Clonal analysis of thelacoperons fromKlebsiellaM5a1 and the Lac plasmid (pRE2) fromKlebsiellaV9A

Abstract

SummaryThe chromosomallacregion of the coliform bacteriumKlebsiellaM5al was cloned into the multicopy plasmid pBR322 to give pHE7 and pHE8. pHE8 contains 12·6 kb of M5al DNA, including its completelacoperon, and pHE7 contains 2·5 kb of M5al DNA and includes the completelac Ygene and a small segment oflacZ. The M5al operon has the same gene order as theEscherichia coli lacoperon. Thelacgenes of the Lac plasmid ofKlebsiellaV9A were cloned into pBR322 to give pHE1 and pHE2, of approximately 39 and 43 kb. Both plasmids were unstable in anE. coli RecA- strain, in contrast to the stability of pHE8. Polyacrylamide gel electrophoresis tests suggested that the M5a1 β-galactosidase monomer is about 5% longer, i.e. has about 50 more amino acids, than that of theE. coli Zgene. Tests made on the enzymes coded by thelacoperons of M5a1, anotherKlebsiellastrain (V9A) and its resident Lac plasmid, and several Lac+Enterobacteria, led to the conclusion that onlyEscherichia coliamong the Enterobacteria contains an activelacAgene.