Lab 9 Quantitation

If you add 1 ml culture to 9 ml diluent, this dilution is

• 1 : 1,000

• 1 : 100

• 1 : 10

A spectrophotometer provides a __________ measurement of the concentration of bacteria.

• quantitative

• qualitative

• dilution

• standard plate count

A measurement of bacterial concentration that tells you the specific CFU/ml in a sample is a _______ measurement

• quantitative

• qualitative

• dilution

• turbidity

If a sample increases in the concentration of bacteria, then it will

• have higher absorbance than before

• have lower transmittance than before

• both answers are true

If a sample is suspected of having very low concentrations of bacteria, then the best method to determine the bacterial concentration would be

• using a spectrophotometere

• serial dilutions

• standard plate counts

• membrane filtration

Which sample has the HIGHEST concentration of bacteria?

• the one with the highest absorbance

• the one with the lowest absorbance

• the one that needs membrane filtration for accurate quantitation

• the one that scatters the least amount of light in a spectrophotometer

Tags

NGSS.HS-PS4-1

A spectrophotometer does NOT (choose all that apply)

• shine light through the bacterial sample

• accurately compare very dilute (unconcentrated) samples

• tell you if the cells are alive

• tell you the CFU/ml in the sample

CFU / ml stands for

• culture forming units per milliliter

• colony forming units per microliter

• colony forming units per milliliter

• culture forming units per microliter

When quantitating dense bacterial samples, what needs to be done before you can do a standard plate count?

• measure turbidity

• measure absorbance

• membrane filtration

• serial dilutions

When analyzing a standard plate count, you should count plates with ____ colonies on them

• the most

• less than 30

• 30 - 300

• less than 100