Microbiology - Serial Dilution
1. An undiluted (stock) solution is termed the 100 dilution. This may be a chemical solution, or a suspension of bacteria or bacteriophage.
2. Typical diluions are 10-fold dilutions; each dilution is 1/10th the concentration of the previous dilution. The first 10-fold dilution is termed the 10-1 dilution.
3. Each subsequent dilution is made from a previous dilution. Here is a series of 10-fold dilutions:
Start: 100 mL 100 100 mL 10-1 100 mL 10-2 100 mL 10-3
Add: +900 mL Buf. +900 mL Buf. +900 mL Buf. +900 mL Buf.
Yield: 1000 mL 10-1 1000 mL 10-2 1000 mL 10-3 1000 mL 10-4
4. Since 100 mL of the 10-1 dilution is used to make the 10-2 dilution, only 900 mL remains for use.
5. The buffer used for dilution depends on the substance being diluted:
Substance Dilution Buffer
Chemical Sterile water
Enzyme Enzyme Dilution Buffer (with Glycerol)
Bacteriophage P1 5 mM CaCl2, 10 mM MgSO4
Bacterial cells 0.9% NaCl
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