Metagenome - a challenging source of enzyme discovery

Evolution over very long periods of time has generated a vast pool of physiologies and molecular adaptations to enable microorganisms to thrive in a wide range of living conditions. These solutions may be valuable tools in the rational design of technical processes. However, molecular ecological studies have proven that the vast majority of microorganisms cannot be cultivated in the laboratory and was therefore ignored when traditional screening procedures were applied to search for novel enzymes and bioactives. Cultivation-independent approaches now open up the roads to analyze and screen the genetically and metabolically rich microbial communities in their entirety. In these approaches DNA is directly isolated from environmental samples and cloned into suitable vectors to construct complex genomic libraries. These libraries can be analyzed for novel genes and pathways with sequence-based techniques or through screening proteins and drugs that are being produced in surrogate hosts. The approach of directly cloning environmental DNA greatly enhances the opportunities to take full advantage of the enormous naturally occurring microbial resources. (C) 2002 Elsevier Science B.V. All rights reserved.