Pre-Lab Quiz 5

Question 1

You will only see a typical bacterial growth curve when bacteria are grown in a

Answer 1

closed system/batch culture

Question 2

What phase of growth occurs when the population of cells has stopped dividing due to the lack of available nutrients?

Answer 2

stationary phase

Question 3

Which phase of growth occurs when the number of cells in the population is doubling at a constant rate?

Answer 3

exponential phase

Question 4

Which phase of growth occurs immediately after the inoculation of the cells into a fresh medium?

Answer 4

lag phase

Question 5

Which phase of growth is marked by an exponential decrease in the number of viable cells?

Answer 5

death phase

Question 6

What reagent is used in the starch hydrolysis test?

Answer 6

iodine

Question 7

What indicates a positive starch hydrolysis test?

Answer 7

areas where the starch is digested remain clear

Question 8

What enzyme must the bacteria produce to test positive for starch hydrolysis?

Answer 8

amylase

Question 9

What type of medium is used for the casein hydrolysis test?

Answer 9

skim milk agar

Question 10

What indicates a positive casein hydrolysis test?

Answer 10

agar appears clear/transparent

Question 11

What does SIM stand for?

Answer 11

sulfide indole motility

Question 12

What color indicates the production of hydrogen sulfide?

Answer 12

black

Question 13

What is Kovac’s reagent used to detect and what indicates a positive reaction?

Answer 13

indole, positive reaction will turn red

Question 14

What amino acid are the bacteria capable of breaking down if they are positive for the indole test?

Answer 14

tryptophan

Question 15

What are the products of urea hydrolysis?

Answer 15

CO2 and ammonia

Question 16

If a bacterium produces urease, what will happen to the pH of the culture medium?

Answer 16

pH will rise

Question 17

What indicator is used for the urease test?

Answer 17

phenol red

Question 18

What indicates a positive urease test?

Answer 18

turns red

Question 19

Where is the oxygen concentration the lowest in a tube of fluid thioglycolate medium?

Answer 19

at the bottom of the tube

Question 20

What is an obligate aerobe?

Answer 20

• a bacteria that will only live with plentiful oxygen

- will grow at the top of the tube

Question 21

What is an obligate anaerobe?

Answer 21

• a bacteria that will die in the presence of significant oxygen
• will grow at the bottom of the tube

Question 22

What is a facultative anaerobe?

Answer 22

• a bacteria that can either live in aerobic or anaerobic conditions but prefers oxygen
• can grow anywhere in the tube but will tend to cluster towards the top

Question 23

What is a microaerophile?

Answer 23

• a bacteria that lives in a narrow window of oxygen concentrations
• will cluster in a certain area of the tube

Question 24

What is an aerotolerant anaerobe?

Answer 24

• a bacteria that is indifferent to the presence of oxygen

- can grow anywhere in the tube

Question 25

Most bacteria grow at a pH between ___ and ___

Answer 25

6.5, 7.5

Question 26

What does microbial fermentation do the the pH of food?

Answer 26

• decreases the pH (more acidic)

- eliminates most pathogens

Question 27

What is the pH range for neutrophiles?

Answer 27

5.5-8.5

Question 28

What is the pH range for acidophiles?

Answer 28

1.0-5.5

Question 29

What is the pH range for alkaliphiles?

Answer 29

7.5-11.5

Question 30

Water activity is the concentration of ____ water in a sample.

Answer 30

unbound

Question 31

A water activity of zero means that there is __ free water

Answer 31

no

Question 32

Halophiles are microbes that require the presence of ___ in their environment

Answer 32

salt

Question 33

What does halotolerant mean?

Answer 33

the ability to survive or thrive at salt concentrations higher than those necessary for growth