title: ISSag1 in streptococcal strains of human and animal origin.
abstract: The chromosomal region of Streptococcus agalactiae harboring the C5a peptidase and the lmb genes displays the structure of a composite transposon. Its presence in a streptococcal strain is associated with the origin of this strain from a human host. In S. agalactiae it is flanked by two copies of the insertion element ISSag2, and the nucleotide sequence for a third IS element (ISSag1) can be found in this region. Based on amino acid sequence similarity of the deduced transposase ISSag1 belongs to the IS3 family. It is 1251 bp long and flanked by 37 bp imperfect inverted repeats. Horizontal gene transfer among different bacterial species is facilitated by mobile genetic elements. To investigate if ISSag1 homologues are also present in other streptococcal species, various species of pyogenic streptococci from animal and human origin were analyzed by Southern blot hybridization and PCR. Among the different streptococcal species, multiple copies of an ISSag1 homologue could only be detected in S. dysgalactiae subsp. dysgalactiae strains of animal origin. All of the S. agalactiae strains harbored only a single copy, that was always found in strains with the scpB-lmb composite transposon. A single copy of an ISSag1 homologue could also be detected in some of the S. pyogenes and S. dysgalactiae subsp. equisimilis strains. Nucleotide sequencing of the IS element in S. dysgalactiae subsp. dysgalactiae strains revealed several different variants. One of the variants showed the features of a regular IS3 element. The other two variants that were observed displayed a 500-bp deletion and a mosaic structure composed of ISSag1 and ISSag2 homologues. This mosaic structure suggests that recombination and horizontal gene transfer events in S. dysgalactiae strains of bovine origin could have played a role in the assembly of the scpB-lmb composite transposon structure.
authors.affiliation: Institute of Medical Microbiology and National Reference Center for Streptococci, University Hospital Aachen, Pauwelsstr. 30, D-52057 Aachen, Germany.
authors.forename: Carmen
authors.initials: C
authors.lastname: Franken
authors.forename: Claudia
authors.initials: C
authors.lastname: Brandt
authors.forename: Gerd
authors.initials: G
authors.lastname: Bröker
authors.forename: Barbara
authors.initials: B
authors.lastname: Spellerberg
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D002417:Cattle; D004251:DNA Transposable Elements / Q000235:genetics*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D010450:Endopeptidases / Q000235:genetics*; D022761:Gene Transfer, Horizontal / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011995:Recombination, Genetic / Q000235:genetics; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013292:Streptococcus agalactiae / Q000201:enzymology / Q000235:genetics*
chemical_list: D018829:Adhesins, Bacterial; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D010450:Endopeptidases; C053088:C5a peptidase