Evidence of transcription and redefinition of the ure2 operon of Brucella abortus 2308. The map on top of the figure shows the ure2 region of the large chromosome of Brucella abortus 2308. Below the map the arrows indicate primers designed to check transcription of the region. For each pair of primers marked with a number, three separate PCR reactions were performed: a positive control using genomic DNA as template; a test reaction using cDNA as template, and a control using RNA as template. M, 1 Kb Plus DNA ladder.