Genetic evidence that tcuR and tcuABC are two distinct transcriptional units. In the graphs shown, pBAD30 refers to empty cloning vector, tcuR::MudJ refers to allele tcuR34::MudJ, tcuA::MudJ refers to allele tcuA33::MudJ, and recA refers to allele recA1. Cells were grown aerobically in NCE medium containing tricarballylate (20 mM). (A) Complementation of a tcuR strain. Open diamonds, growth response of a tcuR+ recA1 strain (JE2397); open triangles, growth response of a tcuR34::MudJ recA1 strain (JE7286); solid circles, growth response of a tcuR34::MudJ recA1 strain with tcuR+ provided in trans (plasmid pTCU18) in medium lacking l-(+)-arabinose; solid triangles, growth of the same strain in medium containing 500 μM l-(+)-arabinose. (B) Complementation of a tcuA strain. Open diamonds, growth response of a tcuRABC+ recA1 strain (JE2397); solid squares, growth response of a tcuA33::MudJ recA1 strain (JE7287); open triangles, growth of a tcuA33::MudJ recA1 strain (JE7287) with tcuA+ provided in trans (plasmid pTCU8) in medium containing 500 μM l-(+)-arabinose; solid circles, growth response of a tcuA33::MudJ recA1 strain (JE7287) with tcuABC+ provided in trans (plasmid pTCU21) in medium lacking l-(+)-arabinose; open diamonds, growth of the same strain in medium containing 250 μM l-(+)-arabinose.