Would the standard curve obtained with E Coli grown in TSB broth be valid to measure an coli culture growing NB?

No, the standard curve obtained with _E. coli_ grown in TSB broth would not be valid to measure an _E. coli_ culture growing in NB.

Different culture media can affect the growth characteristics and physiology of bacteria, including _E. coli_. TSB (Tryptic Soy Broth) and NB (Nutrient Broth) are two commonly used culture media, but they have different compositions and provide different nutrients to the bacteria.

The standard curve for _E. coli_ grown in TSB broth is specific to the conditions and nutrient composition of TSB. The growth rate, cell density, and metabolic activity of _E. coli_ can vary when grown in NB compared to TSB. This variation can affect the absorbance or fluorescence measurements used to quantify the _E. coli_ concentration, leading to inaccurate results if the TSB-based standard curve is applied to an _E. coli_ culture grown in NB.

Therefore, to obtain accurate measurements of _E. coli_ concentration in a culture grown in NB, it is necessary to generate a standard curve specifically for _E. coli_ grown in NB under the same experimental conditions. This ensures that the standard curve represents the growth characteristics and optical properties of _E. coli_ in NB, providing reliable quantification of the bacterial concentration.