A novel type of bacterial transcription unit, specifying mRNA, rRNA, and tRNA.
Previously it had been shown that a chromosomal region preceding the rrnB gene of Escherichia coli contains an 867 base pair-long open reading frame and it is co-transcribed with the rrnB gene both in vitro and in vivo. Here we report that minicells programmed by recombinant plasmids carrying this region or a deletion derivative of it, synthetise a protein of the expected size. Thus this transcription unit codes for mRNA, rRNA, and tRNA.