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This study has thoroughly uncovered the characteristics of the marine euphotic zone system in the Beibu Gulf, featuring adjacent semiconducting minerals and electrochemically active microbes, via mineralogical characterization, photoelectrochemical measurements, and microbiological analysis techniques. Notably, results of Raman and ESEM with EDS indicated that anatase, the semiconducting mineral with prominent photocatalytic performance, exists in large quantities in the Beibu Gulf. Photoelectrochemical measurements tested photoelectric response and redox activity of suspended particulate minerals, demonstrating the suspended particulates dominated by titanium and iron oxide semiconducting minerals presented excellent photo-response property and distinct photoelectric catalytic potential under visible light irradiation. Its significant property of photoelectric response with 110.483% increment ratio of the average photocurrent density relative to the dark current density. 16S amplicon sequence analysis revealed that the euphotic zone was dominated by Proteobacteria, Actinobacteria, and Cyanobacteria at the phylum level, and by Synechococcus CC9902, Cyanobium PCC-6307 and unclassified Ilumatobacteraceae at the genus level. Halomonas (0.2–1.2%), Vibrio (0.7–1.8%), and Nautella (0.1–1.1%), closely related to semiconducting minerals reduction reaction, were also presented in YL and RGS samples of the Beibu Gulf. This work firstly revealed that the neglected characteristics of the marine euphotic zone system in the Beibu Gulf of the South China Sea, which is an important natural ecosystem for microorganisms to uptake energy sources. It will provide a new perspective for further research on novel ways for microorganisms to acquire energy sources through semiconducting minerals in the marine euphotic zone system. [ABSTRACT FROM AUTHOR]

Submarine volcanos are the most active areas in the deep sea, but the environmental consequences of frequent volcanic activity on the geophysical fields and biogeochemical processes near hydrothermal chimneys have not been fully understood yet. In particular, how continuous high‐flux thermal energy, the most typical form of energy in active submarine volcanic systems, affects electron transport and geoelectric field remains unknown. This study provides the first evidence that thermal energy can be efficiently converted to electrical energy at an extremely small spatial scale of the submarine black chimneys. The Seebeck coefficient of sulfide chimneys can reach more than 200 μV/K, with high electrical conductivity of 104 S/m and low thermal conductivity of 1.0 W/(m·K) within 300–700 K. A maximal potential gradient of 300 mV/cm under a temperature difference of 300–700 K can be generated by the thermoelectric conversion of sulfide chimneys, with a maximum energy converting efficiency up to 1%. The thermoelectric conversion effect of a global‐scale submarine volcanos could enable electroactive bacteria to fix appromaxiately 105–106 tons of carbon per year. In addition, the thermal‐electrochemical experiments indicated sulfides underwent rapid oxidation under thermoelectric effects, which may help explain the intense oxidative weathering of sulfides in some anoxic deep‐sea hydrothermal zones. Plain Language Summary: Hydrothermal vents are the most active areas for energy and material exchange in the submarine volcanic systems. The conversion of chemical and biomass energy has been considered as the major driving force for biogeochemical processes in hydrothermal vents, while the primary thermal energy has rarely been a concern. This study revealed that hydrothermal black chimneys could achieve stable thermoelectric conversion with a maximum energy conversion efficiency of 1%. The thermoelectric transport performance of sulfides is mainly influenced by crystal structure, chemical composition and substituting ions. Both the generation of natural electric field and the growth and metabolism of electroactive microorganisms in deep sea are clolsely related to the thermoelectric effects of sulfides. The rapid oxidation of sulfides under a thermoelectric potential well explains the intense weathering of minerals in anoxic seafloor regions. Key Points: Proposing a geoelectric mechanism caused by thermoelectric effects of sulfides in submarine volcanic systemsBuilding a quantitative model to estimate the efficiency of thermoelectric conversion and carbon fixationExplaining rapid oxidative weathering of hydrothermal vent sulfides by thermoelectric mechanism [ABSTRACT FROM AUTHOR]

Microbially induced formation and transformation of clay minerals are known to be ubiquitous in nature. This work investigated the smectite-to-kaolinite transformation by Bacillus mucilaginosus, a kind of silicate-weathering bacterium. Results showed that the microbe-smectite system doubled protein production compared with the abiotic controls and enhanced dissolved 1.6% of total Si and 0.9% of total Al from smectite after the 25 days experiment. The formation of kaolinite was verified through its distinguished d(001)-spacing of 0.710 nm revealed by synchrotron radiation X-ray difrac-tion (SR-XRD) and high-resolution transmission electron microscope (HR-TEM). HR-TEM analysis indicated some mixed layers of smectite and kaolinite appeared in the form of a super-lattice structure. Moreover, the compositional and morphological changes of the solids suggested the emergence of kaolinite was associated with the formation of amorphous SiO2 and fragmented clay particles with lower Si/Al ratio and exposed crystal edge. Based on the detection of –C=O species on the smectite surface and the decrease of pH from 8.5 to 6.5, we inferred the organic ligands secreted by Bacillus mucilaginosus complexed with cations, especially for Si, which stripped the tetrahedral sheets and promoted the kaolinization of smectite. To our knowledge, this is the first report of microbially induced smectite-to-kaolinite transformation under ambient conditions in a highly-efficient way. This work could shed light on a novel pathway of microbe-promoted weathering of smectite to kaolinite at the Earth surface conditions. Such a robust and eficient transformation from expansive smectite to non-expansive clays as kaolinite may be of great potential in enhancing oil recovery in reservoirs. [ABSTRACT FROM AUTHOR]

Dolomite exhibits a wide distribution in geological strata. The metabolic activities of microorganisms in marine sediments play a crucial role in the formation of dolomite. Semiconducting minerals, such as hematite, goethite, and rutile, generate photoelectrons when exposed to sunlight, which can impact the community structure and metabolic activities of microorganisms. In this study, a simulated photoelectron system was conducted to investigate the response of the microbial community, as well as the regulation of sulfate reduction, to photoelectrons using high-throughput sequencing of the 16S rRNA gene. The regulatory effect of semiconducting mineral photoelectrons on the induction of carbonate precipitation by sulfate-reducing bacteria was explored. X-ray diffraction and Raman spectroscopy were used to characterize carbonate precipitation. During cultivation, the pH values of the system increased from 8.0 to approximately 8.5 and the rate of sulfate reduction was significantly enhanced under the influence of simulated photoelectrons. The alpha diversity of the microbial community decreased, and the semiconducting mineral photoelectronic system had a promoting effect on the enrichment of sulfate-reducing bacteria, mainly Desulfovibrio. Under the regulation of photoelectrons, sulfate-reducing bacteria can effectively oxidize organic matter and reduce sulfate in the environment, and proto-dolomite can be formed at a low Mg/Ca ratio. This process has important implications for carbon and sulfur element cycling in estuarine and oceanic photic zones, and provides a new explanation for the formation of large amounts of dolomite in geological history. [ABSTRACT FROM AUTHOR]

In the estuary and nearshore environments, suspended particulate matter (SPM) plays a particularly important role. This article presents a study on the suspended particulate matter and microbial communities in the euphotic zone of China's nearshore and estuarine regions. The study used various analytical techniques, including ICP-OES, SR-XRD, confocal Raman microscopy, ESEM, and EDX, to investigate the spatial distribution and elemental and mineral compositions of the suspended particulate matters. The study found that semiconducting minerals, such as iron oxide, sulfide minerals (hematite, goethite, and pyrrhotite), and titanium oxide minerals (rutile and anatase), were widely present in the suspended particulate matter. This discovery highlights the photochemical activity of suspended particulate matter in the euphotic zone. Furthermore, a correlation analysis of microbial communities revealed that the content of suspended particulate matter was positively correlated with denitrifying bacteria and metal-reducing bacteria in seawater. This study provides valuable insight into the ecosystem dynamics and biogeochemical cycling of estuaries and coastal seas, which are critical for sustaining the biodiversity and productivity of these ecosystems. [ABSTRACT FROM AUTHOR]

Marine euphotic zone is the pivotal region for interplay of light-mineral–microorganism and elements cycle, in which semiconducting minerals exist widely and iron-bearing goethite is a typical and widespread one. In this work, we have conducted in-depth researches on the effect of ferrous [Fe(II)] ions dissolved by photoreduction of goethite on microbial community structure and diversity. The mineral phase, structure and morphology of synthesized goethite were characterized by Raman, X-ray diffraction (XRD), energy disperse spectroscopy (EDS), environmental scanning electron microscope (ESEM), and atomic force microscope (AFM). Photoelectrochemical measurements tested photoelectric response and redox activity of goethite, having proved its significant property of photoelectric response with 44.11% increment of the average photocurrent density relative to the dark current density. The photoreduction experiments of goethite were conducted under light condition in simulated seawater. It has suggested the photoreduction of goethite could occur and Fe(III) was reduced to Fe(II). The dissolved Fe(II) from the photoreduction of goethite under light condition was nearly 11 times than that group without light after a 10-day reaction. Furthermore, results of microbial community sequencing analysis indicated that dissolved Fe(II) could affect the structure and regulate the decrease of microbial community diversity. The emergence of dominant bacteria associated with iron oxidation and transport protein has suggested their obvious selectivity and adaptability in the environment with adding dissolved Fe(II). This work revealed the photoreduction process of semiconducting goethite was remarkable, giving rise to a non-negligible dissolved Fe(II) and its selective effect on the structure, diversity, as well as the function of microbial community. This light-induced interaction between minerals and microorganisms may also further regulate correlative metabolic pathways of carbon cycle in the marine euphotic zone. [ABSTRACT FROM AUTHOR]

Based on the most active hydrosphere on the earth, the interplay between adjacent semiconducting minerals and electrochemically active microorganisms was scientifically researched in the marine euphotic zone of the Yellow Sea, China. Fe and Ti were found in suspended minerals by ICP-MS and EDS, probing the element composition of suspended minerals from macro to micro. Moreover, SR-XRD and Raman indicated that semiconducting minerals of iron and titanium metal oxide in situ such as anatase, rutile, brookite, and goethite consisted in suspended minerals, notably, which retained prominent photo-response property and distinct photoelectric catalytic potential under visible light. 16S rRNA gene systematically emerged that electrochemically active microorganisms, such as Pseudomonas and Paraclostridium, were pivotal in the solution and preponderant on the electrode respectively after a period of cultivation. Whereupon a dual-chamber reactor was established to probe into the mechanism of redox reaction and electron transfer process between microorganisms and suspended minerals. Importantly, compared with a graphite electrode, the maximum power density of the reaction was 2.78 times with the increase of suspended minerals as the electron acceptor under dark conditions, as well as 236.53% promotion with visible light. Experiments gave an index that semiconducting minerals could interact with electroactive microorganisms, effectively promoting the process of extracellular electron transfer in the euphotic zone, which will make a foundation for further research on electron energy transfer based on the interactions of semiconducting minerals and electrochemically active microorganisms, as well as the regulation mechanism of elements cycling. [ABSTRACT FROM AUTHOR]

The photoelectrochemical characteristic of semiconducting minerals plays an imperative role in supporting the growth of many electroactive microorganisms. In order to study the effects of photoelectrons triggered from semiconducting mineral by solar energy on the marine microbial growth, metabolism, and community structure, a dual-chamber electrochemical system was established by incubating seawater microbial community with varying simulated electrochemical conditions. The absolute quantifications of 16S rRNA and 18S rRNA genes suggested that photoelectrons could support the growth and reproduction of bacteria with an increase of two magnitudes from 1.34 ± 0.76 × 1012 to 1.41 ± 0.93 × 1014, and archaea with a slight increase from 0.50–8.74 × 1011 to 2.37–14.80 × 1011, whereas not for the growth of eukaryote in consideration of the complicated regulating mechanism of eukaryotic cells. The bacterial and archaeal communities were shaped by the supplement of photoelectron, also not for the eukaryotic community. Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria accounted for over 80% of the total bacterial community. Photoelectrons with appropriate energy could stimulate the diversity and maintain the community structure of bacteria and archaea while lower or higher electric potential caused lower diversity and more divergent microbial assemblages. The abundance of genes related to the electron transport chain was significantly higher in photoelectron regulated setups than that in open circuit ones, indicating that the extracellular photoelectrons experienced the transmembrane transition and entered the bacterial electron transport chain coupling cell anabolism and catabolism. This study proposed the potential impact of photoelectrons produced by semiconducting minerals on marine microorganisms and the putative electron flow under sunlight in the natural environments. [ABSTRACT FROM AUTHOR]

Cs2SnI6‐xBrx (x = 0–6) solid solutions have been synthesized by chemical solid solution reaction in conjunction with sintering under vacuum. The Rietveld refinements of powder X‐ray diffraction (XRD) patterns indicate that all the samples are cubic, with a symmetry of Fm3m. The lattice parameter a decreases linearly as a function of the Br content in Cs2SnI6‐xBrx. Raman spectra suggest that the new Raman peaks might derive from the short‐range ordering of I/Br anions. The UV/Vis reflection spectra reveal a nonlinear trend of energy band gap (Eg) from 1.25 eV to 3.01 eV with increasing Br content. Hence the wide range of Eg of Cs2SnI6‐xBrx solid solutions are capable to overlay almost the entire visual spectrum. Thermogravimetric analysis (TGA) results suggest that the thermal stability of Cs2SnI6‐xBrx increases gradually with increasing Br content. Cs2SnI6‐xBrx with the fine thermal stability and tunable Eg indicate high potential in the applications of solar cell devices. [ABSTRACT FROM AUTHOR]

Rock varnish is a thin coating enriched with manganese (Mn) and iron (Fe) oxides. The mineral composition and formation of rock varnish elicit considerable attention from geologists and microbiologists. However, limited research has been devoted to the semiconducting properties of these Fe/Mn oxides in varnish and relatively little attention is paid to the mineral–microbe interaction under sunlight. In this study, the mineral composition and the bacterial communities on varnish from the Gobi Desert in Xinjiang, China were analyzed. Results of principal components analysis and t -test indicated that more electroactive genera such as Acinetobacter , Staphylococcus , Dietzia , and Pseudomonas gathered on varnish bacterial communities than on substrate rock and surrounding soils. We then explored the culture of varnish, substrate and soil samples in media and the extracellular electron transfer (EET) between bacterial communities and mineral electrodes under light/dark conditions for the first time. Orthogonal electrochemical experiments demonstrated that the most remarkable photocurrent density of 6.1 ± 0.4 μA/cm2 was observed between varnish electrode and varnish microflora. Finally, based on Raman and 16S rRNA gene–sequencing results, coculture system of birnessite and Pseudomonas (the major Mn oxide and a common electroactive bacterium in varnish) was established to study underlying mechanism. A steadily growing photocurrent (205 μA at 100 h) under light was observed with a stable birnessite after 110 h. However, only 47 μA was generated in the dark control and birnessite was reduced to Mn2+ in 13 h, suggesting that birnessite helped deliver electrons instead of serving as an electron acceptor under light. Our study demonstrated that electroactive bacterial communities were positively correlated with Fe/Mn semiconducting minerals in varnish, and diversified EET process occurred on varnish under sunlight. Overall, these phenomena may influence bacterial–community structure in natural environments over time. [ABSTRACT FROM AUTHOR]

The interplay between electrochemically active microorganisms (EAMs) and adjacent minerals universally occurs in natural environments, in which soil is an extremely typical and active one. We stimulated the extracellular electron transfer (EET) process between the bacterial community and birnessite in red soil (collected from Hainan, China) by constructing a microbial fuel cell equipped with synthetic birnessite cathode. Compared to graphite-cathode, the cell voltage of birnessite-cathode was increased by 22% when loading a 1000 Ω-resistance, indicating the EET between microbes and birnessite. Eleven genera of EAMs in red soil were confirmed through 16S rRNA analysis. Neither palpable novel mineral formation nor change of birnessite crystallinity was observed after reaction by Raman and SEM. As oxygen pumped into cathode chamber was the terminal electron acceptor, birnessite principally performed as an intermediate of holistic electron transfer process to favor the cathodic oxygen reduction. [ABSTRACT FROM AUTHOR]

Developing simple and cheap electrocatalysts or photocatalysts for cathodes to increase the oxygen reduction process is a key factor for better utilization of microbial fuel cells (MFCs). Here, we report the investigation of natural wolframite employed as a low-cost cathode photocatalyst to improve the performance of MFCs. The semiconducting wolframite was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The band gap and photo respond activities were determined by UV-vis spectroscopy and linear sweep voltammetry (LSV), respectively. Compared with the normal graphite cathode, when MFCs were equipped with a wolframite-coated cathode, the maximum power density was increased from 41.47 mW·m−2 to 95.51 mW·m−2. Notably, the maximum power density further improved to 135.57 mW·m−2 under light irradiation, which was 2.4 times higher than with a graphite cathode. Our research demonstrated that natural wolframite, a low-cost and abundant natural semiconducting mineral, showed promise as an effective photocathode catalyst which has great potential applications related to utilizing natural minerals in MFCs and for environmental remediation by MFCs in the future. [ABSTRACT FROM AUTHOR]

Nearly all karst stones have partial dark and light color sections under the same condition. In this study, 24662 operational taxonomic units (OTUs) were examined from karst stones surface samples. Dark samples showed higher abundance of 18,115 OTUs (73.5%) and containing clustered bacterial communities, as indicated by the results of principal component and cluster analyses. Additionally, heatmap analysis showed microorganisms distinction between different color samples and 19 genera of electroactive microorganisms gathered in the dark samples. Furthermore, iron manganese oxides were detected as the main mineral composition difference. Notably, dark samples exhibited remarkable photoelectrochemical activity in response to visible light. Under sunlight, both microorganisms and minerals displayed close relationship with extracellular electron transfer process, which enhanced the understanding for microorganism--mineral interactions in natural karst environments. [ABSTRACT FROM AUTHOR]

Biogenic birnessite is the most prevalent form of Mn-oxide in nature and it plays important roles in controlling the mobility of heavy metals such as Cu(ii). This study focuses on the fine mineralogical characteristics of Cu(ii)-incorporated biogenic (bio-) birnessite produced by the Pseudomonas putida strain MnB1, and discusses the structural stability of Cu-binding birnessite. Compared to the structural analog, hexagonal (abio-) birnessite, the X-ray diffraction (XRD) patterns of bio-birnessite showed an enlarged interlayer space from 7.33 to ∼9.17 Å. The reduced in-plane crystallinity and increased lattice parameter b were indicated after Cu(ii) adsorption. The linear combination fitting of the Mn K-edge X-ray absorption near-edge structure (XANES) indicated ∼13% Mn(ii), and only a small amount of Mn(iii) was present. The saturated sorption amount of Cu(ii) was 0.17 and 0.25 mol Cu/mol Mn for bio- and abio-birnessite, respectively. By conducting extended X-ray absorption fine structure (EXAFS) spectroscopic analysis, multiple coordination paths of Cu–Mn ∼2.85 Å, Cu–Cu ∼3.00 Å and Cu–Mn ∼3.43 Å were shown to exist in both bio- and abio-birnessite, showing the diversity of the Cu coordination structure. The fitted coordination numbers for these three paths were much larger (with identical Debye–Waller factors) in bio-birnessite (1.9, 1.9 and 2.5, respectively) compared to abio-birnessite (1.1, 1.1, 1.6), indicating that Cu had more surrounding atoms in bio-birnessite. The results indicate that Cu sorption by vacant sites, i.e. incorporation into the vacancy (INC species) or adsorption on the vacancy (TCS species), was more dominant for bio-birnessite, which may have benefitted from the larger interlayer space for accommodation of the Cu inner-sphere complex and the very low content of structural Mn(iii) competing for vacant sites. In turn, the Cu inner-sphere complex modified both the layer and interlayer structures of bio-birnessite. In abio-birnessite, Cu binds favorably at abundant edge sites as dimers or multinuclear clusters, which contributes to a larger sorption amount. This binding style was depressed in bio-birnessite because the organic ligands released by microbial activity could block the layer edges. Theoretically, the structural stability of Cu clusters at the edges should be weaker than the TCS and INC species. This work also provides insight into the geochemical behaviors of Cu(ii) controlled by widespread biogenic birnessite. [ABSTRACT FROM AUTHOR]

The structural transformation of cesium lead iodine (CsPbI3) has been investigated in diamond anvil cells up to ∼15 GPa at room temperature by employing synchrotron radiation X-ray diffraction and Raman spectroscopy. One reversible transformation from orthorhombic (Pnma) to monoclinic (P21/m) phase has been observed at 3.9 GPa. Isothermal pressure–volume relationship of orthorhombic CsPbI3is well fitted by the third-order Birch–Murnaghan equation of state withK0= 14(3) GPa,K′0= 6(2) andV0= 891(7) Å3. The ultralow value of bulk modulusK0demonstrates the high compressible nature of CsPbI3, similar to those of organic–inorganic metal halide perovskites. The present results provide essential information on the intrinsic properties and stability of CsPbI3, which may be applied in photovoltaic devices. [ABSTRACT FROM AUTHOR]

Birnessite films on fluorine-doped tin oxide (FTO) coated glass were prepared by cathodic reduction of aqueous KMnO 4 . The deposited birnessite films were characterized with X-ray diffraction, Raman spectroscopy, scanning electron microscopy and atomic force microscopy. The photoelectrochemical activity of birnessite films was investigated and a remarkable photocurrent in response to visible light was observed in the presence of phenol, resulting from localized manganese d – d transitions. Based on this result, the photoelectrocatalytic oxidation of phenol was investigated. Compared with phenol degradation by the electrochemical oxidation process or photocatalysis separately, a synergetic photoelectrocatalytic degradation effect was observed in the presence of the birnessite film coated FTO electrode. Photoelectrocatalytic degradation ratios were influenced by film thickness and initial phenol concentrations. Phenol degradation with the thinnest birnessite film and initial phenol concentration of 10 mg/L showed the highest efficiency of 91.4% after 8 hr. Meanwhile, the kinetics of phenol removal was fit well by the pseudofirst-order kinetic model. [ABSTRACT FROM AUTHOR]

Bioleaching of sulfide minerals at neutral pH has been rarely reported. In this study, a bacterium, Bacillus megaterium QM B1551, was isolated from Jinchuan sulfide tailings and used to leach a complex sulfide flotation concentrate for the extraction of Co2+, Ni2C and Cu2+ at near neutral pH. A total of 38.2% Co, 44.7% Ni and 3.6% Cu were extracted from the sulfide concentrate in 5 days with an initial pH of 6. An enhanced Co2C, Ni2C and Cu2C extraction extent was achieved by first bioleaching the concentrate with Bacillus megaterium QM B1551 at 35°C and then followed by chemical leaching with 4 M sulfuric acid at 90°C. As a result, a total of 60.7% Co2+, 76.3% Ni2+ and 39.8% Cu2+ were extracted. On an industrial scale, the profits from the metal recovery by such a combined leaching procedure are optimum if considering the cost-benefit ratio. [ABSTRACT FROM AUTHOR]