Biology subjects

Dundas, C. M.

Publications and source records attributed to Dundas, C. M..

3 recordsLinked to original sources

bioRxiv2018

Extracellular Electron Transfer by Shewanella oneidensis Controls Pd Nanoparticle Phenotype

AbstarctBiological production of inorganic materials is impeded by relatively few organisms possessing genetic and metabolic linkage to material properties. The physiology of electroactive bacteria is intimately tied to inorganic transformations, which makes genetically tractable and well-studied electrogens, such as Shewanella oneidensis, attractive hosts for material synthesis. Notably, this species is capable of reducing a variety of transition-metal ions into functional nanoparticles, but exact mechanisms of nanoparticle biosynthesis remain ill-defined. We report two key factors of extracellular electron transfer by S. oneidensis, the outer membrane cytochrome, MtrC, and soluble redox shuttles (flavins), that affect Pd nanoparticle formation. Changes in the expression and availability of these electron transfer components drastically modulated particle phenotype, including particle synthesis rate, structure, and cellular localization. These relationships may serve as the basis for biologically tailoring Pd nanoparticle catalysts and could potentially be used to direct the biogenesis of other metal nanomaterials.

synthetic biology↗

bioRxiv2018

Microbial Reduction of Metal-Organic Frameworks Enables Synergistic Chromium Removal

Microbe-material redox interactions underpin many emerging technologies, including bioelectrochemical cells and bioremediation. However, commonly utilized material substrates, such as metal oxides, suffer from a lack of tunability and can be challenging to characterize. In contrast, metal-organic frameworks, a class of porous materials, exhibit well-defined structures, high crystallinity, large surface areas, and extensive chemical tunability. Here, we report that metal-organic frameworks can support the growth of the electroactive bacterium Shewanella oneidensis. Specifically, we demonstrate that Fe(III)-containing frameworks, MIL-100 and Fe-BTC, can be reduced by the bacterium via its extracellular electron transfer pathways and that reduction rate/extent is tied to framework structure, surface area, and particle morphology. In a practical application, we show that cultures containing S. oneidensis and reduced frameworks can remediate lethal concentrations of Cr(VI), and that pollutant removal exceeds the performance of either component in isolation or bioreduced iron oxides. Repeated cycles of Cr(VI) dosing had little effect on bacterial viability or Cr(VI) adsorption capacity, demonstrating that the framework confers protection to the bacteria and that no regenerative step is needed for continued bioremediation. In sum, our results show that metal-organic frameworks can serve as microbial respiratory substrates and suggest that they may offer a promising alternative to metal oxides in applications seeking to combine the advantages of bacterial metabolism and synthetic materials.

microbiology↗

bioRxiv2016

Super-resolution Imaging of Synaptic and Extra-synaptic Pools of AMPA Receptors with Different-sized Fluorescent Probes

Whether AMPA receptors (AMPARs) enter into neuronal synapses, by exocytosis from an internal pool, or by diffusion from an external membrane-bound pool, is hotly contested. 3D super-resolution fluorescent nanoscopy to measure the dynamics and placement of AMPAR is a powerful method for addressing this issue. However, probe size and accessibility to tightly packed spaces can be limiting. We have therefore labeled AMPARs with differently sized fluorophores: small organic fluorescent dyes (~ 4 nm), small quantum dots (sQD, ~10 nm in diameter), or big (commercial) quantum dots (bQD, ~ 20 nm in diameter). We then compared their diffusion rate, trajectories, and placement with respect to a postsynaptic density (PSD) protein, Homer 1c. Labeled with the small probes of sQDs or organic fluorophores, we find that AMPARs are located largely within PSDs (~73-93%), and generally reside in \"nanodomains\" with constrained diffusion. In contrast, when labeled with bQDs, only 5-10% of AMPARs are within PSDs. The results can be explained by relatively free access, or lack thereof, to synaptic clefts of the AMPARs when labeled with small or big probes, respectively. This implies that AMPARs primarily enter PSDs soon after their exocytosis and not from a large diffusive pool of extrasynaptic AMPARs.

neuroscience↗