Module 3 Bacterial Growth

Question 1

Requirements for Chemical Growth?

Answer 1

● Carbon
● Nitrogen
● Sulfur
● Phosphorus
● Oxygen

Question 1

Requirements for Physical Growth?

Answer 1

● Temperature
● pH
● Osmotic pressure

Question 2

●Organisms capable of growing at 0 degrees celsius
● Most of these organisms are so sensitive to higher temperature that they cannot grow in arm room (25 degrees celsius)
● Found mostly in the ocean’s depth or polar regions thus seldom cause problems in food preservation

Answer 2

Psychrophiles (cold-loving microbes)

Question 3

● The most common type of microbe
● Optimum temperature for many pathogenic bacteria is about 37 degree celsius

Answer 3

Mesophiles (moderate-temperature-loving microbes)

Question 4

● Microorganisms capable of growth at high temperatures
● Optimum growth: 50-60 degree celsius
● Not considered a public health concern
● Important in organic compost piles

Answer 4

Thermophiles (heat-loving microbes)

Question 5

● Microbes that have an optimum growth temperature of 80 degree celsius

Answer 5

Hyperthermophiles or extreme thermophiles

Question 6

Most bacteria grow best in a narrow pH range near neutrality, between pH?

Answer 6

6.5 and 7.5

Question 7

Microorganisms that are tolerant of acidity

Answer 7

Acidophiles

Question 8

Can adapt to high salt concentrations

Answer 8

Halophiles

Question 9

What are the Trace elements?

Answer 9

iron, copper, molybdenum, zinc)

Question 10

Requires oxygen to live

Answer 10

Obligate aerobes

Question 11

Can use oxygen when present but
continues to grow using fermentation/ anaerobic respiration when oxygen is not available (e.g. E. coli)

Answer 11

Facultative anaerobes

Question 12

Bacteria that are unable to use molecular oxygen for energy- yielding reactions (e.g. Clostridium)

Answer 12

Anaerobes

Question 13

Fermentative and cannot use
oxygen for growth, but they tolerate it fairly well

Answer 13

Aerotolerant anaerobes

Question 14

Aerobic; require oxygen; can grow only in oxygen concentrations lower than those in air

Answer 14

Microaerophiles

Question 15

How does bacteria reproduce?

Answer 15

Binary fission

Question 16

What phase?
● Period of little or no cell division
● Can last for 1 hour or several days
● Cells are not dormant
● Period of intense metabolic activity such as synthesis of enzymes

Answer 16

The Lag Phase

Question 17

● Cells begin to divide and enter a period of growth or logarithmic increase
● Cellular reproduction is most active
● Generation reaches a constant minimum

Answer 17

The Log Phase/ Exponential Growth Phase

Question 18

● The growth rate slows
● Number of microbial deaths balances the number of new cells
● Population stabilizes
● Period of equilibrium
● The population exceeds the carrying capacity (the no. Of organisms that an environment can support) and run out of nutrients and space

Answer 18

The Stationary Phase

Question 19

● Number of deaths exceeds the number of new cells formed
● The population is diminished to a tiny fraction of the number of cells or until the population dies out entirely

Answer 19

The Death Phase/ Logarithmic Decline Phase