Fig 2.

ArpR and RpoS positively regulate the expression of arsA. (A) Expression of arsA of strain SW136 (WT) and its isogenic mutants SW7 (arpR::Tn5) and SW9 (rpoS::Sp) as measured by qRT-PCR. The data are presented as fold changes of arsA mRNA levels of the SW7 and SW9 mutant strains relative to that of the parental strain (SW136). (B) Expression of arsA, quantified as β-glucuronidase activities, in strains YRR30 (WT derivative), YRR32 (SW7 derivative) and YRR34 (SW9 derivative), containing a chromosomal arsA::gusA transcriptional fusion. One unit of β-glucuronidase activity corresponds to 1 nmol of substrate (X-Gluc) hydrolyzed min⁻¹ mg protein⁻¹. Determinations for both panels were made from bacterial cultures grown for 36 h in liquid BBOH medium at 30°C. Error bars represent standard deviations.