Nanofibrillated cellulose offers new technological solutions for the development of paper products. Here, composites of nanofibrillated cellulose (NFC) and Ag nanoparticles (NP) were prepared for the first time via the electrostatic assembly of Ag NP (aqueous colloids) onto NFC. Distinct polyelectrolytes have been investigated as macromolecular linkers in order to evaluate their effects on the building-up of Ag modified NFC and also on the final properties of the NFC/Ag composite materials. The NFC/Ag nanocomposites were first investigated for their antibacterial properties towards S. aureus and K. pneumoniae microorganisms as compared to NFC modified by polyelectrolytes linkers without Ag. Subsequently, the antibacterial NFC/Ag nanocomposites were used as fillers in starch based coating formulations for Eucalyptus globulus-based paper sheets. The potential of this approach to produce antimicrobial paper products will be discussed on the basis of complementary optical, air barrier and mechanical data.

No abstract

No abstract

Here we report on the functional characterization of the hypothetical protein Slr1270, a TolC homologue in Synechocystis sp. PCC 6803. Analysis of a slr1270 insertion deletion mutant and respective wild-type revealed that the mutant presents increased susceptibility to antibiotics. In addition, a detailed study of the exoproteome showed that Slr1270 mediates protein secretion. Among the protein substrates dependent on Slr1270 function, we found the S-layer structural component. Electron microscopy studies of the slr1270 mutant showed that the S-layer is indeed absent. The requirement of functional Slr1270 for protein secretion and drug resistance mechanisms suggests that Slr1270 plays a role similar to that described for TolC in other bacteria. Additional phenotypic traits could also be observed, including slower growth rates at low temperature, impairment in biofilm formation and increased activity of enzymes detoxifying reactive oxygen species. Furthermore, an increased capacity of outer membrane vesicles (OMVs) formation and release was also found in the slr1270 mutant, a feature that has not yet been observed in bacteria lacking TolC. This work highlights the marked physiological fitness that the TolC-like Slr1270 bestows to the photosynthetic model Synechocystis sp. PCC 6803 and presents a valuable model for studying OMVs formation and release.