Question

PLEASE TYPE & EXPLAIN which covers both parts A&B

A) You conduct a serial dilution where you repeatedly dilute .5mL of solution into 4.5 mL of diluent three times. What is the dilution of your solution?

A.1:10 B.1:100 C.1:1000 D.1: 3, ALSO imagine you put 1ml of milk onto a plate and after 24 hours observed 135 colonies on the plate, how many CFU/mL are in the milk? NOW Imagine you put 1ml of milk onto a plate and after 24 hours observed 135 colonies on the plate, how many CFU/ mL are in the milk?

B) what do we learn of this experiment that will continue to influence us for many years to come?  

Answer 1

Ans. #A. 1. Total volume made upto = 0.5 mL + 4.5 mL = 5.0 mL

Immediate dilution factor (IDF) = Vol. of inoculum / Total vol. made upto

                                                            = 0.5 mL / 5.0 L

                                                            = 0.1

# Since all the three dilutions are prepared similarly, the IDF for them remains to be 0.1.

Now,

Total dilution factor (TDF) = IDF for 1^st dilution x IDF for 2^nd dilution x IDF for 3^rd dilution

                                                = 0.1 x 0.1 x 0.1

                                                = 0.001 = 1 : 1000

So, correct option is- C. 1 : 1000

#2. CFU count of milk = Observed CFU on plate / Vol. of inoculum

                                    = 135 CFU / 1.0 mL

                                    = 135 CFU/mL

#B. Serial dilution and enumeration and microbes is an inevitable practice of microbiology-based platforms like food industry (for example, determining microbial load of the food sample), pharmaceutical industry, research, etc. So, learning these skills would benefit you (and us all, too) in all such aspects in next coming years, may even give a boost to your careers.