Omics analysis of Arabidopsis halleri populations with contrasting strategies of Cd hypertolerance

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Modelling the fate of Listeria monocytogenes during manufacture and ripening of smeared cheese made with pasteurised or raw milk.

The dynamics of the physicochemical characteristics of foods help to determine the fate of pathogens throughout processing. The aim of this study was to assess the behaviour of Listeria monocytogenes during cheesesmaking and ripening and to model the growth observed under the dynamic conditions of the cheese. A laboratory scale cheese was made in 4 independent replicates from pasteurised or raw cow's milk, artificially contaminated with L. monocytogenes. No growth of L. monocytogenes occurred during raw milk cheese-making, whereas growth did occur in pasteurised milk. During ripening, growth occurred in raw milk cheese, but inactivation occurred in pasteurised milk cheese. The behaviour observed for L. monocytogenes was modelled using a logistic primary model coupled with a secondary cardinal model, taking into account the effect of physicochemical conditions (temperature, pH, water activity and lactate). A novel statistical approach was proposed to assess the optimal growth rate of a microorganism from experiments performed in dynamic conditions. This complex model had an acceptable quality of fit on the experimental data. The estimated optimum growth rates can be used to predict the fate of L. monocytogenes during cheese manufacture in raw or pasteurized milk in different physicochemical conditions. The data obtained contributes to a better understanding of the potential risk that L. monocytogenes presents to cheese producers (growth on the product, if it is contaminated) and consumers (the presence of high numbers) and constitutes a very useful set of data for the completion of chain-based modelling studies

Absence of Listeria monocytogenes growth during raw milk cheesemaking: a modelling approach

The presence of Listeria monocytogenes in certain foods and the risk that this poses to public health and food quality is still a problem. Currently, the field of food mi- crobiology focuses on obtaining data on the behaviour of microorganisms in food, but the responses obtained provide little insight into the relationship between physiological processes and growth or survival. This link can be made through mathematical models. In a simple form, a mathematical model is a simple mathe- matical description of a process. The application of mathematical models to food microbiology has been developed in recent years and now constitutes a new disci- pline named as Predictive Microbiology. However, most predictive models are based on laboratory experiments in microbiological media under static conditions. As such models tend to be inaccurate, we have undertaken our experiments in a food system under dynamic conditions. Cheese was made with raw and pasteurised milk deliberately contaminated with L. monocytogenes . Listeria was monitored through the manufacture and ripening period of the cheese. The results showed that L. monocytogenes did not grow during manufacture of raw milk cheese, but did grow during manufacture of pasteurised milk cheese. The data obtained for growth, survival and inactivation was modelled. The application of models that can explain the behaviour of Listeria in cheese and the further predictions that can be obtained from these models are useful for the improvement of ongoing re- search on biotraceability and for the better understanding of the general behaviour of these microorganisms under dynamic conditions, such as in dairy product

Predictive models developed in cheese for growth of Listeria monocytogenes

peer reviewe

Adaptation of Arabidopsis halleri to extreme metal pollution through limited metal accumulation involves changes in cell wall composition and metal homeostasis

peer reviewedMetallophytes constitute powerful models to study metal homeostasis, adaptation to extreme environments and the evolution of naturally-selected traits. Arabidopsis halleri is a pseudometallophyte which shows constitutive Zn/Cd tolerance and Zn hyperaccumulation but high intraspecific variability in Cd accumulation. To examine the molecular basis of the variation in metal tolerance and accumulation, ionome, transcriptome and cell-wall glycan array profiles were compared in two genetically close A. halleri populations from metalliferous and non-metalliferous sites in Northern Italy. The metallicolous population displayed increased tolerance to, reduced hyperaccumulation of Zn and limited accumulation of Cd, as well as altered metal homeostasis, compared to the non-metallicolous population. This correlated well with the differential expression of transporter genes involved in trace metal entry and in Cd/Zn vacuolar sequestration in roots. Many cell wall-related genes were also more expressed in roots of the metallicolous population. Glycan array and histological staining analyses supported major differences between the two populations in the accumulation of specific root pectins and hemicelluloses epitopes. Our results supported a role for specific cell wall components and regulation of transporter genes of Arabidopsis halleri in limiting accumulation of metals on contaminated sites

Adaptation of Arabidopsis halleri to extreme metal pollution through limited metal accumulation involves changes in cell wall composition and metal homeostasis

Metallophytes constitute powerful models to study metal homeostasis, adaptation to extreme environments and the evolution of naturally-selected traits. Arabidopsis halleri is a pseudometallophyte which shows constitutive Zn/Cd tolerance and Zn hyperaccumulation but high intraspecific variability in Cd accumulation. To examine the molecular basis of the variation in metal tolerance and accumulation, ionome, transcriptome and cell-wall glycan array profiles were compared in two genetically close A. halleri populations from metalliferous and non-metalliferous sites in Northern Italy. The metallicolous population displayed increased tolerance to, reduced hyperaccumulation of Zn and limited accumulation of Cd, as well as altered metal homeostasis, compared to the non-metallicolous population. This correlated well with the differential expression of transporter genes involved in trace metal entry and in Cd/Zn vacuolar sequestration in roots. Many cell wall-related genes were also more expressed in roots of the metallicolous population. Glycan array and histological staining analyses supported major differences between the two populations in the accumulation of specific root pectins and hemicelluloses epitopes. Our results supported a role for specific cell wall components and regulation of transporter genes of Arabidopsis halleri in limiting accumulation of metals on contaminated sites

Adaptation of Arabidopsis halleri to extreme metal pollution through limited metal accumulation involves changes in cell wall composition and metal homeostasis

info:eu-repo/semantics/publishe