Streptomyces as a Source of Antimicrobials: Novel Approaches to Activate Cryptic Secondary Metabolite Pathways

Streptomyces is the most important bacterial genus for bioactive compound production. These soil bacteria are characterized by a complex differentiation cycle. Streptomyces is extremely important in biotechnology, producing approximately two thirds of all antibiotics, as well as many compounds of medical and agricultural interest. Drug discovery from streptomycetes became challenging once the most common compounds were discovered, and the system was basically abandoned by industry. Simultaneously, antibiotic resistance is increasing dramatically, and new antibiotics are required. Screening from nature is being resumed (exploring new environments, looking for elicitors, metagenome, etc.). Secondary metabolism is conditioned by differentiation; although the relationship between both has long remained elusive, differentiation as a trigger for antibiotic production remains basically unexplored. Most cultures used in screening campaigns for new bioactive molecules have been performed empirically, and workflow was extremely productive during the so-called golden age of antibiotics; however, currently there is a bottleneck. Streptomyces is still the most important natural source of antibiotics, and it also harbors many cryptic secondary metabolite pathways not expressed under laboratory conditions. In this chapter, we review strategies based on differentiation, one of the keys improving secondary metabolite production and activating cryptic pathways to face the challenges of drug discovery

Streptomyces differentiation in liquid cultures as a trigger of secondary metabolism

We thank the Spanish “Ministerio de Economía y Competitividad” (MINECO; BIO2015-65709-R) for financial support

Mycelium Differentiation and Development of <em>Streptomyces</em> in Liquid Nonsporulating Cultures: Programmed Cell Death, Differentiation, and Lysis Condition Secondary Metabolite Production

Streptomycetes are mycelium-forming sporulating bacteria that produce two thirds of clinically relevant secondary metabolites. Secondary metabolite production is activated at specific developmental stages of Streptomyces life cycle. Despite this, Streptomyces differentiation in liquid nonsporulating cultures (flasks and industrial bioreactors) tends to be underestimated and the most important parameters managed are only indirectly related to differentiation: modifications to the culture media, optimization of productive strains by random or directed mutagenesis, analysis of biophysical parameters, etc. In this chapter, we review the relationship between differentiation and antibiotic production in liquid cultures. Morphological differentiation in liquid cultures is comparable to that occurring during pre-sporulation stages in solid cultures: an initial compartmentalized mycelium suffers a programmed cell death, and remaining viable segments then differentiate to a second multinucleated antibiotic-producing mycelium. Differentiation is one of the keys to interpreting biophysical fermentation parameters and to rationalizing the optimization of secondary metabolite production in liquid cultures

Cell immobilization of Streptomyces coelicolor : effect on differentiation and actinorhodin production

Streptomycetes are mycelium-forming bacteria that produce two thirds of the clinically relevant secondary metabolites. Despite the fact that secondary metabolite production is activated at specific developmental stages of the Streptomyces spp. life cycle, different streptomycetes show different behaviors, and fermentation conditions need to be optimized for each specific strain and secondary metabolite. Cell-encapsulation constitutes an interesting alternative to classical fermentations, which was demonstrated to be useful in Streptomyces, but development under these conditions remained unexplored. In this work, the influence of cell-encapsulation in hyphae differentiation and actinorhodin production was explored in the model Streptomyces coelicolor strain. Encapsulation led to a delay in growth and to a reduction of mycelium density and cell death. The high proportion of viable hyphae duplicated extracellular actinorhodin production in the encapsulated cultures with respect to the non-encapsulated ones. [Int Microbiol 2014; 17(2):75-80]Keywords: Streptomyces coelicolor &middot; encapsulation &middot; differentiation &middot; antibiotics &middot; cell deat

Cell immobilization of Streptomyces coelicolor : effect on differentiation and actinorhodin production

Streptomycetes are mycelium-forming bacteria that produce two thirds of the clinically relevant secondary metabolites. Despite the fact that secondary metabolite production is activated at specific developmental stages of the Streptomyces spp. life cycle, different streptomycetes show different behaviors, and fermentation conditions need to be optimized for each specific strain and secondary metabolite. Cell-encapsulation constitutes an interesting alternative to classical fermentations, which was demonstrated to be useful in Streptomyces, but development under these conditions remained unexplored. In this work, the influence of cell-encapsulation in hyphae differentiation and actinorhodin production was explored in the model Streptomyces coelicolor strain. Encapsulation led to a delay in growth and to a reduction of mycelium density and cell death. The high proportion of viable hyphae duplicated extracellular actinorhodin production in the encapsulated cultures with respect to the non-encapsulated ones. [Int Microbiol 2014; 17(2):75-80]Keywords: Streptomyces coelicolor &middot; encapsulation &middot; differentiation &middot; antibiotics &middot; cell deat

Tratamiento de la información económica en la gestión de proyectos: convencionales vs ágiles

El tratamiento de la información económica es un aspecto relevante en todos los proyectos de desarrollo de software. En muchas ocasiones los proyectos no pueden acabarse dentro de los márgenes presupuestarios establecidos, por lo que hay que buscar nuevos enfoques que permitan invertir esta situación. Las metodologías agiles han irrumpido desde hace unos años en el desarrollo de software como una alternativa válida para atenuar las desviaciones presupuestarias. Este artículo presenta una aproximación entre el tratamiento de la información económica en los proyectos convencionales y los agiles. El objetivo es mostrar que la gestión económica en proyectos agiles no está fuera del alineamiento de las metodologías convencionales y que la gestión de costes puede controlarse con los mismos parámetros que en las metodologías convencionale

Geología de los materiales volcánicos y volcanoclásticos en el área de Laspaúles (Huesca)

El vulcanismo del Carbonífero Superior - Pérmico de los Pirineos aragonés y catalán fue emplazado en cuencas pequeñas y fuertemente subterráneas. Este estudio se enfoca en los materiales volcánicos y volcaniclásticos que rellenan la Cuenca de Castejón-Laspaules en las inmediaciones de Laspaules (Huesca) y, específicamente, sobre los materiales volcaniclásticos riolíticos que configuran la base del depósito. El mapa geológico del área ha sido revisado y completado en un nuevo mapa georreferenciado. Los materiales volcánicos se estudiaron en tres secciones estratigráficas. La base de las secciones está formada aglomerados riolíticos o brechas que se superponen discordantemente sobre las calizas de la Fm. Renanue(Devónico). Estos materiales van seguidos por otras rocas riolíticas, que van desde aglomerados hasta tobas de ceniza, frecuentemente ignimbríticos. Las tres terminan, tras un tramo cubierto, en la base de las unidades andesiticas. Estas rocas andesíticas son macizas o clásticas, y probablemente fueron emplazadas como flujos o pequeñas cúpulas que produjeron material fragmentario cuando estallaron. Ambas unidades riolíticas y andesíticas se ven afectados por una fuerte alteración que dificulta el estudio petrográfico y textural. Esta secuencia de productos volcánicos es la expresión de un volcanismo riolítico explosivo inicial, probablemente relacionado con las primeras etapas de la evolución de la cuenca, que luego cambió drásticamente al desarrollo de un volcanismo andesítico básico. La etapa riolítica produjo depósitos muy variables, asociados a depresiones topográficas controlado por a la estructura de la cuenca. Las rocas emplazadas durante la etapa andesítica son distribuidas a lo largo del área y se superponen a las unidades riolíticas

ArgR of Streptomyces coelicolor is a pleiotropic transcriptional regulator: effect on the transcriptome, antibiotic production, and differentiation in liquid cultures

[EN] ArgR is a well-characterized transcriptional repressor controlling the expression of arginine and pyrimidine biosynthetic genes in bacteria. In this work, the biological role of Streptomyces coelicolor ArgR was analyzed by comparing the transcriptomes of S. coelicolor ΔargR and its parental strain, S. coelicolor M145, at five different times over a 66-h period. The effect of S. coelicolor ArgR was more widespread than that of the orthologous protein of Escherichia coli, affecting the expression of 1544 genes along the microarray time series. This S. coelicolor regulator repressed the expression of arginine and pyrimidine biosynthetic genes, but it also modulated the expression of genes not previously described to be regulated by ArgR: genes involved in nitrogen metabolism and nitrate utilization; the act, red, and cpk genes for antibiotic production; genes for the synthesis of the osmotic stress protector ectoine; genes related to hydrophobic cover formation and sporulation (chaplins, rodlins, ramR, and whi genes); all the cwg genes encoding proteins for glycan cell wall biosynthesis; and genes involved in gas vesicle formation. Many of these genes contain ARG boxes for ArgR binding. ArgR binding to seven new ARG boxes, located upstream or near the ectA-ectB, afsS, afsR, glnR, and redH genes, was tested by DNA band-shift assays. These data and those of previously assayed fragments permitted the construction of an improved model of the ArgR binding site. Interestingly, the overexpression of sporulation genes observed in the ΔargR mutant in our culture conditions correlated with a sporulation-like process, an uncommon phenotypeSIGrant BIO2013-34723 from the Spanish Ministry of Science and Innovation to PL. Work in the AM's laboratory was funded by the European Research Council (ERC Starting Grant; Strp-differentiation 280304) and by the Spanish Ministry of Economy and Competitiveness (Grant BIO2015-65709-R)