

Question 24

Psychrophile

Answer 24

below 20°C

Question 25

Psychrotroph

Answer 25

0°C - 30°C

Question 26

Mesophile

Answer 26

15°C - 45°C | (human pathogen)

Question 27

Thermophile

Answer 27

above 45°C

Question 28

Extreme Thermophile

Answer 28

above 65°C

Question 29

Acidophile

Answer 29

Acidic environments below **pH 5.5**

Question 30

Neutrophile

Answer 30

pH levels between **5.5** and **8.5**

Question 31

Alkaliphile

Answer 31

Alkaline/basic conditions above **8.5**

Question 32

Selective Media

Answer 32

Used to isolate microoorganisms by inhibiting the growth of some organisms while encouraging the growth of others

Question 33

Differential Media

Answer 33

Media that contains indicators, which help differentiate microorganism based on a variety of factors | (ex. fermentation)

Question 34

Mannitol Salt Agar (MSA)

Answer 34

Used for the isolation and differentiation of Staphylococcus * Testing for the inhibition of growth by NaCl and Mannitol fermentation **Only Staphylococcus genus are able to grow on this media**

Question 35

Mannitol

Answer 35

Carbohydrate serves as the substrate for fermantation * is what makes MSA differential *(only microorganism that are able to ferment mannitol will produce acid by products turning the media (MSA) acidic and triggering the indicator to turn yellow)*

Question 36

Sodium Chloride

Answer 36

7.5% Sodium Chloride (NaCl) concentration * makes it selective *(only microorganisms that area able to grow in high concentration of salt will grow on MSA media)*

Question 37

Phenol Red

Answer 37

Indicator for fermentation of mannitol Yellow = Acidic (+)

Question 38

# What is A dipicting?

Answer 38

Inhibition of growth

Question 39

# What is B dipicting?

Answer 39

(+) Growth (-) Fermentation

Question 40

# What is C depicting?

Answer 40

(+) Growth (+) Fermentation

Question 41

MacConkey Agar (MCA)

Answer 41

Used for the isolation of Gram (-) microorganisms - coliforms * Testing for the inhibition of Gram (+) growth by bile salts and crystal violet within the media and lactose fermentation **Only Gram (-) will grow on MCA**

Question 42

Lactose | MacConkey Agar (MCA)

Answer 42

Carbohydrate serves as the substrate for fermentation * Makes MCA differential **(only microorganism that are able to ferment Lactose will produce acid by products turning the media acidic and triggering the indicator to turn pink → colonies will appear pink)

Question 43

Bile Salts and Crystal Violet

Answer 43

Are within the media and inhibit the growth of Gram (+) microorganisms * Make MCA selective *(only microorganisms that area able to grow in or tolerate the presence of bile salt and crystal violet will grow on this media)*

Question 44

Neutral Red

Answer 44

Indicator for fermentation of lactose * Red/pink colonies → decrease in pH → Acidic ( + for lactose fermentation) * Colorless colonies → pH 6.8 or higher → ( - for lactose fermentation)

Question 45

# Neutral Red Colorless Colonies

Answer 45

pH 6.8 or higher * ( **-** for lactose fermentation)

Question 46

# Neutral Red Red/Pink Colonies

Answer 46

**Decrease** in pH * **Acidic** ( **+** for lactose fermentation)

Question 47

# Identify A

Answer 47

Lactose negative

Question 48

# Identify B

Answer 48

Lactose positive

Question 49

# Identify C

Answer 49

Lactose positive

Question 50

Eosin Methylene Blue (EMB)

Answer 50

Used for the isolation of Gram (-) microorganisms - coliforms * Testing for the inhibition of Gram (+) growth by eosin y and methylene blue dye within the media and lactose fermentation

Question 51

Lactose | Eosin Methylene Blue (EMB)

Answer 51

Carbohydrate serves as the substrate for fermentation * Makes EMB media differential *(only microorganisms that area able to grow in or tolerate the presence of Eosin y and Methylene Blue will grow on this media)*

Question 52

Dyes | Eosin Methylene Blue (EMB)

Answer 52

Indicator for fermentation of lactose / pH indicator → increases dye absorption by the colonies

Question 53

# Eosin Methylene Blue (EMB) Dyes: Purple/pink colonies

Answer 53

decrease in pH → Acidic (+) for lactose fermentation and (-) for coliforms ***medium lactose fermenters***

Question 54

# Eosin Methylene Blue (EMB) Dyes: Metallic green sheen

Answer 54

decrease in pH → Acidic (+) for lactose fermentation and (+) for coliforms ***vigorous lactose fermenters***

Question 55

Dark Purple-Black

Answer 55

(+) for lactose fermentation ***agressive lactose fermenter***

Question 56

# Eosin Methylene Blue (EMB) Dyes: Colorless colonies

Answer 56

pH 6.8 or higher → Neutral/ Basic (-) for lactose fermentation and (-) for coliforms

Question 57

# Identify A

Answer 57

Lactose negative | colorless colonies

Question 58

# Identify B

Answer 58

Lactose positive *medium lactose fermenter* | purple/pink colonies

Question 59

# Identify C

Answer 59

Lactose positive *agressive lactose fermenter* | metallic green sheen

Question 60

Fastidious organisms

Answer 60

Require special growth factors such as blood, brain extracts, vitamins, etc.

Question 61

Answer 61

Beta-hemolysis

Question 62

Answer 62

Alpha hemolysis

Question 63

Answer 63

Gamma hemolysis