Unit 3

Question 1

Increase in
cell number, not cell size!

Answer 1

Microbial Growth

Question 2

are increasing in number,
accumulating into colonies of
hundreds of thousands of
cells or populations of billions
of cells.

Answer 2

Microbes that are “growing”

Question 3

The Requirements for Growth

Physical Requirements

Answer 3

Temperature
pH
Osmotic pressure

Question 4

Chemical requirements

Answer 4

Carbon
Nitrogen, sulfur, and phosphorus
Trace elements
Oxygen
Organic growth factor

Question 5

Temperature

Answer 5

Minimum growth temperature
Optimum growth temperature
Maximum growth temperature

Question 6

Five groups based on optimum growth temperature

Answer 6

Psychrophiles : cold-loving microbes
2. Psychrotrophs
3. Mesophiles : moderate-temperature loving microbes
4. Thermophiles: heat-loving microbes
5. Hyperthermophiles

Question 7

Low
temperatures decrease microbial reproduction
rates, which is the basic principle of
refrigeration.

Answer 7

Food preservation temperatures

Question 8

Most bacteria grow best between pH 6.5 and 7.5:

Answer 8

Neutrophils

Question 9

Some bacteria are very tolerant of acidity or thrive in
it: (preferred pH range 1 to 5)

Answer 9

Acidophiles

Question 10

grow best between pH 5 and 6

Answer 10

Yeast and mold