chapter 6

Question 0

what is cfu?

Answer 0

colony forming units

- may arise from a cell or a group of cells to form a mass of cells(colony). ex: count plates with 30-300 colonies

Question 1

what methods are used in plate count to measure bacterial growth?

Answer 1

• pour plate

- spread plate

Question 2

equation to determine cfu of a sample?

Answer 2

CFU= number of colonies * DF(dilution factor)
—————————-
volume plated

Question 3

what is dilution?

Answer 3

D= amount added
      ---------------
      total volume(amount mL)

Question 4

what is dilution factor?

Answer 4

reverse or reciprocal

EX: 10/1=1

Question 5

explain the principle of spectrophotometry in measuring bacterial growth:

Answer 5

• based on the scattering of light by bacteria in a broth culture.
• light scattering is measured as absorbance or optical density.
• absorbance is directly proportional to the concentration of bacteria in suspension.
• absorption indirectly proportional to transmission.