CHARACTERIZATION OF A NOVEL INSERTION-SEQUENCE, IS1194, IN STREPTOCOCCUS-THERMOPHILUS

A novel insertion sequence, IS1194, has been identified in the lactic acid bacterium Streptococcus thermophilus CNRZ368. This 1200-bp elemen t has 16-bp imperfect terminal inverted repeats. The single large open reading frame of this element encodes a 332-amino-acid protein that d isplays similarities with transposases encoded by bacterial insertion sequences belonging to the IS5 group of the IS4 family. A single copy of IS1194 was detected by hybridization in only 2 of the 19 S. thermop hilus strains tested and in 4 of the 13 Lactococcus lactis strains inv estigated. This suggests that this IS element was acquired by horizont al transfer. The unique IS1194 copy of S. thermophilus CNRZ368 is loca ted in a region of at least 12 kb that was probably acquired by horizo ntal transfer from L. lactis. Furthermore, the IS1194 right end is ide ntical to sequences found in a broad-host-range conjugative plasmid fr om Streptococcus pyrogenes, pSM19035. (C) 1998 Academic Press.