FIG. 6.

Effect of increasing or decreasing the length of 3′CIS by full turns of the helix (i.e., ∼10.5 bp) on the copy number of the IncB replicon of pMU1598 and pMU1599. The length of 3′CIS was altered by replacing nt 1844 to 1911 by spacers of appropriate length, except for the +42 mutant, which was constructed by insertion of a 42-bp polylinker at map position 1844. The copy number was determined by assaying the CAT activity of E. coli JP3438 carrying pMU1598, pMU1599, or their derivatives in the absence of IPTG and is expressed relative to the value obtained for the parental plasmid (i.e., either pMU1598 or pMU1599, as appropriate). The values shown are the averages (± standard deviations) of at least six independent determinations. WT, wild type.