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

Los componentes de la matriz extracelular de Bacillus subtilis son necesarios para proteger la colonia de la invasión de Pseudomonas y para la co-colonización en plantas

Las plantas son colonizadas por una gran variedad de microorganismos, y entre ellas las bacterias son las más predominantes dada su capacidad para adaptarse a cambios ambientales y comunicarse con otros organismos. La formación de comunidades de células de una misma especie en estructuras conocidas como biofilms les permite un mayor éxito en este escenario competitivo. La matriz extracelular que recubre a las bacterias es una estructura que confiere protección, modula el flujo de señales y controla la diferenciación celular, por lo que es importante conocer no solo su composición sino además la funcionalidad de los componentes. En este trabajo estudiamos la interacción de dos bacterias beneficiosas para plantas, Bacillus subtilis 3610 y Pseudomonas chlororaphis PCL1606. Mediante un abordaje pluridisciplinar, demostramos el papel de la matriz extracelular, y específicamente del EPS en la protección de colonias de B. subtilis frente a la colonización por Pseudomonas. La utilización de microscopía confocal nos ha permitido realizar un estudio completo del comportamiento de las bacterias y nos ha permitido medir velocidades de expansión de las colonias en distintas situaciones. El estudio transcriptómico de la interacción nos ha permitido destacar al sistema de secreción tipo VI (T6SS) de Pseudomonas como uno de los elementos clave en el contacto directo célula-célula frente a células de Bacillus desprovistas de su matriz extracelular. En respuesta a la infiltración por Pseudomonas, demostramos que B. subtilis activa la esporulación como un mecanismo de defensa secundario. Finalmente, análisis microbiológicos y microscopía confocal de las interacciones en distintos órganos de plantas de melón demuestran la importancia funcional de las distintas estrategias para la co-existencia estable de estas bacterias en comunidades bacterianas. Nuestros descubrimientos amplían la comprensión del papel funcional jugado por los biofilms durante las interacciones bacterianas.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec