ABLE C Competent Cells for toxic clones enhance the probability of cloning DNA encoding toxic proteins. By reducing the copy number of ColE1-derived plasmids, the ABLE C strain decreases the levels of cloned gene products and enhances the probability of propagating a toxic clone. The ABLE C Competent Cells provide a viable alternative to commonly used cloning vectors with high copy numbers. Positive clones observed on initial screening of lambda libraries can be excised or re-cloned into any convenient vector and can be introduced into ABLE C strains.