Self-photosensitization of nonphotosynthetic bacteria for solar-to-chemical production

Bringing carbon to life via one-carbon metabolism

One-carbon (C1) compounds found in greenhouse gases and industrial waste streams are underutilized carbon and energy sources. While various biological and chemical means exist for converting C1 substrates into multicarbon products, major challenges of C1 conversion lie in creating net value. Here, we review metabolic strategies to utilize carbon across oxidation states. Complications arise in biochemical C1-utilization approaches because of the need for cellular energy currency ATP. ATP supports cell maintenance and proliferation and drives thermodynamically challenging reactions by coupling them with ATP hydrolysis. Powering metabolism through substrate cofeeding and energy transduction from light and electricity improves ATP availability, relieves metabolic bottlenecks, and upcycles carbon. We present a bioenergetic, engineering, and technoeconomic outlook for bringing elements to life.

Engineering live cell surfaces with polyphenol-functionalized nanoarchitectures

Cell surface functionalization has emerged as a powerful strategy for modulating cellular behavior and expanding cellular capabilities beyond their intrinsic biological limits. Natural phenolic molecules present as 'green' and versatile building blocks for constructing cell-based biomanufacturing and biotherapeutic platforms. Due to the abundant catechol or galloyl groups, phenolic molecules can dynamically and reversibly bind to versatile substrates via multiple molecular interactions. A range of self-assembled cytoadhesive polyphenol-functionalized nanoarchitectures (cytoPNAs) can be formed via metal coordination or macromolecular self-assembly that can rapidly attach to cell surfaces in a cell-agnostic manner. Additionally, the cytoPNAs attached on the cell surface can also provide active sites for the conjunction of bioactive payloads, further expanding the structural repertoire and properties of engineered cells. This Perspective introduces the wide potential of cytoPNA-mediated cell engineering in three key applications: (1) creating inorganic-organic biohybrids as cell factories for efficient production of high-value chemicals, (2) constructing engineered cells for cell-based therapies with enhanced targeting specificity and nano-bio interactions, and (3) encapsulating microbes as biotherapeutics for the treatment of gastrointestinal tract-related diseases. Collectively, the rapid, versatile, and modular nature of cytoPNAs presents a promising platform for next-generation cell engineering and beyond.

Unlocking interfacial electron transfer in biophotoelectrochemical processes: Role of extracellular polymeric substances in aquatic environments

The biophotoelectrochemical process (BPECs) integrates the light-absorbing capabilities of nano-semiconductors with the catalytic efficiency of microorganisms, demonstrating significant potential for the development, utilization, transformation, and ecological restoration of water resources. In aquatic environments, extracellular polymeric substances (EPS) serve as a critical interfacial barrier between microorganisms and semiconductor materials, with the underlying electron transfer mechanisms playing a pivotal role in determining the efficiency of bio-photochemical reactions. Despite their importance, the rapidity and complexity of the electron transfer process within EPS pose significant challenges to a comprehensive understanding of BPECs. In this study, an in-situ characterization strategy was employed to rapidly and accurately analyze the components and pathways of photogenerated electron transfer involving EPS at interfaces. The findings indicate that EPS significantly accelerates the transfer of photogenerated electrons within BPECs. Specifically, proteins and redox-active substances within EPS act as efficient conduits for electron transfer, accounting for up to 84.2% of the increased speed in electron transfer rates at bio-abiotic interfaces. Conversely, polysaccharides within EPS impede the electron transfer process but serve as substrates that facilitate methane (CH4) production. The in-situ characterization approach used in this research provides valuable insights into the interfacial electron transfer mechanisms of EPS in BPECs, emphasizing their relevance in aquatic environments. This study establishes a theoretical framework for designing high-performance BPECs, with significant implications for the energy utilization of water resources and the transformation of water pollutants.

The cytotoxicity of photoexcited CdS in an E. coli-CdS hybrid system and the roles of the sacrificial agent to reduce this toxic effect

This study investigates the biosynthesis of CdS nanoparticles (NPs) by Escherichia coli CD-2 to develop an E. coli-CdS hybrid system. The hybrid system was exposed to light in the presence and absence of cysteine (Cys) as a sacrificial agent. The finding revealed that in the absence of Cys, photo-induced holes led to a sharp increase in oxidative stress, disrupting the oxidative/antioxidative balance within bacterial cells. Consequently, cellular components were oxidized under elevated oxidative stress, lending to functional loss. This oxidative damage resulted in reduced cell viability, and in severe cases, cell disruption. Fortunately, the inclusion of the sacrificial agent alleviated these toxic effects. Cys quenched the photo-induced holes, markedly lowering oxidative stress within the cells. This mitigation enabled the maintenance of essential cellular functions during treatment. The majority of bacterial cells preserved their vitality and utilized the extra photoelectrons for cell growth under these conditions.

Natural biomolecules for cell-interface engineering

Cell-interface engineering is a way to functionalize cells through direct or indirect self-assembly of functional materials around the cells, showing an enhancement to cell functions. Among the materials used in cell-interface engineering, natural biomolecules play pivotal roles in the study of biological interfaces, given that they have good advantages such as biocompatibility and rich functional groups. In this review, we summarize and overview the development of studies of natural biomolecules that have been used in cell-biointerface engineering and then review the five main types of biomolecules used in constructing biointerfaces, namely DNA polymers, amino acids, polyphenols, proteins and polysaccharides, to show their applications in green energy, biocatalysis, cell therapy and environmental protection and remediation. Lastly, the current prospects and challenges in this area are presented with potential solutions to solve these problems, which in turn benefits the design of next-generation cell engineering.

Amplifying Persistent Luminescence in Heavily Doped Nanopearls for Bioimaging and Solar-to-Chemical Synthesis

Lanthanides are widely codoped in persistent luminescence phosphors (PLPs) to elevate defect concentration and enhance luminescence efficiency. However, the deleterious cross-relaxation between activators and lanthanides inevitably quenches persistent luminescence, particularly in heavily doped phosphors. Herein, we report a core-shell engineering strategy to minimize the unwanted cross-relaxation but retain the charge trapping capacity of heavily doped persistent luminescence phosphors by confining the activators and lanthanides in the core and shell, respectively. As a proof of concept, we prepared a series of codoped ZnGa2O4:Cr, Ln (CD-Ln, Ln = Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) and core-shell structured ZnGa2O4:Cr@ZnGa2O4:Ln (CS-Ln) nanoparticles. First-principles investigations suggested that lanthanide doping elevated the electron trap concentration for enhancing persistent luminescence, but energy transfer (ET) from Cr3+ to Ln3+ ions quenched the persistent luminescence. The spatial separation of Cr3+ and Ln3+ ions in the core-shell structured CS-Ln nanoparticles suppressed the ET from Cr3+ to Ln3+. Due to the efficient suppression of deleterious ET, the optimal doping concentration of Ln in CS-Ln was elevated 50 times compared to CD-Ln. Moreover, the persistent luminescence intensity of CS-5%Ln was up to 60 times that of the original ZnGa2O4:Cr. The CS-5%Ln displayed significantly improved signal-to-noise ratios in bioimaging. Further, the CS-Ln was interfaced with the lycopene-producing bacteria Rhodopseudomonas palustris for solar-to-chemical synthesis, and the lycopene productivity was increased by 190%. This work provides a reliable solution to fulfill the potential of lanthanides in enhancing persistent luminescence and can further promote the applications of persistent luminescence phosphors in biomedicine and solar-to-chemical synthesis.

A one-step route for the conversion of Cd waste into CdS quantum dots by Acidithiobacillus sp. via unique biosynthesis pathways

Microorganisms serve as biological factories for the synthesis of nanomaterials such as CdS quantum dots. Based on the uniqueness of Acidithiobacillus sp., a one-step route was explored to directly convert cadmium waste into CdS QDs using these bacteria. First, an exhaustive study was conducted to reveal the specific pathways involved in the biosynthesis of CdS QDs. The widely known homologous enzyme, cysteine desulfhydrase, which catalyzes the synthesis of CdS QDs from a cysteine substrate, is also present in Acidithiobacillus sp. and is referred to as the OSH enzyme. The structure of the OSH enzyme was determined through X-ray crystallography. Moreover, we identified two new pathways. One involved the SQR enzyme in Acidithiobacillus sp., which catalyzed the formation of sulfur globules and subsequently catalyzed further reactions with GSH to release H2S; subsequently, a CdS QD biosynthesis pathway was successfully constructed. The other pathway involved extracellular polyphosphate, a bacterial metabolic product, which with the addition of GSH and Cd2+, resulted in the formation of water-soluble fluorescent CdS QDs in the supernatant. Based on the above-described mechanism, after the bioleaching of Cd2+ from cadmium waste by Acidithiobacillus sp., CdS QDs were directly obtained from the bacterial culture supernatants. This work provides important insights into cleaner production and cadmium bioremediation with potential industrial applications.

Assessing environmental gradients in relation to dark CO2 fixation in estuarine wetland microbiomes

The rising atmospheric concentration of CO2 is a major concern to society due to its global warming potential. In soils, CO2-fixing microorganisms are preventing some of the CO2 from entering the atmosphere. Yet, the controls of dark CO2 fixation are rarely studied in situ. Here, we examined the gene and transcript abundance of key genes involved in microbial CO2 fixation along major environmental gradients within estuarine wetlands. A combined multi-omics approach incorporating metabarcoding, deep metagenomic, and metatranscriptomic analyses confirmed that wetland microbiota harbor four out of seven known CO2 fixation pathways, namely, the Calvin cycle, reverse tricarboxylic acid cycle, Wood-Ljungdahl pathway, and reverse glycine pathway. These pathways are transcribed at high frequencies along several environmental gradients, albeit at different levels depending on the environmental niche. Notably, the transcription of the key genes for the reverse tricarboxylic acid cycle was associated with high nitrate concentration, while the transcription of key genes for the Wood-Ljungdahl pathway was favored by reducing, O2-poor conditions. The transcript abundance of the Calvin cycle was favored by niches high in organic matter. Taxonomic assignment of transcripts implied that dark CO2 fixation was mainly linked to a few bacterial phyla, namely, Desulfobacterota, Methylomirabilota, Nitrospirota, Chloroflexota, and Pseudomonadota.

IMPORTANCE

The increasing concentration of atmospheric CO2 has been identified as the primary driver of climate change and poses a major threat to human society. This work explores the mostly overlooked potential of light-independent CO2 fixation by soil microbes (a.k.a. dark CO2 fixation) in climate change mitigation efforts. Applying a combination of molecular microbial tools, our research provides new insights into the ecological niches where CO2-fixing pathways are most active. By identifying how environmental factors, like oxygen, salinity and organic matter availability, influence these pathways in an estuarine wetland environment, potential strategies for enhancing natural carbon sinks can be developed. The importance of our research is in advancing the understanding of microbial CO2 fixation and its potential role in the global climate system.

Chain assembly of Rhodococcus bacteria with O-doped g-C3N4 for photocatalysis mediated high-performance partial nitrification: From nitrite resource evolution to device application

Nitrogen conversion via partial nitrification-anammox (PN/A), utilizing nitrite as a key intermediate, is an ideal low-carbon approach for wastewater nitrogen removal. However, the partial nitrification process, which is rate-limited and relies on less common bacteria with slow reaction kinetics, poses challenges for high-throughput PN/A implementation. Herein, we developed a microbial/photocatalysis coupling system using Rhodococcus bacterial and O-doped g-C3N4 (OCN) photocatalysts. This approach leverages photogenerated electrons and free radicals from photocatalysts to directly activate microorganisms, enhancing the redox gradient. This intensification selectively inhibits the enzymatic conversion of nitrite to nitrate and its reduction to nitrogen in Rhodococcus bacteria. Consequently, it promotes a highly selective partial nitrification process, generating ample nitrite to facilitate anammox reactions. Transmission electron microscopy and electrochemical characterization showed bacteria forming chain-like assemblies on OCN particles, with the composite exhibiting a favorable redox profile, low impedance, and high stability. Ammonia conversion to nitrite reached 96 % in 3 days, with an enriched NO2- concentration of 36.3 mg/L, 10 times higher than the raw bacterial control. Hence, this strategy of constructing bacterial-photocatalysis system achieved high selectivity and efficiency in partial nitrification. Transcriptome and qPCR analyses showed upregulation of genes linked to the short-cut denitrification metabolic pathway. Photocatalyst band structure and redox potential analysis suggest a new bio-photoelectrochemical partial nitrification pathway. Finally, the feasibility and applicability in future industrial and ecological water treatment were validated through demo H-type reactors and aquarium experiments. These findings offer innovative perspectives for controlled modulation of ammonia nitrogen conversion focus on nitrite intermediate, advancing an energy-efficient, low-carbon nitrogen cycle.

Biochemical mechanism underlying the synthesis of PbS nanoparticle and its in-situ photo effect on Shinella zoogloeoides PQ7

Metal sulfide nanoparticles (NPs) with semiconductor potentials are valuable bioremediation end-products that attract great research interests. However, biochemical mechanisms underlying their biosynthesis and photo-effects remain elusive. In this study, we found that biofilm lifestyle remarkably improved lead resistance and PbS-NP biosynthesis in Shinella zoogloeoides PQ7. Surprisingly, biosynthesis of PbS-NP required more than cysteine and H2S production. Transcriptomic and metabolomic analysis indicated that PQ7 responded to lead stress by changing metabolic activities in ABC transporters, oxidative phosphorylation, EPS production, quorum sensing, protein de novo synthesis, flagella assembly and antioxidative reactions, etc. The elevated EPS production and quorum sensing gene expression echoed the favorable roles of biofilm formation in lead resistance. Biosynthesis of PbS-NP required proper oxygen supply, and was impeded by adding kanamycin or using yeast extract as the sole nutrient supply. Investigations on NAD/NADH, ATP, ROS and GSH productions indicated that biosynthesis of PbS-NP was corelated with cellular respiration, energy metabolism, and redox status. Finally, we proved that PbS-NP had the dose-dependent in-situ photo effect on PQ7's growth and ROS production. This is the first report that pinpoints the role of cellular respiration in PbS-NP biosynthesis, which is essential for further mechanism study and the development of bioremediation techniques.

A new-to-nature photosynthesis system enhances utilization of one-carbon substrates in Escherichia coli

Photosynthesis harvests solar energy to convert CO2 into chemicals, offering a potential solution to reduce atmospheric CO2. However, integrating photosynthesis into non-photosynthetic microbes to utilize one-carbon substrates is challenging. Here, a photosynthesis system is reconstructed in E. coli, by integrating light and dark reaction to synthesize bioproducts from one-carbon substrates. A light reaction is reconstructed using the photosystem of photosynthetic bacteria, increasing ATP and NADH contents by 337.9% and 383.7%, respectively. A dark reaction is constructed by designing CO2 fixation pathway to synthesize pyruvate. By assembling the light and dark reaction, a photosynthesis system is established and further programmed by installing an energy adapter, enabling the production of acetone, malate, and α-ketoglutarate, with a negative carbon footprint of -0.84 ~ -0.23 kgCO2e/kg product. Furthermore, light-driven one-carbon trophic growth of E. coli is achieved with a doubling time of 19.86 h. This photosynthesis system provides a green and sustainable approach to enhance one-carbon substrates utilization in the future.

Carbon-negative bio-production of short-chain carboxylic acids (SCCAs) from syngas via the sequential two-stage bioprocess by Moorella thermoacetica and metabolically engineered Escherichia coli

Syngas can be efficiently converted to acetate by Moorella thermoacetica under anaerobic conditions, which is environmentally friendly. Coupled with acetate production from syngas, using acetate to synthesize value-added compounds such as short-chain carboxylic acids (SCCAs) becomes a negative-carbon process. Escherichia coli is engineered to utilize acetate as the sole carbon source to produce SCCAs. By knocking out some acetyltransferase genes, introducing exogenous pathway and additional cofactor engineering, the strains can synthesize 3.79 g/L of 3-hydroxypropionic acid (3-HP), 1.83 g/L of (R)-3-hydroxybutyric acid (R-3HB), and 2.31 g/L of butyrate. We used M. thermoacetica to produce acetate from syngas. Subsequently, all engineered E. coli strains were able to produce SCCAs from syngas-derived acetate. The titers of 3-HP, R-3HB, and butyrate are 3.75, 1.68, and 2.04 g/L, with carbon sequestration rates of 51.1, 26.3, and 38.1 %. This coupled bioprocess has great potential for producing a range of other value-added chemicals from syngas.

Advancements in Biological Conversion of C1 Feedstocks: Sustainable Bioproduction and Environmental Solutions

The use of one-carbon (C1) feedstocks, including carbon dioxide (CO2), carbon monoxide (CO), formate (HCO2H), methanol (CH3OH), and methane (CH4), presents a significant opportunity for sustainable bioproduction and environmental conservation. This Perspective explores the development of biological methods for converting C1 feedstocks into valuable products, emphasizing major progress from engineering native C1 assimilation pathways to the creation of synthetic autotrophs and methylotrophs that utilize these carbon sources. Additionally, we discuss hybrid approaches that merge biological and electrochemical systems, particularly for the conversion of CO2. This Perspective underscores the importance of C1 bioconversion in promoting sustainable biotechnological strategies for a low-carbon future.

Novel Photoelectron-Assisted Microbial Reduction of Arsenate Driven by Photosensitive Dissolved Organic Matter in Mine Stream Sediments

The microbial reduction of arsenate (As(V)) significantly contributes to arsenic migration in mine stream sediment, primarily driven by heterotrophic microorganisms using dissolved organic matter (DOM) as a carbon source. This study reveals a novel reduction pathway in sediments that photosensitive DOM generates photoelectrons to stimulate diverse nonphototrophic microorganisms to reduce As(V). This microbial photoelectrophic As(V) reduction (PEAsR) was investigated using microcosm incubation, which showed the transfer of photoelectrons from DOM to indigenous sediment microorganisms, thereby leading to a 50% higher microbial reduction rate of As(V). The abundance of two marker genes for As(V) reduction, arrA and arsC, increased substantially, confirming the microbial nature of PEAsR rather than a photoelectrochemical process. Photoelectron ion is unlikely to stimulate photolithoautotrophic growth. Instead, diverse nonphototrophic genera, e.g., Cupriavidus, Sphingopyxis, Mycobacterium, and Bradyrhizobium, spanning 13 orders became enriched by 10-50 folds. Metagenomic binning revealed their genetic potential to mediate the photoelectron-assisted reduction of As(V). These microorganisms contain essential genes involved in respiratory As(V) reduction, detoxification As(V) reduction, dimethyl sulfoxide reductase family, c-type cytochromes, and multiple heavy-metal resistance but lack a complete photosynthesis system. The novel microbial PEAsR pathway offers new insights into the interaction between photoelectron utilization and nonphototrophic As(V)-reducing microorganisms, which may have profound implications for arsenic pollution transportation in mine stream sediment.

Long-Term Autotrophic Growth and Solar-to-Chemical Conversion in Shewanella Oneidensis MR-1 through Light-Driven Electron Transfer

Members of the genus Shewanella are known for their versatile electron accepting routes, which allow them to couple decomposition of organic matter to reduction of various terminal electron acceptors for heterotrophic growth in diverse environments. Here, we report autotrophic growth of Shewanella oneidensis MR-1 with photoelectrons provided by illuminated biogenic CdS nanoparticles. This hybrid system enables photosynthetic oscillatory acetate production from CO2 for over five months, far exceeding other inorganic-biological hybrid system that can only sustain for hours or days. Biochemical, electrochemical and transcriptomic analyses reveal that the efficient electron uptake of S. oneidensis MR-1 from illuminated CdS nanoparticles supplies sufficient energy to stimulate the previously overlooked reductive glycine pathway for CO2 fixation. The continuous solar-to-chemical conversion is achieved by photon induced electric recycling in sulfur species. Overall, our findings demonstrate that this mineral-assisted photosynthesis, as a widely existing and unique model of light energy conversion, could support the sustained photoautotrophic growth of non-photosynthetic microorganisms in nutrient-lean environments and mediate the reversal of coupled carbon and sulfur cycling, consequently resulting in previously unknown environmental effects. In addition, the hybrid system provides a sustainable and flexible platform to develop a variety of solar products for carbon neutrality.

Enhanced denitrification by sunlight-hematite: A neglected nitrogen flow pattern in red soil

Mineral-microbe interactions in the Earth's Critical Zone significantly influence elemental biogeochemical cycling and energy flow processes. This study addresses the key scientific question of how semiconducting minerals drive microbial nitrogen cycling. In the red soil environment, the presence of semiconducting minerals enhances the denitrification process mediated by facultative microorganisms (Pseudomonas aeruginosa PAO1) with denitrifying activity. Compared to darkness, light significantly enhanced the synergistic denitrification kinetic process of red soil and Pseudomonas aeruginosa PAO1 (1.87 times). Cyclic voltammetry shows that the P. aeruginosa PAO1-red soil synergistic system exhibits distinct redox peaks under light. The constant potential current curve and electrochemical impedance spectroscopy measurements reveal a high photocurrent density (1.0 μA/cm2) and minimal polarization resistance (102 Ω) under this condition. These findings confirm that the sunlight-red soil-P. aeruginosa PAO1 synergistic process has excellent electron generation and migration capacity, active redox reactions, and good electron compatibility. Additionally, the photoelectrons of semiconductive minerals in red soil profoundly impact the metabolic processes of microbial denitrification functional genes. Using real-time polymerase chain reaction (qPCR) gene array technology, the abundance of nitrogen metabolism functional genes in P. aeruginosa PAO1 increased by 200 % during the light-red soil synergistic process. Notably, denitrification-related genes (ureC, nirS1, gdhA, and nosZ2) were significantly upregulated. This study confirms that semiconducting minerals are involved in the nitrogen cycle pathway of microbial denitrification and supplements the theory of mineral-microbial synergistic element biogeochemical cycling in the natural environment.

Photoelectron-Promoted Sulfate Reduction for Heavy Metal Removal without Organic Carbon Addition

Sulfate-reducing microorganisms (SRMs) show promise for heavy metal removal from contaminated environments, but their scalability is limited by reliance on organic carbon, sludge formation, and CO2 emissions. This study investigates using photoelectrons from biogenic (Bio-ZnS) and abiogenic (Abio-ZnS) sphalerite nanoparticles to enhance the activity of Desulfovibrio desulfuricans G20 (G20) for sulfate reduction and lead removal without organic substrates. Both Abio-ZnS and Bio-ZnS NPs promote sulfate reduction and energy production in G20 cells under illumination without the addition of organic substrates, with Bio-ZnS achieving 1.6 times greater sulfate reduction and 3.1 times higher ATP production compared to Abio-ZnS. This superior performance of Bio-ZnS NPs is due to their wider band gap, higher photoconversion efficiency, lower charge-transfer resistance, and closer proximity to cells, which enable more efficient photoelectron uptake, enhanced intracellular electron transfer, and reduced energy consumption for motion and filamentation. The uptake of photoelectrons also promotes G20s resistance to high Pb2+ concentrations through enhanced PbS precipitation, biofilm formation, enzymatic detoxification, and Pb2+ efflux, thus improving long-term and cyclic lead removal by G20 under substrate-depleted conditions. This approach harnesses solar energy, reduces reliance on organic substrates, and lowers costs and CO2 emissions, offering a sustainable solution for utilizing SRMs in bioremediation.

Photocatalytic material-microorganism hybrid systems in water decontamination

Biological processes are widely used technologies for water decontamination, but they are often limited by insufficient bioavailable carbon sources or biorecalcitrant contaminants. The recently developed photocatalytic material-microorganism hybrid (PMH) system combines the light-harvesting capacities of photocatalytic materials with specific enzymatic activities of whole cells, efficiently achieving solar-to-chemical conversion. By integrating the benefits of both photocatalysis and biological processes, the PMH system shows great potential for water decontamination. While recent reviews have focused primarily on its application in green energy development, this review emphasizes the latest advancements in PMH systems for water decontamination, covering various applications, key considerations, and synergistic mechanisms. This review aims to provide a fundamental understanding of the PMH system and explore its broader potential in environmental remediation.

Controlled electron transfer by molecular wires embedded in ultrathin insulating membranes for driving redox catalysis

Organic bilayers or amorphous silica films of a few nanometer thickness featuring embedded molecular wires offer opportunities for chemically separating while at the same time electronically connecting photo- or electrocatalytic components. Such ultrathin membranes enable the integration of components for which direct coupling is not sufficiently efficient or stable. Photoelectrocatalytic systems for the generation or utilization of renewable energy are among the most prominent ones for which ultrathin separation layers open up new approaches for component integration for improving efficiency. Recent advances in the assembly and spectroscopic, microscopic, and photoelectrochemical characterization have enabled the systematic optimization of the structure, energetics, and density of embedded molecular wires for maximum charge transfer efficiency. The progress enables interfacial designs for the nanoscale integration of the incompatible oxidation and reduction catalysis environments of artificial photosystems and of microbial (or biomolecular)-abiotic systems for renewable energy.

Harnessing microbes to pioneer environmental biophotoelectrochemistry

In seeking sustainable environmental strategies, microbial biophotoelectrochemistry (BPEC) systems represent a significant advancement. In this review, we underscore the shift from conventional bioenergy systems to sophisticated BPEC applications, emphasizing their utility in leveraging solar energy for essential biochemical conversions. Recent progress in BPEC technology has facilitated improved photoelectron transfer and system stability, resulting in substantial advancements in carbon and nitrogen fixation, degradation of pollutants, and energy recovery from wastewater. Advances in system design and synthetic biology have expanded the potential of BPEC for environmental clean-up and sustainable energy generation. We also highlight the challenges of environmental BPEC systems, ranging from performance improvement to future applications.

Light-driven biodegradation of chloramphenicol by photosensitized Shewanella oneidensis MR-1

Efficient and sustainable degradation of chloramphenicol has piqued the interest of the scientific community. This study constructed a photosensitized biohybrid system using Shewanella oneidensis MR-1 and cadmium sulfide (CdS). This system could efficiently degrade chloramphenicol with robust stability. Inhibitor experiments and transcriptome analysis revealed that reduced nicotinamide adenine dinucleotide dehydrogenase, iron-sulfur cluster, menaquinone, cytochrome b561, cytochrome c, cytochrome P450, and formate dehydrogenase/hydrogenase are involved in direct electron transfer from S. oneidensis MR-1 to photogenerated holes of CdS. The S. oneidensis MR-1/CdS biohybrid alleviated chloramphenicol-induced physiological impairments, which can be attributed to the decreased levels of extracellular polymeric substances, malondialdehyde, and extracellular membrane permeability and the increased levels of superoxide dismutase and catalase activities. The GCN5-related N-acetyltransferase, alkene reductase, and carboxymuconolactone decarboxylase promoted the inactivation and further degradation of chloramphenicol. In summary, this study demonstrated the potential applications of the S. oneidensis MR-1/CdS biohybrid in the remediation of chloramphenicol contamination.

The Photothermal Synergistic Mechanism of Rock Varnish Photoconductance Under Laser Irradiation

Rock varnishes, complex structures formed by long-term deposition on rocks, exhibit unique light absorption characteristics and are widely distributed across arid environments on Earth's surface. The varnishes possess the ability to absorb and convert photons from solar radiation into electrons, which represents a newly discovered fundamental energy form in nature, with further elucidation required regarding the underlying mechanism of how semiconductor minerals respond to light radiation. The regulations governing the photoconductive responses of samples from the Alashan region in Gobi, China, and the mechanisms exhibited by rock rock varnishes under various bias voltages and irradiation wavelengths (532 nm, 808 nm, and 1064 nm) were studied. The photoconductivity response is positively correlated with the applied external bias, and the response caused by shorter wavelengths is larger. The synergistic effect was quantitatively assessed by monitoring and fitting the correlation between photoconductivity, temperature, and time during laser irradiation. As an effective method to study the fundamental physical properties of semiconductor minerals, the photoconductivity testing will help to establish a fundamental framework for investigating the intrinsic physical characteristics of natural rock varnishes.

Intracellular Gold Nanocluster/Organic Semiconductor Heterostructure for Enhancing Photosynthesis

Photosynthetic microorganisms, which rely on light-driven electron transfer, store solar energy in self-energy carriers and convert it into bioenergy. Although these microorganisms can operate light-induced charge separation with nearly 100 % quantum efficiency, their practical applications are inherently limited by the photosynthetic energy conversion efficiency. Artificial semiconductors can induce an electronic response to photoexcitation, providing additional excited electrons for natural photosynthesis to improve solar conversion efficiency. However, challenges remain in importing exogenous electrons across cell membranes. In this work, we have developed an engineered gold nanocluster/organic semiconductor heterostructure (AuNCs@OFTF) to couple the intracellular electron transport chain of living cyanobacteria. AuNCs@OFTF exhibits a prolonged excited state lifetime and effective charge separation. The internalized AuNCs@OFTF permits its photogenerated electrons to participate in the downstream of photosystem II and construct an oriented electronic highway, which enables a five-fold increase in photocurrent in living cyanobacteria. Moreover, the binding events of AuNCs@OFTF established an abiotic-biotic electronic interface at the thylakoid membrane to enhance electron flux and finally furnished nicotinamide adenine dinucleotide phosphate. Thus, AuNCs@OFTF can be exploited to spatiotemporally manipulate and enhance the solar conversion of living cyanobacteria in cells, providing an extended nanotechnology for re-engineering photosynthetic pathways.

Light-Controlled Bioorthogonal Chemistry Altered Natural Killer Cell Activity for Boosted Adoptive Immunotherapy

Natural killer (NK) cell-based immunotherapy has received much attention in recent years. However, its practical application is still suffering from the decreased function and inadequate infiltration of NK cells in the immunosuppressive microenvironment of solid tumors. Herein, we construct light-responsive porphyrin Fe array-armed NK cells (denoted as NK@p-Fe) for cell behavior modulation via bioorthogonal catalysis. By installing cholesterol-modified porphyrin Fe molecules on the NK cell surface, a catalytic array with light-harvesting capabilities is formed. This functionality transforms NK cells into cellular factories capable of catalyzing the production of active agents in a light-controlled manner. NK@p-Fe can generate the active antineoplastic drug doxorubicin through bioorthogonal reactions to enhance the cytotoxic function of NK cells. Beyond drug synthesis, NK@p-Fe can also bioorthogonally catalyze the production of the FDA-approved immune agonist imiquimod (IMQ). The activated immune agonist plays a dual role, inducing dendritic cell maturation for NK cell activation and reshaping the tumor immunosuppressive microenvironment for NK cell infiltration. This work represents a paradigm for the modulation of adoptive cell behaviors to boost cancer immunotherapy by bioorthogonal catalysis.

Polymer semiconductor films and bacteria hybrid artificial bio-leaves

Bio-artificial photosynthetic systems can reduce CO2 into multicarbon compounds by simulating natural photosynthesis. Here, inspired by organic photovoltaic structures, we demonstrate a bio-artificial photosynthetic system based on the hybridization of polymer semiconductor films and bacteria. The study suggests that the polymer-based semiconductor film can efficiently drive the non-photosynthetic bacteria to convert CO2 to acetate. By systematically characterizing the charge transport behavior of the bio-artificial photosynthetic system, the bulk-heterojunction structure and charge transport layers are proven to enhance the system performance markedly. The scalable floating artificial bio-leaf system can produce acetate to gram scale in a week. Notably, the semiconductor film is easy to recycle and maintains stable performance, showing good sustainable production capability of the system. A quasi-solid-state artificial bio-leaf is successfully prepared using agar to simulate the morphology and function of natural leaves. Last, the acetate production converted from CO2 was used to grow yeast for food production, thus achieving a complete simulation of natural photosynthesis.

New Strategies for constructing and analyzing semiconductor photosynthetic biohybrid systems based on ensemble Machine learning Models: Visualizing complex mechanisms and yield prediction

Photosynthetic biohybrid systems (PBSs) composed of semiconductor-microbial hybrids provide a novel approach for converting light into chemical energy. However, comprehending the intricate interactions between materials and microbes that lead to PBSs with high apparent quantum yields (AQY) is challenging. Machine learning holds promise in predicting these interactions. To address this issue, this study employs ensemble learning (ESL) based on Random Forest, Gradient Boosting Decision Tree, and eXtreme Gradient Boosting to predict AQY of PBSs utilizing a dataset comprising 15 influential factors. The ESL model demonstrates exceptional accuracy and interpretability (R2 value of 0.927), offering insights into the impact of these factors on AQY while facilitating the selection of efficient semiconductors. Furthermore, this research propose that efficient charge carrier separation and transfer at the bio-abiotic interface are crucial for achieving high AQY levels. This research provides guidance for selecting semiconductors suitable for productive PBSs while elucidating mechanisms underlying their enhanced efficiency.

Engineered Cell Elongation Promotes Extracellular Electron Transfer of Shewanella Oneidensis

To investigate how cell elongation impacts extracellular electron transfer (EET) of electroactive microorganisms (EAMs), the division of model EAM Shewanella oneidensis (S. oneidensis) MR-1 is engineered by reducing the formation of cell divisome. Specially, by blocking the translation of division proteins via anti-sense RNAs or expressing division inhibitors, the cellular length and output power density are all increased. Electrophysiological and transcriptomic results synergistically reveal that the programmed cell elongation reinforces EET by enhancing NADH oxidation, inner-membrane quinone pool, and abundance of c-type cytochromes. Moreover, cell elongation enhances hydrophobicity due to decreased cell-surface polysaccharide, thus facilitates the initial surface adhesion stage during biofilm formation. The output current and power density all increase in positive correction with cellular length. However, inhibition of cell division reduces cell growth, which is then restored by quorum sensing-based dynamic regulation of cell growth and elongation phases. The QS-regulated elongated strain thus enables a cell length of 143.6 ± 40.3 µm (72.6-fold of that of S. oneidensis MR-1), which results in an output power density of 248.0 ± 10.6 mW m-2 (3.41-fold of that of S. oneidensis MR-1) and exhibits superior potential for pollutant treatment. Engineering cellular length paves an innovate avenue for enhancing the EET of EAMs.

Assembly strategies for microbe-material hybrid systems in solar energy conversion

Microbe-material hybrid systems which facilitate the solar-driven synthesis of high-value chemicals, harness the unique capabilities of microbes, maintaining the high-selectivity catalytic abilities, while concurrently incorporating exogenous materials to confer novel functionalities. The effective assembly of both components is essential for the overall functionality of microbe-material hybrid systems. Herein, we conducted a critical review of microbe-material hybrid systems for solar energy conversion focusing on the perspective of interface assembly strategies between microbes and materials, which are categorized into five types: cell uptake, intracellular synthesis, extracellular mineralization, electrostatic adsorption, and cell encapsulation. Moreover, this review elucidates the mechanisms by which microbe-material hybrid systems convert elementary substrates, such as carbon dioxide, nitrogen, and water, into high-value chemicals or materials for energy generation.

Particle on a Rod: Surface-Tethered Catalyst on CdS Nanorods for Enzymatically Active Nicotinamide Cofactor Generation

The photochemical generation of nicotinamide cofactor 1,4-NADH, facilitated by inorganic photosensitizers, emerges as a promising model system for investigating charge transfer phenomena at the interface of semiconductors and bacteria, with implications for enhancing photosynthetic biohybrid systems (PBSs). However, extant semiconductor nanocrystal model systems suffer from achieving optimal conversion efficiency under visible light. This study investigates quasi-one-dimensional CdS nanorods as superior light absorbers, surface modified with catalyst Cp*Rh(4,4'-COOH-bpy)Cl2 to produce enzymatically active NADH. This model subsystem facilitates easy product isolation and achieves a turnover frequency (TOF) of 175 h-1, one of the highest efficiencies reported for inorganic photosensitizer-based nicotinamide cofactor generation. Charge transfer kinetics, fundamental for catalytic solar energy conversion, range from 106 to 108 s-1 for this system highlighting the superior electron transfer capabilities of NRs. This model ensures efficient cofactor production and offers critical insights into advancing systems that mimic natural photosynthesis for sustainable solar-to-chemical synthesis.

Eradicating the Photogenerated Holes in a Photocatalyst-Microbe Hybrid System: A Review

Finding advanced technologies to store solar energy in chemical bonds efficiently is of great significance for the sustainable development of our society. The recently reported photocatalyst-microbe hybrid (PMH) system couples photocatalysts intimately with microbes and endows heterotrophic microbes with light-harvesting capacity. Generally, when PMH systems are exposed to light, photocatalytic reactions occur on the surface of photocatalysts and the photogenerated electrons enter microbial cells to promote the generation of energy carriers (such as nicotinamide adenine dinucleotide phosphate hydrogen and adenosine triphosphate) and the following chemical synthesis. PMH system applications have expanded from synthesizing value-added products (chemicals, fuels, and polymers) to treating pollutants. However, the successful operation of the PMH system relies on the timely eradication of the photogenerated holes as they recombine with the photogenerated electrons and cause the photocorrosion of the photocatalyst. This review summarizes the strategies for scavenging the photogenerated holes in PMH systems and provides insight into the current gaps and outlooks for future opportunities in this field.

The Influence of Exogenous CdS Nanoparticles on the Growth and Carbon Assimilation Efficiency of Escherichia coli

This study investigated the impact of CdS nanoparticles (NPs) on Escherichia coli growth and metabolism under varying conditions. Under illumination, CdS NPs significantly enhanced bacterial growth, glucose assimilation, and biomass accumulation. Key metabolic and stress response genes showed increased expression, indicating improved ATP synthesis and oxidative stress resistance. Additionally, CdS NPs enhanced the electrochemical properties of E. coli, promoting efficient electron transfer. No significant changes were observed in the dark. These findings suggest that light-activated CdS NPs promote E. coli growth and metabolic efficiency by upregulating crucial genes involved in growth and oxidative stress management.

Study on confined interface electron enhanced ethanol to hydrogen conversion by Rhodopseudomonas palustris

Conjugated polymer coatings enhance bacteria with eco-friendly energy use. A new hybrid system boosts hydrogen production by Rhodopseudomonas palustris@polypyrrole (R. palustris@PPy) through interface electron transfer and hydrogel encapsulation. To maximize the output, we studied hydrogen metabolism using various techniques and found that conductive polymer modification facilitated electron transfer, affecting intracellular pathways. This technology offers enhanced green hydrogen production for sustainable energy.

Pd-, Cu-, and Ni-Catalyzed Reactions: A Comprehensive Review of the Efficient Approaches towards the Synthesis of Antibacterial Molecules

A strong synthetic tool for many naturally occurring chemicals, polymers, and pharmaceutical substances is transition metal-catalyzed synthesis. A serious concern to human health is the emergence of bacterial resistance to a broad spectrum of antibacterial medications. The synthesis of chemical molecules that are potential antibacterial candidates is underway. The main contributions to medicine are found to be effective in transition metal catalysis and heterocyclic chemistry. This review underlines the use of heterocycles and certain effective transition metals (Pd, Cu, and Ni) as catalysts in chemical methods for the synthesis of antibacterial compounds. Pharmaceutical chemists might opt for clinical exploration of these techniques due to their potential.

Proteomic and metabolic analysis of Moorella thermoacetica-g-C3N4 nanocomposite system for artificial photosynthesis

Artificial photosynthesis by microbe-semiconductor biohybrid systems has been demonstrated as a valuable strategy in providing sustainable energy and in carbon fixation. However, most of the developed biohybrid systems for light harvesting employ heavy metal materials, especially cadmium sulfide (CdS), which normally cause environmental pollution and restrict the widespread of the systems. Herein, we constructed an environmentally friendly biohybirid system based on a typical acetogenic bacteria, Moorella thermoacetica, coupling with a carbon-based semiconductor, graphitic carbon nitride (g-C3N4), to realize light-driven carbon fixation. The proposed biohybrid system displayed outstanding acetate productivity with a quantum yield of 2.66 ± 0.43 %. Non-targeted proteomic analysis indicated that the physiological activity of the bacteria was improved, coupling with the non-toxic material. We further proposed the mechanisms of energy generation, electron transfer and CO2 fixation of the irradiated biohybrid system by proteomic and metabolomic characterization. With the photoelectron generated in g-C3N4 under illumination, CO2 is finally converted to acetate via the Wood-Ljungdahl pathway (WLP). Other associated pathways were also proved to be activated, providing extra energy or substrates for acetate production. The study reveals that the future focus of the development of biohybrid systems for light harvesting can be on the metal-free biocompatible material, which can activate the expression of the key enzymes involved in the electron transfer and carbon metabolism under light irradiation.

Biological self-protection inspired engineering of nanomaterials to construct a robust bio-nano system for environmental applications

Nanomaterials can empower microbial-based chemical production or pollutant removal, e.g., nano zero-valent iron (nZVI) as an electron source to enhance microbial reducing pollutants. Constructing bio-nano interfaces is critical for bio-nano system operation, but low interfacial compatibility due to nanotoxicity challenges the system performance. Inspired by microorganisms' resistance to nanotoxicity by secreting extracellular polymeric substances (EPS), which can act as electron shuttling media, we design a highly compatible bio-nano interface by modifying nZVI with EPS, markedly improving the performance of a bio-nano system consisting of nZVI and bacteria. EPS modification reduced membrane damage and oxidative stress induced by nZVI. Moreover, EPS alleviated nZVI agglomeration and probably reduced bacterial rejection of nZVI by wrapping camouflage, contributing to the bio-nano interface formation, thereby facilitating nZVI to provide electrons for bacterial reducing pollutant via membrane-anchoring cytochrome c. This work provides a strategy for designing a highly biocompatible interface to construct robust and efficient bio-nano systems for environmental implication.

In-situ construction of biomineralized cadmium sulfide-Rhodopseudomonas palustris hybrid system: Mechanism of synergistic light utilization

Sulfide biomineralization is a microorganism-induced process for transforming the environmentally hazardous cadmium into useful resource utilization. This study successfully constructed cadmium sulfide nanoparticles-Rhodopseudomonas palustris (Bio-CdS NPs-R. palustris) hybrids. For the self-assembling hybrids, Bio-CdS NPs were treated as new artificial-antennas to enhance photosynthesis, especially under low light (LL). Bacterial physiological results of hybrids were significantly increased, particularly for cells under LL, with higher enhancement photon harvesting ability. The enhancement included the pigment contents, and the ratio of the peripheral light-harvesting complex Ⅱ (LH2) to light-harvesting Ⅰ (1.33 ± 0.01 under LL), leading to the improvements of light-harvesting, transfer, and antenna conversion efficiencies. Finally, the stimulated electron chain of hybrids improved bacterial metabolism with increased nicotinamide adenine dinucleotide (NADH, 174.5% under LL) and adenosine triphosphate (ATP, 41.1% under LL). Furthermore, the modified photosynthetic units were induced by the up-regulated expression of fixK, which was activated by reduced oxygen tension of the medium for hybrids. fixK up-regulated genes encoding pigments (crt, and bch) and complexes (puf, pucAB, and pucC), leading to improved light-harvesting and transfer, and transform ability. This study provides a comprehensive understanding of the solar energy utilization mechanism of in-situ semiconductor-phototrophic microbe hybrids, contributing to further theoretical insight into their practical application.

Enhanced nitrate reduction in hypotrophic waters with integrated photocatalysis and biodegradation

Addressing nitrate contamination in water bodies is a critical environmental challenge, and Intimately Coupling Photocatalysis and Biodegradation (ICPB) presents a promising solution. However, there is still debate about the effectiveness of ICPB in reducing nitrate under hypotrophic conditions. Further research is needed to understand its microbial metabolic mechanism and the functional changes in bacterial structure. Here we explored microbial metabolic mechanisms and changes in bacterial structure in ICPB reactors integrating a meticulously screened TiO2/g-C3N4 photocatalyst with biofilm. We achieved a 26.3% increase in nitrate reduction using 12.2% less organic carbon compared to traditional biodegradation methods. Metagenomic analysis of the microbial communities in ICPB reactors revealed evolving metabolic pathways conducive to nitrate reduction. This research not only elucidates the photocatalytic mechanism behind nitrate reduction in hypotrophic conditions but also provides genomic insights that pave the way for alternative approaches in water remediation technologies.

A biocompatible surface display approach in Shewanella promotes current output efficiency

The biology-material hybrid method for chemical-electricity conversion via microbial fuel cells (MFCs) has garnered significant attention in addressing global energy and environmental challenges. However, the efficiency of these systems remains unsatisfactory due to the complex manufacturing process and limited biocompatibility. To overcome these challenges, here, we developed a simple bio-inorganic hybrid system for bioelectricity generation in Shewanella oneidensis (S. oneidensis) MR-1. A biocompatible surface display approach was designed, and silver-binding peptide AgBP2 was expressed on the cell surface. Notably, the engineered Shewanella showed a higher electrochemical sensitivity to Ag+, and a 60 % increase in power density was achieved even at a low concentration of 10 μM Ag+. Further analysis revealed significant upregulations of cell surface negative charge intensity, ATP metabolism, and reducing equivalent (NADH/NAD+) ratio in the engineered S. oneidensis-Ag nanoparticles biohybrid. This work not only provides a novel insight for electrochemical biosensors to detect metal ions, but also offers an alternative biocompatible surface display approach by combining compatible biomaterials with electricity-converting bacteria for advancements in biohybrid MFCs.

Harnessing acetogenic bacteria for one-carbon valorization toward sustainable chemical production

The pressing climate change issues have intensified the need for a rapid transition towards a bio-based circular carbon economy. Harnessing acetogenic bacteria as biocatalysts to convert C1 compounds such as CO2, CO, formate, or methanol into value-added multicarbon chemicals is a promising solution for both carbon capture and utilization, enabling sustainable and green chemical production. Recent advances in the metabolic engineering of acetogens have expanded the range of commodity chemicals and biofuels produced from C1 compounds. However, producing energy-demanding high-value chemicals on an industrial scale from C1 substrates remains challenging because of the inherent energetic limitations of acetogenic bacteria. Therefore, overcoming this hurdle is necessary to scale up the acetogenic C1 conversion process and realize a circular carbon economy. This review overviews the acetogenic bacteria and their potential as sustainable and green chemical production platforms. Recent efforts to address these challenges have focused on enhancing the ATP and redox availability of acetogens to improve their energetics and conversion performances. Furthermore, promising technologies that leverage low-cost, sustainable energy sources such as electricity and light are discussed to improve the sustainability of the overall process. Finally, we review emerging technologies that accelerate the development of high-performance acetogenic bacteria suitable for industrial-scale production and address the economic sustainability of acetogenic C1 conversion. Overall, harnessing acetogenic bacteria for C1 valorization offers a promising route toward sustainable and green chemical production, aligning with the circular economy concept.

Revisiting Solar Energy Flow in Nanomaterial-Microorganism Hybrid Systems

Nanomaterial-microorganism hybrid systems (NMHSs), integrating semiconductor nanomaterials with microorganisms, present a promising platform for broadband solar energy harvesting, high-efficiency carbon reduction, and sustainable chemical production. While studies underscore its potential in diverse solar-to-chemical energy conversions, prevailing NMHSs grapple with suboptimal energy conversion efficiency. Such limitations stem predominantly from an insufficient systematic exploration of the mechanisms dictating solar energy flow. This review provides a systematic overview of the notable advancements in this nascent field, with a particular focus on the discussion of three pivotal steps of energy flow: solar energy capture, cross-membrane energy transport, and energy conversion into chemicals. While key challenges faced in each stage are independently identified and discussed, viable solutions are correspondingly postulated. In view of the interplay of the three steps in affecting the overall efficiency of solar-to-chemical energy conversion, subsequent discussions thus take an integrative and systematic viewpoint to comprehend, analyze and improve the solar energy flow in the current NMHSs of different configurations, and highlighting the contemporary techniques that can be employed to investigate various aspects of energy flow within NMHSs. Finally, a concluding section summarizes opportunities for future research, providing a roadmap for the continued development and optimization of NMHSs.

Weakly Confined Semiconductor Nanocrystals Excel in Photochemical and Optoelectronic Properties: Evidence from Single-Dot Studies

Single-molecule spectroscopy offers state-resolved measurements on charge-transfer reactions of single semiconductor nanocrystals, leading to the discovery of up to six single-charge transfer reactions with seven transient states for single CdSe/CdS core/shell nanocrystals with water (or oxygen) as the hole (or electron) acceptors. Kinetic rates of three photoinduced single-hole transfer reactions decrease significantly upon increasing the number of excess electrons in a nanocrystal, mainly due to efficient Auger nonradiative recombination of the charged single excitons. Conversely, the kinetic rates of three single-electron transfer reactions of an unexcited nanocrystal increase proportionally to the number of excess electrons in it. Results here reveal that charge-transfer reactions of nanocrystals, at the center of nearly all their functions, could only be deciphered at a state-resolved level on a single nanocrystal. Size-dependent studies validate the weakly confined semiconductor nanocrystals, instead of strongly confined ones (quantum dots), as optimal candidates for photochemical and optoelectronic applications.

Reprogramming cellular metabolism to increase the efficiency of microbial cell factories

Recent studies are increasingly focusing on advanced biotechnological tools, self-adjusting smart microorganisms, and artificial intelligent networks, to engineer microorganisms with various functions. Microbial cell factories are a vital platform for improving the bioproduction of medicines, biofuels, and biomaterials from renewable carbon sources. However, these processes are significantly affected by cellular metabolism, and boosting the efficiency of microbial cell factories remains a challenge. In this review, we present a strategy for reprogramming cellular metabolism to enhance the efficiency of microbial cell factories for chemical biosynthesis, which improves our understanding of microbial physiology and metabolic control. Current methods are mainly focused on synthetic pathways, metabolic resources, and cell performance. This review highlights the potential biotechnological strategy to reprogram cellular metabolism and provide novel guidance for designing more intelligent industrial microbes with broader applications in this growing field.

Toward Photosynthetic Mammalian Cells through Artificial Endosymbiosis

Photosynthesis in plants occurs within specialized organelles known as chloroplasts, which are postulated to have originated through endosymbiosis with cyanobacteria. In nature, instances are also observed wherein specific invertebrates engage in symbiotic relationships with photosynthetic bacteria, allowing them to subsist as photoautotrophic organisms over extended durations. Consequently, the concept of engineering artificial endosymbiosis between mammalian cells and cyanobacteria represents a promising avenue for enabling photosynthesis in mammals. The study embarked with the identification of Synechocystis PCC 6803 as a suitable candidate for establishing a long-term endosymbiotic relationship with macrophages. The cyanobacteria internalized by macrophages exhibited the capacity to rescue ATP deficiencies within their host cells under conditions of illumination. Following this discovery, a membrane-coating strategy is developed for the intracellular delivery of cyanobacteria into non-macrophage mammalian cells. This pioneering technique led to the identification of human embryonic kidney cells HEK293 as optimal hosts for achieving sustained endosymbiosis with Synechocystis PCC 6803. The study offers valuable insights that may serve as a reference for the eventual achievement of artificial photosynthesis in mammals.

Hierarchical NiCo2Se4 Arrays Composed of Atomically Thin Nanosheets: Simultaneous Improvements in Thermodynamics and Kinetics for Electrocatalytic Water Splitting in Neutral Media

The inefficiency of electrocatalysts for water splitting in neutral media stems from a comprehensive impact of poor intrinsic activity, a limited number of active sites, and inadequate mass transport. Herein, hierarchical ultrathin NiCo2Se4 nanosheets are synthesized by the selenization of NiCo2O4 porous nanoneedles. Theoretical and experimental investigations reveal that the intrinsic hydrogen evolution reaction (HER) activity primarily originate from the NiCo2Se4, whereas the high oxygen evolution reaction (OER) performance is related to the NiCoOOH due to the structural reconstruction. The abundant Se and O vacancies introduced by atomically thin nanostructure modulate the electronic structure of NiCo2Se4 and NiCoOOH, thereby improving the intrinsic HER and OER activities, respectively. COMSOL simulation demonstrate the edges of extended nanosheets from the main body significantly promote the charge aggregation, boosting the reduction and oxidation current during HER/OER process. This charge aggregation effect notably exceeds the tip effect for the nanoneedle, highlighting the unique advantage of the hierarchical nanosheet structure. Benefiting from abundant vacancies and unique nanostructure, the hierarchical ultrathin nanosheet simultaneously improve the thermodynamics and kinetics of the electrocatalyst. The optimized samples display an overpotential of 92 mV for HER and 214 mV for OER at 100 mA cm-2, significantly surpassing the performance of currently reported HER/OER catalysts in neutral media.

Ultrathin silica-tiling on living cells for chemobiotic catalysis

Harnessing the power of cell biocatalysis for sustainable chemical synthesis requires rational integration of living cells with the modern synthetic catalysts. Here, we develop silica-tiling strategy that constructs a hierarchical, inorganic, protocellular confined nanospace around the individual living cell to accommodate molecularly accessible abiotic catalytic sites. This empowers the living microorganisms for new-to-nature chemical synthesis without compromising the cellular regenerative process. Yeast cell, a widely used biocatalyst, is upgraded via highly controlled self-assembly of 2D-bilayer silica-based catalytic modules on cell surfaces, opening the avenues for diverse chemobiotic reactions. For example, combining [AuPt]-catalyzed NADH regeneration, light-induced [Pd]-catalyzed C-C cross-coupling or lipase-catalyzed esterification reactions-with the natural ketoreductase activity inside yeast cell. The conformal silica bilayer provides protection while allowing proximity to catalytic sites and preserving natural cell viability and proliferation. These living nanobiohybrids offer to bridge cell's natural biocatalytic capabilities with customizable heterogeneous metal catalysis, enabling programmable reaction sequences for sustainable chemical synthesis.

Engineering of bespoke photosensitiser-microbe interfaces for enhanced semi-artificial photosynthesis

Biohybrid systems for solar fuel production integrate artificial light-harvesting materials with biological catalysts such as microbes. In this perspective, we discuss the rational design of the abiotic-biotic interface in biohybrid systems by reviewing microbes and synthetic light-harvesting materials, as well as presenting various approaches to coupling these two components together. To maximise performance and scalability of such semi-artificial systems, we emphasise that the interfacial design requires consideration of two important aspects: attachment and electron transfer. It is our perspective that rational design of this photosensitiser-microbe interface is required for scalable solar fuel production. The design and assembly of a biohybrid with a well-defined electron transfer pathway allows mechanistic characterisation and optimisation for maximum efficiency. Introduction of additional catalysts to the system can close the redox cycle, omitting the need for sacrificial electron donors. Studies that electronically couple light-harvesters to well-defined biological entities, such as emerging photosensitiser-enzyme hybrids, provide valuable knowledge for the strategic design of whole-cell biohybrids. Exploring the interactions between light-harvesters and redox proteins can guide coupling strategies when translated into larger, more complex microbial systems.

A Self-Assembled MOF-Escherichia Coli Hybrid System for Light-Driven Fuels and Valuable Chemicals Synthesis

The development of semi-artificial photosynthetic systems, which integrate metal-organic frameworks (MOFs) with industrial microbial cell factories for light-driven synthesis of fuels and valuable chemicals, represents a highly promising avenue for both research advancements and practical applications. In this study, an MOF (PCN-222) utilizing racemic-(4-carboxyphenyl) porphyrin and zirconium chloride (ZrCl4) as primary constituents is synthesized. Employing a self-assembly process, a hybrid system is constructed, integrating engineered Escherichia coli (E. coli) to investigate light-driven hydrogen and lysine production. These results demonstrate that the light-irradiated biohybrid system efficiently produce H2 with a quantum efficiency of 0.75% under full spectrum illumination, the elevated intracellular reducing power NADPH is also observed. By optimizing the conditions, the biohybrid system achieves a maximum lysine production of 18.25 mg L-1, surpassing that of pure bacteria by 332%. Further investigations into interfacial electron transfer mechanisms reveals that PCN-222 efficiently captures light and facilitates the transfer of photo-generated electrons into E. coli cells. It is proposed that the interfacial energy transfer process is mediated by riboflavin, with facilitation by secreted small organic acids acting as hole scavengers for PCN-222. This study establishes a crucial foundation for future research into the light-driven biomanufacturing using E. coli-based hybrid systems.

A Customized Biohybrid Presenting Cascade Responses to Tumor Microenvironment

Intrinsic characteristics of microorganisms, including non-specific metabolism sites, toxic byproducts, and uncontrolled proliferation constrain their exploitation in medical applications such as tumor therapy. Here, the authors report an engineered biohybrid that can efficiently target cancerous sites through a pre-determined metabolic pathway to enable precise tumor ablation. In this system, DH5α Escherichia coli is engineered by the introduction of hypoxia-inducible promoters and lactate oxidase genes, and further surface-armored with iron-doped ZIF-8 nanoparticles. This bioengineered E. coli can produce and secrete lactate oxidase to reduce lactate concentration in response to hypoxic tumor microenvironment, as well as triggering immune activation. The peroxidase-like functionality of the nanoparticles extends the end product of the lactate metabolism, enabling the conversion of hydrogen peroxide (H2O2) into highly cytotoxic hydroxyl radicals. This, coupled with the transformation of tirapazamine loaded on nanoparticles to toxic benzotriazinyl, culminates in severe tumor cell ferroptosis. Intravenous injection of this biohybrid significantly inhibits tumor growth and metastasis.

The enhancement of energy supply in syngas-fermenting microorganisms

After the second industrial revolution, social productivity developed rapidly, and the use of fossil fuels such as coal, oil, and natural gas increased greatly in industrial production. The burning of these fossil fuels releases large amounts of greenhouse gases such as CO2, which has caused greenhouse effects and global warming. This has endangered the planet's ecological balance and brought many species, including animals and plants, to the brink of extinction. Thus, it is crucial to address this problem urgently. One potential solution is the use of syngas fermentation with microbial cell factories. This process can produce chemicals beneficial to humans, such as ethanol as a fuel while consuming large quantities of harmful gases, CO and CO2. However, syngas-fermenting microorganisms often face a metabolic energy deficit, resulting in slow cell growth, metabolic disorders, and low product yields. This problem limits the large-scale industrial application of engineered microorganisms. Therefore, it is imperative to address the energy barriers of these microorganisms. This paper provides an overview of the current research progress in addressing energy barriers in bacteria, including the efficient capture of external energy and the regulation of internal energy metabolic flow. Capturing external energy involves summarizing studies on overexpressing natural photosystems and constructing semiartificial photosynthesis systems using photocatalysts. The regulation of internal energy metabolic flows involves two parts: regulating enzymes and metabolic pathways. Finally, the article discusses current challenges and future perspectives, with a focus on achieving both sustainability and profitability in an economical and energy-efficient manner. These advancements can provide a necessary force for the large-scale industrial application of syngas fermentation microbial cell factories.

Cryomicroneedle delivery of nanogold-engineered Rhodospirillum rubrum for photochemical transformation and tumor optical biotherapy

Tumor metabolite regulation is intricately linked to cancer progression. Because lactate is a characteristic metabolite of the tumor microenvironment (TME), it supports tumor progression and drives immunosuppression. In this study, we presented a strategy for antitumor therapy by developing a nanogold-engineered Rhodospirillum rubrum (R.r-Au) that consumed lactate and produced hydrogen for optical biotherapy. We leveraged a cryogenic micromolding approach to construct a transdermal therapeutic cryomicroneedles (CryoMNs) patch integrated with R.r-Au to efficiently deliver living bacterial drugs. Our long-term storage studies revealed that the viability of R.r-Au in CryoMNs remained above 90%. We found that the CryoMNs patch was mechanically strong and could be inserted into mouse skin. In addition, it rapidly dissolved after administering bacterial drugs and did not produce by-products. Under laser irradiation, R.r-Au effectively enhanced electron transfer through Au NPs actuation into the photosynthetic system of R. rubrum and enlarged lactate consumption and hydrogen production, thus leading to an improved tumor immune activation. Our study demonstrated the potential of CryoMNs-R.r-Au patch as a minimally invasive in situ delivery approach for living bacterial drugs. This research opens up new avenues for nanoengineering bacteria to transform tumor metabolites into effective substances for tumor optical biotherapy.