Final Report Summary - STRP-DIFFERENTIATION (BIOMOLECULAR CHARACTERIZATION OF STREPTOMYCES DIFFERENTIATION AND ITS RELATIONSHIP WITH SECONDARY METABOLITE PRODUCTION) Streptomyces produces two thirds of clinically relevant secondary metabolites (antibiotics, antitumourals, immunosuppressants, etc.). Streptomyces is considered a “multicellular” prokaryotic model that includes programmed cell death (PCD) and sporulation in solid cultures. Industrial fermentations are mainly produced in liquid cultures (large bioreactors), conditions in which most species do not sporulate, and it was traditionally considered that there was no differentiation. Our research group pioneered the application of new experimental methods to analyse Streptomyces biology, defining a new developmental cycle in solid and liquid cultures, and identifying the antibiotic producing mycelium. Deep in the understanding of the differentiation and activation of secondary metabolism was the primary objective of the Strp-differentiation project. This includes the study of the application of this knowledge to the optimisation of hyphal differentiation in industrial fermentations, and more importantly, to improve the screening of new bioactive compounds from natural Actinomycetes strains, an issue which is becoming critical in biomedicine. Our main outcomes were: the identification of an unprecedented type of cell division based on cross-membranes instead of peptidoglycan-based cross-walls that changed the old dogma that Streptomyces vegetative hyphae have scarce compartmentalisation; we demonstrated that the loss of selective membrane permeability during Streptomyces PCD is gradual, resembling eukaryotic apoptosis, and forming internal membrane vesicles before the loss of membrane permeability occurs; we identified the differences in the transcriptomes, proteomes and phosphoproteomes of MI (vegetative) and MII (reproductive) mycelia in solid sporulating cultures and liquid non-sporulating cultures; we demonstrated that hyphal differentiation is one of the keys to improve and activate secondary metabolism in industrial bioreactors; we made 81 mutants in genes differentially expressed during development, and 55 of them (68% of the total) had clear and distinctive phenotypes that leaded to the characterisation of novel mechanisms controlling germination, antibiotic production and differentiation.
