Search Results (181)

The genus Streptomyces is a major driver of the soil microbial community. These filamentous, exospore-producing bacteria are copious producers of bioactive compounds that are not only used as antibiotics but also affect the soil microbial community in composition and activity. With an average of about 30 different bioactive compounds produced per species, the bacteria use complex regulatory mechanisms that respond to environmental as well as community signals. Understanding these mechanisms will be useful in harnessing the full potential of Streptomyces in biotechnology, e.g., to tackle the antibiotic resistance crisis. This includes the discovery of new antibiotics that are not produced under standard laboratory conditions, as well as being able to modulate the signaling cascades to produce other biotechnology products. As an example, the genus Streptomyces, as one of the few bacterial and archaeal taxa, produces cobalamin de novo through both the oxic and anoxic biosynthesis pathways. This feature adds to the importance of this genus for the soil microbial communities, as well as for applications in fermentation. Full article

Methanogens, or methanogenic archaea (MA), are among the most ancient and widely distributed microorganisms, characterized by a unique metabolism that generates methane (CH₄) as the terminal product of anaerobic respiration. Their ability to grow and/or survive across a wide range of environmental conditions has made methanogens key contributors to biogeochemical cycles throughout most of Earth’s history. Most importantly, these oxygen-sensitive microorganisms have regulated the climate since the early Archean and impacted biogeochemical cycles throughout Earth’s history by producing the potent greenhouse gas, CH₄, while consuming H₂, CO₂, and small organic molecules. Hence, methanogens are attributed a key role in the start and end of several Proterozoic glaciations and mass extinction events. Their specific roles in the long-term carbon cycle that focus on CH₄ production are well-established, but, in contrast, only very few studies report on interactions with CaCO₃ and long-term carbon storage. Methanogens evolved early during Earth’s history, likely during the Archaean Eon, in layered benthic microbial communities called microbial mats. When lithified, these mats form microbialites that represent some of the earliest evidence of life in the fossil record, dating back >3.5 Gy. Methanogens are an integral part of contemporary microbial mats and have been identified both in the anoxic and oxic zones of these sedimentary ecosystems; however, their adaptations to apparently unfavorable oxic conditions and their role in the precipitation of carbonate in mats are unclear. In addition to an important role in the evolution of our planet by producing CH₄, methanogens may also produce a biosignature that could be relevant for astrobiology research. This review will discuss the diversity, physiology, and ecology of methanogens in detail to clarify their role in some of the major biogeochemical processes and ecological climatic events through the fluctuating environmental conditions on Earth through geologic time. Full article

To clarify the organic matter enrichment regularity of Permian shales in the Kaijiang–Liangping Trough, as well as the differential characteristics of their reservoir lithology, mineral assemblage, and nanopore structure—and thereby provide a geological basis for the exploration and development of Permian marine shales in the eastern Sichuan Basin—core samples from different depths of the Wujiaping Formation and Dalong Formation in Well DY-1H were analyzed using a series of micro–nano technical research methods, including whole-rock X-ray diffraction, major/trace element analysis, conventional porosity-permeability measurement, high-pressure mercury intrusion porosimetry, nitrogen adsorption, and field emission scanning electron microscopy. Research finds that the Dalong Formation shale contains Type I organic matter with high abundance, whereas the Wujiaping Formation shale is dominated by Type II₂ organic matter. The Wujiaping Formation experienced stronger terrigenous input and higher weathering intensity, while the Dalong Formation was deposited under persistently anoxic conditions, in contrast to the frequent oxic–anoxic alternations in the Wujiaping Formation. Paleoproductivity indicators suggest higher productivity in the Dalong Formation than in the Wujiaping Formation. Mo/TOC ratios below 4.5 indicate deposition in a strongly restricted water body. Enrichment factors of multiple elements further support the enhanced paleoproductivity of the Dalong Formation. The Dalong Formation shale has higher contents of quartz and carbonate minerals, while the Wujiaping Formation shale has a higher content of clay minerals. The Wujiaping Formation shale is more developed with inorganic micropores, whereas the Dalong Formation shale is characterized by more developed organic nanopores. During the sedimentary period of the Dalong Formation shale, the paleoproductivity was high, the sedimentary waterbody had high reducibility and restriction, and the reservoir was well-developed with nanopores. The Dalong Formation is a more favorable interval for Permian shale gas exploration and development in the Kaijiang–Liangping Trough. Full article

Saline and highly alkaline soda lakes are often characterized by a persistent nitrogen loss and high sulfide levels. Cyanobacteria are key aerobic diazotrophs in soda lakes, where light-dependent nitrogen fixation (NF) is crucial for sustaining ecosystem functioning. While sulfide is a well-known inhibitor of oxygenic photosynthesis, some cyanobacteria may tolerate it and utilize it via anoxygenic photosynthesis. In this study, we investigated the NF and anoxygenic photosynthesis in the genus Sodalinema, including non-heterocystous cyanobacteria widely distributed in soda and saline environments around the world and possessing an anaerobe-like nitrogenase. Our data suggest that their nif-operon could have been more likely acquired in soda or saline–alkaline lakes from natronophilic sulfate-reducing bacteria of the family Desulfonatronovibrionaceae than in the marine environment. It was shown that Sodalinema sp. P-1104, isolated from a southwestern Siberian soda lake, is capable of NF only in a light/dark switching mode, both in oxic and anoxic conditions. Sulfide did not suppress photosynthesis and stimulated NF up to threefold in oxygenic conditions. Anaerobic NF was obligately sulfide-dependent and supported by anoxygenic photosynthesis. However, removal of photosynthetic oxygen due to the high reducing potential of sulfide stimulated NF to a greater extent than does the use of sulfide through anoxygenic photosynthesis. Full article

Inatlar limestone, which is dated to the Middle Jurassic–Lower Cretaceous, is exposed between the villages of Kabulbaba and Söğütalan in the Mustafakemalpaşa district of Bursa, Turkey. This study investigates its mineralogical, petrographic, and geochemical characteristics, focusing on major, trace, and rare earth element (REEs) compositions to interpret the depositional environment, paleoenvironmental conditions, and diagenetic processes. Petrographic analysis identified four main limestone types: siliceous, micritic, fossiliferous, and dolomitic. REEs geochemistry indicates enrichment in heavy REEs (HREEs), depletion in light REEs (LREEs), and characteristic anomalies with negative Ce and Eu and positive La, suggesting an open marine depositional environment and early diagenesis. Trace element data point to deposition in settings ranging from continental margins to open marine environments. Ni and V concentrations reflect a spectrum of depositional conditions, including terrestrial, transitional (oxic–dysoxic), and marine anoxic settings. Z values support the theory that the limestones have a marine origin. δ¹³C and δ¹⁸O isotope values indicate deposition in both hydrothermal and typical marine carbonate environments. Y/Ho and Er/Nd ratios reveal the influence of terrestrial input, as well as diagenetic and detrital material. Furthermore, V/(V + Ni) ratios reflect fluctuating oxic to suboxic/anoxic conditions, while Ni/Co ratios indicate predominantly euxinic and, to a lesser extent, anoxic conditions. Altogether, these geochemical signatures suggest that the Inatlar limestone was deposited in a dynamic marine system characterized by variable redox states and salinity fluctuations. Full article

Late-Archean seawater functioned as a vast, redox-tuned colloidal system for which its kinetics were largely governed by the surface chemistry of silica–iron nanoparticles. By reproducing Archean seawater (≈0.7 M ionic strength, 25 °C) in laboratory anoxic-to-mildly oxic reactors, the ζ potential (zeta-potential(ζ)) of silica–iron nanoparticles was investigated, and we tracked how transient O₂ pulses (≤9 mg L⁻¹) regulated it. The zeta (ζ) potential was applied as the key diagnostic parameter to quantify both the sign of the ζ potential and the colloidal stability of simulated silica–iron particles in dispersion. Under strictly anoxic conditions, silica colloids (SiO₂(aq)) exhibit a persistently negative ζ potential (ζ ≈ −25 mV) in the simulated seawater (pH 6.5), arising from deprotonated silanol groups (≡Si–O⁻). Upon the addition of Fe²⁺, the inner-sphere complexation of ferrous ions on SiO₂ colloids partially replaces ≡Si–O⁻ with ≡Si–O–Fe⁺/≡Si–O–Fe–OH sites; the net negative charge density at the outer Stern plane nevertheless increases, and the ζ potential shifts from −25 mV to −30 mV. As the simulated seawater was oxygenated, the dissolved and surface-bound Fe²⁺ ions were oxidized to Fe³⁺, causing the ζ potential to exceed −30 mV. This study demonstrates that Fe²⁺–silica interactions generate electrostatic destabilization, suspending micron-scale aggregates and thus modulating the solubility and speciation of SiO₂ in early oceans. Also, transient micro-oxic pulses are shown to shift silica–iron colloids between metastable aggregation and dispersion by modulating their ζ potential. Subsequently, AFM and TEM were used to characterize the morphological changes in the colloidal particles from the liquid state to the dry state. Furthermore, infrared and XPS analyses were conducted on the colloidal samples. These findings provide certain reference significance for reconstructing the chemical evolution process of seawater in the Late-Archean period and for understanding the factors influencing the silicon–iron cycle of seawater in the Late-Archean era. Full article

Forest–wetland ecotones are transitional ecosystems characterized by pronounced hydrological and biogeochemical heterogeneity, yet the microbial mechanisms regulating nutrient cycling in these zones remain insufficiently understood. This study investigated how vegetation transitions across a forest–wetland ecotone in the black-soil region of Northeast China shape soil microbial communities and nitrogen–cycling functions. Soils were collected from four vegetation types: mixed forest (MF), coniferous forest (CF), wetland edge (WE), and natural wetland (NW). Quantitative PCR was used to quantify key nitrogen–cycling functional genes (nifH, amoA, amoB, norB, nosZ), and PICRUSt2 was applied to predict microbial functional potentials. Forest soils (MF and CF) exhibited higher microbial diversity, stronger network connectivity, and greater abundances of nifH and amoA, indicating enhanced nitrogen fixation and nitrification under oxic conditions. In contrast, wetland soils harbored denitrification-enriched communities with higher norB and nosZ abundances but lower diversity. The WE vegetation type acted as a functional hotspot where alternating oxic–anoxic conditions facilitated the coexistence of nitrifiers and denitrifiers, thereby enhancing carbon–nitrogen coupling and functional resilience. Redundancy and Mantel analyses identified soil organic carbon, total nitrogen, water content, and enzyme activities as major environmental drivers of microbial structural and functional variation. This study reveals that vegetation transitions reorganize microbial community assembly and nitrogen-cycling functions through hydrological and biogeochemical heterogeneity, providing mechanistic insights into nutrient turnover and ecological regulation in black-soil ecotones. Full article

Acid mine drainage (AMD) is an environmental concern that needs to be addressed by some mining industries because of its high concentrations of metals and acidity that destroy affected ecosystems. Its formation typically persists beyond the operating life of a mine site. Its management is even more challenging for sites that are abandoned without rehabilitation. In this study, a legacy copper–gold mine located in Sto. Niño, Tublay, Benguet, Philippines, generating a copper- and manganese-rich AMD (Cu, maximum 17.2 mg/L; Mn, maximum 2.90 mg/L) at pH 4.59 (minimum) was investigated. With its remote location inhabited by the indigenous people local community (IPLC), a novel limestone-based hybrid passive treatment system that combines a limestone leach bed (LLB) and a controlled modular packed bed reactor (CMPB) has been developed from the laboratory and successfully deployed in the field while investigating the effective hydraulic retention time (HRT), particle size, and redox conditions (oxic and anoxic) in removing Cu and Mn and increasing pH. Laboratory-scale and pilot-scale systems using simulated and actual AMD, respectively, revealed that a 15 h HRT and both oxic and anoxic conditions were effective in treating the AMD. Considering these results and unsteady conditions of the stream in the legacy mine, a hybrid multi-stage limestone leach bed and packed bed were deployed having variable particle size (5 mm to 100 mm) and HRT. Regular monitoring of the system showed the effective removal of Cu (88.5%) and Mn (66.83%) as well as the increase of pH (6.26), addressing the threat of AMD in the area. Improvement of the lifespan of the system needs to be addressed, as issues of Cu-armoring were observed, resulting in reduced performance over time. Nonetheless, the study presents a novel technique in implementing passive treatment systems beyond the typical treatment trains reported in the literature. Full article

This study investigates the environmental stability of ferronickel slag (FNS) and primary lead slags (GCS and FCS) from historical metallurgical complexes in Greece, in rainwater and seawater media. Leaching experiments revealed that nickel is the most mobile element from FNS (43.5 μg·g⁻¹ in seawater after 90 days). Chromium release, on the other hand, is very limited, not exceeding 0.04 μg·g⁻¹. In lead slags, zinc and lead exhibit significant leaching (up to 650 and 230 μg·g⁻¹, respectively), while arsenic release reaches 22.6 μg·g⁻¹. GCS contains pores primarily in the range of 50–90 Å. The majority of pore volume in FCS is centered around 30 Å. The porosity appears to have a significant effect on the element’s leachability. Pb, Zn, As, Sb, and Cd are released in significantly higher amounts from the finely porous FCS compared to GCS. Thermodynamic modeling was used to identify the pollutant speciation in water media in relation to the oxygen concentration. The release of toxic elements such as Cr from FNS and As from lead slags is enhanced under oxic (open-air) conditions. Therefore, their land disposal poses a greater environmental threat compared to sea disposal, where anoxic conditions prevail. Full article

In the context of global carbon neutrality, municipal wastewater treatment plants (WWTPs), as key sources of greenhouse gas emissions, urgently require quantification of carbon emissions and implementation of mitigation strategies. This study establishes a life-cycle carbon footprint model encompassing the stages of pretreatment, biological treatment (AAO process), and sludge treatment, with integrated consideration of municipal sewer networks. Key findings reveal the following: The biological treatment stage contributes 68.14% of total carbon emissions. N₂O (nitrous oxide), due to its high global warming potential (GWP), is the primary source of direct emissions (0.333 kg CO₂eq/m³). In the pretreatment stage, 80.4% of carbon emissions originate from the electricity consumption of sewage lifting pump stations (0.030 kg CO₂eq/m³). During the sludge treatment stage, carbon emissions are concentrated in residual sludge lifting (0.0086 kg CO₂eq/m³) and sludge dewatering/pressing (0.0088 kg CO₂eq/m³). Accordingly, this study proposes the following mitigation strategies: novel nitrogen removal processes should be implemented to optimize aeration control and enhance methane (CH₄) recovery during the biological period, and variable frequency drive (VFD) pumps and IoT (Internet of Things) technologies should be employed to reduce energy consumption during the pretreatment period, and during the sludge treatment period, low-carbon dewatering technologies should be adopted. This work provides a theoretical foundation for process-specific carbon management in WWTPs and facilitates the synergistic advancement of environmental stewardship and dual-carbon objectives through technology–system integration. Full article

Multiple ironstone beds formed during the Callovian-Oxfordian times as a consequence of intense continental weathering, upwelling, and hydrothermal activity. This study examines the compositional differences between core and rim, and the origin of iron ooids along the northwestern margin of the Neo-Tethys Ocean to highlight sea-level fluctuations, redox conditions, and elemental influx. An integrated sedimentological study, including petrography, mineralogy, micro-texture, and mineral chemistry, was carried out to explain the origin and implications of ironstones. The ~14 m thick Callovian-Oxfordian, marginal marine deposits in the Kutch Basin, in western India, exhibit iron ooids, predominantly formed in oolitic shoals during transgression, associated with lagoonal siliciclastics. Callovian shoals interbedded with lagoonal facies record minor sea-level fluctuations, whereas the Oxfordian deposit records a major transgression and condensation, resulting in extensive ironstone deposits. The ooid cortices and nuclei exhibit distinctive mineralogy and micro-textures: glauconitic smectite exhibits poorly-developed rosettes, chamosite displays flower-like, and goethite shows rod-like features. Three types of ooids are formed: (i) monomineralic ooids are entirely of chamosite or goethite, (ii) quartz-nucleated ooids, and (iii) composite ooids with either chamosite core and goethite rim, or chamosite core and glauconitic smectite rim. The assemblages within iron ooids reflect variation in depositional redox conditions: glauconitic smectite develops under suboxic lagoonal flank, chamosite forms in anoxic central lagoon, and goethite precipitates on oxic shoals. Full article

Oxygenic and anoxygenic photosynthesis have long been considered defining traits of cyanobacteria. However, whether the important cyanobacterial genus Synechococcus is capable of anoxygenic photosynthesis remains unconfirmed. Here, we report that Synechococcus sp. PCC 7002 is capable of anoxygenic photosynthesis when sulfide (H₂S) is supplied as the sole electron donor. Combining the targeted deletion of the sulfide: quinone oxidoreductase gene (Δsqr) with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) mediated the inhibition of photosystem II. We demonstrated that SQR-mediated H₂S oxidation sustains light-dependent CO₂ fixation in the absence of O₂ evolution. Our genome-wide transcriptomic profiling further revealed that polysulfide (H₂S_n) and hydrogen peroxide (H₂O₂) function as distinct signaling molecules in oxygenic and anoxygenic photosynthesis, modulating central carbon and energy metabolism. In central carbon metabolism, H₂S_n markedly upregulates the expression of key genes, including psbA, petC, rbcL, and rbcS, whereas H₂O₂ downregulates these genes. Within energy metabolism, both molecules converge on oxidative phosphorylation by upregulating genes encoding NADH dehydrogenase and ATP synthase. Furthermore, H₂Sₙ treatment uniquely induces sulfur-assimilation and ROS-detoxifying enzymes, conferring a markedly higher tolerance than H₂O₂. These findings provide direct evidence of anoxygenic photosynthesis in the genus Synechococcus and uncover a dual regulatory network that allows Synechococcus sp. PCC 7002 to balance redox homeostasis under fluctuating oxic/anoxic conditions. Full article

The Dongping manganese (Mn) deposit, located within the Lower Triassic Shipao Formation of the Youjiang Basin, is one of South China’s most significant sedimentary Mn carbonate ore deposits. To resolve longstanding debates over its metallogenic pathway, we conducted integrated sedimentological, mineralogical, and geochemical analyses on three drill cores (ZK5101, ZK0301, and ZK1205) spanning the Mn ore body. X-ray diffraction and backscatter electron imaging reveal that the ores are dominated by kutnohorite, with subordinate quartz, calcite, dolomite, and minor sulfides. The low enrichment of U/Al, V/Al, and Mo/Al, as well as positive Ce anomalies, consistently suggest that Mn, in the form of oxides, was deposited in an oxic water column. Carbon isotope compositions of Mn carbonate ores (δ¹³C_VPDB: −2.3 to −6.1‰) and their negative correlation with MnO suggest that Mn carbonate, predominantly kutnohorite, show a diagenetic reduction in pre-existing Mn oxides via organic-matter oxidation in anoxic sediments pore waters. Elemental discrimination diagramms (Mn-Fe-(Co+Ni+Cu) × 10 and Co/Zn vs. Co+Cu+Ni) uniformly point to a hydrothermal Mn source. We therefore propose that hydrothermal fluids supplied dissolved Mn²⁺ to an oxic slope-basin setting, precipitating initially as Mn oxides, which were subsequently transformed to Mn carbonates during early diagenesis. This model reconciles both the hydrothermal and sedimentary-diagenetic processes of the Dongping Mn deposit. Full article

Current models of sedimentary environments and organic matter (OM) enrichment for the Lower Cambrian black shales in the Yangtze Platform have not yet incorporated its northern carbonate platform margin where the related research is lacked. This study focuses on the SNZ1 well in the northern carbonate platform margin, utilizing total organic carbon (TOC) content and major and trace element data to reveal the main controlling factors of OM enrichment during the Early Cambrian. The results show that the shale stratum is tentatively ascribed to the Lower Cambrian Stage 3 and that, during its deposition, the redox transitioned from anoxic to suboxic–oxic conditions, the hydrodynamic conditions weakened initially and then strengthened, the primary productivity first increased and then decreased, the paleoclimate shifted from arid–cold to warm–humid conditions, and the terrigenous clastic input gradually diminished. Overall, the OM enrichment is primarily controlled by preservation conditions. By systematically analyzing the data from the intraplatform basin to the deep-sea basin across the Yangtze Block, a model of the sedimentary environments and OM enrichment during the Early Cambrian was suggested. Additionally, this study highlights the intrinsic link between the expansion of oxygenated surface water and the Cambrian explosion. These results provide critical insights for shale gas exploration in this region. Full article

The Anaerobic–Swing Aerobic–Anoxic–Oxic (ASAO) process was developed to tackle problems such as temperature sensitivity during the Anaerobic–Oxic–Anoxic (AOA) process. By introducing a swing zone (S zone) with adjustable dissolved oxygen (DO), during the 112-day experimentation period, the ASAO system achieved removal rates of 88.18% for total inorganic nitrogen (TIN), 78.23% for total phosphorus (TP), and 99.78% for ammonia nitrogen. Intermittent aeration effectively suppressed nitrite-oxidizing bacteria (NOB), and the chemical oxygen demand (COD) removal rate exceeded 90%, with 60% being transformed into internal carbon sources like polyhydroxyalkanoates (PHAs) and glycogen (Gly). The key functional microorganisms encompassed Dechloromonas (denitrifying phosphorus-accumulating bacteria), Candidatus Competibacter, and Thauera, which facilitated simultaneous nitrification–denitrification (SND) and anaerobic ammonium oxidation (ANAMMOX). The enrichment of Candidatus Brocadia further enhanced the ANAMMOX activity. The flexibility of DO control in the swing zone optimized microbial activity and mitigated temperature dependence, thereby verifying the efficacy of the ASAO process in enhancing the removal rates of nutrients and COD in low-C/N wastewater. The intermittent aeration strategy and the continuous low-dissolved-oxygen (DO) operating conditions inhibited the activity of nitrite-oxidizing bacteria (NOB) and accomplished the elimination of NOB. Full article