2. Quantifying bacteria

Question 1

preparing a 100-fold serial dilution

Answer 1

1. mix suspension well
2. add o.1ml of culture to 9.9ml water (10-2 dilution) or ringers solution (water and salt)
3. repeat
4. plate solution (0.1ml)

Question 2

turbidimetric counts

Answer 2

• 2-fold dilution series in cuvettes
• better on a large scale e.g. in a fermenter
• make sure spectrophotometer is set to measure at 600nm wavelength and there is a blank medium (nutrient broth)
• read attenuance of undiluted stock culture and dilutions using a spectrophotometer
• attenuance decreases with dilution
• smaller range at which it works,