Microbial growth

Question 1

Definition?

Answer 1

• Increase in cell-mass
• Increase in cell-number
Bacteria multiply through binary fission
Generation-time
• Time required for cell-division

Question 2

Lag phase?

Answer 2

• Low number of cell divisions
o ATP is missing
o Growth-factors are missing
o Ribosomes downregulated
o Specific enzymes are missing
o Cells can be damaged

Question 3

Exponential growth?

Answer 3

• Maximal number of cell divisions

Question 4

Stationary phase?

Answer 4

• The cells stop dividing
o Lack of nutrients
o Oxygen-levels are changing
o Acidic waste-products are accumulated and pH drops
o Production of secondary metabolites

Question 5

Death phase?

Answer 5

• The cells are dying

Question 6

What affects the growth-rate?

Answer 6

Water Temp Nutrients Oxygen pH

Question 7

Access to water?

Answer 7

Bacteria differs in susceptibility to dehydration
• Thick cell-wall helps bacteria not to dry out
• Bacteria can sporulate

Question 8

Kind of nutrients?

Answer 8

Bacteria differs in types of nutrients required
• They all need carbon, oxygen, nitrogen
and hydrogen

Question 9

Oxygen-levels?

Answer 9

Bacteria differs in oxygen-requirements
• Correct levels are required to maintain a
functional metabolism

Question 10

pH-levels?

Answer 10

Bacteria differs in pH-requirements
• Most optimal for human-pathogens is a
neutral environment

Question 11

Temperature?

Answer 11

Bacteria differs in temperature-requirements

• Most optimal for human-pathogens is 37 °C

Question 12

How do we control bacterial growth

in our living?

Answer 12

Growth-control
Refrigeration
Lowering water activity
Adding acids
Modification of atmosphere
Chemical preservatives