Fig 3.

Inactivation of arpR or rpoS negatively affects arsA expression from a single promoter. (A) Primer extension mapping of arsA transcription initiation 36 h after encystment induction in A. vinelandii SW136 (lane 1) and mutant derivatives carrying the arpR::Tn5 mutation (lane 2) or rpoS::Sp (lane 3). (B) Nucleotide sequence of the upstream regulatory region of arsA. The transcription start site mapped by primer extension is shown in bold and marked by a black triangle. The −35 and −10 consensus sequences for the P1 promoter are shown in bold and underlined. The arsA translation initiation codon is shown in bold and marked by an arrow. The analysis was performed using the primer 5′-GAGGATCGACGAACGGAC-3′ and 50 μg of RNA isolated from cells grown for 36 h in liquid BBOH medium.