Serial Dilutions: Salmonella Typhimurium Culture

Decent Essays
Serial dilutions, also known as limiting dilution series, help to determine an estimation of how many phages/viruses are in a given culture (Zelterman et al., 2010). In this experiment we determined how many phages were in our given Salmonella typhimurium culture by doing three serial dilutions of an original phage suspension. This is important because it will allow us to get a rough estimation of how many phages where in our original sample and also provide us with knowledge on how to perform serial dilutions with phages which can be used to determine an unknown sample in the future. We expect that there will be less plaques on the last dilution than in the first plated dilution because the more diluted each test tube is the less phages are…show more content…
Each test tube containing 9-ml of a dilution blank (distilled water) was aseptically inoculated with 1ml of Salmonella typhimurium phage. One test tube was a control that contained no phage and was diluted into a tube and poured on the plate. The first inoculation was the original phage suspension and from there we diluted it three more times in 9-ml dilution blank test tubes. Once the test tubes were inoculated .5-ml of each dilution was placed in soft agar tubes quickly, so that it would not solidify, and then were poured on the trypticase-soy agar plates. The TS agar plates were left to incubate for 6-10 hours. Once done incubating each plate was then counted to see how many plaques had formed on the bacteria lawn.
The results of the plaque assay showed that the 10^-2 plated dilution contained more than 300 plaques and was too many to count. For the 10^-3 plated dilution there were 37 plaques which indicated there were 3.7*10^4 pfu/ml. The last plate which was a 10^-4 dilution had four plaques on it and was too small of an amount to use to find the original phages in the suspension.
Get Access