Soil biodiversity as a major driver for the control of populations of the pathogenic bacterium Listeria monocytogenes in soil

Disease regulation is one of the many services that ecosystems provide. Agroecosystems are dedicated to the provision of high quality, safe food and sustainability is a major issue. Biological contamination of the food supply may raise food safety issues. Prevention of contamination of the food supply requires a thorough understanding of the ecology of pathogenic microorganisms. Listeria monocytogenes is a food pathogen found in many habitats including soil, plants, water systems and food processing factories. We designed microcosm experiments to decipher extrinsic factors that drive the fate of this model of Human pathogen in soil. We analysed population dynamics over 80 days after inoculation of a large set of 100 soils selected from the French Réseau de la Qualité des Sols (RMQS), a country-wide venture of monitoring of the quality of soils in France. The population of L. monocytogenes decreased over time but the survival ratio depended on the soil under scrutiny. Detailed information such as soil characteristics and land use were integrated into an analysis of variance. Chemical properties, especially the basic cation saturation ratio and soil texture were factors affecting survival of L. monocytogenes. Analysis of the results collected under similar experimental conditions in the same set of soils but sterilised by ionisation indicated that the endogenous soil microbiota had a major impact on the decrease of the population of L. monocytogenes. This prompted us to investigate the relationship between the biodiversity of the soil microbiota and the inhibition of the population of L. monocytogenes. By a dilution to extinction approach, we investigated the consequences of soil diversity erosion on the fate of a human bacterial pathogen in the telluric environment. Diversity analysis showed that both soil diversity and phylogenetic composition affected survival of L. monocytogenes. Overall, our results demonstrate that soil biodiversity is a major driver that limit invasion of soil by pathogenic bacteria