Streptomyces coelicolor Vesicles: Many Molecules To Be Delivered.

Streptomyces coelicolor is a model organism for the study of Streptomyces, a genus of Gram-positive bacteria that undergoes a complex life cycle and produces a broad repertoire of bioactive metabolites and extracellular enzymes. This study investigated the production and characterization of membrane vesicles (MVs) in liquid cultures of S. coelicolor M145 from a structural and biochemical point of view; this was achieved by combining microscopic, physical and -omics analyses. Two main populations of MVs, with different sizes and cargos, were isolated and purified. S. coelicolor MV cargo was determined to be complex, containing different kinds of proteins and metabolites. In particular, a total of 166 proteins involved in cell metabolism/differentiation, molecular processing/transport, and stress response were identified in MVs, the latter functional class also being important for bacterial morpho-physiological differentiation. A subset of these proteins was protected from degradation following treatment of MVs with proteinase K, indicating their localization inside the vesicles. Moreover, S. coelicolor MVs contained an array of metabolites, such as antibiotics, vitamins, amino acids, and components of carbon metabolism. In conclusion, this analysis provides detailed information on S. coelicolor MVs under basal conditions and on their corresponding content, which may be useful in the near future to elucidate vesicle biogenesis and functions. IMPORTANCE Streptomycetes are widely distributed in nature and characterized by a complex life cycle that involves morphological differentiation. They are very relevant in industry because they produce about half of all clinically used antibiotics, as well as other important pharmaceutical products of natural origin. Streptomyces coelicolor is a model organism for the study of bacterial differentiation and bioactive molecule production. S. coelicolor produces extracellular vesicles that carry many molecules, such as proteins and metabolites, including antibiotics. The elucidation of S. coelicolor extracellular vesicle cargo will help us to understand different aspects of streptomycete physiology, such as cell communication during differentiation and response to environmental stimuli. Moreover, the capability of these vesicles for carrying different kinds of biomolecules opens up new biotechnological possibilities related to drug delivery. Indeed, decoding the molecular mechanisms involved in cargo selection may lead to the customization of extracellular vesicle content.

Particle size-related limitations of persistent phosphors based on the doped Y3Al2Ga3O12 system.

Co-doped Ce3+, Cr3+ and Pr3+ yttrium-aluminium-gallium garnet powders of various sizes were obtained by co-precipitation method. The microstructure and morphology were investigated by XRPD, TEM and gas porosimetry. The luminescence properties were studied by excitation and emission spectra, quantum yield and decay times. Thermoluminescence measurements were performed to evaluate the activation energy, traps redistribution and frequency factor. Limitation in the energy transfer between dopant ions in the small particles, traps depth and surface defects were considered and investigated as responsible for the quenching of persistent luminescence. The phosphors annealed at 1100 °C show the optimal persistent luminescence and nano-particle size.

Biogenic iron-silver nanoparticles inhibit bacterial biofilm formation due to Ag+ release as determined by a novel phycoerythrin-based assay.

Silver nanoparticles (Ag-NPs) can be considered as a cost-effective alternative to antibiotics. In the presence of Fe(III)-citrate and Ag+, Klebsiella oxytoca DSM 29614 produces biogenic Ag-NPs embedded in its peculiar exopolysaccharide (EPS). K. oxytoca DSM 29614 was cultivated in a defined growth medium-containing citrate (as sole carbon source) and supplemented with Ag+ and either low or high Fe(III) concentration. As inferred from elemental analysis, transmission and scanning electron microscopy, Fourier transform infrared spectrometry and dynamic light scattering, Ag-EPS NPs were produced in both conditions and contained also Fe. The production yield of high-Fe/Ag-EPS NPs was 12 times higher than the production yield of low-Fe/Ag-EPS NPs, confirming the stimulatory effect of iron. However, relative Ag content and Ag+ ion release were higher in low-Fe/Ag-EPS NPs than in high-Fe/Ag-EPS NPs, as revealed by emission-excitation spectra by luminescent spectrometry using a novel ad hoc established phycoerythrin fluorescence-based assay. Interestingly, high and low-Fe/Ag-EPS NPs showed different and growth medium-dependent minimal inhibitory concentrations against Staphylococcus aureus ATCC 29213 and Pseudomonas aeruginosa ATCC 15442. In addition, low-Fe/Ag-EPS NPs exert inhibition of staphylococcal and pseudomonal biofilm formation, while high-Fe/Ag-EPS NPs inhibits staphylococcal biofilm formation only. Altogether, these results, highlighting the different capability of Ag+ release, support the idea that Fe/Ag-EPS NPs produced by K. oxytoca DSM 29614 can be considered as promising candidates in the development of specific antibacterial and anti-biofilm agents.Key points • Klebsiella oxytoca DSM 29614 produces bimetal nanoparticles containing Fe and Ag.• Fe concentration in growth medium affects nanoparticle yield and composition.• Phycoerythrin fluorescence-based assay was developed to determine Ag+release.• Antimicrobial efficacy of bimetal nanoparticle parallels Ag+ions release.

Ce:YAG nanoparticles embedded in a PMMA matrix: preparation and characterization.

A Ce:YAG-poly(methyl methacrylate) composite was prepared using in situ polymerization by embedding the Ce:YAG nanopowder in a blend of methyl methacrylate (MMA) and 2-methacrylic acid (MAA) monomers and activating the photopolymerization using a radical initiator. The obtained nanocomposite was yellow and transparent. Its characterization was performed using transmission electron microscopy, small angle X-ray scattering, (13)C cross-polarization magic-angle spinning nuclear magnetic resonance, and photoluminescence spectroscopy. Results showed that Ce:YAG nanoparticles are well dispersed in the polymeric matrix whose structure is organized in a lamellar shape. The luminescence properties of the nanocomposite do not show quenching or a significant spectral shift, indicating that the nanocomposite can be useful for advanced applications such as white LED construction.