Review
Scaling up is technique used to estimate the size of huge population of bacteria based on the calculations from smaller sample.
Serial dilution is a step by step dilution of concentrated solution into diluted solution, where each dilution gets you closer to your goal.
You can multiply together all of the dilution factors to get total dilution factor.
It is very important to dilute sample up to a certain extent, so that the number of cells/bacteria are in countable range. If after a dilution, the number of cells/bacteria is between 25 and 250, they are both easy to count and valid for scaling up.
It is also important to know that even if you have perfect technique in mixing and pipetting, you can only estimate the number of bacteria present in your sample. It is impossible to know the exact number of bacteria.
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