Laboratory Exercise 5 Preparation of Culture Media

Question 1

Basic Requirements of Microorganisms

Answer 1

Water
Carbon
Energy
Nitrogen
Minerals
Growth factor
Hydrogen ion concentration

Question 2

Basic Requirements of Microorganisms
Water

Answer 2

70-85% component of living organisms

Question 3

Basic Requirements of Microorganisms
Carbon

Answer 3

autotrophs (CO2) vs heterotrophs (more than 1 carbon source)

Question 4

Basic Requirements of Microorganisms
Energy

Answer 4

chemosynthetic autotrophs (inorganic) vs heterotrophs (need organic source, glucose)

Question 5

Basic Requirements of Microorganisms
Nitrogen

Answer 5

amino acids, peptides, peptones, proteases

Question 6

Basic Requirements of Microorganisms
Minerals

Answer 6

Na, K, Mg, Mn, Fe, Zn, Cu, P, Co

Question 7

Basic Requirements of Microorganisms
Growth factor

Answer 7

beef extract

Question 8

Basic Requirements of Microorganisms
Hydrogen ion concentration

Answer 8

pH

Question 9

Type of media according to Solidity

Answer 9

1. Solid media
2. Liquid media
3. Semi-solid media

Question 10

Types of Media According to Solidity

Agar is used to hardening the media at 1.5-2.0% concentration
Allows growth of bacteria as colonies by streakin on the medium
Solidifies at 37 degrees C
Colonies identification is done on this medium

Answer 10

Solid media

Question 11

An unbranched polysaccharide extracted from red algae species like Gelidium

Answer 11

Agar

Question 12

Types of Media According to Solidity

Contains no agar
Bacteria grows faster

Answer 12

Liquid media

Question 13

Types of Media According to Solidity

Contains half the actual concentration of agar (1% only) and is used mainly for studying motility of bacteria
Since the agar molecules are not so condensed, it will encourage motile bacteria to pass through these molecules and go far from inoculated area forming what is called a brush-like growth around the stabbed area

Answer 13

Semi-solid media

Question 14

Calculating agar concentration

If 1.5% agar is the desired concentration, how much agar is required for 100 mL?

Answer 14

1.5% x 100 mL = 1.5g

Question 15

Calculating agar concentration

If 2% agar is the desired concentration, how much agar is required for to make 2 liters?

Answer 15

2% x 2000 mL = 40g

Question 16

Recipe for nutrient broth and agar

To prepare 1 L of nutrient broth/agar:

Answer 16

Nutrient broth:
Beef extract 3g
Peptone 5g
Distilled water up to 1000 mL

Nutrient agar:
Add Agar 15g

Question 17

Recipe for nutrient broth and agar

Autoclave (temperature and time?)

Answer 17

121 degrees C for a minimum of 30 minutes

Question 18

Agar dissolves at about _ and remains in a liquid state until it is cooled to approximately _ at which temperature it will solidify

Answer 18

Dissolves at about 97 degrees C
Will solidify 40 degrees C

Question 19

Types of media

Answer 19

Basal
Enriched
Enrichment
Selective
Differential
Maintenance
Synthetic or Defined