Metabolome

The metabolome refers to the complete set of small-molecule chemicals found within a biological sample.

as well as exogenous chemicals (such as drugs, environmental contaminants, food additives, toxins and other xenobiotics) that are not naturally produced by an organism.

A primary metabolite is directly involved in the normal growth, development, and reproduction.

A secondary metabolite is not directly involved in those processes, but usually has important ecological function.

Secondary metabolites may include pigments, antibiotics or waste products derived from partially metabolized xenobiotics.

As a result, an organism's metabolome can serve as an excellent probe of its phenotype (i.e. the product of its genotype and its environment).

Metabolites can be measured (identified, quantified or classified) using a number of different technologies including NMR spectroscopy and mass spectrometry.

As an analytical technique, NMR is non-destructive, non-biased, easily quantifiable, requires little or no separation, permits the identification of novel compounds and it needs no chemical derivatization.

The charged molecules are then propelled through space using electrodes or magnets and their speed, rate of curvature, or other physical characteristics are measured to determine their mass-to-charge ratio.

This separation step is required to simplify the resulting mass spectra and to permit more accurate compound identification.

Some mass spectrometry methods also require that the molecules be derivatized or chemically modified so that they are more amenable for chromatographic separation (this is particularly true for GC-MS).

MS instruments can also be configured for very high throughput metabolome analyses (hundreds to thousands of samples a day).

LC-MS is particularly amenable to detecting hydrophobic molecules (lipids, fatty acids) and peptides while GC-MS is best for detecting small molecules (<500 Da) and highly volatile compounds (esters, amines, ketones, alkanes, thiols).

Unlike the genome or even the proteome, the metabolome is a highly dynamic entity that can change dramatically, over a period of just seconds or minutes.

This makes it particularly useful for metabolomic researchers who are studying yeast as a model organism or who are looking into optimizing the production of fermented beverages (wine, beer).

Secondary electrospray ionization-high resolution mass spectrometry SESI-HRMS is a non-invasive analytical technique that allows us to monitor the yeast metabolic activities.

Secondary electrospray ionization (SESI-MS) can discriminate between eleven E. Coli strains thanks to the volatile organic compound profiling.