SpoHis

Control of spore-forming bacteria is still one of the main challenges faced by the food industry and regulatory agencies since they give rise to a metabolically inert spores with extreme resistance to common preservation methods. Spores, especially from Bacillus and Clostridium spp., can germinate and restore growth in foods, causing spoilage and substantial economic losses. Some species are also causative agents of foodborne diseases.

In this context, the loss of food quality and expired shelf lives are the main causes of food waste in industrialized countries. Indeed, reducing food waste has become a priority in worldwide policy towards sustainable development and the circular economy. Increasing food shelf life while maintaining appropriate levels of safety is essential to combat food wastage. In the industry, spores are generally inactivated by intense thermal sterilization, but this comes at the expense of food quality.

The design of gentler methods aims to prevent spore germination and/or outgrowth during food storage by combining stresses (i.e., acidification, refrigeration, etc.) and germination-inactivation strategies. These strategies first induce germination and then take advantage of the loss of resistance in germinating cells through mild inactivating methods. However, the effectiveness of these methods is limited by the large heterogeneity in spore behaviour (i.e., germination, damage resistance, and subsequent resuscitation), which results from inter- and intraspecific eco-physiological differences, intercellular variations, and extrinsic factors acting at different stages of the spore-formers' life cycle. To better anticipate spore responses and design feasible preservation methods, it is necessary to improve our current understanding of the dynamics of spore behaviour.

Although this topic has attracted a lot of research, most studies have focused on the effect of a certain environmental factor on spore survival or germination, thus ignoring upstream or intermediate stages and being limited to phenotypic characterization at the population level. Therefore, the main objective of this 3-year project is to study the impact of environmental stresses occurring during the sporulation history on the single-cell behaviour of downstream spores of the model organism B. subtilis based on physio-molecular insights.

To this end, we have selected a number of spore populations obtained in extreme environments that entail changes in germination, damage resistance, and/or resuscitation fitness compared to those obtained in optimal conditions. These will be analyzed by a combination of population-wise molecular techniques, genetic engineering approaches, and single-cell biology tools to shed light on the cellular features and stress responses involved in their phenotypes.

These activities will be performed by a 6-member research team belonging to the group A03_23R: Novel Food Processing Technologies, along with international collaborators. The outcomes of this research will have a techno-scientific impact in the microbiology and biotechnology field and a significant socio-economic impact in the food field, as it will facilitate the design of effective strategies to improve food shelf life and safety.