factors affecting the growth of bacteria

Question 1

List the five factors that affect the growth of bacteria

Answer 1

temperature, oxygen concentration, pH, external solute concentration, pressure

Question 2

What are limiting factors?

Answer 2

Factors that slow down a process when in short supply are called limiting factors

Question 3

At what temperature do bacteria grow best? What is an exception to this?

Answer 3

20 to 30 degrees C but some bacteria can tolerate much higher temperatures without their enzymes being denatured

Question 4

How do low temperatures affect the rate of bacteria growth?

Answer 4

They slow down the rate of bacterial growth

Question 5

What do aerobic bacteria require?

Answer 5

They require oxygen for respiration

Question 6

What do anaerobic bacteria require?

Answer 6

They do not require oxygen to respire

Question 7

Are most bacteria aerobic or anaerobic?

Answer 7

aerobic

Question 8

What does a low concentration of oxygen cause?

Answer 8

It often slows down bacterial growth, especially in liquids.

Question 9

Give an example of aerobic bacteria

Answer 9

streptococcus bacteria that cause sore throat are aerobic bacteria

Question 10

Give an example of anaerobic bacteria

Answer 10

clostridium (causes tetanus or botulism)

Question 11

What can facultative anaerobes do?

Answer 11

They can respire with or without oxygen

Question 12

Give an example of facultative anaerobes and where can they be found?

Answer 12

Escherichia coli are found in the intestines

Question 13

What can obligate anaerobes do?

Answer 13

They can only respire in the absence of oxygen

Question 14

Give an example of obligate anaerobes and what it causes and where it can be found

Answer 14

Clostridium tetani causes tetanus (or lockjaw) by infecting deep cuts, where there is a poor oxygen supply.

Question 15

What are bacterial enzymes designed to do?

Answer 15

They are designed to work at specific pH values.

Question 16

What happens when bacterial enzymes when they are placed in an unsuitable pH?

Answer 16

They become denatured

Question 17

What do most bacteria grow at?

Answer 17

at or near neutral pH (i.e. pH 7)

Question 18

What can some bacteria tolerate?

Answer 18

They can tolerate very low (acidic) or very high (alkaline) pH values.

Question 19

Why is the growth of bacteria affected by the external solute concentration?

Answer 19

This is because bacteria gain or lose water by osmosis

Question 20

What happens when the external solution has a higher solute concentration than the bacterial cytoplasm?

Answer 20

Water will move out of the bacteria and this dehydrates the bacteria and stops their enzymes from working.

This is the principle behind the methods of food preservation such as salting or sugaring.

Question 21

What happens when the external solution has a lower solute concentration than the bacterial cytoplasm?

Answer 21

Water will enter the bacteria.

The cell walls of bacteria can normally prevent bacterial cells from bursting in these circumstances.

Question 22

What type of concentrated solutions do most bacteria live in

Answer 22

Most bacteria live in less concentrated solutions.

Question 23

What is the growth of most bacteria inhibited by?

Answer 23

inhibited by high pressures.

Question 24

Why are most bacteria inhibited by high pressures?

Answer 24

This is because the bacterial walls are not strong enough to withstand the high pressure.