Oxygen-dependent effects of L-Cysteine and SigB on thermal tolerance of Listeria monocytogenes 10403S

Soyler, I., Mahide Muge, Y. T. and Karatzas, K.-A. (2026) Oxygen-dependent effects of L-Cysteine and SigB on thermal tolerance of Listeria monocytogenes 10403S. ITU Journal of Food Science and Technology, 4 (1). pp. 23-29. ISSN 3023-7327

Abstract/Summary

Listeria monocytogenes is a resilient foodborne pathogen capable of surviving diverse environmental stresses, including heat, oxidative, and osmotic conditions. The alternative sigma factor SigB plays a central role in mediating stress adaptation. However, its function under oxygen-limited conditions and in nutrient-rich environments remains insufficiently understood. L-cysteine, commonly present in food matrices, may influence bacterial stress tolerance by acting as both a metabolic signal and a precursor for antioxidant systems. This study investigated the effect of extracellular L-cysteine supplementation on the heat resistance of L. monocytogenes and evaluated the contribution of SigB under both aerobic and anaerobic conditions. Wild-type L. monocytogenes 10403S and an isogenic ΔsigB mutant were subjected to heat stress in defined medium supplemented with 1.57 mM L-cysteine. Bacterial survival was quantified and compared across strains and environmental conditions. L-cysteine supplementation significantly enhanced bacterial survival under anaerobic heat stress. Notably, the ΔsigB mutant exhibited greater resistance than the wild-type strain under these conditions. This observation suggests that L-cysteine-associated metabolic pathways may compensate, at least partially, for the absence of SigB-mediated stress regulation. The enhanced survival in the mutant strain points to alternative protective mechanisms, potentially linked to redox balance or sulphur metabolism. Overall, the findings demonstrate that L-cysteine availability, oxygen conditions, and SigB interact in a complex and context-dependent manner to influence heat stress survival in L. monocytogenes. These results highlight the importance of metabolic state in shaping bacterial stress responses and suggest that sulphur metabolism may serve as a key compensatory pathway under oxygen-limited conditions. A deeper understanding of these interactions could support the development of more effective strategies for controlling L. monocytogenes in food systems and processing environments.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/129468
Refereed	Yes
Divisions	Life Sciences > School of Chemistry, Food and Pharmacy > Department of Food and Nutritional Sciences > Food Microbial Sciences Research Group
Publisher	Istanbul Technical University
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