Lab QUIZ 6

Question 1

Aerobes

Answer 1

require oxygen for growth

Question 2

T/F Obligate aerobes can carry out fermentation

Answer 2

FALSE
they must respire with free oxygen

Question 3

Examples of aerobes

Answer 3

Micrococcus luteus
most fungi
excludes yeasts

Question 4

Anaerobes

Answer 4

grow in the absence of oxygen

Question 5

Example of obligate anaerobe

Answer 5

Clostridium species

Question 6

Facultative anaerobes

Answer 6

Can grow both in the presence and absence of oxygen

Question 7

How do facultative anaerobes grow in the absence of oxygen?

Answer 7

carrying out fermentation

Question 8

Examples of facultative anaerobe

Answer 8

E. coli
P. aeruginosa
Saccharomyces cerevisiae (eukaryote)

Question 9

Fermentative organisms/ aerotolerant

Answer 9

grow in the presence of or absence of oxygen
carry out fermentation
sometimes they are slightly inhibited by oxygen

Question 10

Example of fermetative organisms

Answer 10

E. faecalis

Question 11

Microaerophiles

Answer 11

can grow in low oxygen environments
cannot tolerate high levels of oxygen

Question 12

Examples of Microaerophiles

Answer 12

magnetotactic bacteria
Helicobacter pylori

Question 13

Two approaches to grow obligate anaerobes

Answer 13

1. exclude oxygen from growth environment
2. protect culture from toxic effects of oxygen

Question 14

Gaspack EZ pouch contains:

Answer 14

H2 and CO2 generator pouch
methylene blue indicator disc

Question 15

How does Gas pack work

Answer 15

H2 reacts with O2 to remove oxygen by producing water
Methylene blue indicator is blue when oxidized and white when reduces

Question 16

How are we doing the two approaches in lab

Answer 16

1. Gaspack EZ ouch
2. Sodium Thioglycolate Broth tubes

Question 17

What do thioglycolate broth tubes contain:

Answer 17

nutritive components
indicator- resazurin
agar-

Question 18

How do thioglycolate broth tubes work

Answer 18

reduces O2 to produce CO2 to maintain anaerobic environment in media
agar reduces rate of diffusion
resazurin is pink when oxidized and colorless when reduced

Question 19

How do reducing agents work

Answer 19

lower the oxidation-reduction potential (Eh)

Question 20

What is another method to reduce air in media?

Answer 20

layer of sterile mineral oil at the surface

Question 21

Obligate aerobe growth in Thioglycolate broth

Answer 21

growth only at surface

Question 22

obligate anaerobe growth in Thioglycolate broth

Answer 22

growth only at the bottom

Question 23

facultative organism growth in Thioglycolate broth

Answer 23

Growth throughout the tube but with more concentration at the top

Question 24

fermenting organisms growth in Thioglycolate broth

Answer 24

growth throughout but lacking growth at the surface

Question 25

Microaerophile growth in Thioglycolate broth

Answer 25

narrow band of growth below the surface

Question 26

Many organisms can use ___ as the electron acceptor in absence of O2

Answer 26

nitrate (NO3-)

Question 27

Aerobic respiration

Answer 27

converts O2 into H2O

Question 28

Nitrate reduction

Answer 28

nitrate to nitrite (NO2-)

Question 29

T/F some organisms can further reduce nitrite

Answer 29

TRUE
further reduces to nitrogen gas (N2)

Question 30

Denitrification

Answer 30

nitrite to nitrogen gas

Question 31

What genre can do denitrification?

Answer 31

Pseudomonas

Question 32

Fermentation tube results

Answer 32

if growth in tubes doesn’t result in the production of acid or gas- the bubble in nitrate tubes is from nitrate gas

Question 33

Process for nitrate broth tubes

Answer 33

1. addition of reagents A and B
2. addition of zinc
3. fermentation tubes

Question 34

Result from adding reagents

Answer 34

red- bacteria reduces nitrate
colorless- must add zinc
If there is gas bubble- fermentation tubes to determine source

Question 35

results from adding zinc

Answer 35

red- bacteria does not reduces nitrate (zinc did)
colorless- bacteria reduced nitrate to N2