Explain for Procedure Quantitative Determination of Viable Microbes?
Now carry out the exercise following the steps included herewith:
1. Label the diluent tubes from 10-1 through 10-7 and prepare dilutions.
2. Label the nutrient agar plates as 10-5, 10-6 and 10-7 in duplicate.
3. Pour 0.1 ml of each dilution from 10-5 through 10-7 over the agar surface of labeled plates in the centre.
4. Spread the inoculum over the entire surface by means of a sterile bent glass rod (spreader) till it is absorbed completely. Spreader can be made sterile by dipping in alcohol followed by passing through a flame of Bunsen burner or by autoclaving.
5. Keep the plates for incubation at 37°C for 24 hours.
6. Following incubation, observe and made the colony count. Calculate colony forming units/ml of the original sample by multiplying the number of colonies counted by the dilution factor and divided by the volume used. Use only dilution plates yielding colonies between 30 and 300 for calculations. Plates with more than 300 colonies are designated as too numerous to count (TNTC) and with fewer than 30 colonies are designated as too few to count (TFTC).