Salmonella is one of the most important enteropathogenic bacteria. It is responsible for about 5000 reported cases of human gastroenteritis each year in Sweden. Salmonellosis is a zoonotic disease, and the bacterium has the ability to infect a variety of both domestic and wild animal species. In studies of Swedish wild bird populations, we found that Black-headed gull may be the main reservoir for Salmonella in birds, and that Salmonella infection is expressed as carriage with no obvious disease manifestations. Black-headed gull is a migratory bird and can transport strains of Salmonella with virulence traits like antibiotic resistance, from sources outside Sweden. Genetic molecular methods, PFGE and IS200, also demonstrate that Black-headed gull play a role in the transmission chain of Salmonella in Sweden. In a study of the Swedish Peregrine Falcon population, Salmonella amager and Campylobacter jejuni were found. There were indications, based on serotyping of Salmonella and genetical typing by PFGE of Campylobacter that these isolates were transmitsted to the falcons from a human or domestic animal source. This bird of prey has sparse contact with humans but may be infected by Salmonella of human origin by feeding on other birds, like gull. Salmonella was found in penguins, albatrosses and mainly in seals in a study in Antarctica. Several features of the Salmonella serotypes found indicate a human source for Salmonella infection in these animals, and also a spread of Salmonella within and between animal species in Antarctica. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 2002</p> / digitalisering@umu

4 ABSTRACT (English) This thesis is based on three published research papers studying bacterial REP (repetitive extragenic palindrome) elements. REP elements are one of the best-characterized groups of bacterial DNA repeats, distributed mostly in gammaproteobacteria, including enterobacteria. They are present in noncoding parts of host genomes, usually occurring in hundreds of copies. REPs are typically aggregated in higher order repeats. In the Gram-negative model Escherichia coli, interactions of several proteins important for cell's physiology with REPs were described, indicating significant role for these elements for host cells. The first work (Nunvar et al. 2010) presents the discovery of a protein class, related to IS200/IS605 transposases. These proteins, termed RAYTs (REP-associated tyrosine transposases), contain characteristic motifs in their amino acid sequences, which are absent in canonical IS200/IS605 transposases. Another attribute of RAYTs is the arrangement of their encoding genes. These are single copy genes, always flanked at both termini by at least two REPs in inverted orientation. Based on the similarity between the REP-rayt-REP unit and insertion sequences of the IS200/IS605 family, between RAYTs and tyrosine transposases and between REPs and subterminal sequences of the IS200/IS605...