Freshwater cyanobacteria produce highly toxic secondary metabolites, which can be transported downstream by rivers and waterways into the sea. Estuarine and coastal aquaculture sites exposed to toxic cyanobacteria raise concerns that shellfish may accumulate and transfer cyanotoxins in the food web. This study aims to describe the competitive pattern of uptake and depuration of a wide range of microcystins (MC-LR, MC-LF, MC-LW, MC-LY, [Asp3]-MC-LR/[Dha7]-MC-LR, MC-HilR) and nodularins (NOD cyclic and linear) within the common blue mussel Mytilus edulis exposed to a combined culture of Microcystis aeruginosa and Nodularia spumigena into the coastal environment.Different distribution profiles of MCs/NODs in the experimental system were observed. The majority of MCs/NODs were present intracellularly which is representative of healthy cyanobacterial cultures, with MC-LR and NOD the most abundant analogues. Higher removal rate was observed for NOD (≈96%) compared to MCs (≈50%) from the water phase. Accumulation of toxins in M. edulis was fast, reaching up to 3.4 μg/g shellfish tissue four days after the end of the 3-days exposure period, with NOD (1.72 μg/g) and MC-LR (0.74 μg/g) as the dominant toxins, followed by MC-LF (0.35 μg/g) and MC-LW (0.31 μg/g). Following the end of the exposure period depuration was incomplete after 27 days (0.49 μg/g of MCs/NODs). MCs/NODs were also present in faecal material and extrapallial fluid after 24 h of exposure with MCs the main contributors to the total cyanotoxin load in faecal material and NOD in the extrapallial fluid. Maximum concentration of MCs/NODs accumulated in a typical portion of mussels (20 mussels, ≈4 g each) was beyond greater the acute, seasonal and lifetime tolerable daily intake. Even after 27 days of depuration, consuming mussels harvested during even short term harmful algae blooms in close proximity to shellfish beds might carry a high health risk, highlighting the need for testing.

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.

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.

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.

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.

Different pH conditions have been demonstrated to affect the activities of dechlorinating populations participating in the successive dechlorination of trichloroethylene to ethylene. However, the mechanism of the effect of pH conditions on the assembly of dechlorinating populations and their relations to the structure, function, and dynamics of the microbiome are unclear. In this study, we evaluated the effects of pH on microbiomes assembled in anaerobic trichloroethylene-dechlorinating reactors under neutral (pH 7.2), acidic (pH 6.2), and alkaline (pH 8.2) conditions. The results revealed that among the reactors, the acidic reactor had the highest efficiency for dechlorination without accumulation of dechlorinated metabolites, even at high loading rates. The results of high-throughput sequencing of the 16S rRNA gene indicated that the microbiomes in the 3 reactors underwent varied dynamic succession. The acidic reactor harbored a higher degree of complex microbes, dechlorinator diversity, and abundance of the Victoria subgroup of Dehalococcoides (1.2 ± 0.1 × 10⁶ cell/mL), which were approximately 10–10²-fold higher than those at neutral and alkaline conditions. The pH settings altered species–species connectivity and complexity of microbial interaction networks, with more commensal interactions in the dechlorinators of the acidic reactor. As predicted, abundances of several functional gene categories were in strong linearity with pH values, and the microbiome possessed significantly more abundant functions in the acidic reactor (P < 0.001), such as potentially stimulating hydrogen production, cobalamin synthesis, cobalt transport, transport and metabolism of amino acids and secondary metabolites, cell motility, and transcription. All results of microbiomic analyses consistently revealed the observed superior dechlorination process and suggested an association of the reductive dechlorination process with the pH-dependent microbiome. The results of this study provide a new insight into the trichloroethylene dechlorination with regards to pH, and they will be useful for improving bioremediation and management of trichloroethylene-contaminated sites.

The ecological toxicity of hexabromocyclododecane (HBCD) on animals, including fish and mice, has been reported, but its effects in plants, particularly its toxic mechanism, have rarely been investigated. An untargeted metabolomics approach for comprehensive assessment was selected to study the alterations in the metabolic profiles in pak choi leaves induced by exposure to trace-level amounts of HBCD diastereomers over 30 days. A supervised orthogonal partial least-squares-discriminant analysis (OPLS-DA) was performed to investigate differences between the HBCD and control groups. The discriminating metabolites were identified using public databases. The results indicated that the toxicity of the HBCD diastereomers was ordered as γ-HBCD > α-HBCD > β-HBCD. 13 metabolites were identified as potential biomarkers to discriminate the presence of HBCD toxicity. The lipid, carbohydrate, nucleotide and amino acid metabolic pathways affected were found in accordance with animals and humans, and also HBCD could induce the interference of the secondary metabolite pathways. The system of the stress defences was activated, including signalling pathway, antioxidant defence system, shikimate and phenylpropanoid metabolism. The carbohydrate and amino acid metabolism were disturbed by HBCD intervention, and the lipid, amino acid and secondary metabolite metabolism were regulated for HBCD stress prevention. These results provide insights into the mechanism and degree of HBCD phytotoxicity.

Mycotoxin is toxic secondary metabolite formed by certain filamentous fungi. This toxic compound can enter the food chain through contamination of food (e.g., by colonization of toxigenic fungi on food). In light of the growing concerns on the health hazards posed by mycotoxins, it is desirable to develop reliable analytical tools for their detection in food products in both sensitive and efficient manner. For this purpose, the potential utility of molecularly imprinted polymers (MIPs) has been explored due to their meritful properties (e.g., large number of tailor-made binding sites, sensitive template molecules, high recognition specificity, and structure predictability). This review addresses the recent advances in the application of MIPs toward the sensing of various mycotoxins (e.g., aflatoxins and patulin) along with their fabrication strategies. Then, performance evaluation is made for various types of MIP- and non-MIP-based sensing platforms built for the listed target mycotoxins in terms of quality assurance such as limit of detection (LOD). Further, the present challenges in the MIP-based sensing application of mycotoxins are discussed along with the future outlook in this research field.

Rice paddy fields are major sources of atmospheric methane (CH₄) and nitrous oxide (N₂O). Rice variety is an important factor affecting CH₄ and N₂O emissions. However, the interactive effects of rice metabolites and microorganisms on CH₄ and N₂O emissions in paddy fields are not clearly understood. In this study, a high greenhouse gas-emitting cultivar (YL 6) and a low greenhouse gas-emitting cultivar (YY 1540) were used as experimental materials. Metabolomics was used to examine the roots, root exudates, and bulk soil metabolites. High-throughput sequencing was used to determine the microbial community composition. YY 1540 had more secondary metabolites (flavonoids and isoflavonoids) in root exudates than YL 6. It was enriched with the uncultured members of the families Gemmatimonadanceae and Rhizobiales_Incertae_Sedis in bulk soil, and genera Burkholderia-Caballeronia-Paraburkholderia, Magnetospirillum, Aeromonas, and Anaeromyxobacter in roots, contributing to increased expression of pmoA and nosZ genes and reducing CH₄ and N₂O emissions. YL 6 roots and root exudates contained higher contents of carbohydrates [e.g., 6-O- acetylarbutin and 2-(3- hydroxyphenyl) ethanol 1′-glucoside] than those of YY 1540. They were enriched with genera RBG-16-58-14 in bulk soil and Exiguobacterium, and uncultured member of the Kineosporiaceae family in roots, which contributed to increased expression of mcrA, ammonia-oxidizing archaea, ammonia-oxidizing bacteria, nirS, and nirK genes and greenhouse gas emissions. In general, these results established a link between metabolites, microorganisms, microbial functional genes, and greenhouse gas emissions. The metabolites of root exudates and roots regulated CH₄ and N₂O emissions by influencing the microbial community composition in bulk soil and roots.

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.