BRAINCAKETurbidity
As bacteria multiply in a liquid broth, the broth becomes cloudy, or turbid. The more cells there are, the more light they absorb and scatter. Turbidity can therefore be used as an indirect measure of cell number.
Turbidity is measured with a colorimeter (or spectrophotometer):
1. Put sterile broth in a cuvette and use it as a blank to set the colorimeter to zero absorbance.
2. Place a well-mixed sample of the culture in a clean cuvette and measure its absorbance (or transmission).
3. Repeat at intervals to follow growth. The higher the absorbance, the more cells are present.
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Key terms in this lesson
- absorbance
- A measure of how much light of a given wavelength is absorbed by a sample, used to estimate quantities such as cell density.
More in Bacteria and Disease
- Aseptic Culture Techniques
- Selective Media
- Growing a Pure Culture
- Counting the Number of Cells
- Dilution Plating
- Area and Mass of Fungi
- Growth of Bacterial Colonies
- Logarithmic Scale
All 30 lessons in Bacteria and Disease · All Edexcel A-level Biology topics