title: Exposure of Salmonella enterica Serovar Typhimurium to Three Humectants Used in the Food Industry Induces Different Osmoadaptation Systems.
abstract: Common salt (NaCl) is frequently used by the food industry to add flavor and to act as a humectant in order to reduce the water content of a food product. The improved health awareness of consumers is leading to a demand for food products with reduced salt content; thus, manufacturers require alternative water activity-reducing agents which elicit the same general effects as NaCl. Two examples include KCl and glycerol. These agents lower the water activity of a food matrix and also contribute to limit the growth of the microbiota, including foodborne pathogens. Little is currently known about how foodborne pathogens respond to these water activity-lowering agents. Here we examined the response of Salmonella enterica serovar Typhimurium 4/74 to NaCl, KCl, and glycerol at three time points, using a constant water activity level, compared with the response of a control inoculum. All conditions induced the upregulation of gluconate metabolic genes after 6 h of exposure. Bacteria exposed to NaCl and KCl demonstrated the upregulation of the osmoprotective transporter mechanisms encoded by the proP, proU, and osmU (STM1491 to STM1494) genes. Glycerol exposure elicited the downregulation of these osmoadaptive mechanisms but stimulated an increase in lipopolysaccharide and membrane protein-associated genes after 1 h. The most extensive changes in gene expression occurred following exposure to KCl. Because many of these genes were of unknown function, further characterization may identify KCl-specific adaptive processes that are not stimulated by NaCl. This study shows that the response of S. Typhimurium to different humectants does not simply reflect reduced water activity and likely involves systems that are linked to specific humectants.
authors.affiliation: UCD Centre for Food Safety, School of Public Health, Physiotherapy & Population Science, University College Dublin, Belfield, Dublin, Ireland.
authors.forename: Sarah
authors.initials: S
authors.lastname: Finn
authors.affiliation: Conway Institute, UCD School of Biomolecular & Biomedical Science, University College Dublin, Belfield, Dublin, Ireland.
authors.forename: Lisa
authors.initials: L
authors.lastname: Rogers
authors.affiliation: Moyne Institute of Preventive Medicine, Trinity College Dublin, Dublin, Ireland.
authors.forename: Kristian
authors.initials: K
authors.lastname: Händler
authors.affiliation: Unilever, Safety and Environmental Assurance Centre, Sharnbrook, Bedfordshire, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: McClure
authors.affiliation: Unilever, Safety and Environmental Assurance Centre, Sharnbrook, Bedfordshire, United Kingdom.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Amézquita
authors.affiliation: Moyne Institute of Preventive Medicine, Trinity College Dublin, Dublin, Ireland Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Jay C D
authors.initials: JC
authors.lastname: Hinton
authors.affiliation: UCD Centre for Food Safety, School of Public Health, Physiotherapy & Population Science, University College Dublin, Belfield, Dublin, Ireland Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland sfanning@ucd.ie.
authors.forename: Séamus
authors.initials: S
authors.lastname: Fanning
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D019649:Food Industry; D005990:Glycerol / Q000494:pharmacology; D058427:Hygroscopic Agents / Q000494:pharmacology*; D009995:Osmosis; D011189:Potassium Chloride / Q000494:pharmacology; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D012965:Sodium Chloride / Q000494:pharmacology; D014867:Water / Q000032:analysis / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D058427:Hygroscopic Agents; D014867:Water; D012965:Sodium Chloride; D011189:Potassium Chloride; D005990:Glycerol