Bacterial Growth

Question 1

What is the lag phase in bacterial growth?

Answer 1

Making new enzymes in response to new medium

Question 2

What characterizes the log phase of bacterial growth?

Answer 2

Exponential growth; desired for production of products

Question 3

During which phase are bacteria most sensitive to drugs and radiation?

Answer 3

Log phase

Question 4

What occurs during the stationary phase of bacterial growth?

Answer 4

Nutrients become limiting or waste products become toxic; death rate equals division rate

Question 5

What happens in the death phase of bacterial growth?

Answer 5

Death exceeds division

Question 6

What are the factors regulating bacterial growth?

Answer 6

• Nutrients
• Environmental conditions (temperature, pH, osmotic pressure)
• Generation time
• Transduction

Question 7

What is microbial growth defined as?

Answer 7

Increase in number of cells, not cell size

Question 8

What process do bacteria primarily use for growth?

Answer 8

Binary fission

Question 9

What is generation time?

Answer 9

Time required for cell to divide/for population to double

Question 10

What is the average generation time for bacteria?

Answer 10

1-3 hours

Question 11

What is the generation time for E. coli?

Answer 11

20 minutes

Question 12

What temperature range do psychrophiles thrive in?

Answer 12

0°C to 18°C

Question 13

What temperature range do mesophiles prefer?

Answer 13

25°C to 45°C

Question 14

What defines thermophiles?

Answer 14

Thriving at 45°C to 70°C

Question 15

What is the temperature range for hyperthermophiles?

Answer 15

70°C to 110°C

Question 16

What is the role of oxygen in bacterial growth?

Answer 16

Oxygen is a very reactive molecule affecting cells in several ways

Question 17

What type of bacteria require oxygen for growth?

Answer 17

Obligately aerobic bacteria

Question 18

Where do obligately anaerobic bacteria grow in thioglycollate broth?

Answer 18

At the bottom

Question 19

What are trace elements in the context of bacterial growth?

Answer 19

Inorganic elements required in small amounts, usually as enzyme cofactors

Question 20

What is the significance of carbon for bacterial growth?

Answer 20

Structural organic molecules and energy source

Question 21

What do chemoheterotrophs use for growth?

Answer 21

Organic carbon sources

Question 22

What do autotrophs use for growth?

Answer 22

CO2

Question 23

What is the oxygen requirement for microaerophiles?

Answer 23

Require oxygen but the 20% in air is too toxic

Question 24

What is the defining characteristic of facultative anaerobes?

Answer 24

Can switch to fermentative metabolism in the absence of oxygen

Question 25

What are aerotolerant anaerobes?

Answer 25

Anaerobic bacteria that can grow in the presence of air

Question 26

What is the role of nitrogen in bacterial growth?

Answer 26

In amino acids and proteins; most bacteria decompose proteins

Question 27

What is sulfur's role in bacterial growth?

Answer 27

In amino acids, thiamine, and biotin

Question 28

What is phosphorus essential for?

Answer 28

DNA, RNA, ATP, and membranes

Question 29

What are nonhalophiles?

Answer 29

Microbes that require a high water activity (near or at 1)

Question 30

What are extreme halophiles?

Answer 30

Organisms that require a very high concentration of salt (around saturation)

Question 31

What pH do neutrophiles grow best at?

Answer 31

Around neutral pH (7)

Question 32

What pH do acidophiles prefer?

Answer 32

pH < 7

Question 33

What pH do alkophiles grow best at?

Answer 33

pH > 7

Question 34

What defines acidotolerant bacteria?

Answer 34

Grow best at pH 7 but can also grow at lower pH

Question 35

What defines alkotolerant bacteria?

Answer 35

Grow best at pH 7 but can also grow at higher pH