Figure 1.

Typical workflow for metabolic profiling experiments on microorganisms. Harvesting of microbes for metabolite profiling may involve a rapid quenching step. Frozen samples are extracted with organic solvents, optionally including a grinding step. For GC-MS analysis, extracts have to be chemically derivatized to enhance the thermal stability and volatility of the compounds. Most frequently, the first standardization steps involve normalization to labeled internal standard(s) and to a reference value for the analyzed biomass (e.g. culture optical density (OD)) for the comparison of data from different samples. Logarithmic transformation is commonly utilized to achieve a near normal distribution of the data. For further descriptions, see the text.