XJ Autolysis E. coli strains are a new alternative for bacterial transformation and lysis. These strains are efficiently lysed following arabinose-induced expression of the bacteriophage λ endolysin protein, coupled to a single freeze-thaw cycle. The strains simplify protein expression and purification, and are also applicable for nucleic acid purification. They are also available with a DE3 lysogen encoding the T7 polymerase for expressing recombinant proteins driven by the T7 promoter.