Figure 3

The lethality of ΔtopA cells is not suppressed by increased levels of RNase HI. (A) Expression of a P _araBAD rnhA construct integrated into the chromosome can be regulated by different arabinose concentrations. The expression level is high enough to suppress the synthetic lethality of rnhA recG cells. (B) Expression from the integrated P _araBAD rnhA construct does not suppress the lethality of ΔtopA cells. The P _araBAD rnhA construct has been integrated into a rnhA⁺ background. Thus, expression of the construct will produce RNase HI in addition to the regular rnhA locus. (C) Expression from the integrated P _araBAD rnhA construct does not improve growth of cells in which the ΔtopA defect is partially suppressed by overexpression of DNA topoisomerase III. The image for AS1066 was reproduced from Figure 2 for comparison. Please note that incubation and image capturing procedures are standardised to allow comparison of colony sizes