Gene profiling-based phenotyping for identification of cellular parameters that contribute to fitness, stress-tolerance and virulence of Listeria monocytogenes variants.

Microbial population heterogeneity allows for a differential microbial response to environmental stresses and can lead to the selection of stress resistant variants. In this study, we have used two different stress resistant variants of Listeria monocytogenes LO28 with mutations in the rpsU gene encoding ribosomal protein S21, to elucidate features that can contribute to fitness, stress-tolerance and host interaction using a comparative gene profiling and phenotyping approach. Transcriptome analysis showed that 116 genes were upregulated and 114 genes were downregulated in both rpsU variants.

A modification of the constant-head permeameter to measure saturated hydraulic conductivity of highly permeable media.

The saturated hydraulic conductivity ( ) is a key characteristic of porous media, describing the rate of water flow through saturated porous media. It is an indispensable parameter in a broad range of simulation models that quantify saturated and/or unsaturated water flow. The constant-head permeameter test is a common laboratory method to determine K on undisturbed soil samples collected from the field.

Including hydrological self-regulating processes in peatland models: Effects on peatmoss drought projections.

The water content of the topsoil is one of the key factors controlling biogeochemical processes, greenhouse gas emissions and biosphere - atmosphere interactions in many ecosystems, particularly in northern peatlands. In these wetland ecosystems, the water content of the photosynthetic active peatmoss layer is crucial for ecosystem functioning and carbon sequestration, and is sensitive to future shifts in rainfall and drought characteristics. Current peatland models differ in the degree in which hydrological feedbacks are included, but how this affects peatmoss drought projections is unknown.

Modeling and Validation of the Ecological Behavior of Wild-Type Listeria monocytogenes and Stress-Resistant Variants.

Unlabelled: Listeria monocytogenes exhibits a heterogeneous response upon stress exposure which can be partially attributed to the presence of stable stress-resistant variants. This study aimed to evaluate the impact of the presence of stress-resistant variants of Listeria monocytogenes and their corresponding trade-offs on population composition under different environmental conditions. A set of stress robustness and growth parameters of the wild type (WT) and an rpsU deletion variant was obtained and used to model their growth behavior under combined mild stress conditions and to model their kinetics under single- and mixed-strain conditions in a simulated food chain.

Microbial variability in growth and heat resistance of a pathogen and a spoiler: All variabilities are equal but some are more equal than others.

Quantitative microbiology is used in risk assessment studies, microbial shelf life studies, product development, and experimental design. Realistic prediction is, however, complicated by different sources of variability. The final concentration of microorganisms at the moment of consumption is affected by different sources of variability: variability in the storage times and temperatures, variability in product characteristics, variability in process characteristics, variability in the initial contamination of the raw materials, and last but not least, microbiological variability.