OtcR is essential for OTC production. A. Schematic representation of the strategy used for the disruption of otcR in S. rimosus M4018. The solid arrows indicate the positions of primers used for the confirmation of the disruption mutants (ΔotcR). B. PCR verification of the ΔotcR mutant. Line M: marker; line 1: PCR products (1462 bp) using the genome of S. rimosus M4018 as template; line 2: PCR products (600 bp) using the genome of ΔotcR as template. C. OTC production profiles of S. rimosus M4018, ΔotcR and ΔotcR::otcR were analyzed by HPLC (UV 350 nm).