Dear Rabia,

You have to do dry mass measurements to connect them with OD values for your strain. You can do it as follows:

1. Culture you strain in the same conditions as in your experiments (e.g. the same medium).

2. Take samples in a certain timepoints, e.g. at the end of logarithmic phase or stationary phase. The volume of the single sample should be approximately 5 - 20 ml.

3. Measure the OD.

4. Centrifuge samples to pellet bacterial cells.

5. Get rid of supernatants. Wash pellets twice with water, centrifuge after each washing.

6. Resuspend bacterial pellets in water (5-10 ml).

7. Transfer suspensions to some containers (e.g. single-use aluminium scale pans), which you have weighed before.

8. Place your samples to oven (105 C) for overnight drying.

9. Cool your samples and weight them again. Subtract the mass of empty scale pan from your result.

10. Now, you have your dry mass results. Don't forget about the volume of your sample from the culture in your calculations.

11. Now you can compare dry mass with as OD measurements.

All best,

Piotr

Thann you sooo much. you dont know you have solved my big big problem. i will definitely follow this. 

ragards

rabia

 Very clear explanation Biniarz...this is also useful to me. Thanks

 Dear biniarz

     Kindly tell me in step 5 resuspension of pellet in 5-10 ml water is necessary or we can dry pellets without water

Dear Rabia,

Of course you can do it, if you know the weight of your empty centrifuge-tube.

You have to follow these steps (no. 6 and 7) only if you want to transfer your samples (pellets) to scale pan of known weight. You can also transfer dry pellets, but doing it in a suspension in definitely more precise.

All best,

Piotr

Respected Biniarz

Thanks alots

respected Biniarz:

                            can we use same procedure for the determination of the dry mass of fungus