CHARACTERIZATION AND DISTRIBUTION OF 2 INSERTION SEQUENCES, IS1191 AND ISO-IS981, IN STREPTOCOCCUS-THERMOPHILUS - DOES INTERGENERIC TRANSFER OF INSERTION SEQUENCES OCCUR IN LACTIC-ACID BACTERIA COCULTURES

A chromosomal repeated sequence from Streptococcus thermophilus was id entified as a new insertion sequence (IS), IS1191. This is the first I S element characterized in this species, This 1313bp element has 28 bp imperfect terminal inverted repeats and is flanked by short direct re peats of 8bp. The single large open reading frame of IS1191 encodes a 391-amino-acid protein which displays homologies with transposases enc oded by IS1201 from Lactobacillus helveticus (44.5% amino-acid sequenc e identity) and by the other ISs of the IS256 family. One of the copie s of IS1191 is inserted into a truncated iso-IS981 element. The nucleo tide sequences of two truncated iso-IS981s from S. thermophilus and th e sequence of IS981 element from Lactococcus lactis share more than 99 % identity. The distribution of these insertion sequences in L. lactis and S. thermophilus strains suggests that intergeneric transfers occu r during cocultures used in the manufacture of cheese.