What makes Xanthomonas albilineans unique amongst xanthomonads?

Xanthomonas albilineans causes leaf scald, a lethal disease of sugarcane. Compared to other species of Xanthomonas, X. albilineans exhibits distinctive pathogenic mechanisms, ecology and taxonomy. Its genome, which has experienced significant erosion, has unique genomic features. It lacks two loci required for pathogenicity in other plant pathogenic species of Xanthomonas: the xanthan gum biosynthesis and the Hrp-T3SS (hypersensitive response and pathogenicity-type three secretion system) gene clusters. Instead, X. albilineans harbors in its genome an SPI-1 (Salmonella pathogenicity island-1) T3SS gene cluster usually found in animal pathogens. X. albilineans produces a potent DNA gyrase inhibitor called albicidin, which blocks chloroplast differentiation, resulting in the characteristic white foliar stripe symptoms. The antibacterial activity of albicidin also confers on X. albilineans a competitive advantage against rival bacteria during sugarcane colonization. Recent chemical studies have uncovered the unique structure of albicidin and allowed us to partially elucidate its fascinating biosynthesis apparatus, which involves an enigmatic hybrid PKS/NRPS (polyketide synthase/non-ribosomal peptide synthetase) machinery

Mass Spectrometry Based Molecular 3D-Cartography of Plant Metabolites

Plants play an essential part in global carbon fixing through photosynthesis and are the primary food and energy source for humans. Understanding them thoroughly is therefore of highest interest for humanity. Advances in DNA and RNA sequencing and in protein and metabolite analysis allow the systematic description of plant composition at the molecular level. With imaging mass spectrometry, we can now add a spatial level, typically in the micrometer-to-centimeter range, to their compositions, essential for a detailed molecular understanding. Here we present an LC-MS based approach for 3D plant imaging, which is scalable and allows the analysis of entire plants. We applied this approach in a case study to pepper and tomato plants. Together with MS/MS spectra library matching and spectral networking, this non-targeted workflow provides the highest sensitivity and selectivity for the molecular annotations and imaging of plants, laying the foundation for studies of plant metabolism and plant-environment interactions

Bacillus extracellular matrix modulates Botrytis metabolism and growth

In nature, bacteria often form communities known as biofilms, where cells are embedded in a self-produced extracellular matrix (ECM) that provides protection against external aggressions or facilitates efficient use of resources. Interactions with other microbes can significantly alter the structure of the community and thus the type of relationship with the environment. Here, we study the role of different components of Bacillus ECM in the adhesion to Botrytis hyphae, which could facilitate the efficient release of antifungal metabolites. We also describe how the different purified components of the ECM and certain Bacillus secondary metabolites (TasA, TapA, EPS, Fengycin) modulate the chemical communication between Bacillus and Botrytis, altering the physiology and ultrastructure of Botrytis.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Meta-Mass Shift Chemical (MeMSChem) profiling of metabolomes from coral reefs

Untargeted metabolomics of environmental samples routinely detects thousands of small molecules, the vast majority of which cannot be identified. Meta-mass shift chemical (MeMSChem) profiling was developed to identify mass differences between related molecules using molecular networks. This approach illuminates metabolome-wide relationships between molecules and the putative chemical groups that differentiate them (e.g., H2, CH2, COCH2). MeMSChem profiling was used to analyze a publicly available metabolomic dataset of coral, algal, and fungal mat holobionts (i.e., the host and its associated microbes and viruses) sampled from some of Earth's most remote and pristine coral reefs. Each type of holobiont had distinct mass shift profiles, even when the analysis was restricted to molecules found in all samples. This result suggests that holobionts modify the same molecules in different ways and offers insights into the generation of molecular diversity. Three genera of stony corals had distinct patterns of molecular relatedness despite their high degree of taxonomic relatedness. MeMSChem profiles also partially differentiated between individuals, suggesting that every coral reef holobiont is a potential source of novel chemical diversity

Deciphering the chemical dialogue between Bacillus and pathogenic fungi.

In nature, bacteria frequently form bacterial communities known as biofilms, where cells are embedded within an extracellular matrix (ECM) that provides protection against external aggressions or facilitates the efficient uptake and utilization of available resources. Interactions with other microbes can notably alter the community structure and, consequently, the nature of the relationship with the environment1. Previous studies of our laboratory have demonstrated the significance of biofilm formation in the antagonistic interaction between Bacillus and the phytopathogenic fungi Botrytis in the melon phyllosphere2. Our hypothesis is that the ECM plays a complementary role to the structural aspects of this antagonistic interaction. In this study, we dissect how the different components of Bacillus ECM mediate the adhesion of bacterial cells to Botrytis hyphae, which could enhance the efficient release of antifungal metabolites. We also describe how several purified components of the ECM and specific secondary metabolites of Bacillus participate in the chemical communication between Bacillus and Botrytis, thereby altering the physiology and metabolism of Botrytis. Our findings unveil that during this antagonistic interaction, Botrytis secrets different oxylipins, defence molecules capable of killing Bacillus. In response, Bacillus increases the production of several secondary metabolites, which appears to have antifungal effects. Our results underscore the urgency of further investigation of these interactions with the aim of identifying and describing adaptation processes that either lead to the exclusion or coexistence of two initially antagonistic microorganisms.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec