ch 3 lab

Question 1

chemically defined medium

Answer 1

a medium whose exact chemical composition is known

Question 2

complex media

Answer 2

media for which the exact chemical composition varies slightly form batch to batch

Question 3

nutrient broth

Answer 3

liquid complex medium

Question 4

nutrient agar

Answer 4

agar is added to a liquid complex medium it becomes a solid medium

Question 5

agar

Answer 5

an extract from marine red algae

Question 6

Autoclaving (or steam sterilization)

Answer 6

The process by which steam is heated under pressure to sterilize a wide range of materials in a comparatively short time (minutes to hours). It is effective for most materials except water-resistant substances such as oils,waxes, and powders.

Question 7

petri plates

Answer 7

provide a large surface area for examination of colonies

Question 8

inoculated

Answer 8

intentionally introduced

Question 9

turbid

Answer 9

cloudy, a result of bacterial growth

Question 10

colony-forming unit

Answer 10

a colony that arises from a group of the same microbes attached to one another

Question 11

colony

Answer 11

population of cells that arises from a single bacterial cell

Question 12

when do bacteria that are inoculated into culture media increase in number?

Answer 12

incubation period

Question 13

what procedure is used to avoid introducing unwanted microbes and to prevent spreading microbes where they are not wanted

Answer 13

aseptic techniques

Question 14

what is an inoculating loop?

Answer 14

a nichrome wire held with an insulated handle

Question 15

what do you do to an inoculating loop or needle before and after it is used

Answer 15

sterilize it by using heat or flaming

Question 16

why is condensation on the agar undesirable

Answer 16

it moves the microorganisms

Question 17

clumps of microbial cells, suspended in the broth

Answer 17

flocculent

Question 18

a membrane across the surface of the broth

Answer 18

pellicle

Question 19

microbial cells settled at the bottom of the tube

Answer 19

sediment

Question 20

how is bacterial growth in broth determined?

Answer 20

clear-indicating no growth, turbidity, pellicle, flocculent, sediment

Question 21

What is the minimum number of bacteria present on one of your plates? How do you know?

Answer 21

The minimum number of bacteria will be represented by the number of colonies.

Question 22

What is the value of the Petri plates in microbiology?

Answer 22

Provides a larger surface area for examination

Question 23

What are the bacteria using for nutrients in the nutrient agar?

Answer 23

peptone, beef extract,sodium chloride(NaCl), Agar, Distilled water

Question 24

What is the purpose of the agar?

Answer 24

The agar is a solidifying agent.

Question 25

Why is agar preferable to gelatin as a solidifying agent in culture media?

Answer 25

It stays solid in high heat.