International audience | The proliferation of wireless and other telecommunications equipment brought about by technological advances in the communication industry has substantially increased the radiofrequency radiation levels in the environment. The emphasis is, therefore, placed on investigating the potential impacts of radiofrequency radiation on biota. In this work, the impact of 2850 MHz electromagnetic field radiation (EMF-r) on early development, photosynthetic pigments, and the metabolic profile of two Brassica oleracea L. cultivars (red and green cabbage) was studied. On a daily basis for seven days, seedlings were exposed to homogeneous EMF-r for one, two, and four hours, and observations were carried out at 0-h, 1-h, and 24-h following the final dose. Irrespective of the duration of harvest, exposure to EMF-r resulted in a dose-dependent reduction in both root (from 6.3 cm to 4.0 cm in red; 6.1 cm to 3.8 cm in green) and shoot lengths (from 5.3 cm to 3.1 cm in red; 5.1 cm to 3.1 cm in green), as well as a decrease in biomass (from 2.9 mg to similar to 1.1 mg in red; 2.5 to 0.9 mg in green) of the seedlings when compared to control samples. Likewise, the chlorophyll (from 6.09 to similar to 4.94 mg g(-1) d.wt in red; 7.37 to 6.05 mg g(-1) d.wt. in green) and carotenoid (from 1.49 to 1.19 mg g(-1) d.wt. in red; 1.14 to 0.51 mg g(-1) d.wt. in green) contents of both cultivars decreased significantly when compared to the control. Additionally, the contents of phenolic (28.99-45.52 mg GAE g(-1) in red; 25.49-33.76 mg GAE g(-1) in green), flavonoid (21.7-31.8 mg QE g(-1) in red; 12.1-19.0 mg QE g(-1) in green), and anthocyanin (28.8-43.6 mg per 100 g d.wt. in red; 1.1-2.6 mg per 100 g d.wt. in green) in both red and green cabbage increased with exposure duration. EMF-r produced oxidative stress in the exposed samples of both cabbage cultivars, as demonstrated by dose-dependent increases in the total antioxidant activity (1.33-2.58 mM AAE in red; 1.29-2.22 mM AAE in green), DPPH activity (12.96-78.33% in red; 9.62-67.73% in green), H2O2 content (20.0-77.15 nM g(-1) f.wt. in red; 14.28-64.29 nM g(-1) f.wt. in green), and MDA content (0.20-0.61 nM g(-1) f.wt. in red; 0.18-0.51 nM g(-1) f.wt. in green) compared to their control counterparts. The activity of antioxidant enzymes, i.e., superoxide dismutases (3.83-8.10 EU mg(-1) protein in red; 4.19-7.35 EU mg(-1) protein in green), catalases (1.81-7.44 EU mg(-1) protein in red; 1.04-6.24 EU mg(-1) protein in green), and guaiacol peroxidases (14.37-47.85 EU mg(-1) protein in red; 12.30-42.79 EU mg(-1) protein in green), increased significantly compared to their control counterparts. The number of polyphenols in unexposed and EMF-r exposed samples of red cabbage was significantly different. The study concludes that exposure to 2850 MHz EMF-r affects the early development of cabbage seedlings, modifies their photosynthetic pigments, alters polyphenol content, and impairs their oxidative metabolism.

As an important part of extracellular secondary metabolites, extracellular polymeric substances (EPS) can play a significant role in protecting cells from the threat of exogenous substances, including nanoparticles (NPs). However, the regulation mechanisms of EPS secretion under NPs exposure remain largely unknown. This study investigated the signaling pathways and molecular responses related to EPS secretion of algae (Chlorella pyrenoidosa) upon the exposures to anatase and rutile TiO₂ NPs (nTiO₂-A and nTiO₂-R, respectively) at two similar toxic (20% and 50% of algal growth inhibition) concentrations. The results showed that EPS responded to nTiO₂ stress via excess secretion and compositional variation, and nTiO₂-A induced more EPS secretion than nTiO₂-R at similar toxicity concentrations. The up-regulation of the Ca²⁺ signaling pathway might play a greater role in promoting EPS secretion under nTiO₂-R exposure compared with nTiO₂-A exposure, while the significantly increased intracellular ROS could mainly account for the increased EPS secretion under nTiO₂-A exposure. The up-regulated genes related to biological synthesis and protein metabolism and the enhanced biosynthetic metabolism might be the direct causes of the increased EPS secretion. The increased ROS could have a greater effect on the amino acid metabolism and related genes upon the exposure to nTiO₂-A than nTiO₂-R to induce more EPS secretion. More serious membrane damage caused by nTiO₂-R than nTiO₂-A would affect the intracellular inositol phospholipid metabolism more severely, while the inositol phospholipid pathway and Ca²⁺ signaling pathway might agree and communicate with each other inherently to regulate EPS secretion upon nTiO₂-R exposure. The findings address the regulation mechanisms of algal EPS secretion under nTiO₂ exposure and provide new insights into algal bio-responses to nTiO₂ exposure.

Microcystis blooms and their secondary metabolites microcystins (MCs) occurred all over the world, which have damaged aquatic ecosystems and threatened public health. Techniques to reduce the Microcystis blooms and MCs are urgently needed. This study aimed to investigate the algicidal and inhibitory mechanisms of a red pigment prodigiosin (PG) against the growth and MC-producing abilities of Microcystis aeruginosa (M. aeruginosa). The numbers of Microcystis cells were counted under microscope. The expression of microcystin synthase B gene (mcyB) and concentrations of MCs were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme linked immunosorbent assay (ELISA) methods, respectively. The inhibitory effects of PG against M. aeruginosa strain FACHB 905 with 50% algicidal concentration (LC50) at 120 h was 0.12 μg/mL. When M. aeruginosa cells exposed to 0.08 μg/mL, 0.16 μg/mL, 0.32 μg/mL PG, the expression of mcyB of M. aeruginosa was down-regulated 4.36, 8.16 and 18.51 times lower than that of the control at 120 h. The concentrations of total MC (TMC) also were 1.66, 1.72 and 5.75 times lower than that of the control at 120 h. PG had high algicidal effects against M. aeruginosa, with the activities of superoxide dismutase (SOD) initially increased and then decreased after 72 h, the contents of malondialdehyde (MDA) increase, the expression of mcyB gene down-regulation, and MCs synthesis inhibition. This study was first to report the PG can simultaneously lyse Microcystis cells, down-regulate of mcyB expression and inhibit MCs production effectively probably due to oxidative stress, which indicated PG poses a great potential for regulating Microcystis blooms and MCs pollution in the environment.

Glyphosate, one of the most popular herbicides, has become a prominent aquatic contaminant because of its huge usage. The eco-safety of glyphosate is still in controversy, and it is inconclusive how glyphosate influences aquatic microbial communities. In the present study, the effects of glyphosate on the structure and function of microbial communities in a freshwater microcosm were investigated. 16S/18S rRNA gene sequencing results showed that glyphosate treatment (2.5 mg L⁻¹, 15 days) did not significantly alter the physical and chemical condition of the microcosm or the composition of the main species in the community, but metatranscriptomic analyses indicated that the transcriptions of some cyanobacteria were significantly influenced by glyphosate. The microbial community enhanced the gene expression in pathways related to translation, secondary metabolites biosynthesis, transport and catabolism to potentially withstand glyphosate contamination. In the low phosphorus (P) environment, a common cyanobacterium, Synechococcus, plays a special role by utilizing glyphosate as P source and thus reducing its toxicity to other microbes, such as Pseudanabaena. In general, addition of glyphosate in our artificial microcosms did not strongly affect the aquatic microbial community composition but did alter the community’s transcription levels, which might be potentially explained by that some microbes could alleviate glyphosate’s toxicity by utilizing glyphosate as a P source.

Chinese dark tea is widely enjoyed for its multiple health-promoting effects and pleasant taste. However, its production involves fermentation by microbiota in raw tea, some of which are filamentous fungi and thus potential mycotoxin producers. Accordingly, whether mycotoxins pose health risk on dark tea consumption has become a public concern. In this study, a cleaning method of multi-functional column (MFC) and immunoaffinity column (IAC) in tandem combined to HPLC detection was developed and validated for determining ten mycotoxins of six groups (i.e., aflatoxins of B₁, B₂, G₁ and G₂, ochratoxin A, zearalenone, deoxynivalenol, fumonisins of B₁, B₂, and T-2) in dark teas. The interferences from secondary metabolites were effectively reduced, and the sensitivities and recoveries of the method were qualified for tea matrices. Six groups mycotoxins were determined in 108 samples representing the major Chinese dark teas by using the new method. Subsequently, the dietary exposure and health risks were evaluated for different age and gender groups in Kunming and Pu’er in China and Ulan Bator in Mongolia. The occurrence of zearalenone was 4.63% and that of ochratoxin A was 1.85%, with the other four groups mycotoxins were below the limits of quantification. The hazard index values for the five groups’ non-carcinogenic mycotoxins were far below 1.0. The deterministic risk assessment indicated no non-carcinogenic risks for dark tea consumption in the three areas. Probabilistic estimation showed that the maximum value of 95th percentile carcinogenic risk value for the aflatoxins was 2.12 × 10⁻⁸, which is far below the acceptable carcinogenic risk level (10⁻⁶). Hereby, six groups mycotoxins in Chinese dark tea showed no observed risk concern to consumers.

To elucidate the origin of the wide-spread contaminations of plant derived commodities with various alkaloids, we employed co-cultures of pyrrolizidine alkaloid (PA) containing Senecio jacobaea plants with various alkaloid free acceptor plants. Our analyses revealed that all plants grown in the vicinity of the Senecio donor plants indeed contain significant amounts of the PAs, which previously had been synthesized in the Senecio plants. These findings illustrate that typical secondary metabolites, such as pyrrolizidine alkaloids, are commonly transferred and exchanged between living plants. In contrast to the broad spectrum of alkaloids in Senecio, in the acceptor plants nearly exclusively jacobine is accumulated. This indicates that this alkaloid is exuded specifically by the Senecio roots. Although the path of alkaloid transfer from living donor plants is not yet fully elucidated, these novel insights will extend and change our understanding of plant-plant interactions and reveal a high relevance with respect to the widespread alkaloidal contaminations of plant-derived commodities. Moreover, they could be the basis for the understanding of various so far not fully understood phenomena in cultivation of various crops, e.g. the beneficial effects of crop rotations or the co-cultivation of certain vegetables.

Polybrominated diphenyl ethers (PBDEs) are toxic chemicals widely distributed in the environment, but few studies are available on their potential toxicity to rice at metabolic level. Therefore we exposed ten rice (Oryza sativa) varieties to 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47), a predominant congener of PBDEs, in hydroponic solutions with different concentrations. Two varieties that showed different biological effects to BDE-47, YY-9 and LJ-7, were screened as sensitive and tolerant varieties according to changes of morphological and physiological indicators. Metabolic research was then conducted using gas chromatography−mass spectrometry combined with diverse analyses. Results showed that LJ-7 was more active in metabolite profiles and adopted more effective antioxidant defense machinery to protect itself against oxidative damages induced by BDE-47 than YY-9. For LJ-7, the contents of 13 amino acids and 24 organic acids, especially l-glutamic acid, beta-alanine, glycolic acid and glyceric acid were up-regulated significantly which contributed to scavenging reactive oxygen species. In the treatment of 500 μg/L BDE-47, the contents of these four metabolites increased by 33.6-, 19.3-, 10.6- and 10.2-fold, respectively. The levels of most saccharides (such as d-glucose, lactulose, maltose, sucrose and d-cellobiose) also increased by 1.7–12.4 fold which promoted saccharide-related biosynthesis metabolism. Elevation of tricarboxylic acid cycle and glyoxylate and dicarboxylate metabolism enhanced energy-producing processes. Besides, the contents of secondary metabolites, chiefly polyols and glycosides increased significantly to act on defending oxidative stress induced by BDE-47. In contrast, the levels of most metabolites decreased significantly for YY-9, especially those of 13 amino acids (by 0.9%–67.1%) and 19 organic acids (by 7.8%–70.0%). The positive metabolic responses implied LJ-7 was tolerant to BDE-47, while the down-regulation of most metabolites indicated the susceptible nature of YY-9. Since metabolic change might affect the yield and quality of rice, this study can provide useful reference for rice cultivation in PBDEs-polluted areas.

Mycotoxins are secondary metabolites produced by varieties of fungi that contaminate food and feed resources and are capable of inducing a wide range of toxicity. In the current study, we investigated developmental and behavioural toxicity in zebrafish larvae after exposure to six different mycotoxins; ochratoxin A (OTA), type A trichothecenes mycotoxin (T-2 toxin), type B trichothecenes mycotoxin (deoxynivalenol - DON), and zearalenone (ZEN) and its metabolites alpha-zearalenol (α-ZOL) and beta-zearalenol (β-ZOL). Developmental defects, hatching time, and survival were monitored until 96 h post fertilisation (hpf). The EC₅₀, LC₅₀, and IC₅₀ values were calculated. Subsequently, to assess behavioural toxicity, new sets of embryos were exposed to a series of non-lethal doses within the range of environmental and/or developmental concern. Results indicated that all the tested mycotoxins were toxic, they all induced developmental defects, and with the exception of OTA, all affected hatching time. Behavioural effects were only observed following exposure to OTA and ZEN and its metabolites, α ZOL and β ZOL. These results demonstrate that mycotoxins are teratogenic and can influence behaviour in a vertebrate model.

Plants detoxify toxic metal(loid)s by accumulating diverse metabolites. Beside scavenging excess reactive oxygen species (ROS) induced by metal(loid)s, some metabolites chelate metal(loid) ions. Classically, thiol-containing compounds, especially glutathione (GSH) and phytochelatins (PCs) are thought to be the major chelators that conjugate with metal(loid)s in the cytoplasm followed by transport and sequestration in the vacuole. In addition to this classical detoxification pathway, a role for secondary metabolites in metal(loid) detoxification has recently emerged. In particular, anthocyanins, a kind of flavonoids with ROS scavenging potential, contribute to enhanced arsenic tolerance in several plant species. Evidence is accumulating that, in analogy to GSH and PCs, anthocyanins may conjugate with arsenic followed by vacuolar sequestration in the detoxification event. Exogenous application or endogenous accumulation of anthocyanins enhances arsenic tolerance, leading to improved plant growth and productivity. The application of some plant hormones and signaling molecules stimulates endogenous anthocyanin synthesis which confers tolerance to arsenic stress. Anthocyanin biosynthesis is transcriptionally regulated by several transcription factors, including myeloblastosis (MYBs). The light-regulated transcription factor elongated hypocotyl 5 (HY5) also affects anthocyanin biosynthesis, but its role in arsenic tolerance remains elusive. Here, we review the mechanism of arsenic detoxification in plants and the potential role of anthocyanins in arsenic tolerance beyond the classical points of view. Our analysis proposes that anthocyanin manipulation in crop plants may ensure sustainable crop yield and food safety in the marginal lands prone to arsenic pollution.

Nanotechnology has been recognized as the emerging field for the synthesis, designing, and manipulation of particle structure at the nanoscale. Its rapid development is also expected to revolutionize industries such as applied physics, mechanics, chemistry, and electronics engineering with suitably tailoring various nanomaterials. Inorganic nanoparticles such as silver nanoparticles (Ag-NPs) have garnered more interest with their diverse applications. In correspondence to green chemistry, researchers prioritize green synthetic techniques over conventional ones due to their eco-friendly and sustainable potential. Green-synthesized NPs have proven more beneficial than those synthesized by conventional methods because of capping by secondary metabolites. The present study reviews the various means being used by the researchers for the green synthesis of Ag-NPs. The morphological characteristics of these NPs as obtained from numerous characterization techniques have been explored. The potential applications of bio-synthesized Ag-NPs viz. Antimicrobial, antioxidant, catalytic, and water remediation along with the plausible mechanisms have been discussed. In addition, toxicity analysis and biomedical applications of these NPs have also been reviewed to provide a detailed overview. The study signifies that biosynthesized Ag-NPs can be efficiently used for various applications in the biomedical and industrial sectors as an environment-friendly and efficient tool.