Efficient pyramidal arrangement of an ordered cosmid library: Rapid screening of genes of the tacrolimus-producer Streptomyces sp. ATCC 55098.

A gene library is a useful tool for molecular biology studies, but the classical screening of multiple plates is laborious and time-consuming. Cosmid gene libraries are particularly well suited for isolation of large gene clusters encoding the biosynthetic pathways of secondary metabolites in Streptomyces. A gene library of the immunosuppressant tacrolimus-producer strain Streptomyces sp. ATCC 55098 was constructed in the SuperCos1 vector and 1656 clones were organized in an easy pyramidal arrangement system. This clustering method allows a dual efficient screening (PCR and in situ colony hybridization) of the gene library in a two-step method by using only one 96-well plate. The dual screening combines the advantages of both techniques, the swiftness of PCR and the robustness of colony hybridization.