Abstract: The invention generally relates to metabolic labeling of a target organism with a stable isotope. In a first aspect, the present invention relates to a method for metabolic labeling of a target organism with a stable isotope. The present invention also relates to a method of producing a diet for metabolic labeling of a target organism and to a diet composition for metabolic labeling of a target organism. In a further aspect the invention describes the use of the diet composition according to the present invention for producing a metabolically labeled target organism as a reference for a quantitative proteomic approach. The present invention also relates, in a further aspect, to the use of a diet composition for pulse SILAC labeling. The present invention also relates to the use of a target organism labeled by the method according to the first aspect of the present invention as a spike-in standard in quantitative proteomics approaches.

Abstract: The invention relates to a novel method for the in-vivo labeling of biopolymers such as proteins, nucleic acids, lipids, carbohydrates and biodegradable plastic using isotopes, especially stabile isotopes. The invention also relates to the use of chemolithotrophic bacteria for the in-vivo isotopic labeling of biopolymers. In particular, the invention relates to the use of CO2-fixing bacteria, such as Ralstonia eurtropha and related methanogenic bacteria for the in-vivo isotopic labeling, especially for labeling using the stable isotope 13C alone and in combination with other isotopes. In addition, the invention relates to the use of isotropically labeled biomolecules in therapeutic and diagnostic applications, especially in spectroscopic methods and generally as tracers.