title: Cold growth behaviour and genetic comparison of Canadian and Swiss Listeria monocytogenes strains associated with the food supply chain and human listeriosis cases.
abstract: Sixty-two strains of Listeria monocytogenes isolated in Canada and Switzerland were investigated. Comparison based on molecular genotypes confirmed that strains in these two countries are genetically diverse. Interestingly strains from both countries displayed similar range of cold growth phenotypic profiles. Based on cold growth lag phase duration periods displayed in BHI at 4 °C, the strains were similarly divided into groups of fast, intermediate and slow cold adaptors. Overall Swiss strains had faster exponential cold growth rates compared to Canadian strains. However gene expression analysis revealed no significant differences between fast and slow cold adapting strains in the ability to induce nine cold adaptation genes (lmo0501, cspA, cspD, gbuA, lmo0688, pgpH, sigB, sigH and sigL) in response to cold stress exposure. Neither was the presence of Stress survival islet 1 (SSI-1) analysed by PCR associated with enhanced cold adaptation. Phylogeny based on the sigL gene subdivided strains from these two countries into two major and one minor cluster. Fast cold adaptors were more frequently in one of the major clusters (cluster A), whereas slow cold adaptors were mainly in the other (cluster B). Genetic differences between these two major clusters are associated with various amino acid substitutions in the predicted SigL proteins. Compared to the EGDe type strain and most slow cold adaptors, most fast cold adaptors exhibited five identical amino acid substitutions (M90L, S203A/S203T, S304N, S315N, and I383T) in their SigL proteins. We hypothesize that these amino acid changes might be associated with SigL protein structural and functional changes that may promote differences in cold growth behaviour between L. monocytogenes strains.
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty University of Zurich, Switzerland.
authors.forename: Carolina
authors.initials: C
authors.lastname: Arguedas-Villa
authors.affiliation: Food, Nutrition and Health Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada.
authors.forename: Jovana
authors.initials: J
authors.lastname: Kovacevic
authors.affiliation: Food, Nutrition and Health Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Allen
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty University of Zurich, Switzerland.
authors.forename: Roger
authors.initials: R
authors.lastname: Stephan
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty University of Zurich, Switzerland. Electronic address: tasarat@fsafety.uzh.ch.
authors.forename: Taurai
authors.initials: T
authors.lastname: Tasara
mesh_terms: D000222:Adaptation, Physiological; D001426:Bacterial Proteins / Q000235:genetics; D002170:Canada; D020387:Food Chain; D005516:Food Microbiology; D005523:Food Supply; D006801:Humans; D008089:Listeria monocytogenes / Q000145:classification / Q000235:genetics* / Q000254:growth & development* / Q000302:isolation & purification; D008088:Listeriosis / Q000382:microbiology*; D010802:Phylogeny; D013557:Switzerland; D013696:Temperature
chemical_list: D001426:Bacterial Proteins
keywords: Cold growth phenotypes; Cold shock; Gene expression; Listeria monocytogenes