title: Global gene expression of Listeria monocytogenes to salt stress.
abstract: Outbreaks of listeriosis caused by the ingestion of Listeria-contaminated ready-to-eat foods have been reported worldwide. Many ready-to-eat foods, such as deli meat products, contain high amounts of salt, which can disrupt the maintenance of osmotic balance within bacterial  cells. To understand how Listeria monocytogenes adapts to salt stress, we examined the growth and global gene expression profiles of L. monocytogenes strain F2365 under salt stress using oligonucleotide probe-based DNA array and quantitative real-time PCR (qRT-PCR) analyses.  The growth of L. monocytogenes in brain heart infusion (BHI) medium with various concentrations of NaCl (2.5, 5, and 10%) was significantly inhibited (P < 0.01) when compared with growth in BHI with no NaCl supplementation. Microarray data indicated that growth in BHI medium  with 1.2% NaCl upregulated 4 genes and down-regulated 24 genes in L. monocytogenes, which was confirmed by qRT-PCR. The transcript levels of genes involved in the uptake of glycine betaine/(L)-proline were increased, whereas genes associated with a putative phosphoenolpyruvate-dependent  sugar phosphotransferase system (PTS), metabolic enzymes, and virulence factor were down-regulated. Specifically, the expression levels of PTS transport genes were shown to be dependent on NaCl concentration. To further examine whether the down-regulation of PTS genes is related to decreased  cell growth, the transcript levels of genes encoding components of enzyme II, involved in the uptake of various sugars used as the primary carbon source in bacteria, were also measured using qRT-PCR. Our results suggest that the decreased transcript levels of PTS genes may be caused by salt  stress or reduced cell growth through salt stress. Here, we report global transcriptional profiles of L. monocytogenes in response to salt stress, contributing to an improved understanding of osmotolerance in this bacterium.
authors.affiliation: Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA.
authors.forename: Dongryeoul
authors.initials: D
authors.lastname: Bae
authors.forename: Connie
authors.initials: C
authors.lastname: Liu
authors.forename: Ting
authors.initials: T
authors.lastname: Zhang
authors.forename: Marcus
authors.initials: M
authors.lastname: Jones
authors.forename: Scott N
authors.initials: SN
authors.lastname: Peterson
authors.forename: Chinling
authors.initials: C
authors.lastname: Wang
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D005506:Food Contamination / Q000032:analysis; D020869:Gene Expression Profiling; D006801:Humans; D008089:Listeria monocytogenes / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D009994:Osmolar Concentration; D060888:Real-Time Polymerase Chain Reaction; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological
chemical_list: D012965:Sodium Chloride