title: Growth temperature alters Salmonella Enteritidis heat/acid resistance, membrane lipid composition and stress/virulence related gene expression.
abstract: The influence of growth temperature (10, 25, 37, and 42 °C) on the survival of Salmonella Enteritidis in simulated gastric fluid (SGF; pH=2.0) and during heat treatment (54, 56, 58, and 60 °C), on the membrane fatty acid composition, as well as on stress-/virulence-related gene expression was studied. Cells incubated at temperatures lower or higher than 37 °C did not increase their acid resistance, with the maximum D-value of 3.07 min in cells grown at 37 °C; while those incubated at higher temperature increased their heat resistance, with the maximum D60 °C-values of 1.4 min in cells grown at 42 °C. A decrease in the ratio of unsaturated to saturated fatty acids was observed as the growth temperature increased. Compared to the control cells grown at 37 °C, the expression of rpoS was 16.5- and 14.4-fold higher in cells cultivated at 10 and 25 °C, respectively; while the expression of rpoH was 2.9-fold higher in those cultivated at 42 °C. The increased expression of stress response gene rpoH and the decreased ratio of unsaturated to saturated fatty acids correlated with the greater heat resistance of bacteria grown at 42 °C; while the decreased expression of stress response gene rpoS at 42 °C might contribute to the decrease in acid resistance. Virulence related genes-spvR, hilA, avrA-were induced in cells cultivated at 42 °C, except sefA which was induced in the control cells. This study indicates that environmental temperature may affect the virulence potential of S. Enteritidis, thus temperature should be well controlled during food storage.
authors.affiliation: Food Science & Technology Programme, Department of Chemistry, National University of Singapore, Science Drive 4, Singapore 117543, Singapore.
authors.forename: Yishan
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Food Science & Technology Programme, Department of Chemistry, National University of Singapore, Science Drive 4, Singapore 117543, Singapore.
authors.forename: Wei Jie
authors.initials: WJ
authors.lastname: Khoo
authors.affiliation: Food Science & Technology Programme, Department of Chemistry, National University of Singapore, Science Drive 4, Singapore 117543, Singapore.
authors.forename: Qianwang
authors.initials: Q
authors.lastname: Zheng
authors.affiliation: Department of Food and Nutrition, Inha University, Incheon 402-751, Republic of Korea.
authors.forename: Hyun-Jung
authors.initials: HJ
authors.lastname: Chung
authors.affiliation: Food Science & Technology Programme, Department of Chemistry, National University of Singapore, Science Drive 4, Singapore 117543, Singapore; National University of Singapore (Suzhou) Research Institute, No. 377 Linquan Street, Suzhou Industrial Park, Suzhou, Jiangsu 215123, China. Electronic address: chmyukhg@nus.edu.sg.
authors.forename: Hyun-Gyun
authors.initials: HG
authors.lastname: Yuk
mesh_terms: D000143:Acids / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D008563:Membrane Lipids / Q000737:chemistry; D012477:Salmonella enteritidis / Q000737:chemistry / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D012808:Sigma Factor / Q000235:genetics; D013312:Stress, Physiological / Q000235:genetics*; D013696:Temperature; D014774:Virulence / Q000235:genetics
chemical_list: D000143:Acids; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; D008563:Membrane Lipids; D012808:Sigma Factor; C069774:heat-shock sigma factor 32; C069567:sigma factor KatF protein, Bacteria
keywords: Acid resistance; Gene expression; Growth temperature; Heat resistance; Membrane lipid composition; Salmonella Enteritidis