High-rate production of acetate and other value-added products from the reduction of CO2 in microbial electrosynthesis (MES) using acetogens can be achieved with high reducing power where H2 appears ...as a key electron mediator. H2 evolution using metal cathodes can enhance the availability of H2 to support high-rate microbial reduction of CO2. Due to the low solubility of H2, the availability of H2 remains limited to the bacteria. In this study, we investigated the performances of Sporomusa ovata for CO2 reduction when dual cathodes were used together in an MES, one was regular carbon cathode, and the other was a titanium mesh that allows higher hydrogen evolution. The dual cathode configuration was investigated in two sets of MES, one set had the usual S. ovata inoculated graphite rod, and another set had a synthetic biofilm-imprinted carbon cloth. Additionally, the headspace gas in MES was recirculated to increase the H2 availability to the bacteria in suspension. High-rate CO2 reduction was observed at −0.9 V vs Ag/AgCl with dual cathode configuration as compared to single cathodes. High titers of acetate (up to ∼11 g/L) with maximum instantaneous rates of 0.68–0.7 g/L/d at −0.9 V vs Ag/AgCl were observed, which are higher than the production rates reported in the literatures for S. ovata using MES with surface modified cathodes. A high H2 availability supported the high-rate acetate production from CO2 with diminished electricity input.
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•A simple modification with an additional Ti cathode in MES promoted H2 evolution.•Headspace gas recirculation improves the gas-liquid mass transfer of H2 and CO2.•High rates up to 0.68–0.7 g acetate/L/d from CO2 reduction by Sporomusa ovata.•Long-term stability with up to 11 g/L acetate and 80% efficiency was attained.
Bacterial biofilms are complex biological systems that play significant roles in areas such as infectious diseases and fuel cells. While biofilms are important, our understanding of biofilm ...communities is limited due to barriers in live cell imaging and analysis. Development of effective automatic image analysis techniques for bacterial biofilms can give us new insights into many unknown characteristics of the individual bacteria cells such as structure and cell-to-cell interaction. Single-cell segmentation is the initial step for automatic analyses of the individual cells within a biofilm. While traditional model-based segmentation approaches often fail to accurately segment individual cells within a biofilm due to low image resolution, data-driven deep learning techniques can offer superior solutions by learning the segmentation task from an effective training dataset. Here we propose a framework to simulate 3D synthetic biofilms comprised of realistic-shaped bacteria. Such a synthetic dataset is used to train a deep segmentation network for single-cell segmentation of real biofilm images. We demonstrate that training the network with the synthetic biofilms generated by the proposed framework achieves significantly higher single-cell segmentation accuracy on real biofilm data in comparison to training the network with existing rod-shaped synthetic biofilms (with improvements in the range of 20% to 40% in F1 scores for single-cell segmentation).
The promise of adapting biology to information processing will not be realized until engineered gene circuits, operating in different cell populations, can be wired together to express a predictable ...function. Here, elementary biological integrated circuits (BICs), consisting of two sets of transmitter and receiver gene circuit modules with embedded memory placed in separate cell populations, were meticulously assembled using live cell lithography and wired together by the mass transport of quorum-sensing (QS) signal molecules to form two isolated communication links (comlinks). The comlink dynamics were tested by broadcasting “clock” pulses of inducers into the networks and measuring the responses of functionally linked fluorescent reporters, and then modeled through simulations that realistically captured the protein production and molecular transport. These results show that the comlinks were isolated and each mimicked aspects of the synchronous, sequential networks used in digital computing. The observations about the flow conditions, derived from numerical simulations, and the biofilm architectures that foster or silence cell-to-cell communications have implications for everything from decontamination of drinking water to bacterial virulence.
Noise is inherent to single cell behavior. Its origins can be traced to the stochasticity associated with a few copies of genes and low concentrations of protein and ligands. We have studied the ...mechanisms by which the response of noisy elements can be entrained for biological signal processing. To elicit predictable biological function, we have engineered a gene environment that incorporates a gene regulatory network with the stringently controlled microenvironment found in a synthetic biofilm. The regulatory network leverages the positive feedback found in quorum-sensing regulatory components of the lux operon, which is used to coordinate cellular responses to environmental fluctuations. Accumulation of the Lux receptor in cells, resulting from autoregulation, confers a rapid response and enhanced sensitivity to the quorum-sensing molecule that is retained after cell division as epigenetic memory. The memory of the system channels stochastic noise into a coordinated response among quorum-sensing signal receivers in a synthetic biofilm in which the noise diminishes with repeated exposure to noisy transmitters on the input of a signaling cascade integrated into the same biofilm. Thus, gene expression in the receivers, which are autonomous and do not communicate with each other, is synchronized to fluctuations in the environment.
This chapter describes a method for generating uniform lab-scale biocatalytic nanoporous latex coatings. Nearly everything we come into contact with on a daily basis has been coated with some polymer ...material. High-speed waterborne polymer coating and ink-jet printing techniques are mature technologies. Methods for immobilizing microorganisms in lab-scale waterborne latex biocatalytic coatings draw on existing coating technologies for generating precision industrial paint and paper coatings and would therefore be amenable to scale up in future applications. An inherent problem for many lab-scale techniques is coating uniformity. The method described here has been developed to dramatically increase the uniformity of multiple individual small surface area coatings derived from a single coating template by minimizing edge effects due to emulsion drying adjacent to the edge of the mask.
The multiple protecting and barrier-supporting properties of the creamy, white biofilm vernix caseosa (VC) before and after birth suggest that a VC biomimetic could be an innovative barrier cream for ...barrier-deficient skin. The aim of this study was the rational design and preparation of synthetic biofilms mimicking the unique composition and properties of natural VC.
Hexagonal, highly hydrated hyperbranched polyglycerol microgel particles (30
μm in diameter) were embedded in a synthetic lanolin-based lipid mixture using a micromixer. In these formulations, the water content of the particles (i.e. 50% and 80%), an additional lipid coating of the particles and different particle/lipid ratios were varied. Characterization with confocal laser scanning microscopy (CLSM) showed a homogeneous distribution of the labeled particles in the lipid matrix. Regarding structural appearance, particle density and distribution, the formulations with a high particle/lipid ratio (5:1) resembled native VC very closely. Comparable results between native VC and the synthetic formulations were obtained concerning water handling properties, thermotropic behavior while lower elasticity and lower viscosity were observed for the synthetic biofilms. The biofilm formulations were stable for at least 1 month at 4
°C. In conclusion, our formulations mimic natural VC very closely and are promising candidates for
in vivo studies.
Modeling the complex interactions among organisms found within microbiomes is of great interest for the development of new biological technologies. Challenges remain in culturing cells of multiple ...species with spatial resolutions similar to microbial communities. Here, a fluitrode concept in microfluidics using biofabrication of functional biopolymers is demonstrated to efficiently assemble multiple cell populations in 3D hydrogels of spatial and biological relevance. The fluitrodes are freestanding biopolymer membranes that, similar to electrodes in transmitting electrons, transmit ions and small molecules with spatiotemporal programmability. The individually addressable fluitrodes allow for controlled delivery of nutrients and chemical molecules of interest in situ, live imaging of biological events, effluent collection to perform ex situ diagnostics, and finally, release of cells for downstream molecular and biochemical analyses. This novel coculturing platform can model in vitro ecosystems comprised of multiple species or kingdoms to elucidate cell–cell interactions in complex communities and aid in high throughput screening for drug discovery.
Freestanding, robust, and semipermeable chitosan membranes in microfluidics are exploited as “fluitrodes” that, similar to electrodes transmitting electrons, transmit ions and small molecules with spatiotemporal programmability. The individually addressable fluitrodes allow for assembling patterned cell populations that mimic natural ecosystems, delivering separate nutrients and stimuli, collecting effluents, and releasing cells separately for downstream molecular and biochemical analyses.
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