Microbial Community Activity Research Articles

Strong Effects of Increased Hydrostatic Pressure on Polysaccharide‐Hydrolyzing Enzyme Activities in Coastal Seawater and Sediments

AbstractHeterotrophic microorganisms are responsible for transforming and respiring a substantial fraction of the organic matter produced by phytoplankton in the surface ocean. Much of this organic matter is composed of polysaccharides, high‐molecular weight (HMW) sugars. To initiate degradation of polysaccharides, microorganisms must produce extracellular enzymes of the right structural specificity to hydrolyze these complex structures. To date, most measurements of enzyme activities are made at in situ temperatures, but at atmospheric pressure. However, previous studies have shown that hydrostatic pressure can impact the functionality of enzymes. Since deep sea communities may be seeded by microbes from shallow waters, we aimed to determine if pressure affects the performance of enzymes from coastal waters. To determine the extent to which enzymatic activities of coastal microbial communities are affected by pressure, we quantified the degradation of seven polysaccharides under pressures ranging from 0.1 MPa (atmospheric) to 40 MPa (equivalent to 4,000 m). Enzyme activities of pelagic communities were inhibited with increased pressure, while enzyme activities of benthic microbial communities were more resistant to increased pressure. Addition of HMW organic matter resulted in communities with enzyme activities that were more resistant to increased pressure. However, the freely‐dissolved enzymes (<0.2 μm) produced by these communities were strongly inhibited by increased hydrostatic pressure, suggesting that the pressure‐resistant enzymes were cell‐surface attached. Because pressure inhibition of enzyme activities varied strongly by polysaccharide, we surmise that the structural complexity of a polysaccharide—and therefore the number of distinct enzymes required for hydrolysis—is likely closely associated with pressure inhibition.

Structural and functional responses of soil fungal and bacterial communities to a lithium contamination gradient.

The use of lithium (Li) in decarbonization strategies has positioned it as a central component of modern technological advances, particularly in battery applications. However, the increasing demand for Li has raised concerns about its environmental consequences, which are poorly documented. This study aimed to fill this knowledge gap by examining the impact of Li on soil bacterial/fungal communities. Using a microcosm approach, we explored the impacts of increasing Li concentrations on both microbial community structure and activities. Our results revealed significant changes in bacterial/fungal communities, particularly in the bacterial communities. Most of the indicator species were negatively correlated with the Li gradient, reinforcing the harmful effect of Li. Proteobacteria dominated at low concentrations, whereas Firmicutes were the most abundant at high concentrations. OTUs affiliated with the genus Alicyclobacillus represented >29% of the total affiliated OTUs at the highest Li concentrations. Moreover, Alicyclobacillus fastidiosus showed resilience and specific adaptation to Li. Fungal communities showed less pronounced changes, with Mucoromycota remaining the dominant phylum at all concentrations. Nevertheless, some genera presented correlations with Li concentration, particularly the plant mutualists Leptodontidium, Oidiodendron, and Solicoccozyma. In addition, rapid decreases in several enzymatic activities crucial for the functioning of the carbon, nitrogen and phosphorus cycles were noted. Accordingly, microbial respiration was also impacted by high Li concentrations. Finally, a correlative analysis linked the decreases in enzyme activity to decreases in the abundances of both Proteobacteria and Ascomycota. These results underline the multiple impacts of Li on bacterial/fungal communities, highlighting both structural alterations and changes in microbial activities.

Microphytobenthos spatio-temporal dynamics across an intertidal gradient in a tropical estuary using Sentinel-2 imagery.

Intertidal mudflats are among the most productive coastal ecosystems, largely because of the activity of the photosynthetic microbial community on the sediment surface, known as microphytobenthos (MPB). While the dynamics of MPB have been extensively studied in temperate estuaries, there is limited research in tropical estuaries. To address this knowledge gap, we investigated the spatio-temporal dynamics of MPB in the Nicoya Gulf (Costa Rica), one of the world's most productive tropical estuaries, using Sentinel-2 images at 10m spatial resolution from 2018 to 2022. We used Normalized Difference Vegetation Index (NDVI) values ranging from 0 to 0.4 to monitor MPB cover and growth rates (μNDVI, days-1). Analysis of data using Generalized Additive Models (GAM) showed that up to 62% of the temporal variability in average MPB NDVI, peaking in late wet and early dry seasons (November-December), can be explained by years and months. The high temperatures and irradiance during the dry season (December to April) in the Nicoya estuary may inhibit MPB growth, contrasting with patterns observed in temperate estuaries. We observed higher MPB NDVI in the upper intertidal zone (mean sea level>0.5m) as usually occurs in temperate estuaries. This research highlights the importance of high-resolution satellite imagery for long-term monitoring of MPB dynamics in tropical tidal flats, offering a valuable tool for estimating ecosystem services provided by intertidal MPB, such as primary production, climate regulation, and nutrient cycling on a global scale.

Resilience and response of anaerobic digestion systems to short-term hydraulic loading shocks: Focusing on total and active microbial community dynamics.

Anaerobic digestion is known to be sensitive to operational changes, such as hydraulic loading shock, yet the impact on the microbiome, particularly the active RNA-based community, has not been fully understood. This study aimed to investigate the performance of anaerobic reactors and their microbial communities under short-term hydraulic loading shocks. Using synthetic wastewater, the reactor was subjected to 24-h shocks at three-fold and seven-fold the baseline loading rate, followed by DNA and RNA analyses to assess the system's resiliency and microbial responses. The research focused on shifts in major microbial groups and their functions, paying close attention to the active RNA community during loading shock events to better reflect the system's immediate condition. Findings indicated that although the microbial community structure, particularly among the archaea, was altered, the reactor quickly regained its balance. Differences were observed between DNA and RNA profiles and between regular and shock loadings; however, the alpha diversity and functions of the overall community were sustained. This study offers important insights for the design and operation of wastewater treatment plants, with the goal of achieving stable and efficient anaerobic digestion systems.

Understanding the limitations of substrate degradation in bioelectrochemical systems.

Microbial Fuel Cells (MFCs) are innovative environmental engineering systems that harness the metabolic activities of microbial communities to convert chemical energy in waste into electrical energy. However, MFC performance optimization remains challenging due to limited understanding of microbial metabolic mechanisms, particularly with complex substrates under realistic environmental conditions. This study investigated the effects of substrate complexity (acetate vs. starch) and varying mass transfer (stirred vs. non-stirred) on acclimatization rates, substrate degradation, and microbial community dynamics in air-cathode MFCs. Stirring was critical for acclimating to complex substrates, facilitating electrogenic biofilm formation in starch-fed MFCs, while non-stirred MFCs showed limited performance under these conditions. Non-stirred MFCs, however, outperformed stirred systems in current generation and coulombic efficiency (CE), especially with simple substrates (acetate), achieving 66% CE compared to 38% under stirred conditions, likely due to oxygen intrusion in the stirred systems. Starch-fed MFCs exhibited consistently low CE (19%) across all tested conditions due to electron diversion into volatile fatty acids (VFA). Microbial diversity was higher in acetate-fed MFCs but unaffected by stirring, while starch-fed MFCs developed smaller, more specialized communities. Kinetic analysis identified hydrolysis of complex substrates as the rate-limiting step, with rates an order of magnitude slower than acetate consumption. Combined hydrolysis-fermentation rates were unaffected by stirring, but stirring significantly impacted acetate consumption rates, likely due to oxygen-induced competition between facultative aerobes and electrogenic bacteria. These findings highlight the trade-offs between enhanced substrate availability and oxygen-driven competition in MFCs. For real-world applications, initiating reactors with dynamic stirring to accelerate acclimatization, followed by non-stirred operation, may optimize performance. Integrating MFCs with anaerobic digestion could overcome hydrolysis limitations, enhancing the degradation of complex substrates while improving energy recovery. This study introduces novel strategies to address key challenges in scaling up MFCs for wastewater treatment, bridging the gap between fundamental research and practical applications to advance environmental systems.

Façade eluates affect active and total soil microbiome

The application of biocides in building materials has become a prevalent practice to mitigate the growth of microorganisms such as algae, fungi, and bacteria on the façades. These can leach out from the material and reach the nearby soil environment. This study aimed to characterize the effect of façade eluates generated within different leaching experiments on total and metabolic active soil microbial community composition and functions. Façade eluates were produced by immersion testing DIN EN 16105 and a natural weathering experiment. Afterward, soil microcosms were treated with the respective façade eluate and incubated for 29 days. Subsequently, the active and total soil microbial community compositions were investigated.Fungal internal transcribed spacer region gene and bacterial 16S rRNA gene were sequenced for active (bromodeoxyuridine labeled DNA) microbial community and total community. Façade eluates reduced total bacterial and fungal gene copy numbers. Overall, active bacterial and fungal richness was reduced and altered in community composition in comparison to the total richness and composition, respectively. Façade eluates retrieved of façade samples without biocides did alter the soil microbial communities to the same extent as façade eluates with biocides. Additionally, members of the active microbiome that benefit from the presence of façade eluates and omitted ones could be identified. Our result demonstrated that façade eluates affect active and total soil microbial community composition and function regardless of the leaching procedure and biocides addition.

Tradeoffs among ecosystem services and microbiome impacts associated with two cover crops for cocoa in South Sulawesi, Indonesia

Cover crops could provide numerous benefits on cocoa farms, including promoting nutrient cycling, carbon sequestration, and active soil microbial communities. Despite growing interest in cover crops for cocoa, many knowledge gaps remain, particularly detailed species and management recommendations to maximize ecosystem services and optimize the soil microbiome in different geographies and production contexts. A field experiment was conducted in South Sulawesi, Indonesia to investigate the suitability of two potential cover crops, tropical kudzu (Pueraria javanica) and fodder sweet potato (Ipomoea batatas L. Lam), for cocoa agroforestry systems. Cover crops were terminated after 6 months due to leaf chlorosis and declining yields in 2-year-old cocoa trees, leading to an analysis of tradeoffs among supporting, regulating, and provisioning services and impacts on diversity and community composition of soil prokaryotes and fungi. Kudzu had a slight positive impact on N cycling, but both cover crops appeared to compete with cocoa for K, with lower yields in sweet potato plots. Among regulating services, cover crops tended to increase C sequestration but did not affect pest and disease incidence. Cover crop treatment accounted for a small but significant percentage of soil microbiome variation, likely driven by effects on soil pH and C, and altered the relative abundance of 155 microbial taxa. Functional-trait-based species selection and optimized management could help maximize the ecosystem services delivered by cover crops, including those mediated by the microbiome, and minimize negative impacts on cocoa productivity.

Unveiling the biodeterioration activity of microbial communities to the historical manuscript: Biocontrol using biosynthesized gold and zinc oxide nanoparticles

Unveiling the biodeterioration activity of microbial communities to the historical manuscript: Biocontrol using biosynthesized gold and zinc oxide nanoparticles

Assessment of long-term Site-Specific Nutrient Management (SSNM) on soil organic carbon dynamics and sequestration in a rice-rice cropping system

This study examined the long-term effects of the Site-Specific Nutrient Management Integrated Plant Nutrient System (SSNM-IPNS) on carbon sequestration, stock, loss and mineralization in soil within a 26-year-old ricerice cropping system at wetland of Tamil Nadu Agricultural University, Coimbatore. The research focused on the impact of integrated organic and inorganic nutrient application on carbon fractions compared to conventional fertilization methods under wetland ecosystems. Results indicated that the SSNM-IPNS approach significantly enhances soil total organic carbon (TOC), with levels reaching 1.56% compared to just 0.78% in control treatments. Furthermore, labile carbon fractions such as permanganate-oxidizable carbon (POx-C), microbial biomass carbon (MBC), water-soluble carbon (WSC), and particulate organic carbon (POC) were found to be greater in the SSNM-IPNS management. Increased rates of carbon mineralization and basal respiration also reflected a more active and efficient microbial community in these soils. Soil microbial indices, including the microbial quotient (qMic) and the metabolic quotient (qCO2), further emphasized the benefits of the SSNM-IPNS approach in enhancing soil health. Overall, the findings demonstrate that SSNM -IPNS significantly improves carbon sequestration, nutrient cycling, and soil fertility, promoting sustainable agricultural practices vital for long-term productivity in intensive cropping systems. This research underscores the importance of adopting innovative nutrient management practices for sustainable agriculture.

Hydrothermal biochar enhances the photosynthetic efficiency and yield of alfalfa by optimizing soil chemical properties and stimulating the activity of microbial communities

Hydrothermal biochar has demonstrated potential in enhancing crop growth by improving soil properties and microbial activity; however, its effectiveness varies with application rate, with excessive amounts potentially inhibiting plant growth. This study employed a pot experiment approach to compare varying application rates of hydrothermal biochar (ranging from 0 to 50 t/ha) and to analyze its effects on alfalfa biomass, photosynthetic efficiency, soil nutrient content, and microbial community composition. Biochar application increased alfalfa dry weight by 12.22-21.20% in leaves, 31.60-55.60% in stalks, and 5.62-38.05% in roots. It also enhanced the light utilization efficiency of photosystem II. However, excessive biochar (50 t/ha) reduced biomass and photosynthesis. The addition of biochar amendments enhances soil nutrient availability, particularly increasing the accessibility of carbon, nitrogen, and phosphorus, while also lowering soil pH and enriching microbial interactions within bacterial communities. However, the effects on fungal communities are not pronounced. In conclusion, a moderate application of biochar (10-20t/ha) is recommended to maximize the growth of alfalfa and improve soil health, offering a practical approach for the sustainable cultivation of alfalfa.

Shifts in the Soil Microbial Community and Enzyme Activity Under Picea crassifolia Plantations and Natural Forests

Soil microbes are crucial for regulating biogeochemical cycles and maintaining forest ecosystem sustainability; however, the understanding of microbial communities and enzyme activity under natural and plantation forests in plateau regions remains limited. Using soil samples from 15-, 30-, and 50-year-old Picea crassifolia plantations and a natural forest (NF) in eastern Qinghai, China, this study assessed physicochemical properties, microbial communities, and enzyme activity across three soil layers. Microbial composition was characterized using the phospholipid fatty acid (PLFA) method, which is sensitive to structural changes. The PLFAs of bacteria, fungi, and actinomycetes accounted for 58.31%–74.20%, 8.91%–16.83%, and 3.41%–10.41% of the total PLFAs in all forests, respectively. There were significant differences between the NF and plantations, with the NF exhibiting higher PLFA abundance and enzyme activities than plantations, except for fungal PLFAs. PLFAs in plantations increased with the plantation age. However, the fungi-to-bacteria ratio was lower in the NF than in plantations. Finally, a redundancy analysis revealed that soil properties influence microbial composition and enzyme functionality significantly. These findings highlight the influence of stand age on microbial communities and structure, offering valuable insights for forest management practices aimed at conserving natural forests.

Soil pH modulates the activity of low-affinity methane oxidation in soils from the Amazon region.

In the Amazon region, pastures are the main land use subsequent to deforestation and this change can result in soil acidification and degradation. Liming is a management practice to increase soil pH, important to recover degraded lands and increase soil fertility, but its impacts on soil methane cycling in tropical soils are unknown. Here we investigate the role of soil pH on methane uptake under high concentrations of the gas, manipulating pasture and forest soils pH by liming and evaluating the active methane cycling microbial community. Top layer of forest and pasture soils were subjected to liming treatment and incubated with ∼10 000ppm of 13CH4. Soil DNA was evaluated with Stable Isotopic Probing (SIP-DNA), methanotrophic abundance was quantified (pmoA gene), and high throughput sequencing of 16S rRNA was performed. Liming increased the methane uptake in both forest (∼10%) and pasture (∼25%) soils. Methanotrophs Methylocaldum spp. (type I) and potential methanotrophs in Beijerinckiaceae (type II) were identified to actively incorporate carbon from methane in limed pasture soils. In limed forest soils, Nitrososphaeraceae were identified as 13C-enriched taxa, indicating that ammonia oxidizers can oxidize methane in these soils. Liming Amazonian pasture soils not only contributes to the fertility and recovery of degraded areas but also has the potential to improve the oxidation of methane at high concentrations of this gas.

Promoting the recovery of soil health in As and Sb-polluted soils: new evidence from the biochar-compost option

The role of compost and biochar in the recovery of As and Sb-polluted soils is poorly investigated, as well as the influence of their application rates on soil health and quality. In this study, we therefore investigated the effectiveness over time (2, 4, and 6 months, M) of a municipal solid waste compost (MSWC) and a biochar (BC), applied at 10 and 30% rates, and of selected mixtures (MIX; applied at 10 and 30% total rates, 1:1 ratio of MSWC and BC), on labile As and Sb in a polluted soil from an abandoned Sb mine (Djebel Hamimat, Algeria). At the same timepoints, the amendment impact on soil chemistry was also monitored, while the activity and diversity of the resident microbial communities were investigated at 6 M. After 6 months, MSWC, BC, and MIX applied at the higher rate significantly increased soil pH (from 7.5 up to 8.2), while MSWC and MIX increased soil EC to worrying values. The soil dissolved organic carbon content was also greatly increased by MSWC and MIX at the higher rates (up to 50-fold), while BC showed a negligible impact. All the amendments reduced the concentration of labile Sb in soil, with BC 10% being the most effective treatment (i.e., reducing labile Sb from ~ 60 to 20 mg kg−1 soil). On the contrary, only BC and MIX applied at 10% significantly reduced labile As (e.g., from ~ 12 to 4 mg kg−1 soil in the case of BC). MSWC and MIX at both rates increased up to 2000-fold soil dehydrogenase activity, while BC showed a null impact. The Biolog community level physiological profile and sequencing of the partial 16S rRNA gene showed a reduction of catabolic activity and α-diversity and a change of the community composition of bacterial populations in treated soils. Overall, MIX treatment, especially at 10%, was the most promising option for the chemical and biological recovery of As and Sb-polluted soils.

Microhabitat accessibility determines peptide substrate degradation by soil microbial community.

Soil pore space, considered the most complex biomaterial that exists, generates a complex environment, that gives rise to a wide variety of properties, such as microbial diversity and carbon storage. Soils contain, at the same time, the largest carbon reservoir on earth and an immense amount of nutrient-limited microbial biomass. The reason why this carbon is not consumed by soil microbes is attributed to the complex nature of soil, which forms a labyrinth where carbon and microbes cannot be in direct contact. In the present study, by using microfluidics, we tested the effect of labyrinth-like structures of decreasing accessibility on the decomposing activity of soil microbial communities from a soil inoculum. The two parameters used to study the effect of microhabitat accessibility were either the turning angle in an array of channel-like pore structures or the fractal order in an array of maze-like pore structures. We found that in both cases, channels and mazes, decreasing accessibility produced a higher peptide substrate degradation. When we analyzed the degradation within the structures, we found that most of the activity is concentrated in the regions of intermediate accessibility. We think that the increased degradation activity in low accessibility mazes might be due to the reduced interactions within the microbial communities which leads to a reduction in competition. Lowered competition allows different communities with a wide range of metabolic strategies to cohabit in the structures, which resulted in a bulk increase of the peptide substrate degradation.IMPORTANCEThe role microbes have in the environment is highly influenced by the characteristics of their habitat. Here, we show that a complex habitat enhances the enzymatic activity of a soil microbial inoculum. This might occur due to a reduced competition in complex habitats, which allows a more diverse community to coexist and explore a wider variety of metabolic strategies. The different rates of enzymatic activity in different levels of complexity suggest emergent properties of microbial communities in complex microhabitats which could have important implication for microbial processes, such as soil carbon storage and nutrient cycling.

Microbiome dynamics and functional profiles in deep-sea wood-fall micro-ecosystem: insights into drive pattern of community assembly, biogeochemical processes, and lignocellulose degradation.

Wood-fall micro-ecosystems contribute to biogeochemical processes in the oligotrophic deep ocean. However, the community assembly processes and biogeochemical functions of microbiomes in wood fall remain unclear. This study investigated the diversity, community structure, assembly processes, and functional profiles of bacteria and fungi in a deep-sea wood fall from the South China Sea using physicochemical indices, amplicon sequencing, and metagenomics. The results showed that distinct wood-fall contact surfaces exhibit habitat heterogeneity. The bacterial community of all contact surfaces and the fungal community of seawater contact surface (SWCS) were affected by homogeneous selection. In SWCS and transition region (TR), bacterial communities were influenced by dispersal limitation, whereas fungal communities were affected by homogenizing dispersal. The Venn diagram visualization revealed that the shared fungal community between SWCS and TR was dominated by Aspergillaceae. Additionally, the bacterial community demonstrated a higher genetic potential for sulfur, nitrogen, and methane metabolism than fungi. The sediment contact surface enriched modules were associated with dissimilatory sulfate reduction and methanogenesis, whereas the modules related to nitrate reduction exhibited enrichment characteristics in TR. Moreover, fungi showed a stronger potential for lignocellulase production compared to bacteria, with Microascaceae and Nectriaceae identified as potential contributors to lignocellulose degradation. These results indicate that environmental filtering and organism exchange levels regulated the microbial community assembly of wood fall. The biogeochemical cycling of sulfur, nitrogen, and methane was mainly driven by the bacterial community. Nevertheless, the terrestrial fungi Microascaceae and Nectriaceae might degrade lignocellulose via the combined action of multiple lignocellulases.IMPORTANCEThe presence and activity of microbial communities may play a crucial role in the biogeochemical cycle of deep-sea wood-fall micro-ecosystems. Previous studies on wood falls have focused on the microbiome diversity, community composition, and environmental impact, while few have investigated wood-fall micro-ecosystems by distinguishing among distinct contact surfaces. Our study investigated the microbiome dynamics and functional profiles of bacteria and fungi among distinct wood-fall contact surfaces. We found that the microbiome community assembly was regulated by environmental filtering and organism exchange levels. Bacteria drive the biogeochemical cycling of sulfur, nitrogen, and methane in wood fall through diverse metabolic pathways, whereas fungi are crucial for lignocellulose degradation. Ultimately, this study provides new insights into the driving pattern of community assembly, biogeochemical processes, and lignocellulose degradation in the microbiomes of deep-sea wood-fall micro-ecosystems, enhancing our comprehension of the ecological impacts of organic falls on deep-sea oligotrophic environments.

PRA Melting-ICE Project: Svalbard 2022 Expeditions Report

Arctic regions are among the fastest warming areas of the planet. Increasing average temperatures over the last five decades have deepened the thawing of the upper-most layer of permafrost across the Arctic, which contains significant amounts of organic carbon. The progressive deepening of seasonal thawing releases carbon that is used by active microorganisms which also produce greenhouse gases, potentially onsetting a positive feedback on global warming. Despite their importance in controlling organic matter degradation and greenhouse gas fluxes to the atmosphere, there is a lack of data on activity and dynamics of microbial communities in High Arctic soils in response to seasonal thaw. This report describes three specific expeditions performed on the Svalbard archipelago, carried out within the framework of the PRA (Italian Arctic Research Program) project Melting-ICE, performed between February and October 2022, reporting site characteristics and samples collected. The project aims to investigate the diversity and activity of active layer microbial communities across a full season thaw cycle, correlating microbial diversity with gas fluxes and composition. During these expeditions, a total of eight different sites were selected to investigate the microbiology and geochemistry of soils, as well as to estimate the gas fluxes from the soil to the atmosphere. The data collected in the field, combined with the results obtained in the laboratory, will provide a snapshot of the seasonal activity of the microbial communities present in the permafrost’s active layer. The three campaigns will provide data to estimate the impact of permafrost melting on the carbon cycle and the role of microorganisms in the release of greenhouse gases.

Tracing active members in microbial communities by BONCAT and click chemistry-based enrichment of newly synthesised proteins

Abstract A comprehensive understanding of microbial community dynamics is fundamental to the advancement of environmental microbiology, human health, and biotechnology. Metaproteomics, i.e. the analysis of all proteins in a microbial community, provides insights into these complex systems. Microbial adaptation and activity depend to an important extent on newly synthesized proteins (nP), however, the distinction between nP and bulk proteins is challenging. The application of bioorthogonal non-canonical amino acid tagging (BONCAT) with click chemistry has demonstrated efficacy in the enrichment of nP in pure cultures. However, the transfer of this technique to microbial communities has proven challenging and has therefore not been used on microbial communities before. To address this, a new workflow with efficient and specific nP enrichment was developed using a laboratory-scale mixture of labelled E. coli and unlabelled yeast. This workflow was successfully applied to an anaerobic microbial community with initially low BONCAT efficiency. A substrate shift from glucose to ethanol selectively enriched nP with minimal background. The identification of bifunctional alcohol dehydrogenase and a syntrophic interaction between an ethanol-utilizing bacterium and two methanogens (hydrogenotrophic and acetoclastic) demonstrates the potential of metaproteomics targeting nP to trace microbial activity in complex microbial communities.

Phthalate esters in baltic lagoons: Spatial distribution, ecological risks, and novel insights into their fate using transcriptomics.

Plasticizers such as phthalate esters (PAEs) are organic compounds widely used in various consumer and industrial products, raising strong environmental concerns due to their pervasive presence and potential adverse effects. Lagoon ecosystems are particularly vulnerable to PAE pollution as they are semi-enclosed and receive high loads of organic materials. The present study investigates the distribution of seven common PAEs in three large European lagoons (Curonian, Vistula and Szczecin) in the southern Baltic Sea. The concentration levels of PAEs in the water column, encompassing both the dissolved and particulate-bound phases, and in sediments were assessed to elucidate distribution patterns and potential ecological risks within these lagoon ecosystems. The average concentration of total PAEs in the water column ranged from 0.03 to 1.45μgL-1, whereas sediment concentration varied from 0.008 to 1.06μgg-1, levels comparable to or lower than those found in other European coastal areas. Distribution patterns of PAEs in sediment showed notable similarity across all three lagoons, whereas variations were observed in the water column. Notably, di(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DOP) and dimethyl phthalate (DMP) emerged as the most concerning congeners in studied lagoons, all of which pose a moderate risk to aquatic organisms. This study applied shotgun transcriptomic analysis to field samples, revealing active microbial communities involved in PAEs degradation in the Baltic lagoons for the first time. The degradation of phthalic acid (PA) into intermediate compounds such as protocatechuate was not identified as a rate-limiting step in the studied environment. The degradation activity was primarily localized in the sediment layers, with Gram-negative bacteria playing a major role, while Gram-positive bacteria appeared incapable of degrading PA. These findings provide valuable insights into the distribution and transformation mechanisms of PAEs in estuarine environments.

Enhanced Fermentation of Pu-Erh Tea with Aspergillus niger: Quality and Microbial Community Analysis.

Post-fermented Pu-erh tea (PFPT) is a microbial fermented tea characterized by unique sensory attributes and multiple health benefits. Aspergillus niger is the dominant fungus involved in the fermentation process and plays a significant role in imparting the distinct characteristics of PFPT. To investigate the role of Aspergillus niger in the fermentation of Pu-erh tea, this study inoculated unsterilized sun-dried green tea with Aspergillus niger isolated from Pu-erh tea to enhance the fermentation process. Metabolites and microbial communities in sun-dried green tea (CK), fortified fermented tea (TF), and naturally fermented tea (NF) were analyzed using non-targeted metabolomics, 16S rDNA, and internal transcribed spacer sequencing. Non-targeted metabolomics revealed that Aspergillus niger significantly altered the metabolite profile of the tea samples, identifying a total of 200 different metabolites, with 95 showing significant increases and 105 significant decreases, predominantly enriched in metabolic pathways associated with amino acid biosynthesis and degradation. High-throughput sequencing revealed that although the relative abundance of the fungal community remained largely unchanged, the inoculation of Aspergillus niger significantly increased the abundance of Bacillales and Pseudomonas within the bacterial community, thereby influencing the dynamic balance of the microbial ecosystem. Collectively, the inoculation of Aspergillus niger altered the composition of the microbial community and metabolic activities, resulting in changes to the content of amino acid-dominated metabolites, thereby enhancing the flavor profile and overall quality of Pu-erh tea. These findings provide important insights for optimizing the production processes of Pu-erh tea and the application of microorganisms in other fermented foods.

Dual regulation of As release and soil environment by Fe(Ⅱ) assisted steel slag and coal fly ash: Effects and potential mechanisms

Multiple solid waste-based amendments are used for arsenic (As)-contaminated soil remediation, but their mechanisms in inhibiting As release and the effects on soil health in real sites remain poorly understood. Here, an amendment consisting of steel slag (SS), coal fly ash (CFA) and Fe(Ⅱ), namely, Fe(Ⅱ) assisted SS and CFA, was applied to an As-contaminated mining soil. 120 days field experimental results revealed that amendment addition in low-As soil (LA soil) and high-As soil (HA soil) significantly increased amorphous Fe(Ⅲ) (hydro)oxides content and decreased dissolved organic carbon (DOC), and thus inhibited As mobilization. More importantly, the soil microbial community activity was improved in HA soil, while it significantly decreased in LA soil. Correlation analyses demonstrated that the activation of fungal and bacterial communities was directly correlated with soil pH, amorphous Fe(Ⅲ) (hydro)oxides, soil organic matter (SOM), and DOC. The C-containing functional groups, newly generated Fe(Ⅲ) (hydro)oxides and Fe-As-SOM complexes inhibit As release, while the Fe(Ⅲ) reduction drove the As release. This work highlighted the importance of Fe(Ⅱ) assisted SS and CFA in inhibiting As release and regulating soil microbial communities, providing a new strategy for the remediation of heavy metals contaminated mining soil using solid waste-based amendment.