FIG. 4.

Effect of replacement of the entire CIS and 3′CIS by spacer fragments of equivalent length, amplified from the coding sequence of aminoglycoside 3′-phosphotransferase, on the relative copy number of the IncB replicon of pMU1598 and pMU1599. The copy number was determined by assaying the CAT activity of E. coli JP3438 carrying pMU1598 or its derivatives in the absence of IPTG and is expressed relative to the value obtained for pMU1598. The values shown are the averages of at least six independent determinations. NA, not able to be assayed.