(Multiple) Isotope probing approaches to trace the fate of environmental chemicals and the formation of non-extractable 'bound' residues

Procedures for the analysis of turnover of chemicals (and of natural compounds) are well developed using radio or stable isotope labelled tracer compounds in various standardized OECD tests. Due to the analytical focus on the isotope label the chemical speciation of the so-called non-extractable residues (NER) in soils and sediments often remains unknown. These NER may stem from parent compounds, metabolites, microbial biomass, or from precipitated carbonates after productive microbial degradation. Fate studies mostly do not describe the link to phylogenetic assignment of degraders and microbial ecology although in these fields various isotope tracer applications are well developed, too. We present several options for integrating both approaches in environmental biotechnology and how they can be used to improve knowledge in microbial ecology.