Culture Media Preparation

Question 1

a medium using rich extracts of meat or plants that would supply all the amino acids, nucleotide bases, vitamins, and other growth factors required by our organism

Answer 1

complex medium

Question 2

the specific chemical composition is known and the individual components are weighed out exactly to make up the medium

Answer 2

defined medium

Question 3

Organisms can be divided into two groups based on their carbon requirements:

Answer 3

heterotrophs
autotrophs

Question 4

obtain their carbon from organic compounds such as polysaccharides, carbohydrates, amino acids,
peptides, and proteins

Answer 4

Heterotrophs

Question 5

derive their carbon requirements from fixing carbon dioxide

Answer 5

autotrophs

Question 6

derive their energy needs from the breakdown of organic molecules by fermentation or respiration. Most bacteria belong to this metabolic group.

Answer 6

Chemoorganotrophs

Question 6

oxidize inorganic ions such as nitrate or iron to obtain energy to fix carbon dioxide.

Answer 6

Chemolithotrophs

Question 7

contain photosynthetic pigments such as chlorophyll or bacteriochlorophyll that convert solar energy into chemical energy by the process of photosynthesis

Answer 7

Photoautotrophs

Question 8

These organisms also derive their energy requirements from photosynthesis, but their carbon needs come from growth on organic molecules such as succinate or glutamate

Answer 8

photoheterotrophs

Question 9

are examples of nitrogen-fixing bacteria

Answer 9

Rhizobium and Azotobacter

Question 10

Media can be made with components that will allow
certain bacteria to grow but will inhibit others from
growing. Such a medium is a

Answer 10

selective medium

Question 11

contains substances that
cause some bacteria to take on an appearance that distinguishes them from other bacteria

Answer 11

differential medium

Question 12

a complex polysaccharide isolated from seaweed, is
added in a concentration of 1.5% to solidify liquid
media

Answer 12

agar

Question 13

Many of the media used in microbiology are __________________, such as nutrient agar, which is used to cultivate a variety of bacteria

Answer 13

complex

Question 14

Examples of the chemolithotrophs are the

Answer 14

nitrifying and iron bacteria

Question 15

The
__________________________________________________
are examples of photoautotrophs that carry out photosynthesis

Answer 15

cyanobacteria and the green and purple sulfur bacteria

Question 16

Cells also require _________________, which is important in the
synthesis of ATP

Answer 16

phosphorus

Question 17

are incorporated into complex media to provide a source of
nitrogen for these bacteria

Answer 17

Beef extract and peptones

Question 18

are essential in bacterial metabolism because they are cofactors in enzymatic reactions
and are integral parts of molecules such as cytochromes, bacteriochlorophyll, and vitamins.

Answer 18

metals

Question 19

serve as coenzymes in metabolism

Answer 19

vitamins

Question 20

When preparing media,
it is essential to always use either _________________________ water

Answer 20

deionized or distilled

Question 21

Most bacteria grow best at a neutral pH
value around

Answer 21

7

Question 22

Fungi prefer pH values around ___ for
best growth.

Answer 22

5

Question 23

Media can be made with components that will allow
certain bacteria to grow but will inhibit others from
growing. Such a medium is a ___________________________. Antibiotics, dyes, and various inhibitory compounds are
often incorporated into media to create selective conditions for growing specific organisms.

Answer 23

selective medium

Question 24

contains substances that cause some bacteria to take on an appearance that distinguishes them from other bacteria.

Answer 24

differential medium

Question 25

When ________________________ grows on mannitol-salt agar, it ferments mannitol, changing a pH indicator from red to yellow around colonies.

Answer 25

Staphylococcus aureus

Question 26

are used to grow large volumes of bacteria

Answer 26

Liquid broth cultures

Question 27

Streaking of bacteria and selection of isolated colonies are done on

Answer 27

solid media

Question 28

a complex polysaccharide isolated from seaweed, is added in a concentration of 1.5% to solidify liquid media

Answer 28

agar

Question 29

agar, a complex polysaccharide isolated from seaweed, is added in a concentration of ______ to solidify liquid media

Answer 29

1.5%

Question 30

The use of agar in bacteriological media was first introduced in _____________________ laboratory

Answer 30

Robert Koch’s

Question 31

Agar has unique properties that make it ideal for use in microbiology. First, it melts at __________ but does not solidify until it cools to __________

Answer 31

100C; 45C

Question 32

Before any medium can be used to grow bacteria or other microorganisms, it must be ______________, that is, any contaminating bacteria introduced during preparation must be killed or removed.

Answer 32

sterilized

Question 33

Most media can be _______________ to achieve sterilization. This involves heating the media to ____________ for at least ___ minutes at ____ psi of steam pressure.

Answer 33

autoclaved; 121°C; 15; 15

Question 34

the exact composition and amounts of the individual amino acids, vitamins, growth factors, and other components that make up the medium are not exactly known.

Answer 34

complex medium