Answer:
1.37 x
CFU/mL
Step-by-step explanation:
First, the dilution factor needs to be calculated.
Since four 9 ml dilution blanks were prepared, the dilution factor that yielded 137 colonies is of
.
Next is to divide the colony forming unit from the dilution by the dilution factor:
137/
= 137 x

In order to get the CFU/ml, divide the CFU from the dilution by the plated volume (1 mL) from the final dilution tube.
137 x
/1 = 1.37 x

Hence, the CFU/ml present in the original E. coli sample is 1.37 x
.
cfu/ml = (no. of colonies x dilution factor) / volume of culture plate