Diversity of acid stress resistant variants of Listeria monocytogenes and the potential role of ribosomal protein

Listeria monocytogenes exhibits a heterogeneous response upon stress exposure which can be partially attributed to the presence of stable stress resistant variants. The presence of genetic variants allows for growth and survival of the population under a wide range of environmental conditions with specific fitness and robustness parameters considered a trade-off. A variant may have an advantage under one condition, while this might be a disadvantage under other conditions. This study aims to evaluate the impact of the presence of stress resistant variants and their corresponding trade-offs on population composition under different environmental conditions. A set of robustness and fitness parameters of WT and variants was obtained and used to model their behaviour under combined mild stress conditions and in a simulated food chain. Predictions of performance were validated in single cultures by plate counts and in mixtures by qPCR in which WT and an rpsU deletion variant were distinguished by specific primers. Growth predictions for WT and rpsU deletion variant were matching the experimental data generally well. Validation of performance in the simulated food chain confirmed the trend of higher fitness and lower robustness for the WT compared to the rpsU variant. This study provides insights into the conditions which can select for stress resistant variants in industrial settings and discusses their potential persistence in food processing environments.