Question

Suppose your professor handed you a test tube with 2.0 mL of an E. coli broth culture in it and told you to make a 10–1 dilution of the entire culture. Explain how you would do this?

Answer 1

Serial dilution method

Step-by-step explanation:

To make a dilution of 10-1 dilution, the culture containing the E. coli broth has to be diluted to make it as 0.1 dilution.

STEPS TO BE FOLLOWED:

1. Take the given test tube with 2 ml of E.coli broth culture.
2. Take another new test tube with 9 ml of saline solution or distilled water.
3. From 2 ml of broth solution, take only 1 ml of culture and suspend in 9 ml of saline or distilled water.
4. Now, 1 ml of culture is suspended in 9 ml of saline and the broth is suspended. This constitute 10-1 dilution
5. If this 10-1 is again suspended in another 9 ml of water leads to 10-2 dilution factor.
6. This methods can be used for both solid and liquid samples like soil or sewage.

Uses of serial dilution:

1. Helps in determining the different species of organisms present in soil.
2. Organisms (Bacteria) can be distinctly identified from each other since the organisms suspended count will be less when they are dilutes upto 10-10 dilution.