Incorporating proprietary E. cloni technology, EXPRESS BL21(DE3) competent cells provide efficient cloning and protein expression. With a transformation efficiency of >5 × 109 cfu/μg, E. cloni EXPRESS electrocompetent cells eliminate the need to transfer plasmids from a cloning strain into an expression strain. Increased recombinant yields allow fast production of complex expression libraries using any T7 expression vector. The pLysS cells also produce T7 lysozyme, which suppresses “leaky” T7 RNA polymerase prior to IPTG induction, helping to stabilize inserts coding for products deleterious to the host cell. The pLysE provides a high level of T7 lysozyme expression, for insert stabilization. These strains are also available as chemically competent cells, for routine protein expression.