PLASMID 40, 44–49 (1998) ARTICLE NO. PL981337 Characterization of a Novel Insertion Sequence, IS1194, in Streptococcus thermophilus Florence Bourgoin, Ge ´rard Gue ´don, 1 Brigitte Gintz, and Bernard Decaris Laboratoire de Ge ´ne ´tique et Microbiologie, UA INRA952, Faculte ´ des Sciences, Universite ´ Henri Poincare ´ —Nancy I, BP 239, 54506 Vandoeuvre-le `s-Nancy, France Received July 30, 1997; revised January 18, 1998 A novel insertion sequence, IS1194, has been identified in the lactic acid bacterium Strepto- coccus thermophilus CNRZ368. This 1200-bp element has 16-bp imperfect terminal inverted repeats. The single large open reading frame of this element encodes a 332-amino-acid protein that displays 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. thermophilus strains tested and in 4 of the 13 Lactococcus lactis strains investigated. This suggests that this IS element was acquired by horizontal transfer. The unique IS1194 copy of S. thermophilus CNRZ368 is located in a region of at least 12 kb that was probably acquired by horizontal transfer from L. lactis. Furthermore, the IS1194 right end is identical to sequences found in a broad-host-range conjugative plasmid from Streptococcus pyogenes, pSM19035.  1998 Academic Press Cocultures of Streptococcus thermophilus This paper describes the identification of a novel type of IS element, IS1194, and its and various other lactic acid bacteria including Lactococcus lactis and Lactobacillus del- distribution in strains of various lactic acid bacteria, including S. thermophilus, L. lactis, brueckii subsp. bulgaricus are used as starters in the manufacture of some cheeses. Cocul- and Lb. delbrueckii. tures of S. thermophilus and Lb. delbrueckii subsp. bulgaricus are used as starters in the EXPERIMENTS AND RESULTS manufacture of yogurt. Three different inser- Identification of IS1194 tion sequences (ISs), 2 IS1191, IS981, and ISS1, which belong to the IS256, IS3, and IS6 A 12-kb region in the S. thermophilus families, respectively, have been previously CNRZ368 chromosome bears two of the four identified in S. thermophilus (Gue ´don et al., IS981 copies and the three ISS1 copies and 1995; Bourgoin et al., 1996). Elements almost was probably acquired by a horizontal transfer identical to these, i.e., IS905 (Dodd et al., from L. lactis (Bourgoin et al., 1996). Se- 1994), IS981 (Polzin and McKay, 1991), and quences homologous to I49.6, an AseI frag- ISS1N (Haandrikman et al., 1990), have also ment of the recombinant plasmid pNST49 been found in L. lactis. The quasi-identity and (Bourgoin et al., 1996), which is included the distribution of these ISs suggest that recent within this region (Fig. 1), were present in horizontal transfer took place between these only 2 of the 19 strains of S. thermophilus two bacteria during the cocultures used for tested, A054 and CNRZ368. The two PvuII cheese manufacture. fragments of pNST49 which contain partial I49.6 sequences were subcloned in the EcoRV site of pBCKS/. Partial sequences (GenBank/ 1 To whom correspondence should be addressed. Fax: EMBL Accession No. sequence Y13626) of 33 3 83 91 25 00. E-mail: guedon@ciril.fr. the two plasmids obtained contain a 1200-bp 2 Abbreviations used: IS, insertion sequence; ORF, open reading frame; aa, amino acid; IR, inverted repeat. region that shares the characteristic features 44 0147-619X/98 $25.00 Copyright  1998 by Academic Press All rights of reproduction in any form reserved.