Soil microbial community structure and environmental effects of serpentine weathering under different vegetative covers in the serpentine mining area of Donghai County, China

Synergistic interactions between AMF and MHB communities in the rhizospheric microenvironment facilitated endemic hyperaccumulator plants growth thrive under heavy metal stress in ultramafic soil

Ultramafic outcrop settings are characterized by long-term heavy metal (HM) stress and nutrient imbalances, making plant resilience highly challenging. This study investigated that how native plant types in the serpentine environment influence the variation of synergistic interactions between rhizosphere arbuscular mycorrhizal fungi (AMF) and mycorrhizal helper bacteria (MHB) communities under HM stress and nutrient-deficient conditions, which support native plant endemism and their HM accumulation potential. The results displayed significant enrichment of key MHB (Rhizobium_tropici, Bacillus_subtilis, Pseudomonas_parafulva, Pseudomonas_akapagensis) and AMF species (Glomus_constrictum, Glomus_aggregatum, Rhizophagus_intraradices, Rhizophagus_irregularis) in rhizosphere soils (q < 0.05). Pseudomonas_chlororaphis and Burkholderia_cepacia were strongly associated with Rhizophagus_irregularis and Glomus_mosseae in Panicum maximum Jacq (PMJ) and Bidens pilosa (BP) under chromium (Cr), and cadmium (Cd) and arsenic (As) stress. Pseudomonas_fluorescens and Bacillus_pabuli were linked to Geosiphon_pyriformis and Glomus_aggregatum in Pueraria montana (PM) under nickel (Ni), lead (Pb), and cobalt (Co) stress, while Arthrobacter_globiformis and Rhizobium_leguminosarum were associated with Glomus_intraradices under copper (Cu) stress in Leucaena leucocephala (LL). Pathways related to nitrogen, phosphorous and potassium (NPK) cycling, HM detoxification, and resistance were enriched, with AMF predominantly symbiotrophic root-endophytic, except for one as lichenized nostoc endosymbiont. Canonical correspondence analysis (CCA) showed HM stress and nutrients influence MHB-AMF symbiosis, while pH moisture content (MC) and electric conductivity (EC) significantly regulate their distribution. Rhizobium_leguminosarum, Rhizobium_tropici, Nitrospira_japonica, and Rhizobium_cauense with Glomus_mosseae and Rhizophagus_irregularis drive NPK cycling in HM-stressed rhizosphere soils. This finding suggested that association between plants type and their functional rhizosphere microbiome promote an eco-friendly strategy for HM recovery from serpentine soil.

Root-associated functional microbiome endemism facilitates heavy metal resilience and nutrient poor adaptation in native plants under serpentine driven edaphic challenges

Serpentine soils are characterized by high concentrations of heavy metals (HMs) and limited essential nutrients with remarkable endemic plant diversity, yet the mechanisms enabling plant adaptation to thrive in such harsh environments remain largely unknown. Full-length 16S rRNA amplicon sequencing, coupled with physiological and functional assays, was used to explore root-associated bacterial community composition and their metabolic and ecological functions. The results revealed that serpentine plant species exhibited significantly higher metal transfer factor values compared to non-serpentine plant species, particularly evident in Bidens pilosa, Miscanthus floridulus, and Leucaena leucocephala. The serpentine root-associated microbes showed a higher utilization of carboxylic acid, whereas carbohydrate utilization was higher in the non-serpentine site. Zymomonas mobilis and Flavabacterium sp. exhibited high resistance to heavy metal concentrations, showing greater adaptability, while, Staphylococcus carnosus showed sensitivity to HMs, showing limited adaptability. Moreover, Ni, Cr, and Co resistance genes were found, while nitrogen and phosphorous metabolism genes were less abundant in the serpentine site compared to the non-serpentine site. Furthermore, Flavobacterium sp. had a strong positive relationship with Cd and Cu, Zymomonas mobilis with Ni, and Cr, Streptomyces sp. with Co, and Staphylococcus carnosus with N and P cycling. These findings underscore critical role of root-associated bacterial communities and distinctive soil conditions of serpentine habitats in fostering ecological adaptation of native plant species to the challenges posed by HMs and nutrient deficiencies.

Recent advances in the toxicological effects of difenoconazole: A focus on toxic mechanisms in fish and mammals

The toxicological study of pesticides at sub-lethal and environment-relevant concentrations has become increasingly crucial for human and environmental health. Toxic mechanisms of agrochemicals contribute to discovering green pesticides, assessing the hazards of pesticides comprehensively, and supporting legitimate regulatory decisions. However, the toxicological effects of difenoconazole are not yet fully understood despite being frequently detected in fruits, vegetables, waters, and soils and posing hazards to humans and the environment. This lack of knowledge could lead to flawed risk assessment and administrative oversight. Thus, the review aimed to provide some investigation perspectives for clarifying the toxicological effects of difenoconazole by synthesizing the toxic data of difenoconazole on various organisms, such as bees, Daphnia magna, fish, earthworms, mammals, and plants and summarizing the toxicological mechanisms of difenoconazole, especially in fish and mammals from peer-reviewed publications. Evidence revealed that difenoconazole caused multiple toxicological effects, including developmental toxicity, reproductive toxicity, endocrine disruption effects, neurotoxicity, and transgenerational toxicity. The toxic mechanisms involved in metabolic disturbance, oxidative stress, inflammation, apoptosis, and autophagy by activating reactive oxygen species-mediated signaling pathways and mitochondrial apoptosis routes, disturbing amino acids, lipid, and nucleotide metabolism, and regulating gene transcription and expression in mammals and fish. Based on the review, further studies better focus on the toxic differences of difenoconazole stereoisomers, the toxicological effects of transformation products of difenoconazole, and the mechanism of action of difenoconazole on sex-specific endocrine disruption effects, intestinal damage, and gut dysbacteriosis for its hazard assessment and management synthetically.

Synergistic advantages of volcanic ash weathering in saline soils: CO2 sequestration and enhancement of plant growth

Carbon dioxide (CO2) is a primary greenhouse gas that has experienced a surge in atmospheric concentration due to human activities and lifestyles. It is imperative to curtail atmospheric CO2 levels promptly to alleviate the multifaceted impacts of climate warming. The soil serves as a natural reservoir for CO2 sequestration. The scientific premise of this study is that CO2 sequestration in agriculturally relevant, organically-deficient saline soil can be achieved by incorporating alkaline earth silicates. Volcanic ash (VA) was used as a soil amendment for CO2 removal from saline soil by leveraging enhanced silicate rock weathering (ERW). The study pursued two primary objectives: first, we aimed to evaluate the impact of various doses of VA, employed as an amendment for organically-deficient soil, on the growth performance of key cultivated crops (sorghum and mung bean) in inland saline-alkaline agricultural regions of northeastern China. Second, we aimed to assess alterations in the physical properties of the amended soil through mineralogical examinations, utilizing X-ray diffraction (XRD) and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) analyses, quantifying the increase in inorganic carbon content within the soil. In the potting tests, mung bean plant height exhibited a noteworthy increase of approximately 41 % with the addition of 10 % VA. Sorghum plant height and aboveground and belowground biomass dry weights increased with VA application across all tested doses. At the optimal VA application rate (20 %), the sorghum achieved a CO2 sequestration rate of 0.14 kg CO2·m-2·month-1. XRD and SEM-EDS analyses confirmed that the augmented inorganic carbon in the VA-amended soils stemmed primarily from calcite accumulation. These findings contribute to elucidating the mechanism underlying VA as an amendment for organically-deficient soils and provide an effective approach for enhancing the carbon sink capacity of saline soils.

A comprehensive review on toxicological mechanisms and transformation products of tebuconazole: Insights on pesticide management

Tebuconazole has been widely applied over three decades because of its high efficiency, low toxicity, and broad spectrum, and it is still one of the most popular fungicides worldwide. Tebuconazole residues have been frequently detected in environmental samples and food, posing potential hazards for humans. Understanding the toxicity of pesticides is crucial to ensuring human and ecosystem health, but the toxic mechanisms and toxicity of tebuconazole are still unclear. Moreover, pesticides could transform into transformation products (TPs) that may be more persistent and toxic than their parents. Herein, the toxicities of tebuconazole to humans, mammals, aquatic organisms, soil animals, amphibians, soil microorganisms, birds, honeybees, and plants were summarized, and its TPs were reviewed. In addition, the toxicity of tebuconazole TPs to aquatic organisms and mammals was predicted. Tebuconazole posed potential developmental toxicity, genotoxicity, reproductive toxicity, mutagenicity, hepatotoxicity, neurotoxicity, cardiotoxicity, and nephrotoxicity, which were induced via reactive oxygen species-mediated apoptosis, metabolism and hormone perturbation, DNA damage, and transcriptional abnormalities. In addition, tebuconazole exhibited apparent endocrine-disrupting effects by modulating hormone levels and gene transcription. The toxicity of some TPs was equivalent to and higher than tebuconazole. Therefore, further investigation is necessary into the toxicological mechanisms of tebuconazole and the combined toxicity of a mixture of tebuconazole and its TPs.

Difference Analysis of the Composition of Iron (Hydr)Oxides and Dissolved Organic Matter in Pit Mud of Different Pit Ages in Luzhou Laojiao and Its Implications for the Ripening Process of Pit Mud

Long-term production practice proves that good liquor comes out of the old cellar, and the aged pit mud is very important to the quality of Luzhou-flavor liquor. X-ray diffraction, Fourier transform ion cyclotron resonance mass spectrometry, and infrared spectroscopy were used to investigate the composition characteristics of iron-bearing minerals and dissolved organic matter (DOM) in 2-year, 40-year, and 100-year pit mud and yellow soil (raw materials for making pit mud) of Luzhou Laojiao distillery. The results showed that the contents of total iron and crystalline iron minerals decreased significantly, while the ratio of Fe(II)/Fe(III) and the content of amorphous iron (hydr)oxides increased significantly with increasing cellar age. DOM richness, unsaturation, and aromaticity, as well as lignin/phenolics, polyphenols, and polycyclic aromatics ratios, were enhanced in pit mud. The results of the principal component analysis indicate that changes in the morphology and content of iron-bearing minerals in pit mud were significantly correlated with the changes in DOM molecular components, which is mainly attributed to the different affinities of amorphous iron (hydr)oxides and crystalline iron minerals for the DOM components. The study is important for understanding the evolution pattern of iron-bearing minerals and DOM and their interactions during the aging of pit mud and provides a new way to further understand the influence of aged pit mud on Luzhou-flavor liquor production.

Effect and mechanism of the improvement of coastal silt soil by application of organic fertilizer and gravel combined with Sesbania cannabina cultivation

Jiangsu Province of China has a large area of coastal silt soil (CSS) with poor permeability, high salinity, and poor nutrients, which brings great difficulties to the development and utilization of coastal zones, so that needs to be improved as a matter of urgency. In this study, river-sand, serpentine, and organic fertilizer were used as additives in CSS, and Sesbania cannabina, a salt-tolerant cash crop, was planted in these differently treated soils. Through high-throughput sequencing, analysis of soil physico-chemical properties, and detection of plant growth status, the rhizosphere bacterial diversity of S. cannabina growing in CSS under different treatments and their environmental impact factors were studied, while exploring the effect and mechanism of organic fertilizer combined with gravel as a CSS modifier. The results implied that single application of organic fertilizer could significantly increase the fertility levels of total nitrogen (TN), total organic carbon (TOC) and Avail. P in CSS; then, the application of organic fertilizer with river-sand significantly reduced salt content and alkalinity of soil; meanwhile, in the treatment of single application of organic fertilizer and application of organic fertilizer combined with river-sand, the rhizosphere of S. cannabina enriched the bacterial communities of organic matter degradation and utilization to varying degrees. The soil moisture content and indicators related to saline-alkali soil (including total salt, electrical conductivity (EC), exchangeable sodium percentage (ESP), Avail. Na and Avail. K, etc.) were further reduced significantly by the application of organic fertilizer combined with river-sand and serpentine. The method has greatly improved the growth conditions of S. cannabina and promoted the positive development of its rhizosphere bacterial community. Among them, in the treatment of organic fertilizer combined with river-sand and serpentine, a variety of plant growth-promoting rhizobacteria (PGPR, such as Sphingomonas, Ensifer, and Rhodobacter) and nitrogen-cycle-related bacteria (such as nitrate-reduction-related bacteria, nitrogen-fixing bacteria like Ensifer, and purple non-sulfur photosynthetic bacteria like Rhodobacter) were enriched in the rhizosphere of S. cannabina; moreover, the mutual association and robustness of bacterial co-occurrence networks have been significantly enhanced. The results provide a theoretical basis and reference model for the improvement of coastal saline-alkali silt soil.

Lead oxalates in some Chinese leafy vegetable cultivation: their biomineralization and remediation by oxalate degrading Streptomyces sp

Heavy metal contamination is a global threat with far-reaching effects for both human health and the environment. Biological agents, such as plants and microorganisms, provide uncomplicated and eco-friendly ways of removing toxic metals; thus, they are regarded as successful and alternative tools. In this study, we evaluated the ability of Streptomyces NJ10 (SN10), an oxalotrophic bacterium with outstanding oxalate metabolizing potential, to convert toxic lead oxalate (PbOx) into lead carbonate (PbCO3). SN10 was therefore used to determine the reduction of toxicity of Chinese leafy vegetables grown in the presence of PbOx in the soil. When compared to control, SN10 treated pots showed improved plant growth characters, i.e. shoot length (5.85 ± 0.56 cm), average leaf area (5.5 ± 0.44 cm2) and root length (7.2 ± 0.45 cm), as established by the plant growth attributes and the results obtained are statistically significant (at P ≤ 0.05) (for a period of 30 days). Furthermore, X-ray diffraction (XRD) and Scanning Electronic Microscopy-Energy-Dispersive X-ray Spectroscopy (SEM-EDS) studies revealed that PbOx was successfully transformed into a less toxic, water-insoluble precipitate of Pb-bearing carbonate, Phosgenite. The results provided a new idea for the biotransformation and toxicity mitigation of Pb contamination in soil.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03353-6.