Hello Minal Bhalerao

In case you wish to raise a secondary culture (in a minimal medium) from a primary culture (grown in a nutrient-rich medium, eg: Nutrient broth, Luria broth, etc.), you should wash your cells before inoculating them. This is done to remove the spent (used up) media from the primary cells or any metabolites or nutrients that would contaminate your minimal media.

Whenever we shift down the culture (transferring cells from a nutrient-rich to a minimal or nutritionally-low media), it is recommended that we wash the cells before inoculating them to raise the secondary culture.

Washing will not have any impact on the growth pattern. But, instead change/shift in media will cause a definite and notable change in the growth pattern. Shifting down would certainly extend the lag phase of your culture. If you wish to perform any growth-related experiments, using a common media for raising primary and secondary cultures is advisable. This would not extend your lag phase and your cells will begin to grow quickly.

Good luck!

As Jatin Chadha said, wash to remove all of the culture media, especially is you are trying to model growth in the defined media, you don't want residual amounts of the nutrient broth to skew your results.

Washing the culture is the most preferred method.

How you wash it,is important.

1. Centrifuge the overnight broth culture in Sterile Test tubes at 2000 rpm for 10 minutes.

2. Discard the supernatant.

3. Add sterile saline(0.85% NaCl) and re-suspend it thoroughly.

4. Repeat above steps twice.

5. Adjust cell density and use it.