Microbial Nutrition & Growth Pt.2

Question 1

Identify the major way bacteria divide and define generation time

Answer 1

Binary Fission: Cells grow twice in size
Divides –> 2 daughter cells

Generation Time: time population takes to double

Question 2

know the phases of microbial growth and what occurs during each phase

Answer 2

Lag Phase, Log Phase, Stationary Phase, Death Phase

Question 3

Lag Phase

Answer 3

Intensity activity preparing for population growth but no increase in population

Question 4

Log Phase

Answer 4

Logarithm, or exponential, increase in population

Question 5

Stationary Phase

Answer 5

Period of equilibrium; microbial death balance production of new cells

Question 6

Death Phase

Answer 6

Population is decreasing at a logarithmic rate

Question 7

Describe three direct and three indirect methods of measuring bacterial growth

Answer 7

Direct:
- Plates counts
- Membrane Filtrations
- Microscopic Counts

Indirect:
-Tuberosity
-Dry Weight
-Metabolic Activity

Question 8

Plates Count

Answer 8

Spread plate method
Colony Forming Units (CFU)

Question 9

Membrane Filtrations

Answer 9

Small Quantities of bacteria

• Colony Forming Units
• Bacteria trapped on filter –> filter transferred to culture medium

Question 10

Microscopic Counts

Answer 10

Bacteria mixed with dye

• low volume on cell counter
• living cells counted under scope

Question 11

Tuberosity (Cloudiness)

Answer 11

Bacterial Growth

• Spectrophotometer: light absorbance increases with cloudiness
• More cloudiness=more abundance=more bacteria

Question 12

Dry Weight

Answer 12

Microorganisms removed from medium, dried, and weighted

• more weight = more growth

Question 13

Metabolic Activity

Answer 13

Metabolic product measured

• more acid = more growth