BIOL 3201 Lab 8 - Auburn University
standard plate count (SPC) - Answer one of the most common methods for determining the
numbers of viable (live) bacteria in a sample.
spread plate technique - Answer used with serial dilutions, is one of the common standard
plate count methods.
colony forming units (CFUs) - Answer Only numbers between 30 and 300 CFUs are considered
statistically valid.
Liquid sample counts - Answer based on a 1 mL (milliliter) volume
dry sample counts - Answer based on 1 g (gram) mass of sample
Serial Dilutions - Answer a laboratory procedure in which an amount of one substance (culture
broth, food, blood, etc.) is added to a sterile solvent (a liquid, often water) to reduce the
concentration of the original substance
Spread Plate problems - Answer 1.Choose the plate that is between 30-300 colonies
2.Check to see if it is a 10 fold or 100 fold dilution (10 being 1 mL taken and transferred to 9 mL
each time or 100 fold being 1 mL taken and transferred to 99 mL each time.)
3.Count which plate was used. For example, 5th plate= 10^5 or 100^5
4.Do the math:
Number of colonies on plate x 10/100 ^nth tube chosen
Amount transferred from
spectrophotometer - Answer As the number of cells in a culture increases with time, the
turbidity of the culture will also increase. The turbidity of a bacterial culture can be measured
using an instrument
Absorbance - Answer also known as optical density) determinations made by a
spectrophotometer do not give specific bacterial numbers like those obtained with the standard
plate count
(CPU/ml) - Answer The absorbance values are then graphed versus the plate counts to
generate a standard curve
standard plate count (SPC) - Answer one of the most common methods for determining the
numbers of viable (live) bacteria in a sample.
spread plate technique - Answer used with serial dilutions, is one of the common standard
plate count methods.
colony forming units (CFUs) - Answer Only numbers between 30 and 300 CFUs are considered
statistically valid.
Liquid sample counts - Answer based on a 1 mL (milliliter) volume
dry sample counts - Answer based on 1 g (gram) mass of sample
Serial Dilutions - Answer a laboratory procedure in which an amount of one substance (culture
broth, food, blood, etc.) is added to a sterile solvent (a liquid, often water) to reduce the
concentration of the original substance
Spread Plate problems - Answer 1.Choose the plate that is between 30-300 colonies
2.Check to see if it is a 10 fold or 100 fold dilution (10 being 1 mL taken and transferred to 9 mL
each time or 100 fold being 1 mL taken and transferred to 99 mL each time.)
3.Count which plate was used. For example, 5th plate= 10^5 or 100^5
4.Do the math:
Number of colonies on plate x 10/100 ^nth tube chosen
Amount transferred from
spectrophotometer - Answer As the number of cells in a culture increases with time, the
turbidity of the culture will also increase. The turbidity of a bacterial culture can be measured
using an instrument
Absorbance - Answer also known as optical density) determinations made by a
spectrophotometer do not give specific bacterial numbers like those obtained with the standard
plate count
(CPU/ml) - Answer The absorbance values are then graphed versus the plate counts to
generate a standard curve
