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.

Ethanol Adaptation Strategies in Salmonella enterica Serovar Enteritidis Revealed by Global Proteomic and Mutagenic Analyses

“…The pore, ATPase, and substrate binding proteins in this system are called ProW, ProV, and ProX, respectively. The contribution of compatible solutes (e.g., glycine betaine) transported by ProVWX to bacterial survival under NaCl stress has been outlined (22,23). In the current study, the expression of ProX and ProV was enhanced 1.65-and 1.42-fold, respectively (Table 1).…”

Uncovering chemical signatures of salinity gradients through compositional analysis of protein sequences

“…Only proteins with at least 2-fold expression difference and marked as significant were included. et al, 2015), and glycerol (Finn et al, 2015) compared to controls all show a lower Dn H2O of the associated proteins than for NaCl compared to controls (Fig. 7e).…”

“…The compilations of gene and protein expression data also show small average DZ C , with p = 0.088 and 0.666, respectively. enterica serovar Typhimurium) (Solheim et al, 2014;Han et al, 2017;Kocharunchitt et al, 2014;Finn et al, 2015), there is a marked progression toward lower n H2O of the associated proteins with time. In a transcriptomic experiment for salt stress in Synechocystis sp.…”

Global Screening of Salmonella enterica Serovar Typhimurium Genes for Desiccation Survival

“…Additionally, cellulose and curli fimbriae may play an important role in desiccation resistance in Salmonella . However, Finn et al ( 2015 ) reported that S . Typhimurium genes differentially expressed in response to different humectants, agents that reduce water content of food products, do not simply reflect low low-a w but rather are linked to specific humectants (Finn et al, 2015 ).…”

“…However, Finn et al ( 2015 ) reported that S . Typhimurium genes differentially expressed in response to different humectants, agents that reduce water content of food products, do not simply reflect low low-a w but rather are linked to specific humectants (Finn et al, 2015 ). In addition, differentially expressed transcripts in a cell do not necessarily reflect the functional role of the genes at the given condition.…”