Isolation of Bacteria by Dilution Techniques

Question 1

contamination

Answer 1

the presence of unwanting organisms

Question 2

colony forming unit

Answer 2

a single colony arising from one cell

Question 3

streak plate technique

Answer 3

a loop is used to streak the mixed sample many times over the surface of a solid culture medium in a petri plate

Question 4

what is the purpose of streak plate technique

Answer 4

allows organisms to be distributed all over the agar surface by falling off the loop
ISOLATION

Question 5

pour plate

Answer 5

used to determine the number of bacteria in a sample

QUANITIVE

Question 6

pour plate technique

Answer 6

bacteria are diluted through a series of dilution banks

the melted agar and bacteria are transferred into sterile petri dishes.

Question 7

spread plate

Answer 7

used to determine the number of bacteria in a sample

QUANITIVE

Question 8

spread plate technique

Answer 8

small amount of previously diluted specimen is spread over the surface of a solid medium

Question 9

what is the ideal number of countable colonies?

Answer 9

25-250

Question 10

why is serial dilutions important?

Answer 10

because even just using one mm of milk or water can yield 20,000 colonies
we want to be able to achieve around 25-250

Question 11

significance of agar solidifying temperature to the pour plate technique

Answer 11

agar cools and solidifies at 45 degrees very quickly
if it is retained at 50 degrees it will stay as a liquid
and keeps the organism alive