To calculate the number of bacteria/mL in the original undiluted culture, you can use the following steps:
Step 1: Calculate the dilution factor
The dilution factor is the ratio of the volume plated (200 µL) to the total volume plated (in this case, the total volume plated is equal to the volume of the original culture before dilution).
Dilution Factor = (Volume Plated)/(Total Volume Plated)
Dilution Factor = (200 µL)/(Total Volume Plated)
Step 2: Calculate the total volume plated
The total volume plated is the volume of the original culture before dilution. Since you used 200 µL for plating, the total volume plated is equal to 200 µL.
Total Volume Plated = 200 µL
Step 3: Calculate the total number of bacteria in the original culture
The total number of bacteria in the original culture can be calculated by multiplying the dilution factor by the number of colonies counted on the plate.
Total Number of Bacteria = Dilution Factor x Number of Colonies
Total Number of Bacteria = Dilution Factor x 38
Step 4: Calculate the number of bacteria/mL in the original undiluted culture
To calculate the number of bacteria/mL in the original undiluted culture, we need to divide the total number of bacteria by the total volume plated.
Number of Bacteria/mL (Original Undiluted Culture) = Total Number of Bacteria/Total Volume Plated
Number of Bacteria/mL (Original Undiluted Culture) = Total Number of Bacteria/200 µL
By using these steps and the given information, you can calculate the number of bacteria/mL in the original undiluted culture.