Repeated introduction of micropollutants enhances microbial succession despite stable degradation patterns

Algae-driven bacterial production of extracellular reactive oxygen species for emerging contaminants degradation

Emerging contaminants (ECs) are ubiquitous in natural surface waters, posing significant risks to aquatic ecosystems and human health. Symbiotic systems comprising photoautotrophic algae and associated bacteria offer a promising approach for the bioremediation of aquatic environments. This study investigated the degradation of five ECs (carbamazepine, diclofenac, atenolol, sulfamethoxazole, and ofloxacin) by reactive oxygen species (ROS) generated through algal-bacterial interactions. The algal-bacterial system exhibited superior degradation efficiencies, achieving 96 %, 97 %, 89 %, 72 %, and 77 % removal for the respective ECs after 6 days, far surpassing the performance of pure bacterial or algal systems. Elevated levels of biogenic ROS were observed in the algal-bacterial system, with extracellular superoxide radicals (O2•-) and hydrogen peroxide (H2O2) identified as key drivers of the degradation process. Under ECs stress, the algal-bacterial system maintained cellular integrity and metabolic activity by upregulating pathways related to carbohydrate, lipid, amino acid, and nucleotide metabolism, thereby enhancing its resistance. These findings highlight the significant potential of algal-bacterial systems for the transformation of ECs, offering a sustainable strategy for bioremediation and the restoration of ecosystem health.

Responses of microbial community to the selection pressures of low-concentration contaminants of emerging concern in activated sludge

The activated sludge system used in wastewater treatment plants has demonstrated partial removal capabilities for various contaminants of emerging concern (CECs). However, existing research primarily focuses on the removal efficiency individual or combined CECs, with limited research addressing their impact on microbial community. In this study, three activated sludge systems were developed to investigate the effects of low concentrations of CECs, including five types of antibiotics and five types of non-antibiotic CECs. The results showed that activated sludge could effectively degrade non-antibiotic CECs within 3 -5 days even in the third cycle, whereas the degradation of antibiotics was more variable. Compared to the AA-Group, Alphaproteobacteria, Anaerolineae, Planctomycetes, Gammaproteobacteria, and Bacteroidia shifted to connector in the non-AA treatment as keystones species. Variance partitioning and co-occurrence network analysis showed that CECs exert significant deterministic influences, surpassing traditional environmental factors. Notably, antibiotics promoted microbial interactions more than other CECs, the finding was further validated by null model analysis. Our study provides novel insights into the differential impacts of low-concentration CECs on microbial community dynamics and interactions. Findings highlight the necessity to better understand the complex microbial processes driven by CECs, particularly antibiotics, to further develop more efficient biological treatment processes for CECs removal.

Solid waste based manufactured soil - Stabilization of "organics-microorganisms-inorganic skeleton" and performance evaluation

The safe disposal and utilization of bulk solid waste (SW) are critical challenges. Manufactured soil, a soil-like material composed of SW, offers a novel solution for resource recycling. However, the mechanisms underlying SW-based manufactured soil fertility development remain unclear. This study systematically investigated the performance of SW-based manufactured soil using aerobic compost sludge (ACS-soil) and anaerobic digestion sludge (ADS-soil), focusing on the microbial mechanism which driving manufactured soil fertility development. Results showed that the soil nutrient index (SNI) of SW-based manufactured soil was 5 to 8 times higher than that of natural topsoil. These soils significantly promoted wheatgrass growth. However, ACS-soil exhibited superior fertility and plant performance, maintaining stable nutrient levels, whereas the SNI value and soil pH of ADS-soil decreased by 27.13% and 17.68% respectively. Microbial community analysis revealed that homogeneous selection in ACS-soil drove microbial community succession, maintaining stable nutrition content and increasing humification degree. In ADS-soil, the rich in labile compounds (accounting for 41%) led to lower environmental stress, stochastic processes dominated bacterial succession, which driving declined pH and thus negatively impact the soil fertility. Furthermore, based on life cycle analysis results, using SW to prepare manufactured soils had lower carbon emissions than conventional disposal methods (including safe landfill, incineration and direct land use), which demonstrated that SW-based manufactured soil is a promising method for SW disposal. This research underscores the potential of SW-based manufactured soil for waste disposal and enhanced plant growth, emphasizing the importance of selecting appropriate organic components to optimize soil performance.

Unveiling the mechanism and driving factors of pharmaceutical and personal care product (PPCP) removal in wastewater treatment plants

Wastewater treatment plants (WWTPs) are primary point sources of pharmaceuticals and personal care products (PPCPs) entering the environment; however, few studies have systematically elucidated the PPCP removal mechanism in WWTPs. In this study, we conducted two composite sampling campaigns, collecting water and sludge samples from each treatment stage of four secondary or tertiary WWTPs with various processes. Our goal was to identify the mechanisms and driving factors behind the removal of 30 common PPCPs. The average removal efficiency of all PPCPs was 62.57 %, with significant variations (-308.03 %-91.03 %) among individual PPCPs. The contribution of sludge adsorption, biodegradation and chemical degradation to the removal of 30 PPCPs was quantified. The average biodegradation efficiency of sulfonamides was 44.90 %, but reconversion of chelate products to the sulfonamides after chemical treatment (UV) was the main reason for their low removal efficiency (about 30 %). Base dissociation constant (pKb) and logKow were used to evaluate the contribution of charge interactions and hydrophobic partitioning to the adsorption capacity of PPCPs for the first time. For PPCPs that could ionize into cations, higher pKb increased adsorption capacity, whereas for other PPCPs logKd (distribution coefficient) and logKow showed a significant positive correlation. The biodegradation of sulfonamides was positively correlated with their solubility. The presence of hydroxyl and carboxyl groups promoted microbial degradation of non-antibiotic compounds. This study reveals the universal mechanisms and driving factors behind PPCP removal in WWTPs, providing insights to guide the targeted optimization of treatment processes for PPCP removal.

Methylparaben changes the community composition, structure, and assembly processes of free-living bacteria, phytoplankton, and zooplankton

Parabens are common contaminants in river and lake environments. However, few studies have been conducted to determine the effects of parabens on bacteria, phytoplankton, and zooplankton communities in aquatic environments. In this study, the effect of methylparaben (MP) on the diversity and community structure of the aquatic plankton microbiome was investigated by incubating a microcosm with MP at 0.1, 1, 10, and 100 μg/L for 7 days. The results of the Simpson index showed that MP treatment altered the α-diversity of free-living bacteria (FL), phytoplankton, and zooplankton but had no significant effect on the α-diversity of particle-attached bacteria (PA). Further, the relative abundances of the sensitive bacteria Chitinophaga and Vibrionimonas declined after MP addition. Moreover, the relative abundances of Desmodesmus sp. HSJ717 and Scenedesmus armatus, of the phylum Chlorophyta, were significantly lower in the MP treatment group than in the control group. In addition, the relative abundance of Stoeckeria sp. SSMS0806, of the Dinophyta phylum, was higher than that in the control group. MP addition also increased the relative abundance of Arthropoda but decreased the relative abundance of Rotifera and Ciliophora. The β-diversity analysis showed that FL and phytoplankton communities were clustered separately after treatment with different MP concentrations. MP addition changed community assembly mechanisms in the microcosm, including increasing the stochastic processes for FL and the deterministic processes for PA and phytoplankton. Structural equation modeling analysis showed a significant negative relationship between bacteria richness and phytoplankton richness, and a significant positive relationship between phytoplankton (richness and community composition) and zooplankton. Overall, this study emphasizes that MP, at environmental concentrations, can change the diversity and structure of plankton microbial communities, which might have a negative effect on ecological systems.

COVID-19 pandemic-related drugs and microplastics from mask fibers jointly affect soil functions and processes

The COVID-19 pandemic has led to an unprecedented increase in pharmaceutical drug consumption and plastic waste disposal from personal protective equipment. Most drugs consumed during the COVID-19 pandemic were used to treat other human and animal diseases. Hence, their nearly ubiquitous presence in the soil and the sharp increase in the last 3 years led us to investigate their potential impact on the environment. Similarly, the compulsory use of face masks has led to an enormous amount of plastic waste. Our study aims to investigate the combined effects of COVID-19 drugs and microplastics from FFP2 face masks on important soil processes using soil microcosm experiments. We used three null models (additive, multiplicative, and dominative models) to indicate potential interactions among different pharmaceutical drugs and mask MP. We found that the multiple-factor treatments tend to affect soil respiration and FDA hydrolysis more strongly than the individual treatments. We also found that mask microplastics when combined with pharmaceuticals caused greater negative effects on soil. Additionally, null model predictions show that combinations of high concentrations of pharmaceuticals and mask MP have antagonistic interactions on soil enzyme activities, while the joint effects of low concentrations of pharmaceuticals (with or without MP) on soil enzyme activities are mostly explained by null model predictions. Our study underscores the need for more attention on the environmental side effects of pharmaceutical contamination and their potential interactions with other anthropogenic global change factors.

Ciprofloxacin affects nutrient removal in manganese ore-based constructed wetlands: Adaptive responses of macrophytes and microbes

Ciprofloxacin (CIP) has received considerable attention in recent decades due to its high ecological risk. However, little is known about the potential response of macrophytes and microbes to varying levels of CIP exposure in constructed wetlands. Therefore, lab-scale manganese ore-based tidal flow constructed wetlands (MO-TFCWs) were operated to evaluate the responses of macrophytes and microbes to CIP over the long term. The results indicated that total nitrogen removal improved from 79.93% to 87.06% as CIP rose from 0 to 4 mg L-1. The chlorophyll content and antioxidant enzyme activities in macrophytes were enhanced under CIP exposure, but plant growth was not inhibited. Importantly, CIP exposure caused a marked evolution of the substrate microbial community, with increased microbial diversity, expanded niche breadth and enhanced cooperation among the top 50 genera, compared to the control (no CIP). Co-occurrence network also indicated that microorganisms may be more inclined to co-operate than compete. The abundance of the keystone bacterium (involved in nitrogen transformation) norank_f__A0839 increased from 0.746% to 3.405%. The null model revealed drift processes (83.33%) dominated the community assembly with no CIP and 4 mg L-1 CIP. Functional predictions indicated that microbial carbon metabolism, electron transfer and ATP metabolism activities were enhanced under prolonged CIP exposure, which may contribute to nitrogen removal. This study provides valuable insights that will help achieve stable nitrogen removal from wastewater containing antibiotic in MO-TFCWs.

Unveiling microbial degradation of triclosan: Degradation mechanism, pathways, and catalyzing clean energy

Emerging organic contaminants present in the environment can be biodegraded in anodic biofilms of microbial fuel cells (MFCs). However, there is a notable gap existing in deducing the degradation mechanism, intermediate products, and the microbial communities involved in degradation of broad-spectrum antibiotic such as triclosan (TCS). Herein, the possible degradation of TCS is explored using TCS acclimatized biofilms in MFCs. 95% of 5 mgL-1 TCS are been biodegraded within 84 h with a chemical oxygen demand (COD) reduction of 62% in an acclimatized-MFC (A-MFC). The degradation of TCS resulted in 8 intermediate products including 2,4 -dichlorophenol which gets further mineralized within the system. Concurrently, the 16S rRNA V3-V4 sequencing revealed that there is a large shift in microbial communities after TCS acclimatization and MFC operation. Moreover, 30 dominant bacterial species (relative intensity >1%) are identified in the biofilm in which Sulfuricurvum kujiense, Halomonas phosphatis, Proteiniphilum acetatigens, and Azoarcus indigens significantly contribute to dihydroxylation, ring cleavage and dechlorination of TCS. Additionally, the MFC was able to produce 818 ± 20 mV voltage output with a maximum power density of 766.44 mWm-2. The antibacterial activity tests revealed that the biotoxicity of TCS drastically reduced in the MFC effluent, signifying the non-toxic nature of the degraded products. Hence, this work provides a proof-of-concept strategy for sustainable mitigation of TCS in wastewaters with enhanced bioelectricity generation.

Gaining insight into the effect of laccase expression on humic substance formation during lignocellulosic biomass composting

The aim is to enhance lignin humification by promoting laccase activities which can promote lignin depolymerization and reaggregation during composting. 1-Hydroxybenzotriazole (HBT) is employed to conduct laccase mediator system (LMS), application of oxidized graphene (GO) in combination to strengthen LMS. Compared with control, the addition of GO, HBT, and GH (GO coupled with HBT) significantly improved laccase expression and activities (P < 0.05), with lignin humification efficiency also increased by 68.6 %, 36.7 %, and 107.8 %. GH treatment induces microbial expression of laccase by increasing the abundance and synergy of core microbes. The unsupervised learning model, vector autoregressive model and Mantel test function were combined to elucidate the mechanism of action of exogenous materials. The results showed that GO stabilized the composting environment on the one hand, and acted as a support vector to stabilize the LMS and promote the function of laccase on the other. In GH treatment, degradation of macromolecules and humification of small molecules were promoted simultaneously by activating the dual function of laccase. Additionally, it also reveals the GH enhances the humification of lignocellulosic compost by converting phenolic pollutants into aggregates. These findings provide a new way to enhance the dual function of laccase and promote lignin humification during composting. It could effectively achieve the resource utilization of organic solid waste and reduce composting pollution.

Marine Dehalogenator and Its Chaperones: Microbial Duties and Responses in 2,4,6-Trichlorophenol Dechlorination

Marine environments contain diverse halogenated organic compounds (HOCs), both anthropogenic and natural, nourishing a group of versatile organohalide-respiring bacteria (OHRB). Here, we identified a novel OHRB (Peptococcaceae DCH) with conserved motifs but phylogenetically diverse reductive dehalogenase catalytic subunit (RdhAs) from marine enrichment culture. Further analyses clearly demonstrate the horizontal gene transfer of rdhAs among marine OHRB. Moreover, 2,4,6-trichlorophenol (TCP) was dechlorinated to 2,4-dichlorophenol and terminated at 4-chlorophenol in culture. Dendrosporobacter and Methanosarcina were the two dominant genera, and the constructed and verified metabolic pathways clearly demonstrated that the former provided various substrates for other microbes, while the latter drew nutrients, but might provide little benefit to microbial dehalogenation. Furthermore, Dendrosporobacter could readily adapt to TCP, and sporulation-related proteins of Dendrosporobacter were significantly upregulated in TCP-free controls, whereas other microbes (e.g., Methanosarcina and Aminivibrio) became more active, providing insights into how HOCs shape microbial communities. Additionally, sulfate could affect the dechlorination of Peptococcaceae DCH, but not debromination. Considering their electron accessibility and energy generation, the results clearly demonstrate that bromophenols are more suitable than chlorophenols for the enrichment of OHRB in marine environments. This study will greatly enhance our understanding of marine OHRB (rdhAs), auxiliary microbes, and microbial HOC adaptive mechanisms.

Response and recovery mechanisms of river microorganisms to gradient concentrations of estrogen

As an important ecological system on the earth, rivers have been influenced by the rapid development of urbanization, industrialization, and anthropogenic activities. Increasingly more emerging contaminants, such as estrogens, are discharged into the river environment. In this study, we conducted river water microcosmic experiments using in situ water to investigate the response mechanisms of microbial community when exposed to different concentrations of target estrogen (estrone, E1). Results showed that both exposure time and concentrations shaped the diversity of microbial community when exposed to E1. Deterministic process played a vital role in influencing microbial community over the entire sampling period. The influence of E1 on microbial community could last for a longer time even after the E1 has been degraded. The microbial community structure could not be restored to the undisturbed state by E1, even if disturbed by low concentrations of E1(1 μg/L and 10 μg/L) for a short time. Our study suggests that estrogens could cause long-term disturbance to the microbial community of river water ecosystem and provides a theoretical basis for assessing the environmental risk of estrogens in rivers.

Exploring the variation of bacterial community and nitrogen transformation functional genes under the pressure of heavy metals in different coastal mariculture patterns

Equilibrium in microbial dynamics and nitrogen transformation in the sediment is critical for maintaining healthy mariculture environment. However, our understanding about the impact of heavy metals on the bacterial community and nitrogen transformation functional genes in different mariculture patterns is still limited. Here, we analyzed 30 sediment samples in the vertical distribution from three different mariculture patterns mainly include open mariculture zone (K), closed mariculture pond (F) and pristine marine area (Q). Illumina MiSeq Sequencing was applied to investigate the bacterial community and structure in the sediment. Quantitative polymerase chain reaction (qPCR) was used to determine the effect of heavy metals on nitrogen transformation functional genes. Results showed that bacterial community and structure varied greatly in different mariculture patterns. Chloroflexi, Proteobacteria and Desulfobacterota were predominant phyla in the coastal mariculture area. High concentrations of heavy metals mainly enriched in the up layer (5-40 cm) of the sediment in the mariculture zone. The abundance of functional genes in the closed mariculture pond was much higher than the open mariculture zone and pristine marine area. And the high abundance of nitrification and denitrification functional genes mainly accumulated at the depth from 5 cm to 40 cm. Heavy metals content such as Fe, Cr, Mn, Ni, As, Cd, Pb and nutrient content NH₄⁺-N, NO₃^--N and NO₂^--N were highly associated with bacterial community and nitrogen transformation functional genes. This study comprehensively elaborated the effect of heavy metals on the bacterial community and nitrogen transformation functional genes in different coastal mariculture patterns, indicating the possible role of closed mariculture pond in reducing nitrogen transformation efficiency, which will provide useful information for preventing pollution risk in the mariculture area.