The environmental threat, pollution and damage posed by heavy metals to air, water, and soil emphasize the critical need for effective remediation strategies. This review mainly focuses on microbial electrochemical technologies (MET) for treating heavy metal pollutants, specifically includes Chromium (Cr), Copper (Cu), Zinc (Zn), Cadmium (Cd), Lead (Pb), Nickel (Ni), and Cobalt (Co). First, it explores the mechanisms and current applications of MET in heavy metal treatments in detail. Second, it systematically summarizes the key microbial communities involved, analyzing their extracellular electron transfer (EET) processes and summarizing strategies to enhance the EET efficiencies. Next, the review also highlights the synergistic microbial interactions in bioelectrochemical systems (BES) during the recovery and removal (remediation) processes of heavy metals, underscoring the crucial role of microorganisms in the transfer of the electrons. Then, this paper discussed how factors including pH values, applied voltages, types and concentrations of electron donors, electrode materials, biofilm thickness and other factors affect the treatment efficiencies of some specific metals in BES. BES has shown its great superiority in treating heavy metals. For example, for the treatments of Cr6+, under low pH conditions, the recovery and removal rate of Cr-6(+) by double chambers microbial fuel cell (DCMFC) can generally reach 98-99%, with some cases even achieving 100% (Gangadharan & Nambi, 2015). For the treatments of heavy metal ions such as Cu2+, Zn2+ and Cd2+, BES can also achieve the rates of treatments of more than 90% under the corresponding conditions of appropriate pH values and applied voltages(Choi, Hu, & Lim, 2014; W. Teng, G. Liu, H. Luo, R. Zhang, & Y. Xiang, 2016; Y. N. Wu et al., 2019; Y. N. Wu et al., 2018). After that, the review outlines the future challenges and the research opportunities for understanding the mechanisms of BES and microbial EET in heavy metal treatments. Finally, the prospect of future BES researches are pointed out, including the combinations with existing wastewater treatment systems, the integrations with the wind energy and the solar energy, and the application of machine learning (ML) in future BES. This article has certain significance and value for readers to better understand the working principles of BES and better operate and control BES to deal with heavy metal pollutants.

Soil microorganisms play a pivotal role in the biogeochemical cycles of alpine meadow ecosystems, especially in the context of permafrost thaw. However, the mechanisms driving microbial community responses to environmental changes, such as variations in active layer thickness (ALT) of permafrost, remain poorly understood. This study utilized next-generation sequencing to explore the composition and co-occur rence patterns of soil microbial communities, focusing on bacteria and micro-eukaryotes along a permafrost thaw gradient. The results showed a decline in bacterial alpha diversity with increasing permafrost thaw, whereas micro-eukaryotic diversity exhibi ted an opposite trend. Although changes in microbial community composition were observed in permafrost and seasonally frozen soils, these shifts were not statistically significant. Bacterial communities exhibited a greater differentiation between frozen and seasonally frozen soils, a pattern not mirrored in eukaryotic communities. Linear discriminant analysis effect size analysis revealed a higher number of potential biomark ers in bacterial communities compared with micro-eukaryotes. Bacterial co-occurrence networks were more complex, with more nodes, edges, and positive linkages than those of micro-eukaryotes. Key factors such as soil texture, ALT, and bulk density significantly influenced bacterial community structures, particularly affecting the relative abundan ces of the Acidobacteria, Proteobacteria, and Actinobacteria phyla. In contrast, fungal communities (e.g., Nucletmycea, Rhizaria, Chloroplastida, and Discosea groups) were more affected by electrical conductivity, vegetation coverage, and ALT. This study highlights the distinct responses of soil bacteria and micro-eukaryotes to permafrost thaw, offering insights into microbial community stability under global climate change.

Pesticide application in agriculture has significantly increased to enhance crop productivity. However, its longterm use raises concerns regarding soil microbial communities and water resource contamination. This study examines the prolonged impacts of agropharmaceutic (pesticide category) residues on microbial diversity, soil health, and groundwater pollution. The findings reveal that persistent agropharmaceutic exposure alters microbial community structure, reducing beneficial microorganisms while promoting resistant strains. Additionally, agropharmaceutic leaching into water systems contributes to ecological disturbances and human health risks. This research underscores the urgent need for sustainable pest management practices to mitigate environmental damage while maintaining agricultural efficiency.

Most improved strategies for phytoextraction do not achieve a synergistic enhancement of chromium (Cr) accumulation capacity and biomass. This study investigated the impacts of co-addition of garbage enzyme (GE) and microelectrolytic iron-carbon filler (MF) on soil physicochemical properties, as well as form and uptake of Cr during aging and phytoextraction process. The response of rhizosphere microbial community to co-addition and its role in enhancing the remediation performance of ryegrass was further analyzed. Co-addition of GE and MF during the 12-day aging process resulted in an increase of nutrients, a shift from an oxidising to a reducing soil environment, a decrease of Cr(VI) content, and an enhancement of soil microbial community diversity and richness, creating a suitable environment for subsequent phytoextraction. During the 40-day phytoextraction process, co-addition played a crucial role in facilitating the establishment of a complex, efficient and interdependent ecological network among soil microorganisms and contributed to the evolution of microbial community composition and functional pathways. An increase in the relative abundance of Trichococcus, Azospirillum and g_norank_f_JG30-KF-CM45 elevated soil nutrient levels, while a decrease in the relative abundance of TM7a and Brucella reduced pathogen harbouring. Meanwhile, co-addition increased the relative abundance of Bacillus, Arthrobacter and Exiguobacterium, attenuated Cr phytotoxicity and improved soil biochemical activity. These markedly diminished oxidative damage and improved ryegrass growth by reducing malondialdehyde accumulation. In addition, regular additions of GE and the increase in relative abundance of norank_fnorank_o_Microtrichales led to rhizosphere acidification, which inhibited short-term Cr immobilization and contributed to a notable increase in phytoextraction efficiency. This study presents a strategy to enhance phytoremediation efficiency and soil quality during phytoextraction of Cr-contaminated soils.

Phytoremediation of oil pollution using free-floating aquatic plants is a promising method for water body cleaning. In this study, the influence of Eichhornia crassipes and Pistia stratiotes on the degradation of oil pollution was investigated. The loss of oil alkanes and the rheological characteristics of water were evaluated, and an analysis of the emerging rhizospheric microbial communities was carried out using high-throughput sequencing. The presence of E. crassipes and P. stratiotes plants in oil-contaminated tanks had no effect on the degradation of oil alkanes. However, the presence of plants promoted the development of rhizospheric bacteria capable of growing in oil-contaminated environments. Alpha diversity of microbial communities in oil-contaminated samples was higher in the presence of plants. Additionally, plants significantly reduced the water/oil interfacial tension, which facilitated the availability of hydrocarbons for biodegradation. A difference was noted in the microbiome between E. crassipes and P. stratiotes. Changes in the composition of microbial communities highlight the potential of E. crassipes and P. stratiotes as rhizospheric hosts for microorganisms in the phytoremediation of water bodies.

To foster a circular bioeconomy throughout the management of industrial solid wine residues in the wine industry, this work presents the physicochemical and microbiological dynamics of the composting process with white grape pomace, stalks and wastewater treatment plant sludge from the same winery. Three composting windrows of 41 m3 were constructed with 0, 10 and 20% sludge addition. Physicochemical parameters were assessed following the Test Method for the Examination of Composting and Compost (TMECC), and the diversity and dynamics of the bacterial and fungal communities involved in the composting process were assessed via a high-throughput sequencing metabarcoding approach. The addition of sludge increased the moisture content, bulk density, and pH after six months of turned windrow composting. No effect of sludge addition on the macronutrient composition of the compost was observed. The Shannon-Wiener index differed among stages and treatments. Bacterial diversity increased over time, while the fungal community appeared to be highly affected by the thermophilic stage, which led to a reduction in diversity that slightly recovered by the end of the process. Furthermore, the sludge exhibited high bacterial diversity but very low fungal diversity. Consequently, the design of on-site biologically based strategies to better manage wine residues can produce soil amendments, improve fertilization, reclaim damaged soils, and ultimately reduce management costs, making composting an economically attractive and sustainable alternative for waste management in the wine industry. Physicochemical and microbiological studies of sludge and grape pomace in composting are necessary to foster a circular bioeconomy in the wine industry.Sludge addition improved water retention and bulk density, but no effect on macronutrient composition was observed; nonetheless, an increase in beneficial microorganisms was found.Closing the loop in the management of organic residues via composting in the wine industry will improve economic and environmental performance.

This study evaluates cellular damage, metabolite profiling, and defence-related gene expression in tomato plants and soil microflora during Fusarium wilt disease after treatment with B. tequilensis PBE-1. Histochemical analysis showed that PBE-1 was the primary line of defence through lignin deposition and reduced cell damage. GC-MS revealed that PBE-1 treatment ameliorated stress caused by F. oxysporum infection. PBE-1 also improved transpiration, photosynthesis, and stomatal conductance in tomato. qRT-PCR suggested that the defence-related genes FLS2, SERK, NOS, WRKYT, NHO, SAUR, and MYC2, which spread infection, were highly upregulated during F. oxysporum infection, but either downregulated or expressed normally in PBE-1 + P treated plants. This indicates that the plant not only perceives the bio-control agent as a non-pathogen entity but its presence in normal metabolism and gene expression within the host plant is maintained. The study further corroborated findings that application of PBE-1 does not cause ecological disturbances in the rhizosphere. Activity of soil microflora across four treatments, measured by Average Well Colour Development (AWCD), showed continuous increases from weeks 1 to 4 post-pathogen infection, with distinct substrate usage patterns like tannic and fumaric acids impacting microbial energy source utilization and diversity. Principal Component Analysis (PCA) and diversity indices like McIntosh, Shannon, and Simpson further illustrated significant microbial community shifts over the study period. In conclusion, our findings demonstrate that B. tequilensis PBE-1 is an ideal bio-agent for field application during Fusarium wilt disease management in tomato.

PurposeThe health of rhizosphere soil microorganisms is an important indicator to evaluate soil quality. Therefore, understanding the response of rhizosphere soil microorganisms to tobacco crop succession is crucial for promoting the sustainable development of agriculture.MethodsThe microbial diversity and community structure of rhizosphere soil in continuous cropping and non-cropped tobacco for 7 years were analyzed by the Illumina platform.Result(1) Continuous cropping tobacco cause rhizosphere soil acidification and reduction in alkaline nitrogen (AN) and soil organic matter (SOM). (2) Continuous cropping tobacco reduces the diversity of rhizosphere soil microbial communities, increasing harmful functional microorganisms and declining beneficial ones. (3) The abundance of bacteria that perform nitrification and saprophytic fungi in the rhizosphere soil of continuous cropping areas decreases, inhibiting carbon and nitrogen cycling processes. (4) The composition and diversity of the soil rhizosphere microbial community are affected by the imbalance in the physicochemical property of the rhizosphere.ConclusionContinuous cropping tobacco cause rhizosphere soil acidification and nutrient imbalance, and the carbon and nitrogen cycles involved in microorganisms were damaged. Furthermore, the decreased diversity of rhizosphere soil microorganisms and the increased abundance of pathogenic fungi contribute to the continuous cropping obstacles of tobacco.

Global climate change is altering the amounts of ice and snow in winter, and this could be a major driver of soil microbial processes. However, it is not known how bacterial and fungal communities will respond to changes in the snow cover. We conducted a snow manipulation experiment to study the effects of snow removal on the diversity and composition of soil bacterial and fungal communities. A snow manipulation experiment was carried out on the meadow steppe in Hulunbuir, Inner Mongolia, China, during the winter period October 2019-March 2020. Soil samples were collected from the topsoil (0-10 cm) in mid-March 2020 (spring snowmelt period). Snow removal significantly reduced soil moisture and soil ammonium concentration. Lower snow cover also significantly changed the fungal community structure and beta diversity. Snow removal did not affect the bacterial community, indicating that fungal communities are more sensitive to snow exclusion than bacterial communities. The relative importance analysis (using the Lindeman-Merenda-Gold method) showed that available nitrogen (AN), soil water content (SWC), total organic carbon (TOC), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) together explained 94.59% of the variation in soil fungal beta diversity, where AN was identified as the most important predictor. These finding provide insights into potential impacts of climate warming and associated reduced snow cover on soil microbial communities and processes.

The impact of climate change in the European Alps has been roughly twice the global average, dramatically reducing permafrost extent and thickening of its active layer. Therefore, the study of the abiotic factors (i.e. chemical/physical parameters) affecting the microbial diversity inhabiting Alpine permafrost appears to be of dramatic relevance. Within the European Alps, the Stelvio area exhibits these effects in a particularly evident way, with important consequences on microbial ecosystems. Therefore, microbial communities inhabiting a permafrost core collected in the Scorluzzo active rock glacier (Stelvio Pass, Italian Central Alps) were investigated along a depth gradient (410 to 524 cm from the surface). The taxonomic structures of bacterial and fungal communities were investigated via a next-generation sequencing (NGS) approach (Illumina MiSeq), targeting the bacterial V3-V4 regions of 16S rDNA and the fungal ITS2 region. Abiotic soil factors (grain size, electrical conductivity, ice/water content, pH, Loss-on-Ignition - LOI, total and organic carbon, nitrogen and phosphorous) were analysed. Richness and Shannon-H diversity indices were correlated to abiotic factors. Bacterial diversity was significantly (p < 0.05) correlated with LOI, while fungal diversity was significantly (p < 0.05) correlated with the depth gradient. The Constrained Analysis of Principal (CAP) coordinates were used to study the correlation between abiotic parameters and the taxonomic structure of bacterial and fungal communities. Among all tested variables, the depth gradient, water content, pH and LOI affected the taxonomic structure of bacterial communities (in particular, the abundance of bacterial amplicon sequence variants - ASVs - assigned to Afipia sp., Chloroflexi, Gaiella sp., Oryzihumus sp. and Serratia, sp.), while fungal communities (ASVs assigned to Naganishia sp., Rhodotorula sp., Sordariomycetes and Taphrinales) were affected by the depth gradient. Co-occurrences (calculated by Pearson correlation coefficient) among microbial taxa (i.e. bacteria vs bacteria, bacteria vs fungi, fungi vs fungi) were investigated: the prevalence of significant (p < 0.05) positive co-occurrences was found, suggesting that the coexistence of different microbial taxa could play a crucial role in maintaining the ecological and taxonomic balance of both bacterial and fungal communities inhabiting the Alpine permafrost ecosystem. These findings suggest that the bacterial and fungal diversity of Alpine permafrost are affected in different ways by some abiotic factors.