Microbiology - Serial Dilution


Jeff Lawrence

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
	DNA			TE
	Enzyme			Enzyme Dilution Buffer (with Glycerol)
	Bacteriophage P1	5 mM CaCl2, 10 mM MgSO4
	Bacterial cells		0.9% NaCl
Last Update: Thursday June 19 2014
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Eric Kofoid eckofoid at ucdavis.edu