20 Questions
How many microscope fields are typically counted in the Petroff-Hausser slide method?
10
What is the main disadvantage of using the Petroff-Hausser slide for direct microscopic counting?
It cannot distinguish between living and dead cells during counting.
In the Breed method, bacteria are counted in at least how many different areas under the microscope?
10
What is the basis for counting in the Thoma slide method?
Counting in a volume of 0.1 mm3
What is the final result obtained by the counting method with the Thoma slide?
Number of microorganisms per milliliter
Which method is most suitable for determining the amount of long filament bacteria?
Chemical measurement of cell mass
Why are direct microscopic counting methods not suitable for samples containing low concentrations of microorganisms?
Inability to distinguish between live and dead microorganisms
What is the disadvantage of direct microscopic counting methods?
Inability to distinguish between live and dead microorganisms
What must be done prior to counting motile cells using direct microscopic counting methods?
Cell immobilization
Which method is suitable for determining the amount of single-celled organisms such as bacteria and yeasts?
Total cell count
What is the main disadvantage of direct microscopic counting methods for determining the total cell number?
Inability to distinguish between live and dead microorganisms
Which method is most suitable for determining the amount of long filament bacteria?
Measurement of dry weight of cells
What must be done prior to counting motile cells using direct microscopic counting methods?
Add a chemical fixative to immobilize the cells
In the Breed method, bacteria are counted in at least how many different areas under the microscope?
6 different areas
Why are direct microscopic counting methods not suitable for samples containing low concentrations of microorganisms?
They may not accurately distinguish between live and dead microorganisms
What is the main disadvantage of using the Breed method for direct microscopic counting?
Inability to measure all dead or live cells accurately
In the Thoma slide method, the counting area is divided into how many large squares?
16 large squares
What is the basis for counting in the Petroff-Hausser slide method?
Dividing the middle part of the well area by lines
What is the advantage of using the Thoma slide method for counting blood, sperm, and yeast?
Counting in a volume of 0.1 mm3
Why are direct microscopic counting methods not as accurate as culture methods in measuring all dead or live cells?
Difficulty in distinguishing between live and dead cells
Test your knowledge on the quantification of microorganisms, including cell counting and cell mass measurement methods. Explore techniques for determining the amount of single-celled organisms and long filament bacteria.
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