Dilutions are useful in science when making solutions or growing an acceptable number of bacterial colonies to count.Incubate at 35° ☒ in case of bacterial culture and for fungus incubate at 23°☒.After following these steps, pour media TSA or desired media into the plates and let them solidify.Repeat this procedure until the 10 th plate.After making dilutions, pour 100ul with a pipette from 1st test tube into the respective plate.
From 1st tube transfer 1ml (known volume) in 2nd test tube and repeat steps till 10th test tube.After this, transfer 1 ml (known volume) of the culture from the previously made dilution into the 1st tube having 9ml normal saline.Make dilution in the 1st tube by taking 2ml normal saline in a tube and inoculate the desired culture in it.If using a metal loop, be sure to cool the loop by touching the sterile cooled liquid media.Use either disposable inoculation loop or a metal loop that can be heat sterilized to inoculate plates, slants and liquid tubes.Agar (Tryptic Soy Agar, Selective media).Each dilution will reduce the concentration of bacteria by a specific amount. Like I mention above A serial dilution is a series of sequential dilutions used to reduce a dense culture of cells to a more usable concentration. Usually, the dilution factor at each step is constant, resulting in a geometric progression of the concentration in a logarithmic fashion. Multiple Dilution Serial DilutionĪ serial dilution is the stepwise dilution of a substance in a solution. If the concentration is 35,000 CFU/ml (104), and 35 CFU/ml is the target concentration, the following serial dilutions can be performed. Multiple dilutions are required to decrease the sample concentration by multiple logs. Example: 1:10 dilution – if the concentration is 1,000 CFU, a one log dilution will drop the concentration to 100 CFU. The 10 represents the total size of the final sample.įor example, a sample size of 1 ml is added to 9 ml of diluent to equal a total of 10 ml. The 1 represents the amount of sample added. To complete a tenfold dilution, the ratio must be 1:10. Types of Dilutions Log DilutionsĪ log dilution is a tenfold dilution, meaning the concentration is decreased by a multiple of ten. I have created this guide to provide a better understanding of dilutions and should be used as a guideline, not a replacement for laboratory procedures. In microbiology, serial dilutions (log dilutions) are used to decrease a bacterial concentration to a required concentration for a specific test method, or to a concentration which is easier to count when plated to an agar plate. Facebook Tweet Pin LinkedIn Shares 32 Emailĭilution is the process of making a solution weaker or less concentrated.
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