A ribosomal RNA gene, rrnC, of Escherichia coli, mapped by specialized transducing λdilv and λdrbs phages

Specialized transducing phages carrying segments of the Escherichia coli chromosome from the rbs-ilv region including rrn genes have been isolated. These phages carry rrn transcription units coding for 16S and 23S rRNA with the direction of transcription clockwise towards the ilv operon. While one of the phages (λd279rbs) appears to carry the genuine rrn gene, denoted rrnC, located between rbs and ilv at 82 min on the E. coli chromosome another one isolated as an ilv transducing phage, λd5ilv, carries a hybrid rrn gene, denoted rrnX, which has originated from a recombinational cross-over between the rrnC and one of the other rrn genes.