ABSTRACT Biofilms in drinking water distribution systems pose significant risks by harboring chlorine-resistant bacteria. This study isolated five bacterial strains (Sphingomonas ursincola, Sphingobium amiense, Gordonia amicalis, Microbacterium saccharophilum, Hydrogenophaga laconesensis) from municipal pipelines to evaluate differences in biofilm formation and chlorine resistance. Biofilm formation ability varied notably, with S. ursincola showing the strongest capacity and H. laconesensis the weakest. Quorum sensing (QS) signal molecules (C6-HSL, 3-OXO-C14-HSL; 0.2240–0.2481 μg/L) and extracellular polymeric substances (EPSs: 19.940–32.407 mg/L) were critical in biofilm regulation, where QS molecules influenced EPS composition. Chlorine resistance assays revealed species-specific tolerance: at ≤1.0 mg/L, resistance ranked M. saccharophilum > S. amiense > G. amicalis > S. ursincola > H. laconesensis; above 1.0 mg/L, S. ursincola and S. amiense exhibited robust resistance. Low chlorine levels (0.6 mg/L) damaged only 25.91%–34.80% of bacteria, insufficient to control the biofilm formation of the tested isolates. Optimal disinfection occurred at 1.0–1.5 mg/L, effectively controlling biofilm biomass. These findings highlight EPS-driven chlorine resistance mechanisms and QS-mediated biofilm regulation, providing actionable strategies for pipeline management.IMPORTANCEThis study addressed a critical gap in understanding different bacterial biofilm dynamics and chlorine resistance mechanisms in drinking water systems. By linking quorum sensing to extracellular polymeric substance production, it reveals how bacteria modulate biofilm resilience, elucidating species-specific mechanisms underlying biofilm resilience to chlorine disinfection. The identification of chlorine-resistant species (Sphingomonas ursincola, Sphingobium amiense) and optimal disinfection thresholds (1.0–1.5 mg/L) directly informs municipal water treatment protocols, providing a practical chlorine concentration range (1.0–1.5 mg/L) that effectively controls biofilms while avoiding excessive disinfectant use. These results are pivotal for mitigating secondary contamination risks and safeguarding public health, particularly in aging infrastructure where biofilm-related outbreaks are prevalent.

Soil cadmium (Cd) contamination poses a critical threat to ecosystem safety and human health. However, conventional remediation technologies like soil washing and immobilization induce secondary soil degradation and struggle to reduce the total Cd pool. To address these challenges, a magnetically separable Fe3O4/CaFe-layered double hydroxide (LDH) composite was synthesized hydrothermally, enabling both magnetic separation and Cd immobilization. Adsorption experiments demonstrated that Cd2+ uptake followed the Langmuir model, achieving a maximum capacity of 171.82 mg·g−1 at 25 °C. Material characterization confirmed its layered structure, superparamagnetic behavior, and a high surface area of 38.59 m2·g−1, providing abundant active sites for Cd2+ adsorption. Mechanistic analyses revealed that Cd2+ achieved “super-stable” immobilization via a synergistic mechanism of surface complexation, chemical precipitation, and particularly isomorphic substitution. Soil incubation studies addressed the challenge of extending magnetic separation from aqueous systems to complex soil matrices, achieving 31.61% total Cd removal and reducing Cd mobility factor by 14.88%. This transformation converted the exchangeable fraction into stable carbonate-bound and FeMn oxide-bound fractions. In vitro gastrointestinal simulation revealed reductions in bioaccessible Cd concentration of 36.95% and 40.52% in gastric and intestinal phases, respectively. Overall, this research provides an integrated removal-immobilization strategy that bridges material performance with human health risk mitigation.

Immobilized microorganism technology offers a promising approach for remediating heavy metal-contaminated soils. This study developed a novel bio-mineral composite (B-AM) by coupling acid-modified maifanite (AM) with Bacillus mucilaginosus to enhance lead (Pb) immobilization. Comparative experiments demonstrated that B-AM outperformed conventional amendments, including oyster shell, pristine maifanite, AM and B. mucilaginosus in Pb immobilization. The B-AM treatment optimized soil pH, improved soil fertility with increases in available potassium (1.06-fold) and available phosphorus (1.28-fold). Additionally, B-AM transformed Pb into more stable fractions, reducing labile Pb fractions by 52.52% while increasing the residual fraction by 88.36%. These improvements resulted in an 83.24% reduction in Pb accumulation and a 63.95% increase in the fresh root weight of radish. Mechanistic insights revealed that the enhanced remediation performance stems from both the individual contributions of AM (adsorption capacity) and B. mucilaginosus (biosorption and biomineralization) and their synergistic interaction. Specifically, AM acts as a carrier and pH buffer, promoting microbial proliferation and reducing Pb remobilization from cell lysis. The resulting sustained microbial activity further leads to the formation of stable Pb minerals. Collectively, our results establish a theoretical and practical basis for using B-AM to remediate Pb-contaminated soils.

Extreme climatic events, such as heavy rainstorms, challenge the stability of biological activated carbon (BAC) in drinking water treatment. However, the resilience of the ozone-BAC (O3-BAC) process under such conditions remains underexplored. This study examined BAC filter performance and microbial community dynamics in a full-scale drinking water treatment plant in Southern China following an extreme rainstorm. Samples were collected at 3, 10, and 21 days post-storm to assess microbial shifts on BAC and stability of processed water. Results indicated that despite the deterioration in raw water quality by the storm, the finished water quality remained compliant with national standards. BAC filters were categorized into "new" and "aged" based on service time and physical characteristics. Bacterial abundance on both filter types decreased substantially, but effluent bacterial counts rose in the first 3 days. New BAC filters maintained stable microbial communities, while aged BAC filters exhibited marked shifts, with opportunistic pathogens (Ralstonia, Acinetobacter, Providencia, Enterobacter) dominating after the storm. Hydraulic shock from the extreme rainstorm initially reduced bacterial abundance but later recovered by day 21. Community analysis revealed that new BAC filters maintained stable, whereas those on aged BAC filters exhibited significant changes. These findings underscored that the physicochemical properties and service time of BAC filters played a crucial role in bacterial colonization and stability under extreme climatic events.

Soil lead (Pb) contamination poses a significant global threat to both ecological safety and human health. While conventional immobilizing agents effectively reduce Pb mobility, they exhibit inherent limitations, necessitating the development of novel remediation materials. Furthermore, the remediation efficacy of these agents remains inadequately characterized, as comprehensive evaluations—particularly those assessing the reduction of human health risks via oral ingestion—are frequently omitted. In this comparative study, three types of immobilizing agents, namely, the conventional KH2PO4 and Ca(OH)2, and the promising CaAl-Layered double hydroxide (LDH), were applied to remediate five typical Pb-contaminated soil types in China: red, cinnamon, black, brown, and yellow soils. The remediation efficacy was comprehensively evaluated in terms of the migration factor, ecological risk, and human health risk of soil Pb. The results indicated that at their respective optimal application rates, KH2PO4, Ca(OH)2, and CaAl-LDH significantly reduced the migration factor of soil Pb by averages of 66.7%, 16.1%, and 56.0%, respectively. Furthermore, the leachability and relevant ecological risk associated with soil Pb were reduced by 93.2%, 93.7%, and 56.3%, respectively. Notably, CaAl-LDH exhibited superior performance in mitigating Pb bioaccessibility and relevant human health risk, with average reductions of 42.1% and 48.6% in the gastric and small intestinal phases, respectively. The reduction efficacy of CaAl-LDH in the gastric and small intestinal phases was 4.21 and 3.90 times and 2.17 and 1.17 times that of KH2PO4 and Ca(OH)2, respectively. These results demonstrate the effectiveness of CaAl-LDH for Pb immobilization and its potential for field-scale application. This study provides a scientific foundation for the research and development of highly efficient immobilization agents for Pb-contaminated soils and the improvement of eco-environmental quality and human health.

High-sulfur mining generates severe acid mine drainage (AMD) and heavy metal contamination, posing substantial risks to environmental and human health. Accurate and efficient risk assessment is critical for land management. In a high-sulfur mining region of East China, this study investigated soil contamination by heavy metals (Mn, Pb, Zn, As, Cu, Ni), measured key soil properties (pH, organic matter, available phosphorus, available iron, sulfate), and evaluated human health and ecological risks using the USEPA model and Hakanson potential ecological risk index (RI), respectively. We developed an integrated Random Forest (RF) machine learning framework to enhance assessment accuracy. The framework successfully corrects portable X-ray fluorescence (pXRF) data using environmental covariates, significantly improving reliability (R & sup2; > 0.85 for key metals). The RF models also effectively classified ecological risk categories (accuracy=0.74), identifying sulfate and pH as the most critical influencing factors. Building on this, we proposed an Adapted Ecological Index (AEI) that incorporates RF-derived environmental weights for a refined, site-specific assessment. Results revealed severe contamination dominated by As, posing significant non-carcinogenic and carcinogenic human health risks, primarily via oral ingestion. The AEI confirmed arsenic's dominance in ecological risk, classifying 24.3 % of sites as very high risk. This study successfully developed an integrated, machine learning-enhanced framework to improve pXRF accuracy and refine ecological risk assessments in high-sulfur mining landscapes. This framework provides a robust and rapid tool for environmental risk assessment, offering valuable insights for policymakers and environmental managers in formulating targeted remediation strategies and land-use policies for mining-affected areas globally.

Advanced treatment of plant effluent (tailwater) is critical for mitigating agricultural non-point source pollution; however, plant–substrate synergy in vertical-flow constructed wetlands (VFCWs) remains poorly understood under subtropical conditions. This one-year pilot study evaluated the effects of substrate type (zeolite vs. gravel) and P. australis presence on nutrient removal, seasonal performance stability, and microbial community assembly in tailwater treatment. Methodologically, twelve VFCWs were operated across seasons, and their performance was assessed via water quality monitoring and high-throughput sequencing. The results indicate that all configurations consistently met stringent discharge standards. Planted treatments significantly outperformed unplanted controls in removing TN, COD, and TP (p < 0.05), while no significant difference emerged between zeolite- and gravel-planted systems, confirming vegetation’s dominance over substrate selection under low-concentration loads. Seasonal analysis revealed temperature-dependent TN removal (p < 0.01), whereas TP, COD, and NH4+-N removal remained stable. Microbial analysis showed P. australis selectively enriched functional taxa driving N and organic matter mineralization despite a shared core microbiome at the genus level. Gravel-planted VFCWs exhibited superior long-term resilience compared to the transient sorption of zeolites. We considered that vegetation-driven biological pathways offer a resilient design for polishing nutrients in tailwater, showing potential for agricultural irrigation and nutrient interception.

Cadmium (Cd) contamination of soil is a global environmental issue. Traditional remediation techniques such as immobilization, leaching and phytoextraction have numerous shortcomings, which has led to growing interest in the development of low cost, high-efficiency, and environmentally friendly agents for removing Cd from soil. In this study, Fe3O4/polyaniline (Fe3O4/PANI) was developed as a remediation agent with magnetic separation and regeneration capabilities. Its Cd adsorption isotherms showed a better fit to Langmuir model, exhibiting a high Cd adsorption capacity of 47.62 mg·g-1 at 25°C. In bench-scale experiments, Fe3O4/PANI was first attempted to remediating four typical Chinese soils with Cd concentration of 180 mg·kg-1: black, brown, cinnamon, and red. Results showed that the total Cd removal efficiency was satisfactory at 25.25%–38.91% and that the exchangeable Cd removal efficiency was 36.03% on average. In addition, the soil basic properties did not show major changes after remediation. Regarding the regeneration performance, after the first regeneration cycle, a better total Cd removal efficiency was achieved, i.e., 27.89%–44.96%. After two regeneration cycles, it decreased but still remained above 95% of the initial performance. Fe3O4/PANI has a simple and cost-effective synthetic process, and it combines high Cd removal efficiency with easy recovery and recyclability. It is a promising solution for the sustainable and efficient remediation of Cd-contaminated soils, especially for the reclamation of highly contaminated development land.

Micro-and-nano plastics (MNPs) are pervasive in terrestrial ecosystems and represent an increasing threat to plant health; however, the mechanisms underlying their phytotoxicity remain inadequately understood. MNPs can infiltrate plants through roots or leaves, causing a range of toxic effects, including inhibiting water and nutrient uptake, reducing seed germination rates, and impeding photosynthesis, resulting in oxidative damage within the plant system. The effects of MNPs are complex and influenced by various factors including size, shape, functional groups, and concentration. Recent advancements in omics technologies such as proteomics, metabolomics, transcriptomics, and microbiomics, coupled with emerging technologies like 4D omics, phenomics, spatial transcriptomics, and single-cell omics, offer unprecedented insight into the physiological, molecular, and cellular responses of terrestrial plants to MNPs exposure. This literature review synthesizes current findings regarding MNPs-induced phytotoxicity, emphasizing alterations in gene expression, protein synthesis, metabolic pathways, and physiological disruptions as revealed through omics analyses. We summarize how MNPs interact with plant cellular structures, disrupt metabolic processes, and induce oxidative stress, ultimately affecting plant growth and productivity. Furthermore, we have identified critical knowledge gaps and proposed future research directions, highlighting the necessity for integrative omics studies to elucidate the complex pathways of MNPs toxicity in terrestrial plants. In conclusion, this review underscores the potential of omics approaches to elucidate the mechanisms of MNPs-phytotoxicity and to develop strategies for mitigating the environmental impact of MNPs on plant health.

Soil worms are among the most abundant and functionally diverse soil animals. However, they have been largely overlooked in studies on microplastic (MP) toxicity. MPs and plant secondary metabolites (PSMs) are ubiquitous in soil due to plant litter decomposition and heavy MP contamination, inevitably interacting and exerting combined toxicity on soil organisms. However, little research has been conducted on their joint effects. This study investigates the individual and combined toxic effects of polyethylene (PE) MPs and three PSMs (glycyrrhizic acid, tannic acid, and matrine) on the model organism Caenorhabditis elegans. Physiological and biochemical responses were assessed using fluorescence microscopy, image analysis, and statistical methods. After 42 h of exposure to PE MPs and/or PSMs, worm growth and development were negatively impacted. Under experimental conditions, matrine and PE MPs synergistically inhibited worm growth, exacerbated neurological damage, and induced oxidative stress. In contrast, glycyrrhizic acid and tannic acid alleviated PE MP-induced growth inhibition, mitigated oxidative stress, and demonstrated antioxidant properties that counteracted oxidative damage. This study offers new insights into the combined effects of MPs and PSMs in soil ecosystems, contributing to ecological risk assessments and pollution management strategies.

Growing epidemiological evidence suggests that the diverse and functional gut microbiota plays a vital role in regulating the health and disease of organisms including human. However, organisms are inevitably exposed to widespread environmental pollutants, and the interactions between their gut microbiota and pollutants are relatively underreported. The present paper considers heavy metals (HMs) and microplastics (MPs) as representatives of traditional and emerging pollutants and systematically summarizes their effects on gut microbiota and the effects of gut microbiota on pollutants. The former refers to the alterations in the gut microbiota's abundance, diversity and composition caused by pollutants, whereas the latter focuses on the changes in the metabolism of pollutants by adjusting the dominant bacteria, specific enzymes, and key genes. In particular, some fields were found to be poorly studied, including extension of research to humans, mechanistic exploration of gut microbiota's changes, and the metabolism of pollutants by gut microbiota. Accordingly, we draw attention to the development and application of in vitro test models to more accurately explore the interactions between pollutants and gut microbiota when assessing human health risks. In addition, by combining state-of-the-art biological techniques with culturomics, more gut microbiota can be identified, isolated, and cultured, which helps to confirm the relationship between pollutants and gut microbiota and the potential function of gut microbiota in pollutant metabolism. Furthermore, the phenomenon of coexposure to HMs and MPs is becoming more frequent, and their interactions with gut microbiota and the influence on human health is expected to be one of the frontier research fields in the future. The key information presented in this review can stimulate further development of techniques and methodologies for filling the knowledge gaps in the relationships between combined pollutants (HMs and MPs), gut microbiota, and human health.

Minerals control on the oral bioavailability of arsenic (As) in soil has been evidenced in human health risk assessments. However, little is known about the metabolism of soil mineral-associated As by human gut microbiota. This study evaluated the relative bioavailability (RBA) and bioaccessibility of As in As(V)-sorbed Aluminum (Al) oxides (α-Al2O3 and γ-Al2O3), affected by gut microbiota and Fe(III). The in vitro method yielded higher As bioaccessibility in the small intestinal phase of α-Al2O3 (30.3 %-54.8 %) and in the colon phase of γ-Al2O3 (29.7 %-45.6 %), respectively. In the presence of Fe, As release was decreased by14.5 %-48.1 % in the small intestine but increased by 37.5 %-86.3 % in the colon (p < 0.05). Speciation analysis revealed that gut microbiota reduced nearly half of the As(V) to As(III) in the colon digests, with up to 21.0 % of As(III) remaining in the solid phase. More than 92.0 % of Fe(III) in the colon digests was reduced to Fe(II), which would facilitate As reduction but inhibit methylation. A mouse bioassay was conducted to estimate As-RBA (21.3 %-58.8 %) in Al oxides, decreased by Fe(III) addition under high As exposure. Our findings provide new insights into the role of Al oxides in the risk assessment from inadvertent oral ingestion of As-contaminated soils.

The enrichment of cadmium (Cd) in farmland soil poses serious risks to agricultural safety and remains challenging to remediate. This study evaluated CaAl-layered double hydroxide (CaAl-LDH) as a highly efficient and stable passivator for Cd-contaminated soil. Laboratory adsorption tests demonstrated that Cd2+ adsorption on CaAl-LDH followed pseudo-second-order kinetics and the Langmuir model, indicating monolayer chemisorption, with a maximum capacity of 469.48 mg·g−1 at pH 6. The adsorption mechanisms include surface complexation, interlayer anion exchange, dissolution–precipitation, and isomorphic substitution. A three-year field trial in Yongkang City, China showed that CaAl-LDH promoted the transformation of Cd in rhizosphere soil from the ion exchange state (F2) to the residual state (F7) and Fe–Mn oxidized state (F5), reducing the exchangeable Cd content by 26.71%. Consequently, Cd content in rice grains decreased by 68.42% in the first year and remained over 37% lower in the second year, consistently below the national food safety limit. Future research should focus on the optimization of material’s stability and application protocol. The results demonstrate that CaAl-LDH provides a cost-effective and sustainable strategy for the in situ passivation remediation of Cd-contaminated farmland, contributing to food safety and sustainable agriculture.

Microplastics (MPs) have been widely found in the environment and have exerted non-negligible impacts on the environment and human health. Extensive research has shown that MPs can act as carriers for viruses and interacts with them in various ways. Whether MPs influence the persistence, transmission and infectivity of virus has attracted global concern in the context of increasing MPs contamination. This review paper provides an overview of the current state of knowledge regarding the interactions between MPs and viruses in aquatic environments. Latest progress and research trends in this field are summarized based on literature analysis. Additionally, we discuss the potential risks posed by microplastic-associated viruses to human health and the environmental safety, highlighting that MPs can affect viral transmission and infectivity through various pathways. Finally, we underscores the need for further research to address key knowledge gaps, such as elucidating synergistic effects between MPs and viruses, understanding interactions under real environmental conditions, and exploring the role of biofilms in virus-MPs interactions. This review aims to contribute to a deeper understanding on the transmission of viruses in the context of increasing MPs pollution in water, and promote actions to reduce the potential risks.

Dissolved organic matter (DOM) is important in determining the drinking water treatment and the supplied water quality. However, a comprehensive DOM study for the whole water supply system is lacking and the potential effects of secondary water supply are largely unknown. This was studied using dissolved organic carbon (DOC), absorption spectroscopy, and fluorescence excitation -emission matrices -parallel factor analysis (EEMPARAFAC). Four fluorescent components were identified, including humic-like C1-C2, tryptophan-like C3, and tyrosine -like C4. In the drinking water treatment plants, the advanced treatment using ozone and biological activated carbon (O3-BAC) was more effective in removing DOC than the conventional process, with the removals of C1 and C3 improved by 17.7%-25.1% and 19.2%-27.0%. The absorption coefficient and C1-C4 correlated significantly with DOC in water treatments, suggesting that absorption and fluorescence could effectively track the changes in bulk DOM. DOM generally remained stable in each drinking water distribution system, suggesting the importance of the treated water quality in determining that of the corresponding network. The optical indices changed notably between distribution networks of different treatment plants, which enabled the identification of changing water sources. A comparison of DOM in the direct and secondary water supplies suggested limited impacts of secondary water supply, although the changes in organic carbon and absorption indices were detected in some locations. These results have implications for better understanding the changes of DOM in the whole water supply system to help ensure the supplied water quality.

The production of isolated metallic nanoparticles with multifunctionalized properties, such as size and shape, is crucial for biomedical, photocatalytic, and energy storage or remediation applications. This study investigates the initial particle formations of gold nanoparticles (AuNPs) bioproduced in the cyanobacteria Anabaena sp. using high-resolution transmission electron microscopy images for digital image analysis. The developed method enabled the discovery of cerium nanoparticles (CeNPs), which were biosynthesized in the cyanobacteria Calothrix desertica. The particle size distributions for AuNPs and CeNPs were analyzed. After 10 h, the average equivalent circular diameter for AuNPs was 4.8 nm, while for CeNPs, it was approximately 5.2 nm after 25 h. The initial shape of AuNPs was sub-round to round, while the shape of CeNPs was more roundish due to their amorphous structure and formation restricted to heterocysts. The local PSDs indicate that the maturation of AuNPs begins in the middle of vegetative cells and near the cell membrane, compared to the other regions of the cell.

EDITORIAL article Front. Microbiol., 05 January 2024Sec. Microbiotechnology Volume 14 - 2023 | https://doi.org/10.3389/fmicb.2023.1349701

Plant litter is an important input source of carbon and nitrogen in soil. While microplastics (MPs) and plant litter are ubiquitously present in soil, their combined impact on soil biogeochemical processes remains poorly understood. To address this gap, we examined the soil changes resulting from the coexistence of plant litter (Alfalfa) and polyethylene microplastics (PE). The soil changes included physicochemical properties, composition of soil dissolved organic matter, and structure of the soil microbial community. The results showed that the addition of polyethylene (PE) inhibited the degradation of humus-like substances and decreased the quantity of humic acid-like compounds in soil dissolved organic matter (DOM). PE negatively impacted plant litter decomposition, disrupted soil organic carbon (SOC) breakdown, interfered with the nitrogen cycle, and significantly altered microbial community structures during the process. By day 35, SOC and total nitrogen (TN) levels were reduced by 39.8% and 10.1%, respectively, in the presence of PE. Furthermore, PE significantly decreased the abundance of nitrogen-fixing microbes, including Streptomyces (43.1%) and Bacillus (45.9%), which play key roles in nitrate reduction to ammonium. This study highlights the environmental effects of MPs on plant litter decomposition and their potential implications for soil biogeochemical processes.

给水管网生物稳定性是指管网中微生物的生长导致饮用水水质在输配过程中发生恶化的潜力.准确、合理地评价给水管网的生物稳定性是保障饮用水水质安全的前提,常用方法包括基于生物稳定性评价指标的预测性评价方法和基于微生物丰度、活性及群落组成的直接评价方法.深入理解给水管网中水力条件、管道特征、营养基质、消毒剂和抗生素耐药性等因素对生物稳定性的影响有助于制定更有效的控制策略.然而,如何通过实际管网取样和生物膜培养反应器获得具有代表性的环境样品以及如何利用现代分子生物学技术获取有用信息是该研究领域面临的主要挑战.基于此,从给水管网生物稳定性研究的现状(评价方法、影响因素、控制策略)出发,对当前研究的主要瓶颈进行讨论,并展望该领域未来的发展趋势与可能的研究方向.