Reporter gene assay for MarR function. The reporter strain SPC105ΔmarR, which lacks the marR gene, carries a chromosomal PmarII::lacZ transcriptional fusion. Results are expressed as percentages of transcription activity of the control (SPC105ΔmarR bearing pACT7 and pET13a without the insert) and are the means and standard deviations of results from at least three replicated assays. All assays were performed as described previously (20). The origins of the cloned marR genes were as follows: bar 1, none; bar 2, wild-type marR; bar 3, marR gene encoding the Lys62Arg, Gly103Ser, and Tyr137His mutations; bar 4, marR gene encoding the Gly103Ser and Tyr137His mutations; bar 5, marR gene encoding the Ala53Glu, Gly103Ser, and Tyr137His mutations; bar 6, marRCH4 gene encoding the Gln42Arg, Gly103Ser, and Tyr137His mutations.