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Proteins variations in Listeria monocytogenes exposed to high salinities
1Laboratoire de Microbiologie et Immunologie, UPRES EA 1254, Faculté de Pharmacie, Rennes, France.
Abstract:
Listeria monocytogenes Scott A grown in the minimal chemically defined medium M6LT was challenged to a concentration of either 35 or 65 g l(-1) of NaCl for 1 h in the presence of a [35S]cysteine-[35S]methionine labelling mix. The protein patterns were analysed by 2D-electrophoresis in the two conditions and isoosmotic condition (5 g l(-1) of NaCl in M6LT). A great number of proteins which were synthesized under isoosmotic conditions were either completely repressed or expressed at a reduced level, at 65 g l(-1) and to a lesser extent at 35 g l(-1) of NaCl. At 35 g l(-1) of NaCl, six proteins were up-regulated, five proteins showed no change in expression level and five were repressed. Among the proteins up-regulated at 35 g l(-1) of NaCl, a single one (18.7 kDa, pI 5.05) was up-regulated at 65 g l(-1) too. We observed 21 proteins which were repressed at 65 g l(-1) of NaCl, among which 11 completely disappeared. Some of the up-regulated proteins have characteristics of molecular weight and isoelectric point close to those of stress proteins reported elsewhere: the protein induced both at 35 and 65 g l(-1) might correspond to a previously proposed universal stress protein of Listeria. Some proteins which were repressed at 65 g l(-1) have molecular weights close to those of virulence proteins.
Insights
High salt concentrations significantly alter Listeria monocytogenes protein expression. Some stress proteins were upregulated, while potential virulence proteins were repressed under osmotic stress.
Area of Science:
- Microbiology
- Proteomics
- Bacterial Physiology
Background:
- Listeria monocytogenes is a significant foodborne pathogen.
- Bacterial adaptation to osmotic stress is crucial for survival and virulence.
Purpose of the Study:
- To investigate the impact of high salt concentrations on the proteome of Listeria monocytogenes Scott A.
- To identify specific proteins that are differentially expressed under osmotic stress.
Main Methods:
- Listeria monocytogenes Scott A was cultured in a defined medium (M6LT) and subjected to varying NaCl concentrations (5, 35, and 65 g/L).
- Radioactive labeling with [35S]cysteine-[35S]methionine was employed.
- Two-dimensional electrophoresis (2D-PAGE) was used to analyze protein expression patterns.
Main Results:
- High salt levels (35 and 65 g/L NaCl) led to significant repression of proteins synthesized under isoosmotic conditions.
- At 35 g/L NaCl, six proteins were upregulated, five unchanged, and five repressed.
- At 65 g/L NaCl, 21 proteins were repressed (11 disappeared), and one protein was upregulated at both 35 and 65 g/L, potentially a universal stress protein.
- Repressed proteins at 65 g/L NaCl showed molecular weights similar to known virulence factors.
Conclusions:
- Osmotic stress profoundly impacts Listeria monocytogenes protein synthesis.
- Upregulated proteins suggest an adaptive stress response, including a potential universal stress protein.
- Repression of certain proteins at high salt may indicate a link between osmotic stress and virulence factor regulation.