Cloning and partial characterization of genes for ribosomal ribonucleic acid in Lactococcus lactis subsp. lactis.

A cosmid gene library of the genome of Lactococcus lactis subsp. lactis 712 was probed for the presence of 16S rRNA genes, using 32P 5' end-labelled 16S rRNA fragments. Cosmid DNA from positive clones responsible for hybridisation was subcloned into a high copy number vector and a restriction map was constructed. The location of the 16S, 23S and 5S rRNA genes was determined on this map. Transcriptional promoter activity was identified upstream of the 5' end of the 16S rRNA gene. By probing L. lactis 712 chromosomal DNA cut with a range of restriction endonucleases, with a conserved oligonucleotide to the 5' end of the 16S rRNA gene, 6 copies of rRNA genes were identified.