Interactions between the foodborne pathogen Bacillus cereus and plant foods in the intestinal tract (Project CeFoo !).

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INRAE presentation

The French National Research Institute for Agriculture, Food, and Environment (INRAE) is a major player in research and innovation. It is a community of 12,000 people with 272 research, experimental research, and support units located in 18 regional centres throughout France. Internationally, INRAE is among the top research organisations in the agricultural and food sciences, plant and animal sciences, as well as in ecology and environmental science. It is the world’s leading research organisation specialising in agriculture, food and the environment. INRAE’s goal is to be a key player in the transitions necessary to address major global challenges. Faced with a growing world population, climate change, resource scarcity, and declining biodiversity, the Institute has a major role to play in building solutions and supporting the necessary acceleration of agricultural, food and environmental transitions.

Work environment, missions and activities

You will be welcomed in the SporAlim and Qualim team's, part of the INRAE mixed research unit Security and Quality of Plant-Based Food Products (SQPOV) based in Avignon, France (https://www6.paca.inrae.fr/sqpov_eng).

Spore-forming bacteria represent a major problem for the food industries, due to their ubiquity, their capacity for adaptation and their resistance. Certain pathogenic strains of Bacillus cereus sensu stricto (Bc), capable of contaminating all types of food, are responsible for food poisoning and constitute in France the second cause of FBO (Food born outbreaks).

Plants provide a wide range of antimicrobial microconstituents which could therefore be of interest from a human health point of view. Certain phyto-microconsituents are reported to exhibit antibacterial activity against Bc. Most of the time, the effectiveness of these antimicrobial compounds is tested in vitro, ignoring A) the stresses encountered by bacteria in the digestive tract and the adaptive mechanisms put in place under these conditions; B) the role of the food matrix, in particular that of fibers, in the availability of phyto-microconstituents and C) the role of the different physiological mechanisms (enzymes, pH variation, bile salts, etc.) implemented during the different phases of digestion. The ambition of this project is to take into account the food as a whole to evaluate the anti-microbial potential of products of plant origin on Bc in the digestive tract, (semi dynamic in vitro model) to identify active phyto-microconstituents, the effect of phyto-microconstituaent/fiber interactions and to decipher the response of the bacteria to these compounds.

To answer the scientific questions of the project, the doctoral student will develop approaches in microbial physiology (development and survival of Bc in the intestinal tract), microbial genetics and molecular biology (construction and characterization of mutant bacterial strains, construction of transcriptional fusions of promoters of genes of interest to a gene encoding a fluorescent protein). He/she will also develop in vitro digestion approaches (pH, enzymes, bile salts, etc.) in order to study the fate of phytoconstituents in particular in relation to the structure of fibers, their changes during digestion and their abilities to interact with each other. He/she will analyze and carry out fractionation and purification of fibers and phyto-microconstituents using different chromatographic techniques (GC-MS, GC-FID, UHPLC-HRMS, HPLC-DAD).

The doctoral student will work in a ZRR zone (restrictive regime zone). Final decision of admission is subject to prior security clearance granting access to ZRR.

The doctoral student will respect the rules of secularism of INRAE

« All those who work at INRAE must carry out their duties with dignity, impartiality, integrity and probity, observe the obligation of neutrality, uphold the principle of secularism, and refrain from expressing their religious opinions during the performance of their duties. All employees contributing to INRAE’s work must treat equally all those they may interact with as part of their professional duties and respect their freedom of conscience and their dignity

Training and skills

The candidate will have a Master 2 in microbiology or an equivalent degree (engineering school). He/she should have a strong background in molecular biology, biochemistry and microbial genetics and have an interest for food biochemistry.

Alternately, the candidate will have a Master 2 in food biochemistry and/or or an equivalent degree (engineering school). Experience in one or more of the methods used (phytochemical analysis, fiber analysis, in vitro digestion, etc.) will be appreciated, as well as an interest in microbiology.

Experience in statistical data processing will also be appreciated.

INRAE's life quality

By joining our teams, you benefit from (depending on the type of contract and its duration):

- up to 30 days of annual leave + 15 days "Reduction of Working Time" (for a full time);
- parenting support: CESU childcare, leisure services;
- skills development systems: training, career advise;
- social support: advice and listening, social assistance and loans;
- holiday and leisure services: holiday vouchers, accommodation at preferential rates;
- sports and cultural activities;
- collective catering.

How to apply

I send my CV and my motivation letter