Project description:Salmonella can survive for long periods under extreme desiccation conditions. This stress response poses a risk for food safety, but relatively little is known about the molecular and cellular regulation of this adaptation mechanism. To determine the genetic components involved in Salmonella’s cellular response to desiccation, we performed a global transcriptomic analysis comparing Salmonella Typhimurium cells equilibrated to low water activity (aw 0.11) and cells equilibrated to high water activity (aw 1.0). The analysis revealed that 719 genes were differentially regulated between the two conditions, of which 290 genes were up-regulated at aw 0.11. Most of these genes were involved in metabolic pathways, transporter regulation, DNA replication/repair, transcription and translation, and, more importantly, virulence genes.
Project description:An integrated genomic and proteomic analysis was undertaken to determine the physiological response of Escherichia coli O157:H7 Sakai to steady-state conditions relevant to low temperature and water activity conditions experienced during meat carcase chilling in cold air. The response of E. coli during exponential growth at 25°C aw 0.985, 14°C aw 0.985, 25°C aw 0.967 and, 14°C aw 0.967 was compared to that of a reference culture (35°C aw 0.993).
Project description:This experiment contains the transcriptomic dataset that constitutes part of an integrated transcriptomic and proteomic study monitoring the response of exponential phase E. coli O157:H7 Sakai cultures upon an abrupt downshift in temperature and water activity (from 35°C aw 0.993 to 14°C aw 0.967).
Project description:2D-LC/MS/MS analysis was used to examine time-dependent changes in proteome of E. coli O157:H7 strain Sakai upon an abrupt downshift in water activity (aw) (i.e., from aw 0.993 to aw 0.967) at a constant temperature of 35°C. Bacterial cells were harvested before hyperosmotic shift, and 0 (i.e. immediately after the shift), 30, 80, and 310 min after the shift. It also should be noted that these time points were chosen with the aims to characterize the physiology of E. coli during dynamic changes in growth kinetics induced by an abrupt downshift in water activity. Specifically, the samples taken at time 0 and 30 min were obtained during the period in which the loss of cell culturability was observed, whereas the samples at time 80 and 310 min respectively reflected the physiological state of E. coli during the ‘recovery’ period and during growth after the shift.
