Understanding the metabolic defense and compensation to maintain homeostasis is crucial for assessing the potential health risk of organic pollutants in crops. Currently, limited understanding is available regarding the targeted metabolic pathways and response mechanism under contaminant stress. This study showed that ciprofloxacin (CIP) at the environmental concentrations (1, 5, 25, 50 mg/L) did not significantly inhibit growth or cause severe oxidative damage to rice (Oryza sativa L.). Instead, the increment in CIP concentration induced a series of sequential metabolic disorders, which were characterized predominantly by primary and secondary metabolic disturbances, including phenylpropanoid biosynthesis, the carbohydrate, lipid and amino acid metabolism. After CIP in vivo exceeded a certain threshold level (>0.29 mg/g dry weight), β-glucosidases (BGLUs) mediated the transition from the activation of the genes related to phenylpropanoid biosynthesis to the inhibition of the genes related to carbohydrate metabolism in rice. In particular, starch and sucrose metabolism showed the most profound perturbation stressed by environmental concentrations of CIP (5 mg/L) and other tested organic pollutants (10 μg/L of tricyclazole, thiamethoxam, polybrominated diphenyl ethers, and polychlorinated biphenyls). Besides, the key genes encoding endoglucanase and BGLU were significantly downregulated (|log₂FC| > 3.0) under 100 μg/L of other tested organic pollutants, supporting the transition from the activation of secondary defense metabolism to the disruption of primary energy metabolism. Thus, in addition to bioaccumulation, changes in BGLU activity and starch and sucrose metabolism can reflect the potential adverse effects of pollutants on rice. This study explained the stepwise metabolic and transcriptional responses of rice to organic pollutants, which provided a new reference for the comprehensive evaluation of their environmental risks.

Thiacloprid is widely used in agriculture and may affect pollinators. However, its molecular effects are poorly known. Here, we report the global gene expression profile in the brain of honey bee foragers assessed by RNA-sequencing. Bees were exposed for 72 h to nominal concentrations of 25 and 250 ng/bee via sucrose solution. Determined residue concentrations by LC-MS/MS were 0.59 and 5.49 ng/bee, respectively. Thiacloprid exposure led to 5 and 71 differentially expressed genes (DEGs), respectively. Nuclear genes encoding mitochondrial ribosomal proteins and enzymes involved in oxidative phosphorylation, as well as metabolism enzymes and transporters were altered at 5.49 ng/bee. Kyoto Encylopedia of Genes and Genomes (KEGG) analysis revealed that mitochondrial ribosome proteins, mitochondrial oxidative phosphorylation, pyrimidine, nicotinate and nicotinamide metabolism and additional metabolic pathways were altered. Among 21 genes assessed by RT-qPCR, the transcript of farnesol dehydrogenase involved in juvenile hormone III synthesis was significantly down-regulated. Transcripts of cyp6a14-like and apolipophorin-II like protein, cytochrome oxidase (cox17) and the non-coding RNA (LOC102654625) were significantly up-regulated at 5.49 ng/bee. Our findings indicate that thiacloprid causes transcriptional changes of genes prominently associated with mitochondria, particularly oxidative phosphorylation. This highlight potential effects of this neonicotinoid on energy metabolism, which may compromise bee foraging and thriving populations at environmentally relevant concentrations.

1H-HRMAS NMR-based metabolomics was used to better understand the toxic effects on maize root tips of organochlorine pesticides (OCPs), namely lindane (γHCH) and chlordecone (CLD). Maize seedlings were exposed to 2.5 μM γHCH (mimicking basic environmental contaminations) for 7 days and compared to 2.5 μM CLD and 25 μM γHCH for 7 days (mimicking hot spot contaminations). The 1H-HRMAS NMR-based metabolomic profiles provided details of the changes in carbohydrates, amino acids, tricarboxylic acid (TCA) cycle intermediates and fatty acids with a significant separation between the control and OCP-exposed root tips. First of all, alterations in the balance between glycolysis/gluconeogenesis were observed with sucrose depletion and with dose-dependent fluctuations in glucose content. Secondly, observations indicated that OCPs might inactivate the TCA cycle, with sizeable succinate and fumarate depletion. Thirdly, disturbances in the amino acid composition (GABA, glutamine/glutamate, asparagine, isoleucine) reflected a new distribution of internal nitrogen compounds under OCP stress. Finally, OCP exposure caused an increase in fatty acid content, concomitant with a marked rise in oxidized fatty acids which could indicate failures in cell integrity and vitality. Moreover, the accumulation of asparagine and oxidized fatty acids with the induction of LOX3 transcription levels under OCP exposure highlighted an induction of protein and lipid catabolism. The overall data indicated that the effect of OCPs on primary metabolism could have broader physiological consequences on root development. Therefore, 1H-HRMAS NMR metabolomics is a sensitive tool for understanding molecular disturbances under OCP exposure and can be used to perform a rapid assessment of phytotoxicity.

Anaerobically digested and composted sewage sludge (CSS) has been suggested to be a slow-release fertilizer in forestry and an alternative to quick-release inorganic fertilizers. The effects of CSS with or without added carbohydrate on inorganic nitrogen availability and on soil animals were tested in two Norway spruce plantations. Half of the seedlings were individually fertilized with CSS, and the rest were left as controls. Solid sucrose was added to half of the fertilized and untreated seedlings. Soil samples were taken in the autumn in the first and the second year after the treatments. CSS increased soil NH4–N (2100%), the proportion of soil NO3–N, and the N concentration of spruce needles. CSS greatly reduced the abundances of enchytraeids, tardigrades and collembolans, but increased the proportion and abundance of bacterial-feeding nematodes irrespective of carbohydrate addition. A better stabilization method needs to be developed before CSS can be used as a forest fertilizer.

The massive use of plastic has contributed to huge quantities of hazardous refuse at a global scale and represents one of the most prominent issues of the Anthropocene. Microplastics (MPs) have been detected in almost all environments and pose a potential threat to a variety of plant and animal species. Many studies have reported a variety of effects, from negligible to detrimental, of MPs to aquatic organisms. Conversely, much less is known about their effect on terrestrial biota, and particularly on animal behavior and cognition. We assessed the oral toxicity of polyethylene (PE) MPs at three different concentrations (0.5, 5, and 50 mg L⁻¹), and at different timescales (1 day and 7 days of exposure) and tested for their effects on survival, food intake, sucrose responsiveness, habituation to sucrose and appetitive olfactory learning and memory in the honey bee Apis mellifera. We found that workers were not completely unaffected by acute and prolonged ingestion of this polymer. A significant effect of PE on bee mortality was found for the highest concentration but not for lower ones. PE affected feeding behavior in a concentration-dependent manner, with bees consuming more food than controls when exposed to low concentration PE. Regarding our behavioral and cognitive experiments, the high concentration PE was found to affect only bees’ ability to respond consistently to sucrose but not sucrose sensitivity, habituation to sucrose or learning and memory abilities, even for prolonged exposure to PE. While these last results may look somewhat encouraging, we discussed why caution is warranted before ruling out the possibility that PE particles at environmental concentrations are harmful to honey bees.

Although fungicides were previously considered to be safe for important agricultural pollinators such as honey bees, recent evidence has shown that they can cause a number of behavioral and physiological sublethal effects. Here, we focus on the fungicide Pristine® (active ingredients: 25.2% boscalid, 12.8% pyraclostrobin), which is sprayed during the blooming period on a variety of crops and is known to affect honey bee mitochondria at field-relevant levels. To date, no study has tested the effects of a field-relevant concentration of a fungicide on associative learning ability in honey bees. We tested whether chronic, colony-level exposure at field-relevant and higher concentrations of Pristine® impairs performance on the proboscis extension reflex (PER) paradigm, an associative learning task. Learning performance was reduced at higher field-relevant concentrations of Pristine®. The reductions in learning performance could not be explained by effects on hunger or motivation, as sucrose responsiveness was not affected by Pristine® exposure. To determine whether Pristine®‘s negative effects on learning performance were mediated at a specific life stage, we conducted a cross-fostering experiment that exposed bees to the fungicide either only as larvae, only as adults, or during both stages. We found that exposure across the entire life was necessary to significantly reduce learning performance, although non-significant reductions occurred when bees were exposed during just one stage. Our study provides strong evidence that Pristine® has significant sublethal effects on learning performance. As associative learning is a necessary ability for foraging, our results raise concerns that Pristine® could impair foraging abilities and substantially weaken colony health.

Constructed wetlands integrated with microbial fuel cells (MFC-CWs) have been recently developed and tested for removing antibiotics. However, the effects of carbon source availability, electron transfer flux and cathode conditions on antibiotics removal in MFC-CWs through co-metabolism remained unclear. In this study, four experiments were conducted in MFC-CW microcosms to investigate the influence of carbon source species and concentrations, external resistance and aeration duration on sulfamethoxazole (SMX) and tetracycline (TC) removal and bioelectricity generation performance. MFC-CWs supplied with glucose as carbon source outperformed other carbon sources, and moderate influent glucose concentration (200 mg L⁻¹) resulted in the best removal of both SMX and TC. Highest removal percentages of SMX (99.4%) and TC (97.8%) were obtained in MFC-CWs with the external resistance of 700 Ω compared to other external resistance treatments. SMX and TC removal percentages in MFC-CWs were improved by 4.98% and 4.34%, respectively, by increasing the aeration duration to 12 h compared to no aeration. For bioelectricity generation performance, glucose outperformed sodium acetate, sucrose and starch, with the highest voltages of 386 ± 20 mV, maximum power density (MPD) of 123.43 mW m⁻³, and coulombic efficiency (CE) of 0.273%. Increasing carbon source concentrations from 100 to 400 mg L⁻¹, significantly (p < 0.05) increased the voltage and MPD, but decreased the internal resistance and CE. The highest MPD was obtained when the external resistance (700 Ω) was close to the internal resistance (600.11 Ω). Aeration not only improved the voltage and MPD, but also reduced the internal resistance. This study demonstrates that carbon source species and concentrations, external resistances and aeration duration, all play vital roles in regulating SMX and TC removal in MFC-CWs.

Nitric oxide (NO) and hydrogen sulfide (H₂S) since their discovery have proven to be game changing molecules in alleviating abiotic stress. They individually play role in plant stress management while the pathways of stress regulation through their crosstalk remain elusive. The current study focuses on investigating the interplay of NO and H₂S signalling in the amelioration of arsenate As(V) toxicity in rice seedlings and managing its growth, photosynthesis, sucrose and proline metabolism. Results show that As(V) exposure declined fresh weight (biomass) due to induced cell death in root tips. Moreover, a diminished RuBisCO activity, decline in starch content with high proline dehydrogenase activity and increased total soluble sugars content was observed which further intensified in the presence of Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME, an inhibitor of nitric oxide synthase-like activity), and DL-propargylglycine (PAG, an inhibitor of cysteine desulfhydrase activity). These results correlate with lower endogenous level of NO and H₂S. Addition of L-NAME increased As(V) toxicity. Interestingly, addition of SNP reverses effect of L-NAME suggesting that endogenous NO has a role in mitigating As(V) toxicity. Similarly, exogenous H₂S also significantly alleviated As(V) stress, while PAG further stimulated As(V) toxicity. Furthermore, application of H₂S in the presence of L – NAME and NO in the presence of PAG could still mitigate As(V) toxicity, suggesting that endogenous NO and H₂S could independently mitigate As(V) stress.

or sugar-derived compounds were used as environmentally friendly additives for the depolymerization of Kraft lignin waste and organosolv lignin prepared from Miscanthus giganteus. The yields of the aromatic monomers obtained from Kraft lignin increased from 5.1 to 49.2% with the addition of mannitol, while those obtained from organosolv lignin increased from 44.4 to 83.0% with the addition of sucrose. This improved lignin depolymerization was also confirmed by gel permeation chromatography and nuclear magnetic resonance spectroscopy. The above results clearly indicate the beneficial effects of carbohydrate derivatives on the lignin depolymersization process, more specifically, suggesting that the presence of carbohydrates improve the lignin depolymerization of lignocellulose, as observed for the raw lignocellulose feed.

Extracellular Polymeric Substances (EPS) influenced Poly Cyclic Aromatic Hydrocarbons (PAHs) degrading Klebsiella pneumoniae was isolated from the marine environment. To increase the EPS production by Klebsiella pneumoniae, several physicochemical parameters were tweaked such as different carbon sources (arabinose, glucose, glycerol, lactose, lactic acid, mannitol, sodium acetate, starch, and sucrose at 20 g/L), nitrogen sources (ammonium chloride, ammonium sulphate, glycine, potassium nitrate, protease peptone and urea at 2 g/L), different pH, carbon/nitrogen ratio, temperature, and salt concentration were examined. Maximum EPS growth and biodegradation of Anthracene (74.31%), Acenaphthene (67.28%), Fluorene (62.48%), Naphthalene (57.84%), and mixed PAHs (55.85%) were obtained using optimized conditions such as glucose (10 g/L) as carbon source, potassium nitrate (2 g/L) as the nitrogen source at pH 8, growth temperature of 37 °C, 3% NaCl concentration and 72 h incubation period. The Klebsiella pneumoniae biofilm architecture was studied by confocal laser scanning microscopy (CLSM) and scanning electron microscope (SEM). The present study demonstrates the EPS influenced PAHs degradation of Klebsiella pneumoniae.