Hydrogen Peroxide Is Involved in Methane-Alleviated Cadmium Toxicity in Alfalfa (Medicago sativa L.) Seedlings by Enhancing Cadmium Chelation onto Root Cell Walls.

Although previous studies have demonstrated that methane (CH4) can mitigate the toxicity of cadmium (Cd) in alfalfa seedlings, the CH4-rich water used in these studies may create hypoxic conditions, potentially influencing the experimental outcomes. Therefore, this study aimed to investigate whether CH4 can reduce Cd toxicity in alfalfa seedlings without the interference of hypoxia and to analyze its underlying mechanisms. Here, it was observed that supplementing oxygen with saturated CH4-rich water can significantly alleviate the inhibition of 75 µM CdCl2 on the growth of alfalfa (Medicago sativa L.) seedlings. Less Cd accumulation was also observed in both root and shoot parts, which could be explained by the CH4-altered cell wall components in alfalfa seedling roots, including covalent and ionic soluble pectin, and the degree of demethylation in pectin, thus enabling a higher proportion of Cd binding to the cell walls and reducing the entry of Cd into the cells. The above actions of CH4 were accompanied by an increase in hydrogen peroxide (H2O2) content and NADPH oxidase activity, which could be blocked by the addition of the NADPH oxidase inhibitor diphenylene iodonium (DPI). Taken together, these results implied that exogenously applied CH4 could alleviate Cd toxicity in alfalfa seedlings by enhancing Cd chelation onto the root cell walls, which might be closely associated with NADPH oxidase-dependent H2O2 signals. These findings could provide insight into the mechanism through which CH4 alleviates Cd toxicity in alfalfa plants.

Arbuscular mycorrhizal fungi and Streptomyces: brothers in arms to shape the structure and function of the hyphosphere microbiome in the early stage of interaction.

BACKGROUND: Fungi and bacteria coexist in a wide variety of environments, and their interactions are now recognized as the norm in most agroecosystems. These microbial communities harbor keystone taxa, which facilitate connectivity between fungal and bacterial communities, influencing their composition and functions. The roots of most plants are associated with arbuscular mycorrhizal (AM) fungi, which develop dense networks of hyphae in the soil. The surface of these hyphae (called the hyphosphere) is the region where multiple interactions with microbial communities can occur, e.g., exchanging or responding to each other's metabolites. However, the presence and importance of keystone taxa in the AM fungal hyphosphere remain largely unknown. RESULTS: Here, we used in vitro and pot cultivation systems of AM fungi to investigate whether certain keystone bacteria were able to shape the microbial communities growing in the hyphosphere and potentially improved the fitness of the AM fungal host. Based on various AM fungi, soil leachates, and synthetic microbial communities, we found that under organic phosphorus (P) conditions, AM fungi could selectively recruit bacteria that enhanced their P nutrition and competed with less P-mobilizing bacteria. Specifically, we observed a privileged interaction between the isolate Streptomyces sp. D1 and AM fungi of the genus Rhizophagus, where (1) the carbon compounds exuded by the fungus were acquired by the bacterium which could mineralize organic P and (2) the in vitro culturable bacterial community residing on the surface of hyphae was in part regulated by Streptomyces sp. D1, primarily by inhibiting the bacteria with weak P-mineralizing ability, thereby enhancing AM fungi to acquire P. CONCLUSIONS: This work highlights the multi-functionality of the keystone bacteria Streptomyces sp. D1 in fungal-bacteria and bacterial-bacterial interactions at the hyphal surface of AM fungi. Video Abstract.

A New Species of Nazeris Fauvel from Guangdong, China (Coleoptera, Staphylinidae, Paederinae).

A new species, Nazeris qilinshanensis Guo, Liu & Sun sp. nov. from Qilinshan, Guangdong province is described and illustrated. The external morphological characteristics and genitalia of the new species are described in detail and illustrated. The complete mitochondrial genome of N. qilinshanensis was sequenced and placed in a phylogenetic context. Phylogenetic analysis based on mitochondrial genomes showed that N. qilinshanensis forms a clade with Astenus lyonessius (Joy, 1908), within Lathrobiini.

Arbuscular mycorrhizal fungi enhance mineralisation of organic phosphorus by carrying bacteria along their extraradical hyphae.

Arbuscular mycorrhizal (AM) fungi gain access to nutrient patches outside the rhizosphere by producing an extensive network of fine hyphae. Here, we focused on establishing the mechanism by which AM fungal hyphae reach discrete organic patches with a cohort of functional bacteria transported in a biofilm on their surface. We investigated the mechanisms and impact of the translocation of phosphate solubilising bacteria (PSB) along AM fungal hyphae in bespoke microcosms. An in vitro culture experiment was also conducted to determine the direct impact of hyphal exudates of AM fungi upon the growth of PSB. The extraradical hyphae of AM fungi can transport PSB to organic phosphorus (P) patches and enhance organic P mineralisation both under in vitro culture and soil conditions. Bacteria move in a thick water film formed around fungal hyphae. However, the bacteria cannot be transferred to the organic P patch without an energy source in the form of hyphal exudates. Our results could be harnessed to better manage plant-microbe interactions and improve the ability of biological inocula involving AM fungi and bacteria to enhance the sustainability of agricultural crops in P limited conditions.

Improving UV Resistance of Aramid Fibers by Simultaneously Synthesizing TiO2 on Their Surfaces and in the Interfaces Between Fibrils/Microfibrils Using Supercritical Carbon Dioxide.

Aramid fibers with low density and high strength, modulus, and thermal resistance are widely used in applications such as bulletproof vests and cables. However, owing to their chemical structure, they are sensitive to ultraviolet light, which degrades the fibers' useful mechanical properties. In this study, titanium dioxide (TiO2) nanoparticles were synthesized both on the aramid III fiber surface and in the interfacial space between the fibrils/microfibrils in supercritical carbon dioxide (scCO2) to improve the UV resistance of aramid fibers. The effects of scCO2 treatment pressure on the TiO2 structure, morphology, surface composition, thermal stability, photostability, and mechanical properties were investigated using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, ultraviolet-visible spectroscopy, and single-fiber test. The results show that amorphous TiO2 formed on the fiber surface and the interface between fibrils/microfibrils, and decreased the photodegradation rate of the aramid III fiber. Moreover, this modification can also improve the tensile strength via treatment at low temperature and without the use of a solvent. The simple synthesis process in scCO2, which is scalable, is used for mild modifications with a green solvent, providing a promising technique for synthesizing metal dioxide on polymers.