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International audience; In freshwater ecosystem, phototrophic biofilms play a crucial role through adsorption and sequestration of organic and inorganic pollutants. However, extracellular polymeric substance (EPS) secretion by phototrophic biofilms exposed to metals is poorly documented. This work evaluated the physiological responses of phototrophic biofilms by exposing three microorganisms (cyanobacterium Phormidium autumnale, diatom Nitzschia palea and green alga Uronema confervicolum) to 20 and 200 μg L −1 of Cu or 60 and 600 μg L −1 of Zn, both individually and in combination. Analysis of metal effects on algal biomass and photosynthetic efficiency showed that metals were toxic at higher concentrations for these two parameters together and that all the strains were more sensitive to Cu than to Zn. U. confervicolum was the most impacted in terms of growth, while P. autumnale was the most impacted in terms of photosynthetic efficiency. In consequence to metal exposure at higher concentrations (Cu200, Zn600 and Cu200Zn600), a higher EPS production was measured in diatom and cyanobacterium biofilms, essentially caused by an overproduction of protein-like polymers. On the other hand, the amount of secreted polysaccharides decreased during metal exposure of the diatom and green alga biofilms. Size exclusion chromatography revealed specific EPS molecular fingerprints in P. autumnale and N. palea biofilms that have secreted different protein-like polymers during their development in the presence of Zn600. These proteins were not detected in the presence of Cu200 despite an increase of proteins in the EPS extracts compared to the control. These results highlight interesting divergent responses between the three monospecies biofilms and suggest that increasing protein production in EPS biofilms may be a fingerprint of natural biofilm against metal pollutants in freshwater rivers.

International audience; The plant pathogen Ralstonia solanacearum uses plant resources to intensely proliferate in xylem vessels and provoke plant wilting. We combined automatic phenotyping and tissue/xylem quantitative metabolomics of infected tomato plants to decipher the dynamics of bacterial wilt. Daily acquisition of physiological parameters such as transpiration and growth were performed. Measurements allowed us to identify a tipping point in bacterial wilt dynamics. At this tipping point, the reached bacterial density brutally disrupts plant physiology and rapidly induces its death. We compared the metabolic and physiological signatures of the infection to drought stress, and found that similar changes occur. Quantitative dynamics of xylem content enabled us to identify glutamine (and asparagine) as primary resources R. solanacearum consumed during its colonization phase. An abundant production of putrescine was also observed during the infection process and was strongly correlated with in planta bacterial growth. Dynamic profiling of xylem metabolites confirmed that glutamine is the favored substrate of R. solanacearum. On the other hand, a triple mutant strain unable to metabolize glucose, sucrose and fructose appears to be only weakly reduced for in planta growth and pathogenicity.

International audience; Polyamines are ubiquitous amine molecules found in all living organisms. In plants, beside their role in signaling and protection against abiotic stresses, there is increasing evidence that polyamines play a major role in the interaction between plants and pathogens. Plant polyamines are involved in immunity against pathogens, notably by amplifying PTI (Pattern-triggered immunity) responses through the production of reactive oxygen species. In response, pathogens use phytotoxins and effectors to manipulate the levels of polyamines in the plant, most likely to their own benefit. It also appears that pathogenic microorganisms produce polyamines during infection, sometimes in large quantities. This may reflect different infectious strategies based on the selective exploitation of these molecules and the functions they perform in the cell.

With the development of plant metabolomics, projects like the 10,000 plants genome sequencing project and the growth of other omics, the amount of data describing plant metabolism has never been so big. Genome-scale metabolic models (GEMs) are widely used to integrate and study the available information, and to better understand global responses to metabolic changes. In the first part of this chapter, we will focus on the existing plant GEMs, their history, and the biological questions associated with their reconstruction. Those GEMs were initially reconstructed based on cell suspension systems, but current reconstructions are widely focused on multiorgans and multitissues models, requiring some model integration. Model integration is the focus of the second part of this chapter, with the study of biotic interactions with the integration of GEMs coming from plant-interacting microorganisms and their host plants, modeling either pathogenic and symbiotic interactions. Emphasis will be placed on modeling quantitative interaction between plants and microorganisms. Finally, the third part of this chapter describes how the visualization of networks could be used to improve the understanding of the models and the integration of different omics data, and how good representation of metabolic networks can help the user to perform diverse tasks and put knowledge in context.

Vibrio cholerae is nowadays still problematic in several countries which are exposed to recurrent disease outbreaks. The current disease detection and treatment methods are efficient so this approach focused on the prevention of the disease. Indeed, current solutions are not efficient enough to deal with this situation. As V. cholerae which infects more than a million people each year is usually found in water, a synthetic microbial consortium was designed to detect and kill efficiently the bacteria in water. This work shows that Vibrio harveyi, a non-pathogenic strain to human, can be an efficient detector of V. cholerae. Moreover, it proves that Pichia pastoris, a yeast, can efficiently produce a novel antimicrobial peptide coming from the crocodile Crocodylus siamensis (i.e D-NY15) and that this peptide has a killing action towards V. cholerae. This study also shows that a communication between a prokaryote (Vibrio harveyi) and an eukaryote (Pichia pastoris) may be possible.