FIG. 1.

Physical map of the 4.5-kb HindIII fragment encoding the ureC gene of Synechococcus sp. strain PCC 7002. Arrows indicate the direction of transcription. The aphII gene, which encodes aminoglycoside 3′-phosphotransferase II and confers resistance to kanamycin, was inserted into the unique KpnI site of the ureC gene in both orientations. The ureC mutants were designated strain PR6091, in which the transcription orientation of the aphII gene is the opposite of that of ureC, and strain PR6092, in which the transcription orientation of the aphII gene is the same as that of the ureC gene.