Development of an inducible lytic system for functional metagenomic screening

Functional metagenomic is a powerful tool that allows the discovery of new enzymes with biotechnological potential. During functional screenings of enzymes, the ability of the substrate to enter the surrogate host or the ability of this bacterium to export heterologous extracellular enzymes may hamper the technique. Here we have used an inducible autolysis system that lyses bacteria thus releasing its content in both, liquid and solid cultures, in response to anhydrotetracycline. The lytic cluster is tightly regulated to prevent impaired bacterial growth in absence of the inducer and produced very efficient though not complete bacterial lysis upon induction, which allowed the recovery of live bacteria. The system can be used in combination with specialised fosmids and E. coli strains that maximize transcription of metagenomic DNA. Our results show that colony-lysis on plates allows detection of an endogenous intracellular amylase activity naturally present in E. coli and clearly increased detection of clones coding for cellulase activities in a metagenomic screening, while allowing recovery of survivor positive clones from the lysed colonies in all cases. Therefore, this tool represents an important step towards the effective access to the extraordinary potential of the uncultivated bacteria genetic resources.