Insights on the role of periphytic biofilm in synergism with Iris pseudacorus for removing mixture of pharmaceutical contaminants from wastewater

Pantoea jilinensis D25 enhances tomato salt tolerance via altering antioxidant responses and soil microbial community structure

As a major challenge to global food security, soil salinity is an important abiotic stress factor that seriously affects the crop growth and yield. In this study, the mechanism of salt resistance of Pantoea jilinensis D25 and its improving effect on salt tolerance of tomato were explored with salt resistance-related genes identified in strain D25 by genomic sequencing. The results showed that in comparison with the treatment of NaCl, strain D25 significantly increased the fresh weight, shoot length, root length, and chlorophyll content of tomato under salt stress by 46.7%, 20%, 42.4%, and 44.2%, respectively, with increased absorptions of various macronutrients and micronutrients and decreased accumulation of Na+. The activities of defense enzymes (peroxidase, catalase, superoxide dismutase, phenylalanine ammonia-lyase, and polyphenol oxidase) were enhanced, while the content of malondialdehyde was decreased. The results of quantitative real-time PCR analysis showed that the expressions of genes (SlSOS1, SlNHX1, SlHKT1.1, SlSOD1, SlAPX2, SlAOS, SlPin II, Solyc08g066270.1, Solyc03g083420.2 and SlGA20ox1) related to ion transporters, antioxidant machinery, key defense, serine/threonine protein kinase synthesis, and gibberellin (GA) signal protein were up-regulated and were the highest in the treatment of both NaCl and strain D25. The activities of enzymes (dehydrogenase, urease, invertase, and catalase activities) related to soil fertility were enhanced. The results of 16S rRNA sequencing showed that soil microbial diversity and the abundance of probiotics (e.g., Acidibacter, Limnobacter, and Romboutsia) were significantly increased. Our study provided strong experimental evidence to support the agricultural application of strain D25 in the promotion of growth in crops.

Pilot and full scale applications of floating treatment wetlands for treating diffuse pollution

Floating treatment wetlands (FTW) are nature-based solutions for the purification of open water systems such as rivers, ponds, and lakes polluted by diffuse sources as untreated or partially treated domestic wastewater and agricultural run-off. Compared with other physicochemical and biological technologies, FTW is a technology with low-cost, simple configuration, easy to operate; has a relatively high efficiency, and is energy-saving, and aesthetic. Water remediation in FTWs is supported by plant uptake and the growth of a biofilm on the water plant roots, so the selection of the macrophyte species is critical, not only to pollutant removal but also to the local ecosystem integrity, especially for full-scale implementation. The key factors such as buoyant frame/raft, plant growth support media, water depth, seasonal variation, and temperature have a considerable role in the design, operation, maintenance, and pollutant treatment performance of FTW. Harvesting is a necessary process to maintain efficient operation by limiting the re-pollution of plants in the decay phase. Furthermore, the harvested plant biomass can serve as a green source for the recovery of energy and value-added products.

Iron-Nitrogen Amendment Reduced Perfluoroalkyl Acids' Phyto-Uptake in the Wheat-Soil Ecosystem: Contributions of Dissolved Organic Matters in Soil Solution and Root Extracellular Polymeric Substances

Understanding the mechanisms underlying perfluoroalkyl acids (PFAAs) translocation, distribution, and accumulation in wheat-soil ecosystems is essential for agricultural soil pollution control and crop ecological risk assessment. This study systematically investigated the translocation of 13 PFAAs under different iron and nitrogen fertilization conditions in a wheat-soil ecosystem. Short-chain PFAAs including PFBA, PFPeA, PFHxA, and PFBS mostly accumulated in soil solution (10.43-55.33%) and soluble extracellular polymeric substances (S-EPS) (11.39-14.77%) by the adsorption to amino- (-NH2) and hydroxyl (-OH) groups in dissolved organic matter (DOM). Other PFAAs with longer carbon chain lengths were mostly distributed on the soil particle surface by hydrophobic actions (74.63-94.24%). Iron-nitrogen amendments triggered (p < 0.05) soil iron-nitrogen cycling, rhizospheric reactive oxygen species fluctuations, and the concentration increases of -NH2 and -OH in the DOM structure. Thus, the accumulation capacity of PFAAs in soil solution and root EPS was increased. In sum, PFAAs' translocation from soil particles to wheat root was synergistically reduced by iron and nitrogen fertilization through increased adsorption of soil particles (p < 0.05) and the retention of soil solution and root EPSs. This study highlights the potential of iron-nitrogen amendments in decreasing the crop ecological risks to PFAAs' pollution.

Fate of five bisphenol derivatives in Chlamydomonas mexicana: Toxicity, removal, biotransformation and microalgal metabolism

Bisphenols (BPs) are recognized as emerging contaminants because of their estrogenic properties and frequent occurrence in environmental matrices. Here, we evaluated the toxic effects of five common BPs on freshwater microalga Chlamydomonas mexicana and removal of the BPs by the alga. Bisphenols -AF (BPAF), -B (BPB), and -Z (BPZ) (96 h, EC50 1.78-12.09 mg·L-1) exhibited higher toxicity to C. mexicana compared to bisphenol -S (BPS) and -F (BPF) (96 h, EC50 30.53-85.48 mg·L-1). In contrast, the mixture of BPs exhibited acute toxicity (96 h, EC50 8.07 mg·L-1). After 14 days, C. mexicana had effectively removed 61%, 99%, 55%, 87%, and 89% of BPS, BPF, BPAF, BPB, and BPZ, respectively, at 1 mg L-1. The biotransformed products of all five BPs were analyzed using UHPLC QTOF, and their toxicity was predicted. All biotransformed products were observed to be less toxic than the parent compounds. The fatty acid composition of C. mexicana after exposure to the BP mixture was predominantly palmitic acid (34.14%), followed by oleic acid (18.9%), and γ-linolenic acid (10.79%). The results provide crucial information on the ecotoxicity of these five BPs and their removal by C. mexicana; the resulting biomass is a potential feedstock for producing biodiesel.

Plant -microbe assisted emerging contaminants (ECs) removal and carbon cycling

Continuous increase in the level of atmospheric CO₂ and environmental contaminates has aggravated various threats resulting from environmental pollution and climate change. Research into plant -microbe interaction has been a central concern of ecology for over the year. However, despite the clear contribution of plant -microbe to the global carbon cycle, the role of plant -microbe interaction in carbon pools, fluxes and emerging contaminants (ECs) removal are still a poorly understood. The use of plant and microbes in ECs removal and carbon cycling is an attractive strategy because microbes operate as biocatalysts to remove contaminants and plant roots offer a rich niche for their growth and carbon cycling. However, bio-mitigation of CO₂ and removal of ECs is still under research phase because of the CO₂ capture and fixation efficiency is too low for industrial purposes and cutting-edge removal methods have not been created for such emerging contaminants.

Effects of Graphene Oxide on the Growth and Photosynthesis of the Emergent Plant Iris pseudacorus

The extensive applications of graphene oxide (GO) inevitably lead to entry into the natural aquatic environment. However, information on its toxicity to emergent plants is still lacking. In this study, an emergent plant, Iris pseudacorus, was exposed to GO (1, 20, 80, and 140 mg·L^-1) under hydroponic conditions for 15 weeks. Changes in plant growth were assessed by analyzing plant biomass and photosynthetic pigment contents; the photosynthesis response was verified by measuring chlorophyll a fluorescence; and the nutrient levels of the plant were evaluated. Results showed that GO at 20-140 mg·L^-1 significantly increased plant dry weight by 37-84% and photosynthetic pigment contents by 26-178%, and 80 mg·L^-1 was the optimal concentration. PSII activity, adjustment capacities of electron transport in PSII, the grouping or energetic connectivity between PSII units, light energy conversion efficiency, photosynthesis performance indexes (by 11-51%), and contents of several nutrient elements (N, Fe, and Cu) were increased by 49-69%, 34-84%, and 11-38%, respectively. These findings indicate that GO can enhance plant growth by promoting plant photosynthesis performance and improving plant nutrient levels, and has great application potential in promoting the growth and development of this emergent plant as a phytoremediation agent.

Simultaneous removal of sediment and water contaminants in a microbial electrochemical system with embedded active electrode by in-situ utilization of electrons

In the water environment such as lakes, there is a phenomenon that the sediment and overlying water are polluted at the same time. In this study, A microbial electrochemical system with an embedded active electrode was developed for simultaneous removal of polycyclic aromatic hydrocarbons in sediment and antibiotics in overlying water by in-situ utilization of electrons. In the closed-circuit group, the pyrene concentration in sediment decreased from 9.94 to 2.08 mg/L in 96 d, and the sulfamethoxazole concentration in water decreased from 5.12 to 1.12 mg/L in 168 h. These values were 18.71 % and 31.21 % higher, respectively, than those of the open-circuit group. The pyrene degradation pathway may be from polycyclic aromatic substances to low-cyclic aromatic hydrocarbons via successive breakdown of benzene rings. Multiple metabolites produced by reduction verified that SMX or its intermediates were reductively degraded in water. On the active electrode, the relative abundances of Acetobacterium and Piscinibacter, which were genera related to SMX degradation, was promoted, while the electricity-producing genus Pseudomonas was inhibited. ccdA, pksS, torC, and acsE genes related to extracellular electron transport may accelerate electron transport. Electrons could be transferred to SMX under the influence of proteins involved in extracellular electron transport, and SMX could be degraded reductively as an electron acceptor by microbes. Generation of electrons and in-situ utilization for simultaneous removal of solid-liquid two-phase pollutants will provide mechanistic insight into pollutant biodegradation by microbial electrochemistry and promote the development of sustainable bioremediation strategies for surface water.

Involvement of exogenous arsenic-reducing bacteria in root surface biofilm formation promoted phytoextraction of arsenic

Root surface biofilm (RSB) is the last window for pollutants entering plant roots and thus plays a critical role in the phytoextraction of pollutants. Exogenous arsenic-reducing bacteria (EARB) have been adopted to enhance the phytoextraction of arsenic (As). However, whether EARB would be involved in RSB formation together with indigenous bacteria and the role of EARB involvement in As phytoextraction are still unknown. Herein, two EARB strains and two phytoextractors (wheat and maize) were selected to investigate the involvement of EARB in RSB formation and its role in As phytoextraction. Results showed that EARB successfully participated in RSB formation together with indigenous bacteria, attributing to their strong chemotaxis and biofilm formation abilities induced by root exudates. The involvement of EARB in RSB formation significantly enhanced As accumulation in plant roots, since more arsenite (As(III)) caused by arsenate (As(V)) reduction in RSB was absorbed by roots. Its underlying mechanism was further elucidated. EARB involvement increased phylum Proteobacteria to produce more siderophores in RSB. Siderophores then improved photosynthesis by increasing catalase and peroxidase activities and decreasing the malondialdehyde of plants. These actions further raised the shoot fresh weight to enhance As accumulation in plant roots. Moreover, mesophyll cell in wheat has a stronger As(V) reduction ability than that in maize, resulting in opposite distribution patterns of As(III) and As(V) in wheat and maize shoots. This study provides a new understanding of phytoextraction enhanced by exogenous bacteria and fills the gap in the role of EARB in As phytoextraction from the perspective of the RSB microregion.

Practical and Rapid Membrane-Based Biosensor for Phenol Using Copper/Calcium-Enzyme Hybrid Nanoflowers

Phenol, a pollutant frequently found in chemical industries effluents, is highly toxic even in low concentrations. This study reports a green, simple, and rapid method for qualitative phenol biosensing using horseradish peroxidase (HRP) hybrid nanoflowers made with copper (Cu²⁺-hNF) or calcium (Ca²⁺-hNF) ions. The enzyme was immobilized through protein-inorganic self-assembly into hybrid structures and subsequently supported onto a polyvinylidene fluoride (PVDF) membrane. SEM, EDS, FTIR, and XRD techniques sustained the effective enzyme encapsulation into hybrid structures. The protein concentration in the structures was 0.25 mg.mL^-1 for both ions. The best temperature and pH were 60 °C and 7.4, respectively, for both hybrids and the free enzyme, suggesting that the immobilization did not affect the optimal conditions of the free HRP. Thermal stability from 25 to 70 °C and pH stability from 4.0 to 9.0 of the hybrids were also determined. Finally, using copper and calcium hybrids, both biosensors produced onto a PVDF membrane could detect phenol in concentrations ranging from 0.72 to 24.00 µmol.mL^-1 in 1 min. In contrast, control biosensors produced with free enzyme have not presented a visible color change in the same conditions. The findings suggest a promising application of the developed biosensors in functional phenol detection.

Nutrient dynamics and microbial community response in macrophyte-dominated lakes: Implications for improved restoration strategies

Although lakes dominated by macrophytes are conducive to ecological balance, this balance is easily disrupted by excessive nutrients flowing into the lake. However, knowledge of whether excessive nutrients lead to different microbial environmental vulnerabilities in the lake sediment between macrophyte-dominated areas and macrophyte-free areas is a prerequisite for the implementation of targeted protection measures. In this study, we investigated bacterial communities in sediments using high-throughput sequencing of 16S rRNA genes. Our results showed that the sources of total nitrogen (TN) and organic matter (OM) were related to the macrophytes. The structure, drivers, and interspecific associations of bacterial community, which were more susceptible to increased changes in TN and OM, differed significantly between macrophyte-dominated areas and macrophyte-free areas. More precisely, the lake edge, where was occupied by macrophytes, had a higher proportion of deterministic phylogenetic turnover (88.89%) than other sites, as well as a wider ecological niche and a tighter network structure. Further, as the difference in TN increased, the main assembly processes in surface sediments changed from stochastic to deterministic. However, the majority of phyla from the lake edge showed a greater correlation with excessive nutrients, and the selection of the community by excessive nutrients was more obvious at the edge of the lake. In addition, our results demonstrated that the stability of the bacterial community in macrophyte-free areas is greater than in macrophyte-dominated areas, while an excessively high deterministic process ratio and nutrient (TN and OM) concentration significantly reduced bacterial community stability at macrophyte-dominated areas. Taken together, these results provide a better understanding of the effects of excessive nutrients derived from macrophytes on bacterial community patterns, and highlight the importance of avoiding the accumulation of TN and OM in macrophyte-dominated areas to enhance the sustainability of the ecosystem after restoration of lakes with macrophytes.

Removal of perfluoroalkyl acids and dynamic succession of biofilm microbial communities in the decomposition process of emergent macrophytes in wetlands

Perfluoroalkyl acids (PFAAs) are emerging contaminants that pose significant environmental and health concerns. Water-sediment-macrophyte residue systems were established to clarify the removal efficiency of PFAAs, explore possible removal pathways, and profile the dynamic succession of biofilm microbial communities in the decomposition process. These systems were fortified with 12 PFAAs at three concentration levels. Iris pseudacorus and Alisma orientale were selected as the decomposing emergent macrophytes. The removal rates in the treatments with residues of I. pseudacorus (IP) and A. orientale (AO) were 34.4% to 88.9% and 36.5% to 89.9%, respectively, which were higher than those in the control groups (CG) (30.3% to 86.9%), suggesting that decomposition could alter the removal of PFAAs. Sediment made the greatest contributions (preloaded 14.5% to 77.8% of PFAAs in IP, 14.3% to 78.2% in AO, and 27.4% to 71.9% in CG). PFAAs could also be removed by macrophyte residue sorption (0.0190% to 13.0% in IP and 0.016% to 15.6% in AO) and bioaccumulation of residual biofilm (the contributions of biofilm microbes and their extracellular polymeric substances were 0.0110% to 3.93% and 0.918% to 34.4%, respectively, in IP and 0.0141% to 4.65% and 1.49% to 34.1%, respectively, in AO). Significant correlations were observed between sediment/residue adsorption and bioaccumulation of biofilm microbes, and were significantly correlated with perfluoroalkyl chain length (p < 0.05). The dynamic succession of residual biofilm microbial communities was investigated. The largest difference was found at the preliminary stage. The most similar communities were found in AO on day 70 (with specific genera Macellibacteroides and WCHB1-32) and in IP on day 35 (with specific genera Aeromonas and Flavobacterium). This study is useful to understand the removal of PFAAs during the decomposition process, providing further assistance in removing PFAAs during the life cycle of macrophytes in wetlands.

Molecular insights into plant-microbe interactions for sustainable remediation of contaminated environment

The widespread distribution of organic and inorganic pollutants in water resources have increased due to rapid industrialization. Rhizospheric zone-associated bacteria along with endophytic bacteria show a significant role in remediation of various pollutants. Metaomics technologies are gaining an advantage over traditional methods because of their capability to obtain detailed information on exclusive microbial communities in rhizosphere of the plant including the unculturable microorganisms. Transcriptomics, proteomics, and metabolomics are functional methodologies that help to reveal the mechanisms of plant-microbe interactions and their synergistic roles in remediation of pollutants. Intensive analysis of metaomics data can be useful to understand the interrelationships of various metabolic activities between plants and microbes. This review comprehensively discusses recent advances in omics applications made hitherto to understand the mechanisms of plant-microbe interactions during phytoremediation. It extends the delivery of the insightful information on plant-microbiomes communications with an emphasis on their genetic, biochemical, physical, metabolic, and environmental interactions.

Non-synonymous substitution of evolutionarily conserved residue in Tau class glutathione transferases alters structural and catalytic features

Plant-specific tau glutathione transferases (GSTs) are basically involved in catalysing γ-glutathione (GSH)-dependent conjugation reactions with pesticides and herbicides, which play an important role in the detoxification of pollutants. Given the lack of systematic biochemical and structural information on tau GSTs, the study of their mediated defence mechanisms against toxic compounds has been greatly hindered. Here, we reveal the importance of the Ile residue closely interacting with GSH for the structural stability and catalytic function of GST. Evolutionary conservation analysis indicated that the crucial G-site Ile55 in the SbGSTU6 was converted to Thr53 of SbGSTU7. The comparative biochemical data on SbGSTU6, SbGSTU7 and their mutants showed that the substitution of Ile by Thr caused significant decrease in the affinity and catalytic efficiency of the GSTs. The unfavourable structural flexibility and pKa distribution of the active cavity residues were also demonstrated. Crystallography studies and molecular dynamics simulations showed that the conversion resulted in the hydrogen bond recombination with GSH and conformational rearrangement of GST active cavity, in which the Ile residue was more conducive to the formation of enzyme substrate complexes. The extensive biochemical and structural data not only reveal the critical role of the conserved G-site Ile residue in catalysing GSH-conjugate reactions but also provide valuable resources for the development of GST engineering in analytical and agricultural biotechnology.