Microbe-Mediated Extracellular and Intracellular Mineralization: Environmental, Industrial, and Biotechnological Applications

A paradigm of microbe-mediated green nano-semiconductors and nano-metals

Semiconducting and metallic nanomaterials are essential building blocks for developing modern-age technologies, and their demand is expanding exponentially with a growing population. However, their processing impacts the ecosystem and requires urgently sustainable solutions. This perspective underlines the emergence of microbe-mediated (bacteria, yeast, fungi, microalgae, viruses, cyanobacteria) green nanomaterials, including metal-based, carbon-based, organic and hybrid nanomaterials, with technical challenges of scalability, stability and cytotoxicity restricting their transition from lab-to-market. Besides, it discusses alternative solutions by integrating digital-age technologies like artificial intelligence to establish these green nano-semiconductors/metals for multidimensional applications and subsidizing the UN's sustainable development goals and one health management.

Probiotic-Based Mineralized Living Materials to Produce Antimicrobial Yogurts

Mineralization of living cells represents an evolutionary adaptation that enhances cellular resilience to physicochemical stress. Inspired by this strategy, we have here developed hybrid living materials (HLMs), incorporating probiotics into mineralized collagen 3D matrices, with the aim of protecting and promoting the successful oral delivery of the bacteria. Collagen fibrils are simultaneously self-assembled and mineralized in the presence of the probiotics (Lactobacillus acidophilus, La, was used as model), resulting in the integration of the probiotics into the hybrid matrix (i.e., bulk encapsulation). During this process, probiotics are also coated with a nanofilm of apatite mineral (single-cell encapsulation), which provides them with extra protection and reinforces their viability and activity. In fact, the resulting HLM is metabolically active, and maintain the capacity to ferment milk into yogurt with antibacterial activity against the two major foodborne pathogens Pseudomonas aeruginosa (Pa) and Staphylococcus aureus (Sa). Interestingly, the HLM provides probiotics an additional protection in the gastrointestinal environment (i.e., simulated gastric fluid), which is of special interest for healthcare materials for oral administration. The results pave the way for the creation of innovative healthcare materials with enhanced functionalities and the potential to produce probiotic foods with notable antimicrobial properties.

Biochar enhances Cd mineralization through microbially induced carbonate precipitation as a soil remediation strategy for rice paddies

Microbial induced carbonate precipitation (MICP) is a promising technique for remediating Cd-contaminated soils. However, the high cost and potential disruption to soil micro-ecology due to the excessive urea addition remain significant challenges, limiting the broader application of MICP technology in agricultural soils. This study aims to improve the efficiency of Cd immobilization by MICP under low urea levels by investigating the stimulatory effect of porous materials on urease secretion by ureolytic bacteria. Results demonstrate that these materials, including biochar, activated carbon, zeolite, and oyster shell, can stimulate the growth of ureolytic bacteria strain kp-22, but not diatomite. Urease activity was greatly improved within 12 h, and the Cd removal rate reached over 82.12% within 0.5 h. Notably, biochar supported urealytic bacterium strain kp-22 (BCM) can steadily remove Cd in solution, with the Cd removal rate remaining close to 99% even after multiple additions of Cd. XRD analysis shows that Cd was removed by BCM due to the formation of CdCO3. Soil experiment reveals that BCM significantly decreased the bioavailable Cd content in both flooded and unflooded paddy soils, even when the urea addition was at a dosage suitable for agricultural production. 16S rRNA gene sequencing shows that the disturbance caused by BCM to the soil bacterial community was lower than that caused by strain kp-22 alone. These findings offer new insights into enhancing the efficiency of MICP for Cd remediation, increasing the potential for broader application of MICP technology in sustainable agriculture.

Fungal-mediated nanoparticles for industrial applications: synthesis and mechanism of action

The advancement of safe, eco-friendly, and cost-efficient techniques for nanoparticle production is a crucial objective in nanotechnology. Among the various sustainable methods, the biological synthesis of nanoparticles utilizing fungi, bacteria, yeasts, and plants stands out. Fungi, in particular, are well suited for this task because of their capacity to secrete numerous enzymes and streamline subsequent processes. Using fungal strains for nanoparticle biosynthesis is both technologically appealing and economically viable. The utilization of fungal strains for nanoparticle biosynthesis is both technologically appealing and economically viable. Fungi have long been acknowledged as adept natural engineers capable of creating a wide array of nanoparticles with distinct properties and applications. This article provides an overview of fungus-mediated nanoparticle development, shedding light on the underlying mechanisms of their synthesis and the factors influencing their characteristics. Furthermore, the potential of fungus-mediated nanoparticles in the industrial domain has been explored. These findings emphasize the importance of different fungal species in nanoparticle synthesis, as well as the biocompatibility and environmental friendliness of fungus-mediated nanoparticles. By underscoring the essential role of fungi in connecting natural knowledge with innovative industrial applications, recent progress in enhancing nanoparticle production and optimizing synthesis conditions through fungi has been examined to underscore the feasibility of extensive industrial nanoparticle utilization via fungi.

Understanding microbial biomineralization at the molecular level: recent advances

Microbial biomineralization is a phenomenon involving deposition of inorganic minerals inside or around microbial cells as a direct consequence of biogeochemical cycling. The microbial metabolic processes often create environmental conditions conducive for the precipitation of silicate, carbonate or phosphate, ferrate forms of ubiquitous inorganic ions. Till date the fundamental mechanisms underpinning two of the major types of microbial biomineralization such as, microbially controlled and microbially induced remains poorly understood. While microbially-controlled mineralization (MCM) depends entirely on the genetic makeup of the cell, microbially-induced mineralization (MIM) is dependent on factors such as cell morphology, cell surface structures and extracellular polymeric substances (EPS). In recent years, the organic template-mediated nucleation of inorganic minerals has been considered as an underlying mechanism based on the principles of solid-state bioinorganic chemistry. The present review thus attempts to provide a comprehensive and critical overview on the recent progress in holistic understanding of both MCM and MIM, which involves, organic-inorganic biomolecular interactions that lead to template formation, biomineral nucleation and crystallization. Also, the operation of specific metabolic pathways and molecular operons in directing microbial biomineralization have been discussed. Unravelling these molecular mechanisms of biomineralization can help in the biomimetic synthesis of minerals for potential therapeutic applications, and facilitating the engineering of microorganisms for commercial production of biominerals.

Kinetics of Calcite Nucleation onto Sulfated Chitosan Derivatives and Implications for Water-Polysaccharide Interactions during Crystallization of Sparingly Soluble Salts

Anionic macromolecules are found at sites of CaCO3 biomineralization in diverse organisms, but their roles in crystallization are not well-understood. We prepared a series of sulfated chitosan derivatives with varied positions and degrees of sulfation, DS(SO3 -), and measured calcite nucleation rate onto these materials. Fitting the classical nucleation theory model to the kinetic data reveals the interfacial free energy of the calcite-polysaccharide-solution system, γnet, is lowest for nonsulfated controls and increases with DS(SO3 -). The kinetic prefactor also increases with DS(SO3 -). Simulations of Ca2+-H2O-chitosan systems show greater water structuring around sulfate groups compared to uncharged substituents, independent of sulfate location. Ca2+-SO3 - interactions are solvent-separated by distances that are inversely correlated with DS(SO3 -) of the polysaccharide. The simulations also predict SO3 - and NH3 + groups affect the solvation waters and HCO3 - ions associated with Ca2+. Integrating the experimental and computational evidence suggests sulfate groups influence nucleation by increasing the difficulty of displacing near-surface water, thereby increasing γnet. By correlating γnet and net charge per monosaccharide for diverse polysaccharides, we suggest the solvent-separated interactions of functional groups with Ca2+ influence thermodynamic and kinetic components to crystallization by similar solvent-dominated processes. The findings reiterate the importance of establishing water structure and properties at macromolecule-solution interfaces.

Microbial-induced calcium precipitation: Bibliometric analysis, reaction mechanisms, mineralization types, and perspectives

Microbial-induced calcium precipitation (MICP) refers to the formation of calcium precipitates induced by mineralization during microbial metabolism. MICP has been widely used as an ecologically sustainable method in environmental, geotechnical, and construction fields. This article reviews the removal mechanisms of MICP for different contaminants in the field of water treatment. The nucleation pathway is explained at both extracellular and intracellular levels, with a focus on evaluating the contribution of extracellular polymers to MICP. The types of mineralization and the regulatory role of enzyme genes in the MICP process are innovatively summarized. Based on this, the environmental significance of MICP is illustrated, and the application prospects of calcium precipitation products are discussed. The research hotspots and development trends of MICP are analyzed by bibliometric methods, and the challenges and future directions of MICP technology are identified. This review aims to provide a theoretical basis for further understanding of the MICP phenomenon in water treatment and the effective removal of multiple pollutants, which will help researchers to find the breakthroughs and innovations in the existing technologies, with a view to making significant progress in MICP technology.

Mechanistic and future prospects in rhizospheric engineering for agricultural contaminants removal, soil health restoration, and management of climate change stress

Climate change, food insecurity, and agricultural pollution are all serious challenges in the twenty-first century, impacting plant growth, soil quality, and food security. Innovative techniques are required to mitigate these negative outcomes. Toxic heavy metals (THMs), organic pollutants (OPs), and emerging contaminants (ECs), as well as other biotic and abiotic stressors, can all affect nutrient availability, plant metabolic pathways, agricultural productivity, and soil-fertility. Comprehending the interactions between root exudates, microorganisms, and modified biochar can aid in the fight against environmental problems such as the accumulation of pollutants and the stressful effects of climate change. Microbes can inhibit THMs uptake, degrade organic pollutants, releases biomolecules that regulate crop development under drought, salinity, pathogenic attack and other stresses. However, these microbial abilities are primarily demonstrated in research facilities rather than in contaminated or stressed habitats. Despite not being a perfect solution, biochar can remove THMs, OPs, and ECs from contaminated areas and reduce the impact of climate change on plants. We hypothesized that combining microorganisms with biochar to address the problems of contaminated soil and climate change stress would be effective in the field. Despite the fact that root exudates have the potential to attract selected microorganisms and biochar, there has been little attention paid to these areas, considering that this work addresses a critical knowledge gap of rhizospheric engineering mediated root exudates to foster microbial and biochar adaptation. Reducing the detrimental impacts of THMs, OPs, ECs, as well as abiotic and biotic stress, requires identifying the best root-associated microbes and biochar adaptation mechanisms.

Role of biochar pyrolysis temperature on intracellular and extracellular biodegradation of biochar-adsorbed organic compounds

Immobilizing organic pollutants by adsorption of biochar in farmland soil is a cost-effective remediation method for contaminated soil. As the adsorption capacity of biochar is limited, biodegradation of biochar-adsorbed organic pollutants was a potential way to regenerate biochars and maintain the adsorption performance of biochars to lower the cost. It could be affected by the biochar pyrolysis temperature, but was not evaluated yet. In this study, biodegradation of adsorbed phenanthrene on a series of biochars with pyrolysis temperatures from 150 to 700 °C by Sphingobium yanoikuyae B1 was investigated using batch experiments of biodegradation kinetics at 30 °C, to explore the role of biochar pyrolysis temperature on biodegradation of biochar-adsorbed organic compounds. It was observed that 37.5-47.9% of adsorbed phenanthrene on moderate temperature-pyrolyzed biochars produced at 400 and 500 °C were biodegraded, less than that on high temperature-pyrolyzed biochars produced at ≥600 °C (48.8-60.8%) and low temperature-pyrolyzed biochars produced at ≤300 °C (63.4-92.5%). Phenanthrene adsorbed largely on the low temperature-pyrolyzed biochars by partition mechanism and thus is easily desorbed to water for a dominated intracellular biodegradation. On the high temperature-pyrolyzed biochars, phenanthrene is adsorbed largely by pore-filling mechanism and thus less desorbed to water for intracellular biodegradation. However, high temperature-pyrolyzed biochars can promote microbes to produce siderophore, H2O2 and thus release extracellular •OH for a dominated degradation of adsorbed phenanthrene by Fenton-like reaction. With the increase of biochar pyrolysis temperature, desorption and consequently the intracellular biodegradation of adsorbed phenanthrene on biochars decreased, while the secretion of siderophore and H2O2 by microbes on biochars increased to produce more extracellular •OH for degradation by Fenton-like reaction. The results could provide deep insights into the role of biochar pyrolysis temperature on biodegradation of biochar-adsorbed organic compounds, and optimize the selection of biochar with higher adsorption performance and easier regeneration for soil remediation.

Unraveling the mechanisms behind sodium persulphate-induced changes in petroleum-contaminated aquifers' biogeochemical parameters and microbial communities

Sodium persulphate (PS) is a highly effective oxidising agent widely used in groundwater remediation and wastewater treatment. Although numerous studies have examined the impact of PS with respect to the removal efficiency of organic pollutants, the residual effects of PS exposure on the biogeochemical parameters and microbial ecosystems of contaminated aquifers are not well understood. This study investigates the effects of exposure to different concentrations of PS on the biogeochemical parameters of petroleum-contaminated aquifers using microcosm batch experiments. The results demonstrate that PS exposure increases the oxidation-reduction potential (ORP) and electrical conductivity (EC), while decreasing total organic carbon (TOC), dehydrogenase (DE), and polyphenol oxidase (PO) in the aquifer. Three-dimensional excitation-emission matrix (3D-EEM) analysis indicates PS is effective at reducing fulvic acid-like and humic acid-like substances and promoting microbial metabolic activity. In addition, PS exposure reduces the abundance of bacterial community species and the diversity index of evolutionary distance, with a more pronounced effect at high PS concentrations (31.25 mmol/L). Long-term (90 d) PS exposure results in an increase in the abundance of microorganisms with environmental resistance, organic matter degradation, and the ability to promote functional genes related to biological processes such as basal metabolism, transmission of genetic information, and cell motility of microorganisms. Structural equation modeling (SEM) further confirms that ORP and TOC are important drivers of change in the abundance of dominant phyla and functional genes. These results suggest exposure to different concentrations of PS has both direct and indirect effects on the dominant phyla and functional genes by influencing the geochemical parameters and enzymatic activity of the aquifer. This study provides a valuable reference for the application of PS in ecological engineering.

Enhancing La(III) biosorption and biomineralization with Micromonospora saelicesensis: Involvement of phosphorus and formation of monazite nano-minerals

The release of rare earth elements (REEs) from mining wastes and their applications has significant environmental implications, necessitating the development of effective prevention and reclamation strategies. The mobility of REEs in groundwater due to microorganisms has garnered considerable attention. In this study, a La(III) resistant actinobacterium, Micromonospora saelicesensis KLBMP 9669, was isolated from REE enrichment soil in GuiZhou, China, and evaluated for its ability to adsorb and biomineralize La(III). The findings demonstrated that M. saelicesensis KLBMP 9669 immobilized La(III) through the physical and chemical interactions, with immobilization being influenced by the initial La(III) concentration, biomass, and pH. The adsorption kinetics followed a pseudo-second-order rate model, and the adsorption isotherm conformed to the Langmuir model. La(III) adsorption capacity of this strain was 90 mg/g, and removal rate was 94 %. Scanning electron microscope (SEM) coupled with energy dispersive X-ray spectrometer (EDS) analysis revealed the coexistence of La(III) with C, N, O, and P. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) investigations further indicated that carboxyl, amino, carbonyl, and phosphate groups on the mycelial surface may participate in lanthanum adsorption. Transmission electron microscopy (TEM) revealed that La(III) accumulation throughout the M. saelicesensis KLBMP 9669, with some granular deposits on the mycelial surface. Selected area electron diffraction (SAED) confirmed the presence of LaPO4 crystals on the M. saelicesensis KLBMP 9669 biomass after a prolonged period of La(III) accumulation. This post-sorption nano-crystallization on the M. saelicesensis KLBMP 9669 mycelial surface is expected to play a crucial role in limiting the bioimmobilization of REEs in geological repositories.

Structural and Functional Insights into the Biomineralized Zeolite Imidazole Frameworks

Biomineralization is a natural process of mineral formation mediated by biomacromolecules, allowing access to hierarchical structures integrating biological, chemical, and material properties. In this contribution, we comprehensively investigate the biomineralization of zeolite imidazole frameworks (ZIFs) for one-step synthesis of an enzyme-MOF biocomposite, in terms of differential crystallization behaviors, fine microstructure of resultant ZIF biominerals, the enzyme's conformation evolution, and protective effect of ZIF mineral. We discover that the biomineralization ability is ZIF organic linker dependent and the biocatalytic function is highly related to the ZIF mineral species and their distinguishable topologies and defect structures. Importantly, a side-by-side analysis suggests that the protective effect of ZIF mineral toward the hosted enzyme is highly associated with the synergistic effect of size dimension and chemical microenvironment of the ZIF pores. This work provides important insight into the ZIF-dependent biomineralization behaviors and highlights the important role of the ZIF microstructure in its biocatalytic activity and durability, which has been underestimated previously.

Physicochemical understanding of biomineralization by molecular vibrational spectroscopy: From mechanism to nature

The process and mechanism of biomineralization and relevant physicochemical properties of mineral crystals are remarkably sophisticated multidisciplinary fields that include biology, chemistry, physics, and materials science. The components of the organic matter, structural construction of minerals, and related mechanical interaction, etc., could help to reveal the unique nature of the special mineralization process. Herein, the paper provides an overview of the biomineralization process from the perspective of molecular vibrational spectroscopy, including the physicochemical properties of biomineralized tissues, from physiological to applied mineralization. These physicochemical characteristics closely to the hierarchical mineralization process include biological crystal defects, chemical bonding, atomic doping, structural changes, and content changes in organic matter, along with the interface between biocrystals and organic matter as well as the specific mechanical effects for hardness and toughness. Based on those observations, the special physiological properties of mineralization for enamel and bone, as well as the possible mechanism of pathological mineralization and calcification such as atherosclerosis, tumor micro mineralization, and urolithiasis are also reviewed and discussed. Indeed, the clearly defined physicochemical properties of mineral crystals could pave the way for studies on the mechanisms and applications.

Mitigation of heavy metal stress in the soil through optimized interaction between plants and microbes

Agricultural as well as industrial processes, such as mining and textile activities, are just a few examples of anthropogenic activities that have a long-term negative impact on the environment. Each of the aforementioned factors increases the concentration of heavy metals in soil. Heavy metal contamination in soil causes a wide range of environmental issues and is harmful to microbes, plants, and animals. Because of their non-biodegradability and toxic effects, preventing additional metal contamination and remediating the vast majority of contaminated sites around the world is critical. Hence, this review focuses on the effects of metal contamination on soil microbes, as well as plant-microbe interactions. Plant-associated probiotics reduce metal accumulation; the introduction of beneficial microbes is regarded as one of the most promising approaches to improving metal stress tolerance; thus, the study focuses on plant-microbe interactions as well as their actual implications via phytoremediation. Plant-microbe interaction can play an important role in acclimating vegetation (plants) to metalliferous conditions and should thus be studied to improve microbe-aided metal tolerance in plants. Plant-interacted microbes reduce metal accumulation in plant cells and metal bioaccumulation in the soil through a variety of processes. A novel phytobacterial approach, such as genetically modified microbes, is now being used to improve heavy metal cleanup as well as stress tolerance among plants. This review examines our current understanding of such negative consequences of heavy metal stresses, signaling responses, and the role of plant-associated microbiota in heavy metal stress tolerance and interaction.

Will tomorrow's mineral materials be grown?

Biomineralization, the capacity to form minerals, has evolved in a great diversity of bacterial lineages as an adaptation to different environmental conditions and biological functions. Microbial biominerals often display original properties (morphology, composition, structure, association with organics) that significantly differ from those of abiotically formed counterparts, altogether defining the 'mineral phenotype'. In principle, it should be possible to take advantage of microbial biomineralization processes to design and biomanufacture advanced mineral materials for a range of technological applications. In practice, this has rarely been done so far and only for a very limited number of biomineral types. This is mainly due to our poor understanding of the underlying molecular mechanisms controlling microbial biomineralization pathways, preventing us from developing bioengineering strategies aiming at improving biomineral properties for different applications. Another important challenge is the difficulty to upscale microbial biomineralization from the lab to industrial production. Addressing these challenges will require combining expertise from environmental microbiologists and geomicrobiologists, who have historically been working at the forefront of research on microbe-mineral interactions, alongside bioengineers and material scientists. Such interdisciplinary efforts may in the future allow the emergence of a mineral biomanufacturing industry, a critical tool towards the development more sustainable and circular bioeconomies.

New insights into Saccharomyces cerevisiae induced calcium carbonate precipitation

Our previous study reported that Saccharomyces cerevisiae could induce calcium carbonate (CaCO3) precipitation, but the associated mechanism was unclear. In the present study, Saccharomyces cerevisiae was cultured under various conditions, including the presence of different organic acids and initial pH, and the yields of CaCO3 formation induced by the different organic acids were compared. The metabolism of organic acid by the metabolites of S. cerevisiae was also assessed in vitro. The SEM-EDS and XRD results showed that only acetate acid, pyruvic acid, and α-ketoglutaric acid could induce CaCO3 formation, and the weight order of the produced CaCO3 was pyruvic acid, acetate acid, α-ketoglutaric acid. In addition, the presence of only yeast metabolites and the initial neutral or alkaline environment also limited the CaCO3 formation. These results illustrated that organic acid oxidation intracellularly, especially the tricarboxylic acid cycle, was the major mechanism, and the CaCO3 yield was related to the amount of CO2 produced by the metabolism of organic acids. These findings will deepen the knowledge of the mineralization capacity of S. cerevisiae and provide a theoretical basis for the future application of yeast as an alternative microorganism in MICP.

Organic Matrix Derived from Host-Microbe Interplay Contributes to Pathological Renal Biomineralization

Matrix stones are a rare form of kidney stones. They feature a high percentage of hydrogel-like organic matter, and their formation is closely associated with urinary tract infections. Herein, comprehensive materials and biochemical approaches were taken to map the organic-inorganic interface and gather insights into the host-microbe interplay in pathological renal biomineralization. Surgically extracted soft and slimy matrix stones were examined using micro-X-ray computed tomography and various microspectroscopy techniques. Higher-mineral-density laminae were positive for calcium-bound Alizarin red. Lower-mineral-density laminae revealed periodic acid-Schiff-positive organic filamentous networks of varied thickness. These organic filamentous networks, which featured a high polysaccharide content, were enriched with zinc, carbon, and sulfur elements. Neutrophil extracellular traps (NETs) along with immune response-related proteins, including calprotectin, myeloperoxidase, CD63, and CD86, also were identified in the filamentous networks. Expressions of NETs and upregulation of polysaccharide-rich mucin secretion are proposed as a part of the host immune defense to "trap" pathogens. These host-microbe derived organic matrices can facilitate heterogeneous nucleation and precipitation of inorganic particulates, resulting in macroscale aggregates known as "matrix stones". These insights into the plausible aggregation of constituents through host-microbe interplay underscore the unique "double-edged sword" effect of the host immune response to pathogens and the resulting renal biominerals.

Bacterial mineralization of chromium-copper spinel with highly performance in electroplating effluent

Cr (VI) contamination has posed severe challenges to water quality, food safety, and land resources. Microbial reduction of Cr(VI) to Cr(III) has drawn considerable attention due to its low cost and environmental friendliness. However, recent reports have shown that Cr(VI) generates highly migratable organo-Cr(III) rather than stable inorganic chromium minerals during the biological reduction process. In this work, it was reported for the first time that spinel structure CuCr2O4 was formed by Bacillus cereus in Cr biomineralization process. Different from known biomineralization models (biologically controlled mineralization and biologically induced mineralization), the chromium-copper minerals here appeared as specialized minerals with extracellular distribution. In view of this, a possible mechanism of biologically secretory mineralization was proposed. In addition, Bacillus cereus demonstrated a high conversion ability in the treatment of electroplating wastewater. The Cr(VI) removal percentage reached 99.7%, which satisfied the Chinese emission standard of pollutants for electroplating (GB 21,900-2008), indicating its application potential. Altogether, our work elucidated a bacterial chromium spinel mineralization pathway and evaluated the potential of this system for application in actual wastewater, opening a new avenue in the field of chromium pollution treatment and control.

Recent progress of micro/nanomotors to overcome physiological barriers in the gastrointestinal tract

Oral administration is a convenient administration route for gastrointestinal disease therapy with good patient compliance. But the nonspecific distribution of the oral drugs may cause serious side effects. In recent years, oral drug delivery systems (ODDS) have been applied to deliver the drugs to the gastrointestinal disease sites with decreased side effects. However, the delivery efficiency of ODDS is tremendously limited by physiological barriers in the gastrointestinal sites, such as the long and complex gastrointestinal tract, mucus layer, and epithelial barrier. Micro/nanomotors (MNMs) are micro/nanoscale devices that transfer various energy sources into autonomous motion. The outstanding motion characteristics of MNMs inspired the development of targeted drug delivery, especially the oral drug delivery. However, a comprehensive review of oral MNMs for the gastrointestinal diseases therapy is still lacking. Herein, the physiological barriers of ODDS were comprehensively reviewed. Afterward, the applications of MNMs in ODDS for overcoming the physiological barriers in the past 5 years were highlighted. Finally, future perspectives and challenges of MNMs in ODDS are discussed as well. This review will provide inspiration and direction of MNMs for the therapy of gastrointestinal diseases, pushing forward the clinical application of MNMs in oral drug delivery.

Microbially induced calcium precipitation driven by denitrification: Performance, metabolites, and molecular mechanisms

Microbially induced calcium precipitation (MICP) driven by denitrification has attracted extensive attention due to its application potential in nitrate removal from calcium-rich groundwater. However, little research has been conducted on this technique at the molecular level. Here, Pseudomonas WZ39 was used to explore the molecular mechanisms of nitrate-dependent MICP and the effects of Ca²⁺ on bacterial transcriptional regulation and metabolic response. The results exhibited that appropriate Ca²⁺ concentration (4.5 mM) can promote denitrification and the production of ATP, EPSs, and SMPs. Genome-wide analysis showed that the nitrate-dependent MICP was accomplished through heterotrophic denitrification and CO₂ capture. During this process, EPS biosynthesis and Ca²⁺ signaling regulation were involved in the nucleation template supply and Ca²⁺ homeostasis balance. Untargeted transcriptome- and metabolome-association analyses revealed that the addition of Ca²⁺ triggered the significant up-regulation in several key pathways, such as transmembrane transporter and channel activities, amino acid metabolism, fatty acid biosynthesis, and carbon metabolism, which played a momentous role in the mineral nucleation and energy provision. The detailed information provided novel insights for understanding the active control of bacteria on MICP, and has great significance for deepening the cognition of groundwater remediation using nitrate-dependent MICP technique.

Fungal biorecovery of cerium as oxalate and carbonate biominerals

Cerium is the most sought-after rare earth element (REE) for application in high-tech electronic devices and versatile nanomaterials. In this research, biomass-free spent culture media of Aspergillus niger and Neurospora crassa containing precipitant ligands (oxalate, carbonate) were investigated for their potential application in biorecovery of Ce from solution. Precipitation occurred after Ce3+ was mixed with biomass-free spent culture media and >99% Ce was recovered from media of both organisms. SEM showed that biogenic crystals with distinctive morphologies were formed in the biomass-free spent medium of A. niger. Irregularly-shaped nanoparticles with varying sizes ranging from 0.5 to 2 μm and amorphous biominerals were formed after mixing the carbonate-laden N. crassa supernatant, resulting from ureolysis of supplied urea, with Ce3+. Both biominerals contained Ce as the sole metal, and X-ray diffraction (XRD) and thermogravimetric analyses identified the biominerals resulting from the biomass-free A. niger and N. crassa spent media as cerium oxalate decahydrate [Ce2(C2O4)3·10H2O] and cerium carbonate [Ce2(CO3)3·8H2O], respectively. Thermal decomposition experiments showed that the biogenic Ce oxalates and carbonates could be subsequently transformed into ceria (CeO2). FTIR confirmed that both amorphous and nanoscale Ce carbonates contained carbonate (CO32-) groups. FTIR-multivariate analysis could classify the biominerals into three groups according to different Ce concentrations and showed that Ce carbonate biominerals of higher purity were produced when precipitated at higher Ce3+ concentrations. This work provides new understanding of fungal biotransformations of soluble REE species and their biorecovery using biomass-free fungal culture systems and indicates the potential of using recovered REE as precursors for the biosynthesis of novel nanomaterials.

Weaponising microbes for peace

There is much human disadvantage and unmet need in the world, including deficits in basic resources and services considered to be human rights, such as drinking water, sanitation and hygiene, healthy nutrition, access to basic healthcare, and a clean environment. Furthermore, there are substantive asymmetries in the distribution of key resources among peoples. These deficits and asymmetries can lead to local and regional crises among peoples competing for limited resources, which, in turn, can become sources of discontent and conflict. Such conflicts have the potential to escalate into regional wars and even lead to global instability. Ergo: in addition to moral and ethical imperatives to level up, to ensure that all peoples have basic resources and services essential for healthy living and to reduce inequalities, all nations have a self-interest to pursue with determination all available avenues to promote peace through reducing sources of conflicts in the world. Microorganisms and pertinent microbial technologies have unique and exceptional abilities to provide, or contribute to the provision of, basic resources and services that are lacking in many parts of the world, and thereby address key deficits that might constitute sources of conflict. However, the deployment of such technologies to this end is seriously underexploited. Here, we highlight some of the key available and emerging technologies that demand greater consideration and exploitation in endeavours to eliminate unnecessary deprivations, enable healthy lives of all and remove preventable grounds for competition over limited resources that can escalate into conflicts in the world. We exhort central actors: microbiologists, funding agencies and philanthropic organisations, politicians worldwide and international governmental and non-governmental organisations, to engage - in full partnership - with all relevant stakeholders, to 'weaponise' microbes and microbial technologies to fight resource deficits and asymmetries, in particular among the most vulnerable populations, and thereby create humanitarian conditions more conducive to harmony and peace.

Biologically-induced synthetic manganese carbonate precipitate (BISMCP) for potential applications in heavy metal removal

Heavy metal pollution of water is a burning issue of today's world. Among several strategies involved for heavy metal remediation purpose, biomineralization has shown great potential. Of late, research has been focused on developing effective mineral adsorbents with reduced time and cost consumption. In this present paper, the Biologically-Induced Synthetic Manganese Carbonate Precipitate (BISMCP) was produced based on the biologically-induced mineralization method, employing Sporosarcina pasteurii in aqueous solutions containing urea and MnCl2. The prepared adsorbent was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD) and BET surface area analyzer. EDX analysis showed the elements in the crystal BISMCP were Mn, C, and O. XRD result of BISMCP determined the crystal structure, which is close to rhodochrosite (MnCO3). Spectral peaks of FTIR at 1641.79 cm-1 confirmed the appearance of C[bond, double bond]O binding, with strong stretching of CO32- in Amide I. From the six kinds of BISMCP produced, sample MCP-6 has the higher specific surface area by BET analysis at 109.01 m2/g, with pore size at 8.76 nm and higher pore volume at 0.178 cm3/g. These specifications will be suitable as an adsorbent for heavy metal removal by adsorption process. This study presents a preliminary analysis of the possibility of BISMCP for heavy metals adsorption using ICP multi-element standard solution XIII (As, Cr, Cd, Cu, Ni, and Zn). BISMCP formed from 0.1 MnCl2 and 30 ml of bacteria volume (MCP-6) produced a better adsorbent material than others concentrations, with the adsorption efficiency of total As at 98.9%, Cr at 97.0%, Cu at 94.7%, Cd at 88.3%, Zn at 48.6%, and Ni at 29.5%. Future work could be examined its efficiency adsorbing individual heavy metals.

A Dual-Biomineralized Yeast Micro-/Nanorobot with Self-Driving Penetration for Gastritis Therapy and Motility Recovery

Micro-/nanorobots have attracted great interest in the field of drug delivery and treatment, while preparations for biocompatible robots are extremely challenging. Here, a self-driving yeast micro-/nanorobot (Cur@CaY-robot) is designed via dual biomineralization and acid catalysis of calcium carbonate (CaCO₃). Inner nano-CaCO₃ inside yeast cells (CaY) is biomineralized through cell respiration and provides nanoscaffolds for highly encapsulating curcumin (Cur). Meanwhile, the CaCO₃ crystals outside yeast cells (outer-CaCO₃) through uniaxial growth offer an asymmetric power source for self-propelled motility. The Cur@CaY-robot displays an efficient motion in gastric acid, with the potential for deep penetration to the thick gastric mucus, which significantly improves the accumulation of drug agents in the stomach wall tissue for robust gastritis therapy. More importantly, Ca²⁺ cations released from the Cur@CaY-robot also synergistically repair the gastric motility of gastritis mice. Such yeast micro-/nanorobots exhibit desirable biocompatibility and biodegradability with a good loading capacity for drugs. This work provides an idea for the design of micro-/nanorobots through an environmentally friendly biosynthesis strategy for active drug delivery and precise therapy.

Chitosan as a Canvas for Studies of Macromolecular Controls on CaCO3 Biological Crystallization

A mechanistic understanding of how macromolecules, typically as an organic matrix, nucleate and grow crystals to produce functional biomineral structures remains elusive. Advances in structural biology indicate that polysaccharides (e.g., chitin) and negatively charged proteoglycans (due to carboxyl, sulfate, and phosphate groups) are ubiquitous in biocrystallization settings and play greater roles than currently recognized. This review highlights studies of CaCO₃ crystallization onto chitinous materials and demonstrates that a broader understanding of macromolecular controls on mineralization has not emerged. With recent advances in biopolymer chemistry, it is now possible to prepare chitosan-based hydrogels with tailored functional group compositions. By deploying these characterized compounds in hypothesis-based studies of nucleation rate, quantitative relationships between energy barrier to crystallization, macromolecule composition, and solvent structuring can be determined. This foundational knowledge will help researchers understand composition-structure-function controls on mineralization in living systems and tune the designs of new materials for advanced applications.

Heavy metal bioremediation using microbially induced carbonate precipitation: Key factors and enhancement strategies

With the development of economy, heavy metal (HM) contamination has become an issue of global concern, seriously threating animal and human health. Looking for appropriate methods that decrease their bioavailability in the environment is crucial. Microbially induced carbonate precipitation (MICP) has been proposed as a promising bioremediation method to immobilize contaminating metals in a sustainable, eco-friendly, and energy saving manner. However, its performance is always affected by many factors in practical application, both intrinsic and external. This paper mainly introduced ureolytic bacteria-induced carbonate precipitation and its implements in HM bioremediation. The mechanism of HM immobilization and in-situ application strategies (that is, biostimulation and bioaugmentation) of MICP are briefly discussed. The bacterial strains, culture media, as well as HMs characteristics, pH and temperature, etc. are all critical factors that control the success of MICP in HM bioremediation. The survivability and tolerance of ureolytic bacteria under harsh conditions, especially in HM contaminated areas, have been a bottleneck for an effective application of MICP in bioremediation. The effective strategies for enhancing tolerance of bacteria to HMs and improving the MICP performance were categorized to provide an in-depth overview of various biotechnological approaches. Finally, the technical barriers and future outlook are discussed. This review may provide insights into controlling MICP treatment technique for further field applications, in order to enable better control and performance in the complex and ever-changing environmental systems.

Microbially induced calcium precipitation coupled with medical stone-coated sponges: A targeted strategy for enhanced nitrate and fluoride removal from groundwater

The coexistence of nitrate and fluoride in groundwater is of high concern due to its potential environmental impacts and health risks. Medical stone-coated sponges, as a microbial activity promoter and slow-release calcium source, were introduced into an immobilized bioreactor for enhanced removal of nitrate and fluoride. Under the hydraulic retention time of 3 h, nitrate, fluoride, and calcium contents of 16.5, 3.0, and 100 mg L^-1, the average removal efficiencies of nitrate, fluoride, and calcium reached 99.49%, 74.26%, and 70.43%, respectively. Co-precipitation and chemisorption were the mechanisms for fluoride and calcium removal. Medical stone load improved the competitiveness of dominant bacteria and electron transport activity, accelerated the denitrification process, and stimulated biofilm formation. High fluoride level (5.0 mg L^-1) inhibited the nitrate removal and aromatic protein production. The fluoride content changes altered the carbon source preference of the microbial community, which preferred to use amino acids and carbohydrates under a higher fluoride content. The introduction of medical stones significantly accelerated the fluoride and nitrate removal, providing a new insight for the application of microbially induced calcium precipitation technique in the remediation of low-calcium groundwater.

Self-Assembled Nanoscale Manganese Oxides Enhance Carbon Capture by Diatoms

Continuous CO₂ emissions from human activities increase atmospheric CO₂ concentrations and affect global climate change. The carbon storage capacity of the ocean is 20-fold higher than that of the land, and diatoms contribute to approximately 40% of carbon capture in the ocean. Manganese (Mn) is a major driver of marine phytoplankton growth and the marine carbon pump. Here, we discovered self-assembled manganese oxides (MnO_x) for CO₂ fixation in a diatom-based biohybrid system. MnO_x shared key features (e.g., di-μ-oxo-bridged Mn-Mn) with the Mn₄CaO₅ cluster of the biological catalyst in photosystem II and promoted photosynthesis and carbon capture by diatoms/MnO_x. The CO₂ capture capacity of diatoms/MnO_x was 1.5-fold higher than that of diatoms alone. Diatoms/MnO_x easily allocated carbon into proteins and lipids instead of carbohydrates. Metabolomics showed that the contents of several metabolites (e.g., lysine and inositol) were positively associated with increased CO₂ capture. Diatoms/MnO_x upregulated six genes encoding photosynthesis core proteins and a key rate-limiting enzyme (Rubisco, ribulose 1,5-bisphosphate carboxylase-oxygenase) in the Calvin-Benson-Bassham carbon assimilation cycle, revealing the link between MnO_x and photosynthesis. These findings provide a route for offsetting anthropogenic CO₂ emissions and inspiration for self-assembled biohybrid systems for carbon capture by marine phytoplankton.

Highlighting Bacteria with Calcifying Abilities Suitable to Improve Mortar Properties

Biomineralization, the use of microorganisms to produce calcium carbonate, became a green solution for application in construction materials to improve their strength and durability. The calcifying abilities of several bacteria were investigated by culturing on a medium with urea and calcium ions. The characterization of the precipitates from bacterial cultures was performed using X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The formation of carbonate crystals was demonstrated by optical and scanning electron microscopy. Water absorption and compressive strength measurements were applied to mortars embedded with sporal suspension. The efficiency of the supplementation of mortar mixtures with bacterial cells was evaluated by properties, namely the compressive strength and the water absorption, which are in a relationship of direct dependence, the increase in compressive strength implying the decrease in water absorption. The results showed that Bacillus subtilis was the best-performing bacterium, its introduction into the mortar producing an increase in compressive strength by 11.81% and 9.50%, and a decrease in water absorption by 11.79% and 10.94%, after 28 and 56 days of curing, respectively, as compared to standards. The exploitation of B. subtilis as a calcifying agent can be an interesting prospect in construction materials.

Bioremediation competence of Aspergillus flavus DDN on pond water contaminated by mining activities

This research was performed to evaluate the possibilities of reducing the physicochemical properties of polluted pond water situated around the magnesite mine tailing through indigenous metal tolerant fungi. The physicochemical analysis results revealed that most of the physicochemical properties of pond water sample were crossing the permissible limits. From the muddy pond soil sample, Aspergillus flavus DDN was identified (through molecular characterization) as predominant metal tolerant fungal strain and it showed resistance to Cr(VI), Pb(II), Zn(II), Cd(II), and Mg(IV) up to 1000 μg mL^-1 concentrations. This strain also effectively reduced (through biosorption) these metals in a short duration of the bioremediation process. In a lab-scale bioremediation study, the A. flavus DDN significantly reduced most of the physicochemical parameters crossing the permissible limit in polluted pond water in the presence of FM1 minimal media in 10 days of incubation. The dissolved oxygen level was significantly increased up to 74.91% from 5.86 ± 0.39 to 10.25 ± 0.95 in 10 days of treatment. The metal reduction and other physicochemical properties reduction were directly related to the biomass of A. flavus DDN. These findings suggest that A. flavus DDN can remove pollutants from magnesite mine tailing polluted pond water because elevated fungal biomass resulted in the highest percentage of pollutant reduction from the sample.

Single-step removal of calcium, fluoride, and phenol from contaminated water by Aquabacterium sp. CZ3 via facultative anaerobic microbially induced calcium precipitation: Kinetics, mechanism, and characterization

Confronting the complex contaminated water, Aquabacterium sp. CZ3 could perform microbially induced calcium precipitation (MICP) under facultative anaerobic condition using phenol as supplementary carbon source. Strain CZ3 exhibited a remarkable ability to remove nitrate, fluoride, calcium and phenol with removal rates of 100.00, 87.50, 66.24 and 100.00%, respectively. The Modified Gompertz model was used for kinetic analysis to determine the optimum conditions for denitrification and degradation of phenol. The mechanism of anaerobic MICP was enhanced by measuring the self-aggregation properties of the isolates. The mechanism of fluoride removal was identified as co-precipitation and adsorption by characterization analysis of the bioprecipitation. Furthermore, the changes in soluble metabolites under phenol stress explained the utilization of phenol as a co-substrate by microorganisms. This is a novel report on phenol degradation by anaerobic MICP, which provides a theoretical basis for expanding its practical application.

Periplasmic Bacterial Biomineralization of Copper Sulfide Nanoparticles

Metal sulfides are a common group of extracellular bacterial biominerals. However, only a few cases of intracellular biomineralization are reported in this group, mostly limited to greigite (Fe3 S4 ) in magnetotactic bacteria. Here, a previously unknown periplasmic biomineralization of copper sulfide produced by the magnetotactic bacterium Desulfamplus magnetovallimortis strain BW-1, a species known to mineralize greigite (Fe3 S4 ) and magnetite (Fe3 O4 ) in the cytoplasm is reported. BW-1 produces hundreds of spherical nanoparticles, composed of 1-2 nm substructures of a poorly crystalline hexagonal copper sulfide structure that remains in a thermodynamically unstable state. The particles appear to be surrounded by an organic matrix as found from staining and electron microscopy inspection. Differential proteomics suggests that periplasmic proteins, such as a DegP-like protein and a heavy metal-binding protein, could be involved in this biomineralization process. The unexpected periplasmic formation of copper sulfide nanoparticles in BW-1 reveals previously unknown possibilities for intracellular biomineralization that involves intriguing biological control and holds promise for biological metal recovery in times of copper shortage.

Interplay between arsenic and selenium biomineralization in Shewanella sp. O23S

Bacteria play crucial roles in the biogeochemical cycle of arsenic (As) and selenium (Se) as these elements are metabolized via detoxification, energy generation (anaerobic respiration) and biosynthesis (e.g. selenocysteine) strategies. To date, arsenic and selenium biomineralization in bacteria were studied separately. In this study, the anaerobic metabolism of As and Se in Shewanella sp. O23S was investigated separately and mixed, with an emphasis put on the biomineralization products of this process. Multiple analytical techniques including ICP-MS, TEM-EDS, XRD, Micro-Raman, spectrophotometry and surface charge (zeta potential) were employed. Shewanella sp. O23S is capable of reducing selenate (SeO₄^2-) and selenite (SeO₃^2-) to red Se(-S)⁰, and arsenate (AsO₄^3-) to arsenite (AsO₃^3-). The release of H₂S from cysteine led to the precipitation of AsS minerals: nanorod AsS and granular As₂S₃. When As and Se oxyanions were mixed, both As-S and Se(-S)⁰ biominerals were synthesized. All biominerals were extracellular, amorphous and presented a negative surface charge (-24 to -38 mV). Kinetic analysis indicated the following reduction yields: SeO₃^2- (90%), AsO₄^3- (60%), and SeO₄^2- (<10%). The mix of SeO₃^2- with AsO₄^3- led to a decrease in As removal to 30%, while Se reduction yield was unaffected (88%). Interestingly, SeO₄^2- incubated with AsO₄^3- boosted the Se removal (71%). The exclusive extracellular formation of As and Se biominerals might indicate an extracellular respiratory process characteristic of various Shewanella species and strains. This is the first study documenting a complex interplay between As and Se oxyanions: selenite decreased arsenate reduction, whereas arsenate stimulated selenate reduction. Further investigation needs to clarify whether Shewanella sp. O23S employs multi-substrate respiratory enzymes or separate, high affinity enzymes for As and Se oxyanion respiration.

Manipulating Bacterial Biofilms Using Materiobiology and Synthetic Biology Approaches

Bacteria form biofilms on material surfaces within hours. Biofilms are often considered problematic substances in the fields such as biomedical devices and the food industry; however, they are beneficial in other fields such as fermentation, water remediation, and civil engineering. Biofilm properties depend on their genome and the extracellular environment, including pH, shear stress, and matrices topography, stiffness, wettability, and charges during biofilm formation. These surface properties have feedback effects on biofilm formation at different stages. Due to emerging technology such as synthetic biology and genome editing, many studies have focused on functionalizing biofilm for specific applications. Nevertheless, few studies combine these two approaches to produce or modify biofilms. This review summarizes up-to-date materials science and synthetic biology approaches to controlling biofilms. The review proposed a potential research direction in the future that can gain better control of bacteria and biofilms.

Photocatalyst-mineralized biofilms as living bio-abiotic interfaces for single enzyme to whole-cell photocatalytic applications

There is an increasing trend of combining living cells with inorganic semiconductors to construct semi-artificial photosynthesis systems. Creating a robust and benign bio-abiotic interface is key to the success of such solar-to-chemical conversions but often faces a variety of challenges, including biocompatibility and the susceptibility of cell membrane to high-energy damage arising from direct interfacial contact. Here, we report living mineralized biofilms as an ultrastable and biocompatible bio-abiotic interface to implement single enzyme to whole-cell photocatalytic applications. These photocatalyst-mineralized biofilms exhibited efficient photoelectrical responses and were further exploited for diverse photocatalytic reaction systems including a whole-cell photocatalytic CO2 reduction system enabled by the same biofilm-producing strain. Segregated from the extracellularly mineralized semiconductors, the bacteria remained alive even after 5 cycles of photocatalytic NADH regeneration reactions, and the biofilms could be easily regenerated. Our work thus demonstrates the construction of biocompatible interfaces using biofilm matrices and establishes proof of concept for future sustainable photocatalytic applications.

New Insights Into Microbial Induced Calcium Carbonate Precipitation Using Saccharomyces cerevisiae

Saccharomyces cerevisiae plays an important role in the mineralization of many metal ions, but it is unclear whether this fungus is involved in the mineralization of calcium carbonate. In this study, S. cerevisiae was cultured under various conditions to explore its ability to perform microbially induced calcium carbonate precipitation (MICP). Organic acids, yeast extract, and low-carbon conditions were the factors influencing the biomineralization of calcium carbonate caused by S. cerevisiae, and biomolecules secreted by the fungus under different conditions could change the morphology, size, and crystal form of the biosynthesized mineral. In addition, transcriptome analysis showed that the oxidation of organic acids enhanced the respiration process of yeast. This implied that S. cerevisiae played a role in the formation of calcium carbonate through the mechanism of creating an alkaline environment by the respiratory metabolism of organic acids, which could provide sufficient dissolved inorganic carbon for calcium carbonate formation. These results provide new insights into the role of S. cerevisiae in biomineralization and extend the potential applications of this fungus in the future.

Extracellular proteins of Desulfovibrio vulgaris as adsorbents and redox shuttles promote biomineralization of antimony

Biomineralization is the key process governing the biogeochemical cycling of multivalent metals in the environment. Although some sulfate-reducing bacteria (SRB) are recently recognized to respire metal ions, the role of their extracellular proteins in the immobilization and redox transformation of antimony (Sb) remains elusive. Here, a model strain Desulfovibrio vulgaris Hildenborough (DvH) was used to study microbial extracellular proteins of functions and possible mechanisms in Sb(V) biomineralization. We found that the functional groups (N-H, CO, O-CO, NH₂-R and RCOH/RCNH₂) of extracellular proteins could adsorb and fix Sb(V) through electrostatic attraction and chelation. DvH could rapidly reduce Sb(V) adsorbed on the cell surface and form amorphous nanometer-sized stibnite and/or antimony trioxide, respectively with sulfur and oxygen. Proteomic analysis indicated that some extracellular proteins involved in electron transfer increased significantly (p < 0.05) at 1.8 mM Sb(V). The upregulated flavoproteins could serve as a redox shuttle to transfer electrons from c-type cytochrome networks to reduce Sb(V). Also, the upregulated extracellular proteins involved in sulfur reduction, amino acid transport and protein synthesis processes, and the downregulated flagellar proteins would contribute to a better adaption under 1.8 mM Sb(V). This study advances our understanding of how microbial extracellular proteins promote Sb biomineralization in DvH.

Synergistic removal of fluoride from groundwater by seed crystals and bacteria based on microbially induced calcium precipitation

A new hypothesis that seed crystals (SC) and bacteria based on microbially induced calcium precipitation (MICP) synergistically remove fluoride (F^-) from groundwater was proposed, with a focus on evaluating the defluoridation potential of this method and revealing its F^- removal mechanism. The crucial conditions were optimized to reduce preparation and operation costs. SC furnished more available binding sites due to the existence of bacteria, and the reuse experiments showed that the defluoridation efficiency of SC still remained a high level after 14 cycles (70.10%), with a residual F^- concentration of 0.96 mg L^-1. The SEM-EDS, FTIR and XRD analyses indicated the predominant F^- removal mechanism of SC could be ascribed to the chemisorption, ion exchange, and co-precipitation. Moreover, ion exchange and co-precipitation (PO₄^3- involvement) were validated more contributive than chemisorption (CaCO₃ and CaSO₄ involvement). As a feasible, reusable, and eco-friendly technique, SC suggests promising applications in the treatment of fluoride-contaminated groundwater.

The effect of Bacillus cereus LV-1 on the crystallization and polymorphs of calcium carbonate

The study of CaCO₃ polymorphism is of great significance for understanding the mechanism of carbonate mineralization induced by bacteria and the genesis of carbonate rock throughout geological history. To investigate the effect of bacteria and shear force on CaCO₃ precipitation and polymorphs, biomineralization experiments with Bacillus cereus strain LV-1 were conducted under the standing and shaking conditions. The results show that LV-1 induced the formation of calcite and vaterite under the standing and shaking conditions, respectively. However, the results of mineralization in the media and the CaCl₂ solution under both kinetic conditions suggest the shear force does not affect the polymorphs of calcium carbonate in abiotic systems. Further, mineralization experiments with bacterial cells and extracellular polymeric substances (EPS) were performed under the standing conditions. The results reveal that bacterial cells, bound EPS (BEPS), and soluble EPS (SEPS) are favorable to the formation of spherical, imperfect rhombohedral, and perfect rhombohedral minerals, respectively. The increase in the pH value and saturation index (SI) caused by LV-1 metabolism under the shear force played key roles in controlling vaterite precipitation, whereas bacterial cells and EPS do not play roles in promoting vaterite formation. Furthermore, we suggest that vaterite formed if pH > 8.5 and SI_ACC > 0.8, while calcite formed if pH was between 8.0–9.0 and SI_ACC < 0.8. Bacterial cells and BEPS are the main factors affecting CaCO₃ morphologies in the mineralization process of LV-1. This may provide a deeper insight into the regulation mechanism of the polymorphs and morphologies during bacterially induced carbonate mineralization.

The study of CaCO₃ polymorphism is of great significance for understanding the mechanism of bacterial carbonate mineralization and the genesis of carbonate rock formation throughout geological history.

Microbially Catalyzed Biomaterials for Bone Regeneration

Bone is a complex mineralized tissue composed of various organic (proteins, cells) and inorganic (hydroxyapatite, calcium carbonate) substances with micro/nanoscale structures. To improve interfacial bioactivity of bone-implanted biomaterials, extensive efforts are being made to fabricate favorable biointerface via surface modification. Inspired by microbially catalyzed mineralization, a novel concept to biologically synthesize the micro/nanostructures on bioceramics, microbial-assisted catalysis, is presented. It involves three processes: bacterial adhesion on biomaterials, production of CO₃ ^2- assisted by bacteria, and nucleation and growth of CaCO₃ nanocrystals on the surface of bioceramics. The microbially catalyzed biominerals exhibit relatively uniform micro/nanostructures on the surface of both 2D and 3D α-CaSiO₃ bioceramics. The topographic and chemical cues of the grown micro/nanostructures present excellent in vitro and in vivo bone-forming bioactivity. The underlying mechanism is closely related to the activation of multiple biological processes associated with bone regeneration. The study offers a microbially catalytic concept and strategy of fabricating micro/nanostructured biomaterials for tissue regeneration.

Customized materials-assisted microorganisms in tumor therapeutics

Microorganisms have been extensively applied as active biotherapeutic agents or drug delivery vehicles for antitumor treatment because of their unparalleled bio-functionalities. Taking advantage of the living attributes of microorganisms, a new avenue has been opened in anticancer research. The integration of customized functional materials with living microorganisms has demonstrated unprecedented potential in solving existing questions and even conferring microorganisms with updated antitumor abilities and has also provided an innovative train of thought for enhancing the efficacy of microorganism-based tumor therapy. In this review, we have summarized the emerging development of customized materials-assisted microorganisms (MAMO) (including bacteria, viruses, fungi, microalgae, as well as their components) in tumor therapeutics with an emphasis on the rational utilization of chosen microorganisms and tailored materials, the ingenious design of biohybrid systems, and the efficacious antitumor mechanisms. The future perspectives and challenges in this field are also discussed.

Remediation of soil cadmium pollution by biomineralization using microbial-induced precipitation: a review

In recent years, with industrial pollution and the application of agricultural fertilizers with high cadmium (Cd) content, soil Cd pollution has become increasingly serious. A large amount of Cd is discharged into the environment, greatly endangering the stability of the ecological environment and human health. The use of microorganisms to induce Cd precipitation and mineralization is an important bioremediation method. Itis highly efficient, has a low cost, enables environmental protection, and convenient to operate. This article summarizes the pollution status, pollution source, biological toxicity and existing forms of Cd, as well as the biomineralization mechanism of microbial induced Cd(II) precipitation, mainly including microbial-induced carbonate precipitation, microbial-induced phosphate precipitation and microbial-induced sulfide precipitation. Factors affecting the bioremediation of Cd, such as pH, coexisting ions, and temperature, are introduced. Finally, the key points and difficulties of future microbe-induced Cd(II) biomineralization research are highlighted, providing a scientific basis and theoretical guidance for the application of microbe-induced Cd(II) immobilization in soil.

Acridine-Based Covalent Organic Framework Photosensitizer with Broad-Spectrum Light Absorption for Antibacterial Photocatalytic Therapy

Antibiotic resistance is considered as one of the serious public health issues. Antibacterial photocatalytic therapy, a clinically proven antibacterial therapy, is gaining increasing attention in recent years owing to its high efficacy. Here, an acridine-based covalent organic framework (COF) photosensitizer, named TPDA, with multiple active sites is synthesized via Schiff base condensation between 2,4,6-triformylphloroglucinol (TFP) and 3,6-diaminoacridine (DAA). Owing to the increased conjugation effect of the COF skeleton and outstanding light harvesting ability of DAA, TPDA exhibits a narrow optical band gap (1.6 eV), enhancing light energy transformation and conferring a wide optical absorption spectrum (intensity arbitrary unit > 0.8) ranging from the UV to near-infrared region. Moreover, TPDA shows high antibacterial activities against both gram-negative and gram-positive bacteria within a short time (10 min) of light irradiation and is found to efficiently protect fish from skin infections. Molecular dynamics simulation data show that the introduction of DAA and TFP facilitates the interaction between TPDA and bacteria and is conducive to reactive oxygen species migration, which further improves the antimicrobial performance. These findings indicate the potential of TPDA as a novel photosensitive material for photodynamic therapy.

Microbially induced calcium precipitation based simultaneous removal of fluoride, nitrate, and calcium by Pseudomonas sp. WZ39: Mechanisms and nucleation pathways

A simultaneous denitrifying and mineralizing bacterium, Pseudomonas sp. WZ39 was isolated for fluoride (F^-), nitrate (NO₃^--N), and calcium (Ca²⁺) removal. Strain WZ39 exhibited a remarkable defluoridation efficiency of 87.49% under a pH of 6.90, F^- and Ca²⁺ concentration of 1.99 and 201.88 mg L^-1, respectively. EEM, SEM-EDS, XRD, and FTIR analyses elucidated the chemical adsorption and co-precipitation with calcium salt contributed to the removal of F^-. The mechanisms of biomineralization were also investigated by determining the role of bound and unbound extracellular polymeric substances (EPS), cell wall, and calcium channel in nucleation. The results showed that bacteria can promote nucleation on the templates of cell walls or EPS through the electrostatic effect. The presence of the calcium channel blocker inhibited the transport of intracellular Ca²⁺ to the extracellular environment. The outcome of the present research can provide a theoretical basis for the understanding of MICP phenomenon and the efficient treatment of F^- containing groundwater.

Facet Selectivity Guided Assembly of Nanoarchitectures onto Two-Dimensional Metal-Organic Framework Nanosheets

Facet-selective nanostructures in living systems usually exhibit outstanding optical and enzymatic properties, playing important roles in photonics, matter exchange, and biocatalysis. Bioinspired construction of facet-selective nanostructures offers great opportunities for sophisticated nanomaterials, but remains a formidable task. We have developed a macromolecule-mediated strategy for the assembly of upconversion nanoparticles (UCNPs)/two-dimensional metal-organic frameworks (2DMOFs) heterostructures with facet selectivity. Both experimental and theoretical results demonstrate that polyvinylpyrrolidone (PVP) can be utilized as an interface-selective mediator to further promote the facet-selective assembly of MOFs onto the surface of UCNPs. The UCNPs/2DMOFs nanostructures with facet selectivity display specific optical properties and show great advantages in anti-counterfeiting. Our demonstration of UCNPs/2DMOFs provides a vivid example for the controlled fabrication of facet-selective nanostructures and can promote the development of advanced functional materials for applications in biosensing, energy conversion, and information assurance.

A Survey on Analytical Methods for the Characterization of Green Synthesized Nanomaterials

Nowadays, nanotechnologies are well established and the uses of a great variety of nanomaterials show exponential growth. The development of green synthesis procedures experienced a great development thanks to the contribution of researchers of diverse origins. The versatility of green chemistry allows producing a wide range of organic and inorganic nanomaterials with numerous promising applications. In all cases, it is of paramount importance to carefully characterize the resulting nanomaterials because their properties will determine their correct performance to accomplish the function to which they were synthesized or even their detrimental effects like nanotoxicological behavior. This review provides an overview of frequently employed characterization methods and their applications for green synthesized nanomaterials. However, while several different nanoscale materials and their associated green construction methodology are being developed, other important techniques would be extensively incorporated into this field soon. The aim is to encourage researchers in the field to employ a variety of these techniques for achieving an exhaustive characterization of new nanomaterials and for contributing to the development of validated green synthesis procedures.