Characterization of IS199 from Streptococcus mutans V403.

The complete nucleotide sequence of the insertion sequence IS199 has been determined. This novel element was found in Streptococcus mutans V403 where DNA hybridization studies suggested that it was present in multiple copies on the genome. IS199 is 1220 bp and appears unique to the mutans streptococci. A limited epidemiological survey revealed this element to occur infrequently in this group (4/50 strains examined). IS199 belongs to the IS3 family of procaryotic insertion sequence elements. It contained tandem open reading frames (ORFs) reminiscent of the structure of the IS3 class. Additionally, the larger of the two ORF products (ORFB) exhibited amino acid sequence similarities to comparable proteins from IS3 and other elements of this family. Transposition of IS199 gave rise to a 3-bp target site duplication. We were able to insert an antibiotic resistance gene into IS199 enabling us to follow the transposition of this element in S. mutans V403.