Cell Calculations 1 — Haemocytometer
The data provided are from microscopic observations using a haemocytometer. Estimate the number of cells in a given volume of the original culture.
(For simplicity we ignore the fact that samples from high-density cultures are generally diluted before addition to the haemocytometer chamber.)
A general approach to these calculations is:
- Determine the volume of the haemocytometer, which will be in mm3.
- Convert this to cm3, the units of volume of the culture medium.
- Determine the concentration of cells in the chamber by dividing the number observed by the volume of the chamber.
- Then multiply by the original volume of the medium to get the total number cells.
Here is a specific example:
- 20 cells observed in the haemocytomer above from a sample volume of 5 cm3
- Vol of chamber = 1 mm x 1 mm x 0.02 mm = 0.02 mm3
- 1 cm3 = 1000 mm3 ∴ vol = 2 x 10–5 cm3
- ∴ concentration = 20/(2 x 10–5) = 106 cells per cm3
- ∴ number in 5 cm3 = 5 x 106 cells