Listeria monocytogenes Shows Temperature-Dependent and -Independent Responses to Salt Stress, Including Responses That Induce Cross-Protection against Other Stresses

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>The food-borne pathogen<jats:named-content content-type="genus-species">Listeria monocytogenes</jats:named-content>experiences osmotic stress in many habitats, including foods and the gastrointestinal tract of the host. During transmission,<jats:named-content content-type="genus-species">L. monocytogenes</jats:named-content>is likely to experience osmotic stress at different temperatures and may adapt to osmotic stress in a temperature-dependent manner. To understand the impact of temperature on the responses this pathogen uses to adapt to osmotic stress, we assessed genome-wide changes in the<jats:named-content content-type="genus-species">L. monocytogenes</jats:named-content>H7858 transcriptome during short-term and long-term adaptation to salt stress at 7°C and 37°C. At both temperatures, the short-term response to salt stress included increased transcript levels of<jats:italic>sigB</jats:italic>and SigB-regulated genes, as well as<jats:italic>mrpABCDEFG</jats:italic>, encoding a sodium/proton antiporter. This antiporter was found to play a role in adaptation to salt stress at both temperatures; Δ<jats:italic>mrpABCDEFG</jats:italic>had a significantly longer lag phase than the parent strain in BHI plus 6% NaCl at 7°C and 37°C. The short-term adaptation to salt stress at 7°C included increased transcript levels of two genes encoding carboxypeptidases that modify peptidoglycan. These carboxypeptidases play a role in the short-term adaptation to salt stress only at 7°C, where the deletion mutants had significantly different lag phases than the parent strain. Changes in the transcriptome at both temperatures suggested that exposure to salt stress could provide cross-protection to other stresses, including peroxide stress. Short-term exposure to salt stress significantly increased H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>resistance at both temperatures. These results provide information for the development of knowledge-based intervention methods against this pathogen, as well as provide insight into potential mechanisms of cross-protection.</jats:p>

Transcriptomic Analysis of the Adaptation of Listeria monocytogenes to Growth on Vacuum-Packed Cold Smoked Salmon

“…A number of previous studies have analyzed the transcriptomes of foodborne pathogens under stress conditions commonly present on/in food matrices (including hyperosmotic stress, cold stress, hydrostatic pressure stress, antimicrobial stress, acid stress, and alkali stress), using laboratory media modified to simulate these conditions as a model (15)(16)(17)(18)(19)(20)(21)(22)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60)(61)(62)(63). These laboratory media include BHI broth (18,20,21,59), BHI agar (19), Luria-Bertani broth (60,61), tryptic soy broth (62), M9-glucose (63), and Listeria minimal medium (22) as reference conditions.…”

“…This will facilitate the identification of new compounds that could specifically interfere with these metabolic pathways and thereby control the growth of L. monocytogenes (14). Extensive studies on the transcriptome of L. monocytogenes have been conducted to assess how it responds to the physical, chemical, or biological stresses that it may encounter on/in food matrices (15)(16)(17)(18)(19)(20)(21)(22). The majority of data from these experiments are based on exposure of L. monocytogenes to specific stresses in laboratory media, providing information about specific stress responses and transcriptional profiles in a controlled environment.…”

Responses of Yeast Biocontrol Agents to Environmental Stress

“…Stress adaptation, i.e., exposing an organism to a mild stress in order to increase its tolerance of a much stronger stress, has been reported to induce cross-protection against a variety of abiotic stresses in plants (80,81) and against prokaryotic and eukaryotic microorganisms (82)(83)(84). Specifically regarding yeast antagonists, changes in gene expression during heat stress/oxidative stress adaptation and a subsequent improvement in stress tolerance and biocontrol efficacy have been reported (27,28).…”

Fluoro-Phenyl-Styrene-Sulfonamide, a Novel Inhibitor of σBActivity, Prevents the Activation of σBby Environmental and Energy Stresses in Bacillus subtilis

“…Cells were pelleted (3,600 ϫ g, 10 min, 4°C) after 5 min at room temperature in RNAprotect. Pellets were kept on ice until RNA extraction, which was performed as described previously (40). cDNA was synthesized as described elsewhere (41).…”