I want to calculate bacterial number in water, but the number of bacteria is very low in different water samples. Is it possible to culture water in nutrient broth medium first and then make serial dilution for CFU calculation? and how to calculate CFU in original sample?
Suggest you read Standard Method for examination of Water and Waste Water -https://www.standardmethods.org/
fTo you question - of course not. Numbers obtained after culturing in nutrient broth will in n o way represent inoculum - unless there's no growth.
Consider filtration, MPN
Fatemeh Shayesteh, CFU is dependent on the volume of sample plated. Smaller volumes yield higher reporting levels, and larger volumes yield lower reporting levels.
Report per 100mL of water: count/100mL = (# of colonies/volume of sample analyzed) x 100
So if you counted 10 colonies on an agar plate and used 2 mL of sample, your minimum reporting level would be 50 CFU/100 mL and result would be 500 CFU/100 mL. If you counted 10 colonies and used 0.5 mL of sample, your minimum reporting level would be 200 CFU/100 mL and result would be 2000 CFU/100 mL.
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