title: Genetic diversity and population structure of food-borne Staphylococcus carnosus strains.
abstract: The species Staphylococcus carnosus is a non-pathogenic representative of the coagulase negative staphylococci. Specific strains are applied as meat starter cultures. The species consists of two subspecies, S. carnosus ssp. carnosus and S. carnosus ssp. utilis. In order to place S. carnosus strains, characterized in former studies, in a genetic background that allows a typing of candidates for starter cultures, a Multilocus Sequence Typing (MLST) scheme was developed. Internal fragments of the genes tpiA, xprT, dat, gmk, glpK, narG, cstA, encoding triosephosphate isomerase, xanthine phosphoribosyltransferase, d-amino acid aminotransferase, guanylate kinase, glycerol kinase, the α-chain of the respiratory nitrate reductase, and a carbon starvation protein where chosen. Genes were selected based on their equal distribution in the genome, taxonomic value in subspecies differentiation and metabolic function. This MLST was applied to 44 S. carnosus strains, most of them previously analyzed for their suitability as starter cultures. The number of alleles varied between zero (tpiA) and five (cstA) and allowed the definition of nine sequence types (ST). ST1 was most abundant (18 strains), followed by ST2 (8) and ST4 (6). The nine STs confirmed a close relationship of all strains despite their isolation source and year, but lacked correlation with physiological activities relevant for starter cultures. The low amount of STs in the strain set lets us suggest that recombination between strains is rare. Thus, it is hypothesized that evolutionary events seem to be due to single point mutations rather than intrachromosomal recombination, and that the species possesses a clonal population structure.
authors.affiliation: Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 28, 70599 Stuttgart, Germany. Electronic address: mueller.a@uni-hohenheim.de.
authors.forename: Anne
authors.initials: A
authors.lastname: Bückle Née Müller
authors.affiliation: Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 28, 70599 Stuttgart, Germany. Electronic address: markus.kranz@uni-hohenheim.de.
authors.forename: Markus
authors.initials: M
authors.lastname: Kranz
authors.affiliation: Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 28, 70599 Stuttgart, Germany. Electronic address: herbert.schmidt@uni-hohenheim.de.
authors.forename: Herbert
authors.initials: H
authors.lastname: Schmidt
authors.affiliation: Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 28, 70599 Stuttgart, Germany. Electronic address: agnes.weiss@uni-hohenheim.de.
authors.forename: Agnes
authors.initials: A
authors.lastname: Weiss
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D016000:Cluster Analysis; D004798:Enzymes / Q000235:genetics; D005516:Food Microbiology; D014644:Genetic Variation; D005838:Genotype; D058885:Multilocus Sequence Typing; D010802:Phylogeny; D013210:Staphylococcus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D001426:Bacterial Proteins; D004798:Enzymes
keywords: Genetic diversity; Multilocus Sequence Typing (MLST) scheme; Population structure; Sequence type (ST); Staphylococcus carnosus; Starter culture