Environment can be affected by a variety of micropollutants. In this paper, we develop a system to assess the toxicity on an environmental sample, based on the expression of a nanoluciferase under the control of the STB5 promotor in a yeast. The STB5 gene encodes for a transcription factor involved in a pleiotropic drug resistance and in the oxidative stress response. The response of the modified yeast was assessed using 42 micropollutants belonging to different families (antibiotics, pain killers, hormones, plasticizers, pesticides, etc.). Among them, 26 induced an increase of the bioluminescence for concentration ranges from pg.L⁻¹ to ng.L⁻¹. Surprisingly, for concentrations higher than 100 ng.L⁻¹, no response can be observed, suggesting that other mechanisms are involved when the stress increases. Analyzing the different responses obtained, we highlighted six nonmonotonic types of responses. The type of response seems to be independent of the properties of the compounds (polarity, toxicology, molecular weight) and of their family. In conclusion, we highlighted that a cellular response exists for very low exposition to environmental concentration of micropollutants and that it was necessary to explore the cellular mechanisms involved at very low concentration to provide a better risk assessment.

Dichloromethane (DCM) is a volatile halogenated hydrocarbon with teratogenic, mutagenic and carcinogenic effects. Biodegradation is generally regarded as an effective and economical approach of pollutant disposal. In this study, a novel strain was isolated and its cytochrome P450 was heterologously expressed for DCM degradation. The isolate, Microbacterium keratanolyticum ZY, was characterized as a Gram-positive, rod-shaped and flagella-existed bacterium without spores (GenBank No. SUB8814364; CCTCC M 2019953). After successive whole-genome sequencing, assembly and annotation, eight identified functional genes (encoding cytochrome P450, monooxygenase, dehalogenase and hydrolase) were successfully cloned and expressed in Escherichia coli BL21 (DE3). The recombinant strain expressing cytochrome P450 presented the highest degradation efficiency (90.6%). Moreover, the specific activity of the recombinant cytochrome P450 was more than 1.2 times that of the recombinant dehalogenase (from Methylobacterium rhodesianum H13) under their optimum conditions. The kinetics of DCM degradation by recombinant cytochrome P450 was well fitted with the Haldane model and the value of maximum specific degradation rate was determined to be 0.7 s⁻¹. The DCM degradation might occur through successive hydroxylation, dehydrohalogenation, dechlorination and oxidation to generate gem-halohydrin, formyl chloride, formaldehyde and formic acid. The study helps to comprehensively understand the DCM dechlorination process under the actions of bacterial functional enzymes (cytochrome P450 and dehalogenase).

Electrochemically active bacteria (EAB) are effective for the bioreduction of nitroaromatic compounds (NACs), but the exact reduction mechanisms are unclear yet. Therefore, 3-nitrobenzenesulfonate (NBS) was used to explore the biodegradation mechanism of NACs by EAB. Results show that NBS could be anaerobically degraded by Shewanella oneidensis MR-1. The generation of aminoaromatic compounds was accompanied with the NBS reduction, indicating that NBS was biodegraded via reductive approach by S. oneidensis MR-1. The impacts of NBS concentration and cell density on the NBS reduction were evaluated. The removal of NBS depends mainly on the transmembrane electron transfer of S. oneidensis MR-1. Impairment of Mtr respiratory pathway was found to mitigate the reduction of NBS, suggesting that the anaerobic biodegradation of NBS occurred extracellularly. Knocking out cymA severely impaired the extracellular reduction ability of S. oneidensis MR-1. However, the phenotype of ΔcymA mutant could be compensated by the exogenous electron mediators, implying the trans-outer membrane diffusion of mediators into the periplasmic space. This work provides a new insight into the anaerobic reduction of aromatic contaminants by EAB.

Coastal sediments, where microplastics (MPs) accumulate, support benthic microalgae (BMA) that contribute to ecosystem functions such as primary production, nutrient recycling and sediment biostabilization. The potential interactions between MPs, BMA and associated properties and functions remain poorly understood. To examine these interactions, a survey of 22 intertidal sites was conducted. MP abundance, size and a suite of MP diversity indices (based on color and shape) were determined from surface sediments alongside biochemical and physical properties. MPs were detected at all sites and dominated by polypropylene (34%), polyester (18%) and polyethylene (11%). Fragment and fiber dominance (16–92% and 6–81% respectively) and color-shape category diversity varied significantly by site. Distance-based linear models demonstrated that estuary-wide, mean grain size and mud were the best predictors of MP abundance-diversity matrices, but variance explained was low (9%). Relationships were improved when the data was split into sandy and muddy habitats. In sandy habitats (<8% mud), physical properties of the bed (mean grain size, mud content and distance from the estuary mouth) were still selected as predictors of MP abundance-diversity (14% variance explained); but a number of bivariate relationships were detected with biochemical properties such as BMA associated pigments and organic matter. In muddy habitats (>8% mud), porewater ammonium was lower when fiber abundance and overall MP diversity were higher. The inclusion of porewater ammonium, organic matter content and pheophytins alongside physical properties explained a greater percentage of the variance in MP abundance-diversity for muddy habitats (21%). The results highlight the importance of examining plastic shapes and MP categories in addition to abundance and emphasize that functionally different habitats should be examined separately to increase our understanding of MP-biota-function relationships.

Carbonaceous particles play an important role in climate change, and an increase in their emission and deposition causes glacier melting in the Himalayas and the Tibetan Plateau (HTP). This implies that studying their basic characteristics is crucial for a better understanding of the climate forcing observed in this area. Thus, we investigated characteristics of carbonaceous particles at a typical remote site of southeastern HTP. Organic carbon and elemental carbon concentrations at this study site were 1.86 ± 0.84 and 0.18 ± 0.09 μg m⁻³, respectively, which are much lower than those reported for other frequently monitored stations in the same region. Thus, these values reflect the background characteristics of the study site. Additionally, the absorption coefficient per mass (α/ρ) of water-soluble organic carbon (WSOC) at 365 nm was 0.60 ± 0.19 m² g⁻¹, with the highest and lowest values corresponding to the winter and monsoon seasons, respectively. Multi-dimensional fluorescence analysis showed that the WSOC consisted of approximately 37% and 63% protein and humic-like components, respectively, and the latter was identified as the component that primarily determined the light absorption ability of the WSOC, which also showed a significant relationship with some major ions, including SO²⁻₄, K⁺, and Ca²⁺, indicating that combustion activities as well as mineral dust were two important contributors to WSOC at the study site.

The high density and viscosity of fuel oil leads to its prolonged persistence in the environment and causes widespread contamination. Dispersants with a low environmental impact are necessary for fuel oil spill remediation. This study aimed to formulate bio-based dispersants by mixing anionic biosurfactant (lipopeptides from Bacillus subtilis GY19) with nonionic oleochemical surfactant (Dehydol LS7TH). The synergistic effect of the anionic-nonionic surfactant mixture produced a Winsor Type III microemulsion, which promoted petroleum mobilization. The hydrophilic-lipophilic deviation (HLD) equations for ionic and nonionic surfactant mixtures were compared, and it was found that the ionic equation was applicable for the calculation of lipopeptides and Dehydol LS7TH concentrations. The best formula contained 6.6% w/v lipopeptides and 11.9% w/v Dehydol LS7TH in seawater, and its dispersion effectiveness for bunker fuels A and C was 92% and 78%, respectively. The application of bio-based dispersants in water sources was optimized by Box-Behnken design. The efficiency of the bio-based dispersant was affected by the dispersant-to-oil ratios (DORs) but not by the water salinity. A suitable range of DORs for different oil contamination levels could be identified from the response surface plot. The dispersed fuel oil was further degraded by adding an oil-degrading bacterial consortium to the chemically enhanced water accommodated fractions (CEWAFs). After 7 days of incubation, the concentration of fuel oil was reduced from 3692 mg/L to 356 mg/L (88% removal efficiency). On the other hand, the abiotic control removed less than 40% fuel oil from the CEWAFs. This bio-based dispersant had an efficiency comparable to that of a commercial dispersant. The process of dispersant formulation and optimization could be applied to other surfactant mixtures.

The presence of solid litter and its consequences for coastal ecosystems is now being investigated around the world. Different types of material can be discarded in areas such as salt marshes, and various fouling organisms can associate with such items forming the Plastisphere. This study investigated the distribution of solid litter along zones (dry, middle, flooded) of a salt marsh environment in the Patos Lagoon Estuary (South Brazil) and the association of biofouling organisms with these items. Solid litter quantities were significantly higher in the dry zone when compared to the middle and flooded zones, showing an accumulation area where the water rarely reaches. Most items were made of plastic, as shown for many other coastal areas, and originated from food packaging, fishery and shipping activities and personal use. Although not statistically significant, there was a tendency of increased biofouling towards the flooded zone. Thirteen groups were found in association with solid litter items, mainly algae, amphipods, and gastropods. The preference for salt marsh zones, types of material and items’ colour was highly variable among groups of organisms, which can be related to their varied physiological requirements. In summary, significant plastic contamination of salt marshes of the Patos Lagoon was associated with a heterogeneous distribution of fouling communities.

In this study, we integrated a remote-sensing fire product (MOD14A1) and land-use product (MCD12Q1) to extract the number of crop-residue burning (CRB) spots and the fire radiative power (FRP) in China from 2001 to 2018. Moreover, we conducted three trend analyses and two geographic distribution analyses to quantify the interannual variations and summarize the spatial characteristics of CRB on grid (0.25° × 0.25°) and regional scales. The results indicated that CRB presents distinctive seasonal patterns with each sub-region. All trend analyses suggested that the annual number of CRB spots in China increased significantly from 2001 to 2018; the linear trend reached 2615 spots/year, the Theil-Sen slope was slightly lower at 2557 spots/year, and the Mann-Kendal τ was 0.75. By dividing the study period into two sub-periods, we found that the five sub-regions presented different trends in the first and second sub-periods; e.g., the Theil-Sen slope of eastern China in the first sub-period (2001–2009) was 1021 spots/year but was −1599 spots/year in the second period (2010–2018). This suggests that summer CRB has been effectively mitigated in eastern China since 2010. Further, the average FRP of CRB spots presented a decreasing trend from 27.5 MW/spot in 2001 to only 15.8 MW/spot in 2018; this may be attributable to more scattered CRB rather than aggregated CRB. Collectively, the fire spots, FRP, and average FRP indicated that spring, summer, and autumn CRB had dropped dramatically over previous levels by 2018 due to strict mitigation measures by local governments.

The co-occurrence of polycyclic aromatic hydrocarbons (PAHs) and heavy metals in agricultural soils has become a worldwide food crop security concern. Pot experiments, rhizosphere microbial metagenomic sequencing, and root metatranscriptomic sequencing were performed to investigate the interactions among pyrene, Cu, and Cd in a soil-maize (Zea mays L.) system. This study provided direct evidence that the co-presence of PAHs and heavy metals changed the root physiological functions and the rhizosphere microbial community, which subsequently influenced the fate of the contaminants. Co-contamination at low levels tended to enhance the uptake potential and biodegradation performance of the plant, whereas increased contaminant concentrations produced opposite effects. The co-presence of 1000 mg/kg Cu decreased the abundance of Mycobacterium in the rhizosphere and reduced pyrene degradation by 12%–16%. The presence of 400–750 mg/kg pyrene altered the metabolic processes, molecular binding functions, and catalytic activity of enzymes in the maize roots, thus impeding the phytoextraction of Cu and Cd. Competitive absorption between Cu and Cd was observed for the 800–1000 mg/kg Cu and 50–100 mg/kg Cd co-treatment, in which Cu showed a competitive advantage, enhancing its root-to-shoot translocation. These findings provide important information for the production of safe crops and for the development of phytoremediation technologies.

Acrylamide is a well-known carcinogen and neurotoxic substance that has been discovered in frying or baking carbohydrate-rich foods and is widely found in soils and groundwater. The purpose of this study was to investigate the adverse effects of exposure to acrylamide on skeletal development. After treatment with acrylamide in zebrafish embryos, the survival and hatching rates decreased, and the body length shortened, with cartilage malformation and a decrease in skeletal area. Exposure to acrylamide in maternal rats during the lactation period disturbed bone mineral density, serum levels of parathyroid hormone, and the expression of skeletal development-related genes in neonates. Exposure to acrylamide in pregnant rats during the pregnancy period decreased the trabecular density and inhibited cartilage formation by delaying the differentiation of osteoblasts and promoting the maturation of osteoclasts in rat embryos. Furthermore, acrylamide intervention downregulated the expression of chondrocyte and osteoblast differentiation-related genes (sox9a, bmp2, col2a1, and runx2), and upregulated the expression of osteoclast marker genes (rankl and mcsf) in zebrafish and rat embryos at different gestational stages. Our results indicated that exposure to acrylamide dysregulated signature gene and protein expression profiles of skeletal development by suppressing the differentiation and maturation of osteoblasts and cartilage matrix and promoting the formation of osteoclasts, and ultimately induced skeletal abnormality in morphology, which brings increasing attention to the intergenerational toxicity of acrylamide via mother-to-child transmission.