FIG. 1.

Structure of rrnB operon regions in wild-type, BSV1, and BSV2 strains. rRNA genes (black), the sacB-neo cassette (3,825 bp; grey), and the adjacent genes involved in murein synthesis (murI and murB; white) are shown along with the rrnB promoters (arrows). Dashed lines indicate the region bound by the PCR primers upB and dnB along with the resulting PCR product sizes. BSV1 has the sacB-neo cassette inserted into the BglII site of rrsB (after position 704) and upstream sequence similarity to the other rrn operons, and the promoters P1 and P2 are preserved. BSV2 has the sacB-neo cassette replacing sequence upstream of rrnB, rrsB, the ITS region, and the 5′ end of rrl, leaving no promoters or upstream sequence similarity to the other rrn operons.