Physical and genetic map of Streptococcus mutans GS-5 and localization of five rRNA operons

The physical map of the 2.1 megabase chromosome of Streptococcus mutans GS- 5 has been refined by including all ApaI and SmaI fragments of 5 kbp or gre ater, and by positioning the fragments generated by the endonuclease I-CeuI . Sixty-three new genetic loci have been added to the map, so that it now c ontains 90 loci. The new loci include those for 35 cloned streptococcal gen es of established function and for 23 S. mutans genes of putative function. In addition, five rm operons were identified and placed on the map of the chromosome. The presence of a SmaI site in each of the rrn operons allowed the direction of transcription of each operon to be deduced. The orientatio n of the rrn loci indicates that their transcription is directed away from a small region of the chromosome, identifying a possible region for the ini tiation of chromosome replication.