We hypothesized that low concentrations of H2O2 could be generated through the electrochemical conversion of oxygen by applying an electric potential to a conductive scaffold and produce a low, but constant, concentration of H2O2 that would be sufficient to destroy biofilms. To test our hypothesis we used a multidrug-resistant Acinetobacter baumannii strain, because this species is often implicated in difficult-to-treat biofilm infections. We used conductive carbon fabric as the scaffold material (“e-scaffold”). In vitro experiments demonstrated the production of a maximum constant concentration of ~25 μM H2O2 near the e-scaffold surface. An e-scaffold was overlaid onto an existing A. baumannii biofilm, and within 24 h there was a ~4-log reduction in viable bacteria with an ~80% decrease in biofilm surface coverage. A similar procedure was used to overlay an e-scaffold onto an existing A. baumannii biofilm that was grown on a porcine explant. After 24 h, there was a ~3-log reduction in viable bacteria from the infected porcine explants with no observable damage to the underlying mammalian tissue based on a viability assay and histology. This research establishes a novel foundation for an alternative antibiotic-free wound dressing to eliminate biofilms.
Accurate description of gas adsorption and diffusion in nanoporous materials is crucial in envisioning new materials for adsorption-based and membrane-based gas separations. This study provides the first information about the equilibrium and transport properties of different gas mixtures in a bio-metal organic framework (bio-MOF). Adsorption isotherms and self-diffusivity coefficients of CH 4 , CO 2 , H 2 , and their binary mixtures in bio-MOF-11 were computed using grand canonical Monte Carlo and equilibrium molecular dynamics simulations. Results showed that bio-MOF-11 exhibits significantly higher adsorption selectivity for CO 2 over CH 4 and H 2 than the widely studied MOFs. Bio-MOF-11 outperforms several isoreticular MOFs, traditional zeolites, and zeolite imidazolate frameworks in membrane-based separations of CH 4 /H 2 , CO 2 /CH 4 , and CO 2 / H 2 mixtures due to its high gas permeability and permeation selectivity. The methods used in this work will assess the potential of bio-MOFs in gas separations and accelerate development of new bio-MOFs for targeted applications by providing molecular insights into adsorption and transport of gas mixtures.
Zeolite imidazolate frameworks (ZIFs) offer considerable potential for gas separation applications due to their tunable pore sizes, large surface areas, high pore volumes, and good thermal and mechanical stabilities. Although a significant number of ZIFs has been synthesized in the powder form to date, very little is currently known about the potential performance of ZIFs for membranebased gas separation applications. In this work, we used atomically detailed calculations to predict the performance of 15 different ZIF materials both in adsorption-based and membrane-based separations of CH 4 /H 2 , CO 2 /CH 4 , and CO 2 /H 2 mixtures. We predicted adsorption-based selectivity, working capacity, membrane-based selectivity, and gas permeability of ZIFs. Our results identified several ZIFs that can outperform traditional zeolite membranes and widely studied metal organic framework membranes in CH 4 /H 2 , CO 2 /CH 4 , and CO 2 / H 2 separation processes. Finally, the accuracy of the mixing theories estimating mixture adsorption and diffusion based on single component data was tested.
fWe developed a porcine dermal explant model to determine the extent to which Staphylococcus aureus biofilm communities deplete oxygen, change pH, and produce damage in underlying tissue. Microelectrode measurements demonstrated that dissolved oxygen (DO) in biofilm-free dermal tissue was 4.45 ؎ 1.17 mg/liter, while DO levels for biofilm-infected tissue declined sharply from the surface, with no measurable oxygen detectable in the underlying dermal tissue. Magnetic resonance imaging demonstrated that biofilm-free dermal tissue had a significantly lower relative effective diffusion coefficient (0.26 ؎ 0.09 to 0.30 ؎ 0.12) than biofilm-infected dermal tissue (0.40 ؎ 0.12 to 0.48 ؎ 0.12; P < 0.0001). Thus, the difference in DO level was attributable to biofilm-induced oxygen demand rather than changes in oxygen diffusivity. Microelectrode measures showed that pH within biofilm-infected explants was more alkaline than in biofilm-free explants (8.0 ؎ 0.17 versus 7.5 ؎ 0.15, respectively; P < 0.002). Cellular and nuclear details were lost in the infected explants, consistent with cell death. Quantitative label-free shotgun proteomics demonstrated that both proapoptotic programmed cell death protein 5 and antiapoptotic macrophage migration inhibitory factor accumulated in the infected-explant spent medium, compared with uninfected-explant spent media (1,351-fold and 58-fold, respectively), consistent with the cooccurrence of apoptosis and necrosis in the explants. Biofilm-origin proteins reflected an extracellular matrix-adapted lifestyle of S. aureus. S. aureus biofilms deplete oxygen, increase pH, and induce cell death, all factors that contribute to impede wound healing.
Productivity is a major determinant of ecosystem diversity. Microbial ecosystems are the most diverse on the planet yet very few relationships between diversity and productivity have been reported as compared with macro-ecological studies. Here we evaluated the spatial relationships of productivity and microbiome diversity in a laboratory-cultivated photosynthetic mat. The goal was to determine how spatial diversification of microorganisms drives localized carbon and energy acquisition rates. We measured sub-millimeter depth profiles of net primary productivity and gross oxygenic photosynthesis in the context of the localized microenvironment and community structure, and observed negative correlations between species richness and productivity within the energyreplete, photic zone. Variations between localized community structures were associated with distinct taxa as well as environmental profiles describing a continuum of biological niches. Spatial regions in the photic zone corresponding to high primary productivity and photosynthesis rates had relatively low-species richness and high evenness. Hence, this system exhibited negative speciesproductivity and species-energy relationships. These negative relationships may be indicative of stratified, light-driven microbial ecosystems that are able to be the most productive with a relatively smaller, even distributions of species that specialize within photic zones.
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