Dilution Techniques and Calculations* Bacteria, under good into such large popul

Question

Dilution Techniques and Calculations* Bacteria, under good into such large populations that it B dilute them to isolate single colonies or to obtain esti- mates of their numbers. This requires mixing a small, accurately measured sample with a lauge volume of ster Bxerience has shown chat beitera dlution ile water or saline, which is called the diluent or dilubaned with very large dilutlions tion blank. Accurate dilutions of a sample are obtainedi made out of a series of smaller cdiutlons ia through the use of pipettes. For are usually made in multiples of ten. necessary to ,whichis so*1:10 iletestelomeasurebamplehisoloniteerilingamL 05 +45 5.0 10 or diluE Experience has shown that better accuracy is is made out of a series of smaller dilutions rather than one large dilution. This series is called a serial dilution, and the total dilution is the product of each dilution in the series. For eample, if 1 ml is diluted with 9 ml, and then 1 ml of that dilution is put into a secobd 9 ml dilu- convenience, dilutions A single dilution is calculated as follows Volume of the sample Total (volume of the sample+ the diluen) ent, the fnal dilution will be 1 1 r 1:100 For example, the diution of 1 mililiter into 9 millidites equals 1 which is I and is written 1:10 To facilitate calkculations, the dilution is written in exponential notation. In the example above, the final dilation 1:100 would be written 10-2. Remember, The same formula applis for all dilutions, regardless of the volumes. A dilution of O.1 milliliter into 0.9 milli liter equals 1:100 -001 0-2 1 110 0.1 which is ol 0.1 + 0.9 (See the seetion Exponents, Expopential Notation, and Logrithms, ep page 410.) A serial dilutlon is illustrated Unpablisbed popes Whitewaters, WE Uiveislty of Waconsth, nd 9 ml broth n each tabe Original 1:10-10 1:100-10 Figure B.1 A 1 ml sample fron tube will I sal or ter of cell peesent in I ml of the or the brst tube will cootin 1/10 che number of cells oe bhe A I al sample froa the ast ue il contain 1/100,000 present in in I ral of the criçinal sample the

Explanation / Answer

1. Dilution will be in the order 10-1 - 10-2 - 10-3

2. Dilution will be in the order 10-2-10-4-10-5 -10-6

3. Dilution will be in the order 10-1 - 10-2 -10-3

4. Dilution will be in the order 5*10-2 -5*10-3 - 5*10-5

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