Dilution Problem. A culture of Staphylococcus is diluted as follows: (1) 20 mL are added to 80 mL of water. (2) 10 μL from (1) are then added to 9.99 mL of water. (3) A 10^-2 dilution is made from tube # (2). (4) 100 μL from (3) are plated for a pour plate and incubated. There were 34 colonies counted on one quarter of the plate following incubation. a) What was the overall dilution? b) How many cfu/mL were present in the original culture? Growth Problem. A culture with approximately 2 x 10^3 cells/mL were incubated. After 3 hours, the number of cells had increased to 3 x 10^5. a) How long was the generation time in minutes? b) How many generations have occurred?
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Given dilutions: 1) 20 mL added to 80 mL of water = 1:5 dilution 2) 10 μL from (1) added to 9.99 mL of water = 1:1000 dilution 3) 10^-2 dilution made from tube #2 = 1:100 dilution Overall dilution factor = 5 * 1000 * 100 = 500,000 Show more…
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A culture of Staphylococcus is diluted as follows: (1) 20 mL are added to 80 mL of water. (2) 10 uL from (1) are then added to 9.99 mL of water. (3) A 10^-2 dilution is made from tube # (2). (4) 100 uL from (3) are plated for a pour plate and incubated. There were 34 colonies counted on one quarter of the plate following incubation. a) What was the overall dilution? b) How many cfu/mL were present in the original culture? c) How many milliliters of water is needed to make a 10^-3 dilution using 1000 uL from the original culture?
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