Excretion of the penicillinase of an alkalophilic Bacillus sp. through the Escherichia coli outer membrane is caused by insertional activation of the kil gene in plasmid pMB9.

Most of the cloned penicillinase from alkalophilic Bacillus sp. strain 170 and alkaline phosphatase were released into the culture medium by Escherichia coli strains bearing plasmid pEAP1 or pEAP2 (T. Kudo, C. Kato, and K. Horikoshi, J. Bacteriol. 156:949-951, 1983). We analyzed the basis for excretion of periplasmic enzymes in the cells bearing these plasmids. Several experiments such as subcloning, insertion of a chloramphenicol acetyltransferase cartridge, and DNA sequencing were done. A dormant kil gene in plasmid pMB9 was expressed by a promoter of the inserted DNA fragment of alkalophilic Bacillus sp. strain 170, and as a result, the outer membrane of E. coli became permeable, allowing the proteins to be excreted without cell lysis.