Abstract
The expression of ten genes of Listeria monocytogenes previously identified as penicillin G-inducible was transcriptionally analyzed in the presence of 0.5 M KCl, pH 5.0 and 42 °C. This study revealed that all the genes are upregulated by osmotic stress, seven by acid stress and four by temperature stress conditions. The contribution of a gene encoding a ferritin-like protein (fri), a two-component phosphate-response regulator (phoP) and an AraC/XylS family transcription regulator (axyR) to temperature, acid and osmotic stress tolerance was further examined by analysis of nonpolar deletion mutants. This revealed that a lack of PhoP or AxyR does not affect the ability to grow under the tested stress conditions. However, the Δ fri strain showed slightly delayed growth under osmotic and clearly impaired growth under acid stress conditions, indicating an important role of the ferritin-like protein in acid stress tolerance.
Highlights
Listeria monocytogenes is a foodborne Gram-positive pathogen that causes rare but severe disease in humans and animals
Susceptibility studies showed that ferritin-like protein (Fri) is a mediator of β-lactam tolerance and innate resistance to cephalosporins, and that the protein plays a critical role in the control of L. monocytogenes cell envelope structure and stability under β-lactam pressure, whereas PhoP and AxyR do not influence susceptibility and tolerance to this class of antibiotics (Krawczyk-Balska et al 2012; Krawczyk-Balska and Lipiak 2013)
For osmotic stress and acid stress treatments, the cells were harvested by centrifugation and resuspended in brain heart infusion (BHI) broth containing 0.5 M KCl or resuspended in BHI broth adjusted to pH 5 with HCl, respectively, and incubation was continued for 90 min at 37 °C
Summary
Listeria monocytogenes is a foodborne Gram-positive pathogen that causes rare but severe disease in humans and animals. This bacterium can adapt to survive in different environmental conditions including a wide range. Fri of L. monocytogenes is not a sensu stricto regulator protein It contributes to virulence and plays a role in protection against multiple stresses. Susceptibility studies showed that Fri is a mediator of β-lactam tolerance and innate resistance to cephalosporins, and that the protein plays a critical role in the control of L. monocytogenes cell envelope structure and stability under β-lactam pressure, whereas PhoP and AxyR do not influence susceptibility and tolerance to this class of antibiotics (Krawczyk-Balska et al 2012; Krawczyk-Balska and Lipiak 2013)
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