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Effect of habitat disturbances on the population dynamics of allochthon listeria monocytones in soil
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Edité par CCSD -
EA UB AGROSUP BIOME GESTAD INRA
EAUBAGROSUPBIOMEGESTADINRA. International audience.
Soil is in many cases the first stage in the routes of transmission of foodborne pathogens to plant, farm animals, foodstuff and humans as final consumers. Soil is a complex, heterogeneous environment which shelters many organisms such as allochthon bacteria. The persistence of these organisms depends on abiotic factors (temperature, humidity, texture, chemistry) and on biotic interactions, for example competition with native microflora. Objectives In this study, we used the foodborne pathogen Listeria monocytogenes as model system to investigate how disturbances affect habitat invasion by allochthon organisms. Methods Two soils with contrasting abiotic and microbiome characteristics were used. Inoculated soil microcosms were submitted to two cycles of temperature shifts (either increase to 42°C or freezing at -20°C) separated by 20 days of incubation at 20°C. Control microcosms were kept at 20°C. In order to investigate the impact of the indigenous microbiota, similar experiments were run in γ-irradiated, sterilized soil microcosms. Cultivable L. monocytogenes were evaluated by plate counts throughout the 40 days incubation. Additionally, soil samples were taken at the start of the experiment and after 20 and 40 days for DNA extraction and subsequent 16SrDNA diversity analysis. Variations of diversity were assessed in non-inoculated microcosms to evaluate the influence of L. monocytogenes invasion on the native soil microbiota. Conclusions While growth was observed in sterilized soil, the population of L. monocytogenes decreased in the other experimental conditions. Results showed that the fate of allochthon L. monocytogenes depended on the disturbance regimen. Higher survival was observed in when soil underwent cycles of freezingConclusions The fate of L. monocytogenes is dependent on both abiotic and biotic characteristics and the latter have a major impact on the dynamics of the populations of L. monocytogenes in soil. Major transcriptome reshaping was observed where L. monocytogenes recruits its repertoire of transporters and specific pathways to access and utilise the available substrates. The biotic environment further affects transcriptome and triggers further regulation.
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