I specifically need to know whether the OD reading has to be taken at 600 nm. Generally growth curve analysis is done at 600 nm.
One paper mentions that the turbidity reading for M9 media is taken at 460nm (The Role of Glycerol and Isopropyl Thiogalactoside in Escherichia coli Growth and Lactose Induction of β-Galactosidase, Law et. al, 2002). Can i also take my growth curve readings at 460 nm ?
Another paper (Effect on β-galactosidase synthesis and burden on growth of osmotic stress in Escherichia coli, Malakar et. al, 2014) performs growth curve analysis at 595 nm.
So what is the correct OD for growth curve analysis? Please suggest papers which provide the protocol for the same, if possible.
You can use OD600 for your measurements.
One thing to have in mind though, is that OD600 is sensitive to the size of cells. Some constructs or protocols may influence the size of your E. coli cells so just be wary of that.
Good luck!
You can take your growth curve at whatever wavelength you want -- as long as your medium is not absorbing at the same wavelength. M9 + glycerol will not absorb at any visible wavelength. Nearly no medium absorbs at 600 nm or greater. Therefore 600 nm has been chosen as the standard used by most people. Generally E. coli will scatter more light at shorter wavelengths. So the shorter the wavelength you choose, the higher the values will be.
I think if you are free to choose, then you should use 600 nm, because that will make your values directly comparable to those published by most other people, including those using different media.
I agree with John Schloendorn that 600nm is the normal wavelength (although many also use 595 which is very similar). Measuring turbidity at 460 is pretty unusual.
@Ms. Ana , I will be working with wild type e.coli, strains like e.coli k12.
Thank you for your answer !
Thank you @John Schloendorn and @Micheal J. Benedik for your valuable inputs !
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