Its actually not a fixed 600nm kind of thing. You are measuring the light scattered of medium, so you have to avoid any wavelength which corresponds to absorption of molecules in medium or in bacteria itself e.g. if you will use a 254- 260nm DNA of bacteria will absorb it to maximum, same is case with 280nm. So, you won't get the actual scattered light. 600nm filters are easily available, plus scattering will be in noticeable limit as more the wavelength, lesser is scattering. Although there are many reports where people have used 900nm, 997nm. So, it hardly matters. As customary we take 600nm for mid log phase. Important is
1.you have to avoid a wavelength which corresponds to absorption maxima of a molecule in your preparation
2.Look for references used specific wavelength other than 600nm for your strain.
3.what ever wavelength you take, take the same throughout your experiment.
Do let me know if I answered you satisfactorily.
At 600 nm we actually measure the opacity or turbidity of a cell suspension which is proportional to cell number. I used it many times following bacterial growth. Since we are not measuring absorbance we have to take care in the sample dilution, maintaining the optical density below 0.6. Above this value there is no linear correspondence with cell number. I hope that this will be useful for you
Its actually not a fixed 600nm kind of thing. You are measuring the light scattered of medium, so you have to avoid any wavelength which corresponds to absorption of molecules in medium or in bacteria itself e.g. if you will use a 254- 260nm DNA of bacteria will absorb it to maximum, same is case with 280nm. So, you won't get the actual scattered light. 600nm filters are easily available, plus scattering will be in noticeable limit as more the wavelength, lesser is scattering. Although there are many reports where people have used 900nm, 997nm. So, it hardly matters. As customary we take 600nm for mid log phase. Important is
1.you have to avoid a wavelength which corresponds to absorption maxima of a molecule in your preparation
2.Look for references used specific wavelength other than 600nm for your strain.
3.what ever wavelength you take, take the same throughout your experiment.
Do let me know if I answered you satisfactorily.
Satya explained it very nicely! Everyone uses 600nm, because protocols then can be compared and exchanged more easily.. but you could choose your own wavelength, if you want though ;)
yes, its true that everyone uses 600nm, because protocols can be compared and exchanged more easily. many other describes 620nm, 580nm., etc. too, that is also near by values. But one should choose own wavelength, after standardizing growth in liquid medium, log phase and level of turbidity of your own strain. Ultimately, you should avoid a wavelength which corresponds to absorption maxima of a molecule in your preparation as explained so well by Satya Sharma.
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