DNA-stable isotope probing and metagenomics reveal Fe(II) oxidation by core microflora in microoxic rhizospheric habitats to mitigate the accumulation of cadmium and phenanthrene in rice.

Rice rhizosphere soil-porewater microdomains exist within an iron (Fe)-rich microoxic habitat during paddy soil flooding. However, the response mechanisms of core microflora in this habitat to Fe(II)-oxidation-mediated cadmium (Cd) and phenanthrene (Phen) remain unclear. Using gel-stabilized gradient systems to replicate the microoxic conditions in the rice rhizosphere porewater, we found that microaerophilic rhizobacteria drove Fe(II) oxidation to yield iron oxides, thereby reducing the Cd and Phen contents in the rhizosphere porewater and rice (Cd and Phen decreased by 15.9%-78.0% and 10.1%-37.4%, respectively). However, co-exposure to Cd and Phen resulted in a greater reduction in the Cd uptake and a greater increase in the Phen uptake in rice as compared to those in the Cd or Phen treatments, possibly attributing to the cation-π interactions between Cd and Phen, as well as competition between the adsorption sites on the roots. The elevation of Cd-tolerant genes and Phen-degradation genes in biogenic cell-mineral aggregates unveiled the survival strategies of rhizobacteria with respect to Cd and Phen in the microoxic habitat. Potential Cd-tolerant rhizobacteria (e.g., Pandoraea and Comamonas) and Phen-degradation rhizobacteria (e.g., Pseudoxanthobacter) were identified through the DNA-SIP and 16S rRNA gene amplicon sequencing. Metagenomic analysis further confirmed that these core microbes harbor Cd-tolerant, Phen-degradation, and Fe(II) oxidation genes, supporting their metabolic potential for Cd and/or Phen in the microoxic habitat of the rice rhizosphere. These findings suggest the potential mechanism and ecological significance of core rhizospheric microbial-driven Fe(II) oxidation in mitigating the bioavailability of Cd and Phen in paddy soil during flooding.

Biochar modification accelerates soil atrazine biodegradation by altering bacterial communities, degradation-related genes and metabolic pathways.

Atrazine is one of the most used herbicides, posing non-neglectable threats to ecosystem and human health. This work studied the performance and mechanisms of surface-modified biochar in accelerating atrazine biodegradation by exploring the changes in atrazine metabolites, bacterial communities and atrazine degradation-related genes. Among different types of biochar, nano-hydroxyapatite modified biochar achieved the highest degradation efficiency (85.13 %), mainly attributing to the increasing pH, soil organic matter, soil humus, and some enriched indigenous bacterial families of Bradyrhizobiaceae, Rhodospirillaceae, Methylophilaceae, Micrococcaceae, and Xanthobacteraceae. The abundance of 4 key atrazine degradation-related genes (atzA, atzB, atzC and triA) increased after biochar amendment, boosting both dechlorination and dealkylation pathways in atrazine metabolism. Our findings evidenced that biochar amendment could accelerate atrazine biodegradation by altering soil physicochemical properties, microbial composition and atrazine degradation pathways, providing clues for improving atrazine biodegradation performance at contaminated sites.

Microbial consortium assembly and functional analysis via isotope labelling and single-cell manipulation of polycyclic aromatic hydrocarbon degraders.

Soil microbial flora constitutes a highly diverse and complex microbiome on Earth, often challenging to cultivation, with unclear metabolic mechanisms in situ. Here, we present a pioneering concept for the in situ construction of functional microbial consortia (FMCs) and introduce an innovative method for creating FMCs by utilizing phenanthrene as a model compound to elucidate their in situ biodegradation mechanisms. Our methodology involves single-cell identification, sorting, and culture of functional microorganisms, resulting in the formation of a precise in situ FMC. Through Raman-activated cell sorting-stable-isotope probing, we identified and isolated phenanthrene-degrading bacterial cells from Achromobacter sp. and Pseudomonas sp., achieving precise and controllable in situ consortia based on genome-guided cultivation. Our in situ FMC outperformed conventionally designed functional flora when tested in real soil, indicating its superior phenanthrene degradation capacity. We revealed that microorganisms with high degradation efficiency isolated through conventional methods may exhibit pollutant tolerance but lack actual degradation ability in natural environments. This finding highlights the potential to construct FMCs based on thorough elucidation of in situ functional degraders, thereby achieving sustained and efficient pollutant degradation. Single-cell sequencing linked degraders with their genes and metabolic pathways, providing insights regarding the construction of in situ FMCs. The consortium in situ comprising microorganisms with diverse phenanthrene metabolic pathways might offer distinct advantages for enhancing phenanthrene degradation efficiency, such as the division of labour and cooperation or communication among microbial species. Our approach underscores the importance of in situ, single-cell precision identification, isolation, and cultivation for comprehensive bacterial functional analysis and resource exploration, which can extend to investigate MFCs in archaea and fungi, clarifying FMC construction methods for element recycling and pollutant transformation in complex real-world ecosystems.

Mechanisms and influential factors of soil chromium long-term stability by an accelerated aging system after chemical stabilization.

Chemical stabilization is one of the most widely used remediation strategies for chromium (Cr)-contaminated soils by reducing Cr(VI) to Cr(III), and its performance is affected by human and natural processes in a prolonged period, challenging long-term Cr stability. In this work, we established a method for evaluating the long-term effectiveness of remediation of Cr-contaminated soils, and developed an accelerated aging system to simultaneously simulate acid rain leaching and freeze-thaw cycles. The mechanisms and influencing factors of long-term (50-year) change in soil Cr speciation were unravelled after stabilization with Metafix®. Chemical stabilization remarkably decreased the contents of Cr(VI)soil, Crtotal-leach and Cr(VI)leach, among which the removal rate of Cr(VI) in soil was up to 89.70 %, but it also aggravated soil Cr instability. During the accelerated aging process, Crtotal-leach change rates in chemically stabilized soil samples were 0.0462-0.0587 mg/(L·a), and soil Cr became instable after 20-year accelerated aging. The proportion of Cr bound to organic matter and residual Cr increased in soil, and exchangeable Cr decreased. Linear combination fitting results of XANES also showed that Cr(VI) and Cr3+ were transformed into OM-Cr(III), Fh-Cr(III) and CrFeO3 after restoration. During the accelerated aging process, acid rain leaching activated Cr(III) and dissolved Cr(VI), whereas freeze-thaw cycle mainly affected OM-Cr. Chemical stabilization, acid rain leaching and aging time were the major factors influencing the stability of soil Cr, and the freeze-thaw cycle promoted the influence of acid rain leaching. This study provided a new way to explore the long-term effectiveness and instability mechanisms at Cr-contaminated site after chemical stabilization.

Impacts of organophosphate pesticide types and concentrations on aquatic bacterial communities and carbon cycling.

Organophosphorus pesticides (OPPs) are important chemical stressors in aquatic ecosystems, and they attract increasing more attentions recently. However, the impacts of different OPPs on carbon cycling remain unclear, particularly for those functional-yet-uncultivable microbes. This study investigated the change in lake aquatic microbial communities in the presence of dichlorvos, monocrotophos, omethoate and parathion. All OPPs significantly inhibited biomass (p < 0.05) and the expression of carbon cycle-related cbbLG gene (p < 0.01), and altered aquatic microbial community structure, interaction, and assembly. Variance partitioning analysis showed a stronger impact of pesticide type on microbial biomass and community structure, where pesticide concentration played more significant roles in carbon cycling. From analysis of cbbLG gene and PICRUSt2, Luteolibacter and Verrucomicrobiaceae assimilated inorganic carbon through Wood-Ljungdahl pathway, whereas it was Calvin-Benson-Bassham cycle for Cyanobium PCC-6307. This work provides a deeper insight into the behavior and mechanisms of microbial community change in aquatic system in response to OPPs, and explicitly unravels the impacts of OPPs on their carbon-cycling functions.

Eliminating the stabilizer antagonistic effects for efficiently stabilizing Pb and As co-contaminated soil by innovative stepwise steam flash heating.

Chemical stabilization is frequently used to stabilize lead (Pb) or arsenate (As), but faces challenges in Pb-As co-contaminated soils because of the antagonistic reactions between chemical stabilizers and contaminants. In this work, we innovated an effective and cost-efficient stepwise steam flash heating (SSFH) strategy to simultaneously immobilize Pb and As, and unraveled the underlying mechanisms. The combination of 1.5% Ca(H2PO4)2 and 2% Fe2(SO4)3 only decreased 1.99% Pb by toxicity characteristic leaching procedure (TCLP-Pb) but increased 17.8% of TCLP-As due to the antagonistic effects. SSFH with Ca(H2PO4)2 in the first step and Fe2(SO4)3 in the second step achieved the minimal TCLP-Pb and TCLP-As of 0.778 and 0.327 mg/L, respectively. It also reduced 69.8% of leachable As in 100-year acid rain simulation, indicating a favorable long-term stabilization performance. Additionally, SSFH approach reduced 43.2% stabilizer dosage and 14.9% cost. X-ray absorption near edge structure (XANES) documented that the stepwise SFH promoted the transformation of Pb(NO3)2 and NaAsO2/NaAsO3/As2O3/As2O5 into stable Pb3(PO4)2 and FeAsO4, preventing the formation of AsO43- and FePO4. Our findings proved the state-of-the-art SSFH approach and unraveled its mechanisms to stabilize Pb and As co-contamination in soils, offering a green and sustainable remediation alternative for the management of heavy metal contaminated sites. ENVIRONMENTAL IMPLICATION: A novel stepwise SFH approach can be applied to overcome the stabilizer antagonist effects by separately immobilizing Pb and As in two sequential steps. It also decreased 43.2% of stabilizer dosage and 14.9% of cost comparing to conventional chemical stabilization. This approach can be used for other metal co-contaminated soils facing similar antagonistic challenges, and our work raises a state-of-the-art solution for cost-effective, green and sustainable remediation practices.

Penicillium oxalicum induced phosphate precipitation enhanced cadmium (Cd) immobilization by simultaneously accelerating Cd biosorption and biomineralization.

Soil cadmium (Cd) is immobilized by the progressing biomineralization process as microbial induced phosphate precipitation (MIPP), which is regulated by phosphate (P) solubilizing microorganisms and P sources. However, little attention has been paid to the implications of Cd biosorption during MIPP. In this study, the newly isolated Penicillium oxalicum could immobilize 5.4-12.6 % of Cd2+, while the presence of hydroxyapatite (HAP) considerably enhanced Cd2+ immobilization in P. oxalicum and reached over 99 % Cd2+ immobilization efficiency within 7 days. Compared to P. oxalicum mono inoculation, MIPP dramatically boosted Cd biosorption and biomineralization efficiency by 71 % and 16 % after 96 h cultivation, respectively. P. oxalicum preferred to absorbing Cd2+ and reaching maximum Cd2+ biosorption efficiency of 87.8 % in the presence of HAP. More surface groups in P. oxalicum and HAP mineral involved adsorption which resulted in the formation of Cd-apatite [Ca8Cd2(PO4)6(OH)2] via ion exchange. Intracellular S2-, secreted organic acids and soluble P via HAP solubilization complexed with Cd2+, progressively mineralized into Cd5(PO4)3OH, Cd(H2PO4)2, C4H6CdO4 and CdS. These results suggested that Cd2+ immobilization was enhanced simultaneously by the accelerated biosorption and biomineralization during P. oxalicum induced P precipitation. Our findings revealed new mechanisms of Cd immobilization in MIPP process and offered clues for remediation practices at metal contaminated sites.

Appropriate control measure design by rapidly identifying risk areas of volatile organic compounds during the remediation excavation at an organic contaminated site.

Many organic contaminated sites require on-site remediation; excavation remediation processes can release many volatile organic compounds (VOCs) which are key atmospheric pollutants. It is therefore important to rapidly identify VOCs during excavation and map their risk areas for human health protection. In this study, we developed a rapid analysis and assessment method, aiming to and reveal the real-time distribution of VOCs, evaluate their human health risks by quantitative models, and design appropriate control measures. Through on-site diagonal distribution sampling and analysis, VOCs concentration showed a decreasing trend within 5 m from the excavation point and then increased after 5 m with the increase in distance from the excavation point (p < 0.05). The concentrations of VOCs near the dominant wind direction were higher than the concentrations of surrounding pollutants. In contrast with conventional solid-phase adsorption (SPA) and thermal desorption gas chromatography-mass spectrometry (TD-GC/MS) methods for determining the composition and concentration of VOCs, the rapid measurement of VOCs by photo-ionization detector (PID) fitted well with the chemical analysis and modeling assessment of cancer/non-cancer risk. The targeting area was assessed as mild-risk (PID < 10 ppm), moderate-risk (PID from 10 to 40 ppm), and heavy-risk (PID > 40 ppm) areas. Similarly, the human health risks also decreased gradually with the distance from the excavation point, with the main risk area located in the dominant wind direction. The results of rapid PID assessment were comparable to conventional risk evaluation, demonstrating its feasibility in rapidly identifying VOCs releases and assessing the human health risks. This study also suggested appropriate control measures that are important guidance for personal protection during the remediation excavation process.

Cultivation and characterization of functional-yet-uncultivable phenanthrene degraders by stable-isotope-probing and metagenomic-binning directed cultivation (SIP-MDC).

High-throughput identification and cultivation of functional-yet-uncultivable microorganisms is a fundamental goal in environmental microbiology. It remains as a critical challenge due to the lack of routine and effective approaches. Here, we firstly proposed an approach of stable-isotope-probing and metagenomic-binning directed cultivation (SIP-MDC) to isolate and characterize the active phenanthrene degraders from petroleum-contaminated soils. From SIP and metagenome, we assembled 13 high-quality metagenomic bins from 13C-DNA, and successfully obtained the genome of an active PHE degrader Achromobacter (genome-MB) from 13C-DNA metagenomes, which was confirmed by gyrB gene comparison and average nucleotide/amino identity (ANI/AAI), as well as the quantification of PAH dioxygenase and antibiotic resistance genes. Thereinto, we modified the traditional cultivation medium with antibiotics and specific growth factors (e.g., vitamins and metals), and separated an active phenanthrene degrader Achromobacter sp. LJB-25 via directed isolation. Strain LJB-25 could degrade phenanthrene and its identity was confirmed by ANI/AAI values between its genome and genome-MB (>99 %). Our results hinted at the feasibility of SIP-MDC to identify, isolate and cultivate functional-yet-uncultivable microorganisms (active phenanthrene degraders) from their natural habitats. Our findings developed a state-of-the-art SIP-MDC approach, expanded our knowledge on phenanthrene biodegradation mechanisms, and proposed a strategy to mine functional-yet-uncultivable microorganisms.

Media Use Behavior Mediates the Association Between Family Health and Intention to Use Mobile Health Devices Among Older Adults: Cross-Sectional Study.

BACKGROUND: With the advent of a new era for health and medical treatment, characterized by the integration of mobile technology, a significant digital divide has surfaced, particularly in the engagement of older individuals with mobile health (mHealth). The health of a family is intricately connected to the well-being of its members, and the use of media plays a crucial role in facilitating mHealth care. Therefore, it is important to examine the mediating role of media use behavior in the connection between the family health of older individuals and their inclination to use mHealth devices. OBJECTIVE: This study aims to investigate the impact of family health and media use behavior on the intention of older individuals to use mHealth devices in China. The study aims to delve into the intricate dynamics to determine whether media use behavior serves as a mediator in the relationship between family health and the intention to use mHealth devices among older adults. The ultimate goal is to offer well-founded and practical recommendations to assist older individuals in overcoming the digital divide. METHODS: The study used data from 3712 individuals aged 60 and above, sourced from the 2022 Psychology and Behavior Investigation of Chinese Residents study. Linear regression models were used to assess the relationships between family health, media use behavior, and the intention to use mHealth devices. To investigate the mediating role of media use behavior, we used the Sobel-Goodman Mediation Test. This analysis focused on the connection between 4 dimensions of family health and the intention to use mHealth devices. RESULTS: A positive correlation was observed among family health, media use behavior, and the intention to use mHealth devices (r=0.077-0.178, P<.001). Notably, media use behavior was identified as a partial mediator in the relationship between the overall score of family health and the intention to use mHealth devices, as indicated by the Sobel test (z=5.451, P<.001). Subgroup analysis further indicated that a complete mediating effect was observed specifically between family health resources and the intention to use mHealth devices in older individuals with varying education levels. CONCLUSIONS: The study revealed the significance of family health and media use behavior in motivating older adults to adopt mHealth devices. Media use behavior was identified as a mediator in the connection between family health and the intention to use mHealth devices, with more intricate dynamics observed among older adults with lower education levels. Going forward, the critical role of home health resources must be maximized, such as initiatives to develop digital education tailored for older adults and the creation of media products specifically designed for them. These measures aim to alleviate technological challenges associated with using media devices among older adults, ultimately bolstering their inclination to adopt mHealth devices.

Mechanisms of biochar assisted di-2-ethylhexyl phthalate (DEHP) biodegradation in tomato rhizosphere by metabolic and metagenomic analysis.

The intensive accumulation of di-2-ethylhexyl phthalate (DEHP) in agricultural soils has resulted in severe environmental pollution that endangers ecosystem and human health. Biochar is an eco-friendly material that can help in accelerating organic pollutant degradation; nevertheless, its roles in enhancing DEHP removal in rhizosphere remain unclear. This work investigated the impacts of biochar dosage (0%-2.0%) on DEHP degradation performance in tomato rhizosphere by comprehensively exploring the change in DEHP metabolites, bacterial communities and DEHP-degrading genes. Our results showed a significant increase of rhizosphere pH, organic matter and humus by biochar amendment, which achieved a satisfactorily higher DEHP removal efficiency, maximally 77.53% in treatments with 1.0% of biochar. Biochar addition also remarkably changed rhizosphere bacterial communities by enriching some potential DEHP degraders of Nocardioides, Sphingomonas, Bradyrhizobium and Rhodanobacter. The abundance of genes encoding key enzymes (hydrolase, esterase and cytochrome P450) and DEHP-degrading genes (pht3, pht4, pht5, benC-xylZ and benD-xylL) were increased after biochar amendment, leading to the change in DEHP degradation metabolism, primarily from benzoic acid pathway to protocatechuic acid pathway. Our findings evidenced that biochar amendment could accelerate DEHP degradation by altering rhizosphere soil physicochemical variables, bacterial community composition and metabolic genes, providing clues for the mechanisms of biochar-assisted DEHP degradation in organic contaminated farmland soils.

Biospectroscopic fingerprinting phytotoxicity towards environmental monitoring for food security and contaminated site remediation.

Human activities have resulted in severe environmental pollution since the industrial revolution. Phytotoxicity-based environmental monitoring is well known due to its sedentary nature, abundance, and sensitivity to environmental changes, which are essential preconditions to avoiding potential environmental and ecological risks. However, conventional morphological and physiological methods for phytotoxicity assessment mainly focus on descriptive determination rather than mechanism analysis and face challenges of labour and time-consumption, lack of standardized protocol and difficulties in data interpretation. Molecular-based tests could reveal the toxicity mechanisms but fail in real-time and in-situ monitoring because of their endpoint manner and destructive operation in collecting cellular components. Herein, we systematically propose and lay out a biospectroscopic tool (e.g., infrared and Raman spectroscopy) coupled with multivariate data analysis as a relatively non-destructive and high-throughput approach to quantitatively measure phytotoxicity levels and qualitatively profile phytotoxicity mechanisms by classifying spectral fingerprints of biomolecules in plant tissues in response to environmental stresses. With established databases and multivariate analysis, this biospectroscopic fingerprinting approach allows ultrafast, in situ and on-site diagnosis of phytotoxicity. Overall, the proposed protocol and validation of biospectroscopic fingerprinting phytotoxicity can distinguish the representative biomarkers and interrogate the relevant mechanisms to quantify the stresses of interest, e.g., environmental pollutants. This state-of-the-art concept and design broaden the knowledge of phytotoxicity assessment, advance novel implementations of phytotoxicity assay, and offer vast potential for long-term field phytotoxicity monitoring trials in situ.

E. coli cotransport with composite colloid in unsaturated porous media: Multi-risk on migration and biomolecular response.

The diversity of colloidal types and the differences in the composite ratios in porous media are important factors governing the migration and biological risk of pathogenic microorganisms in the subsurface environment. In this study, E. coli O157:H7 was subjected to co-migration experiments with different compositions of the composite colloid montmorillonite (MMT)-Fe2O3, and the biomolecular response of E. coli under the action of colloids was analyzed by Raman spectroscopy to quantify the risk of E. coli under the action of composite colloids based on both. The results showed that Fe2O3 colloids inhibited E. coli migration mainly by electrostatic adsorption and reduced E. coli metabolism. MMT colloid inhibited E. coli migration mainly by blockage, and E. coli metabolism increased, and surface macromolecules decreased to reduce E. coli adhesion. MMT-Fe2O3 complex colloids inhibited migration through electrostatic attraction between the two and formation of cohesive colloids, with reduced E. coli metabolism and insignificant biomolecular response. It was briefly assessed that the composite colloids reduced E. coli risk less strongly than single colloids, stemming from the difference in the mechanism of influence and the actual need to consider colloid interactions. This conclusion can inform the management and control of pathogen risk in porous media environments.

Effect of early antibiotic treatment strategy on prognosis of acute pancreatitis.

BACKGROUND: Antibiotic use in the early stages of acute pancreatitis is controversial. The purpose of this study was to investigate the effect of early antibiotic application on the prognosis of acute pancreatitis (AP). MATERIALS AND METHODS: Clinical data of patients with primary AP admitted to our emergency ward within 72 hours of onset were retrospectively collected from January 2016 to December 2020. We classified patients with acute pancreatitis according to etiology and disease severity, and compared the differences in hospital stay, laparotomy rate, and in-hospital mortality among AP patients who received different antibiotic treatment strategies within 72 hours of onset. RESULTS: A total of 1134 cases were included, with 681 (60.1%) receiving early antibiotic treatment and 453 (39.9%) not receiving it. There were no significant differences in baseline values and outcomes between the two groups. In subgroup analysis, patients with biliary severe acute pancreatitis (SAP) who received early antibiotics had lower rates of laparotomy and invasive mechanical ventilation, as well as shorter hospital stays compared to those who did not receive antibiotics. In logistic regression analysis, the early administration of carbapenem antibiotics in biliary SAP patients was associated with a lower in-hospital mortality rate. Early antibiotic use in biliary moderate-severe acute pancreatitis (MSAP) reduced hospital stays and in-hospital mortality. Quinolone combined with metronidazole treatment in biliary mild acute pancreatitis (MAP) shortened hospital stays. Early antibiotic use does not benefit patients with non-biliary AP. CONCLUSION: Strategies for antibiotic use in the early stages of AP need to be stratified according to cause and disease severity.

In Situ Discrimination and Cultivation of Active Degraders in Soils by Genome-Directed Cultivation Assisted by SIP-Raman-Activated Cell Sorting.

The identification and in situ cultivation of functional yet uncultivable microorganisms are important to confirm inferences regarding their ecological functions. Here, we developed a new method that couples Raman-activated cell sorting (RACS), stable-isotope probing (SIP), and genome-directed cultivation (GDC)─namely, RACS-SIP-GDC─to identify, sort, and cultivate the active toluene degraders from a complex microbial community in petroleum-contaminated soil. Using SIP, we successfully identified the active toluene degrader Pigmentiphaga, the single cells of which were subsequently sorted and isolated by RACS. We further successfully assembled the genome of Pigmentiphaga based on the metagenomic sequencing of 13C-DNA and genomic sequencing of sorted cells, which was confirmed by gyrB gene comparison and average nucleotide identity determination. Additionally, the genotypes and phenotypes of this degrader were directly linked at the single-cell level, and its complete toluene metabolic pathways in petroleum-contaminated soil were reconstructed. Based on its unique metabolic properties uncovered by genome sequencing, we modified the traditional cultivation medium with antibiotics, amino acids, carbon sources, and growth factors (e.g., vitamins and metals), achieving the successful cultivation of RACS-sorted active degrader Pigmentiphaga sp. Our results implied that RACS-SIP-GDC is a state-of-the-art approach for the precise identification, targeted isolation, and cultivation of functional microbes from complex communities in natural habitats. RACS-SIP-GDC can be used to explore specific and targeted organic-pollution-degrading microorganisms at the single-cell level and provide new insights into their biodegradation mechanisms.

Unveiling the novel role of ryegrass rhizospheric metabolites in benzo[a]pyrene biodegradation.

Rhizoremediation is a promising remediation technology for the removal of soil persistent organic pollutants (POPs), especially benzo[a]pyrene (BaP). However, our understanding of the associations among rhizospheric soil metabolites, functional microorganisms, and POPs degradation in different plant growth stages is limited. We combined stable-isotope probing (SIP), high-throughput sequencing, and metabolomics to analyze changes in rhizospheric soil metabolites, functional microbes, and BaP biodegradation in the early growth stages (tillering, jointing) and later stage (booting) of ryegrass. Microbial community structures differed significantly among growth stages. Metabolisms such as benzenoids and carboxylic acids tended to be enriched in the early growth stage, while lipids and organic heterocyclic compounds dominated in the later stage. From SIP, eight BaP-degrading microbes were identified, and most of which such as Ilumatobacter and Singulisphaera were first linked with BaP biodegradation. Notably, the relationship between the differential metabolites and BaP degradation efficiency further suggested that BaP-degrading microbes might metabolize BaP directly to produce benzenoid metabolites (3-hydroxybenzo[a]pyrene), or utilize benzenoids (phyllodulcin) to stimulate the co-metabolism of BaP in early growth stage; some lipids and organic acids, e.g. 1-aminocyclopropane-1-carboxylic acid, might provide nutrients for the degraders to promote BaP metabolism in later stage. Accordingly, we determined that certain rhizospheric metabolites might regulate the rhizospheric microbial communities at different growth stages, and shift the composition and diversity of BaP-degrading bacteria, thereby enhancing in situ BaP degradation. Our study sheds light on POPs rhizoremediation mechanisms in petroleum-contaminated soils.

Synergistic/antagonistic toxicity characterization and source-apportionment of heavy metals and organophosphorus pesticides by the biospectroscopy-bioreporter-coupling approach.

Many anthropogenic chemicals are manufactured and eventually enter the surrounding environment, threatening food security and human health. Considering the additive or synergistic effects of pollutant mixtures, there is an expanding need for rapid, cost-effective and field-portable screening methods in environmental monitoring. This study used a recently developed biospectroscopy-bioreporter-coupling (BBC) approach to investigate the binary toxicity of Ag(I), Cr(VI) and four organophosphorus pesticides (dichlorvos, parathion, omethoate and monocrotophos). Ag(I) and Cr(VI) altered the toxicity mechanisms of pesticides, explained by the synergistic or antagonistic effect of Ag/Cr-induced cytotoxicity and pesticide-induced genotoxicity. The discriminating Raman spectral peaks associated with organophosphorus pesticides were 1585 and 1682 cm-1, but 750, 1004, 1306 and 1131 cm-1 were found in heavy metal and pesticide mixtures. More spectral alterations were related to pesticides rather than Ag(I) or Cr(VI), hinting at the dominant toxicity mechanisms of pesticides in mixtures. Ag(I) supplement significantly increased the levels of reactive oxygen species induced by organophosphorus pesticides, attributing to the increased permeability of cell membrane and entrance of toxic substances into the cells by the oligodynamic actions. This study lends deeper insights into the interactions between microbes and pollutant mixtures, offering clues to assess the cocktail effects of multiple pollutants comprehensively.

Facilitating New Chromium Reducing Microbes to Enhance Hexavalent Chromium Reduction by In Situ Sonoporation-Mediated Gene Transfer in Soils.

Chromium (Cr) is a heavy metal with a high toxicity and pathogenicity. Microbial reduction is an effective strategy to remove Cr(VI) at contaminated sites but suffers from the low populations and activities of Cr-reducing microorganisms in soils. This study proposed an in situ sonoporation-mediated gene transfer approach, which improved soil Cr(VI) reduction performance by delivering exogenous Cr-transporter chrA genes and Cr-reducing yieF genes into soil microorganisms with the aid of ultrasound. Besides the increasing populations of Cr-resistant bacteria and elevated copy numbers of chrA and yieF genes after sonoporation-mediated gene transfer, three new Cr-reducing strains were isolated, among which Comamonas aquatica was confirmed to obtain Cr-resistant capability. In addition, sonoporation-mediated gene transfer was the main driving force significantly shaping soil microbial communities owing to the predominance of Cr-resistant microbes. This study pioneered and evidenced that in situ soil sonoporation-mediated gene transfer could effectively deliver functional genes into soil indigenous microbes to facilitate microbial functions for enhanced bioremediation, e.g., Cr-reduction in this study, showing its feasibility as a chemically green and sustainable remediation strategy for heavy metal contaminated sites.

Slow release of attapulgite based nano-enabled glyphosate improves soil phosphatase activity, organic P-pool and proliferation of dominant bacterial community.

Glyphosate (Glp) was encapsulated onto the dopamine-modified attapulgite to develop an attapulgite-based nano-enabled Glp (DGlp) in this study with comparable weed control effects to pure Glp and commercial Glp solutions. Within 24 hours, the active Glp molecule was slowly released from DGlp at a maximum remaining rate of over 90%, and then degraded similarly to Glp solution in soil. The addition of DGlp improved soil available phosphorus (P) contents, phosphatase activity, and enzyme extractable P fraction. However, compared to Glp solution, DGlp addition had no effect on the transformation of soil inorganic P fractions. The 16S rRNA sequencing and co-occurrence network results revealed that DGlp had no significant effect on the soil bacterial diversity but diminished the complexity of soil bacterial network. According to the Mantel test, DGlp addition stimulated soil phosphatase activity and proliferation of dominant bacterial taxa (Proteobacteria and Firmicutes) capable of degrading Glp. Proteobacteria and Firmicutes that had been extensively recruited and enriched for their phosphatase activities may have mobilized reactive enzyme-P, significantly enhancing the transformation of reactive organic P and P-pool in soil. These results contributed to our understanding of the ecotoxicity and environmental impacts of nano-enabled Glp prior to its successful and sustainable application in agriculture.

Application of magnetic-nanoparticle functionalized whole-cell biosensor array for bioavailability and ecotoxicity estimation at urban contaminated sites.

The bioavailability and ecotoxicity of pollutants are important for urban ecological systems and human health, particularly at contaminated urban sites. Therefore, whole-cell bioreporters are used in many studies to assess the risks of priority chemicals; however, their application is restricted by low throughput for specific compounds and complicated operations for field tests. In this study, an assembly technology for manufacturing Acinetobacter-based biosensor arrays using magnetic nanoparticle functionalization was developed to solve this problem. The bioreporter cells maintained high viability, sensitivity, and specificity in sensing 28 priority chemicals, seven heavy metals, and seven inorganic compounds in a high-throughput manner, and their performance remained acceptable for at least 20 d. We also tested the performance by assessing 22 real environmental soil samples from urban areas in China, and our results showed positive correlations between the biosensor estimation and chemical analysis. Our findings prove the feasibility of the magnetic nanoparticle-functionalized biosensor array to recognize the types and toxicities of multiple contaminants for online environmental monitoring at contaminated sites.