Lecture 10 Flashcards
What two methods to measure the cell growth?
Cell mass or cell number
What indicates a microbial growth?
A growth in cell mass or cell number,
Define microbial growth.
An increase in volume and in mass, then divides.
What does microbial growth usually indicates?
Cell multiplication.
Explain how to measure cells by the Dry weight determination.
A collection of cells is made from a measured volume of the broth culture. Then you dry the cells overnights in an over of 90 degrees celsius then weight the dried cells.
By what qualificative measure is the cells reported?
x mg/mL.
True of false, the Dry weight determination method distinguishes between living and dead cells.
False, they do not distinguish the difference.
Explain the carbon, nitrogen, proteins content determinations for weighing cells.
This method states that with the increase of these elements, the cell mass increases.
True or False. The carbon, nitrogen, protein content determination does not determine the dead to living cells?
True.
Describe the turbidity measurement method.
This is the preferred method as it’s easily performed. As growth occurs, so does the turbidity of the broth (becomes opaque). The liquid is transferred to a cuvette where it’s placed in a spectrophotometer and reading is obtained. This method does not distinguishes living to dead cells.
Define the measurement of cell mass to cell number.
Cell mass measurement mesures the group and cell count is individual cells.
Define the measurement of the cell number using the direct microscope count method.
The cells are counted using a microscope and a special slide known as a counting chamber. This method does not differentiates living to dead cells.
Define the Coulter counter method for cell number count.
This is an electronic counter that counts cells that are suspended in liquid. This method does not differentiates living to dead cells.
Define the plate count method for cell number count.
This method is primarily based on assumptions that each cell deposited on or in the agar medium multiplies from one visible colony.
As the pour plate method for cell number count, what if you have 1 mL of a suspension containing 100 bacteria / mL is plated out. How many colonies should you expect?
100 colonies to develop.
Define “plated out”.
The addition of the inoculum to the agar medium and districting it over the surface or throughout the agar.
Define confluent growth.
Also know as confluent lawn, it’s a covering of growth or colonies spread across the plate, making it difficult to differentiate the cells due to the lack of separation.
If you have a suspension containing 2,500,000 bacteria / mL that is plated out, should you expect 2,500,000 colonies? Elaborate.
No, the confluent growth would occur. You could use other means to measure the growth.
What means of measurement would be most suitable to measure large numbers of expected colony growths.
Making suitable dilutions of the suspended and plating out these dilutions.
What does TNTC signify?
Too numerous to count.
When given a bacterial culture ans asked to determine the number of visible cell/ mL, what should be the first step to follow?
Prepare a series of ten-fold dilutions.
What frequency should the plating be done at?
Triplicate.
True or false. You will need to apply aseptic technique to not contaminate and decrees the count.
False. Aseptic techniques are use to AVOID inflating the count due to contaminates.
Plates containing between how many colonies should be used in determining the cell count.
30-300
