bacterial concentration

[Silvia_84]

Hi guys,

 

I am following a protocol for the DNA extraction from Gram negative bacteria. I am completely new in this stuff.The protocol says to start from a bacterial suspension of approximately 10⁹ CFUml . My question is : How can I determine and check if I have this concentration?with the spectrophotometer? if yes, how can I get the concentrationj from the absorbance?

 

Thank you very much.

 

 

[CharonY]

Typically this requires the generation of a calibration curve. I.e. you dilute samples to e.g. OD 0.1, 0.2...1. Then, from each concentration you plate the sample (usually you have to dilute them prior plating again) to count the CFUs.

 

After that you will have the CFUs for each given OD which is usually a linear relationship, i.e. you can just use simple linear regression.