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The coexistence of microplastics (MPs) and heavy metals in sediments has caused a potential threat to sediment biota. However, differences in the effects of MPs and heavy metals on microbes and plants in sediments under different sediment conditions remain unclear. Hence, we investigated the influence of polyethylene (PE) and polylactic acid (PLA) MPs on microbial community structure, Pb bioavailability, and wheatgrass traits under sequential incubation of sediments (i.e., flood, drainage, and planting stages). Results showed that the sediment enzyme activities presented a dose-dependent effect of MPs. Besides, 10 % PLA MPs significantly increased the F1 fractions in three stages by 11.13 %, 30.10 %, and 17.26 %, respectively, thus resulting in higher Pb mobility and biotoxicity. MPs altered sediment bacterial composition and structures, and bacterial community differences were evident in different incubation stages. Moreover, the co-exposure of PLA MPs and Pb significantly decreased the shoot length and total biomass of wheatgrass and correspondingly activated the antioxidant enzyme activity. Further correlation analysis demonstrated that community structure induced by MPs was mainly driven by sediment enzyme activity. This study contributes to elucidating the combined effects of MPs and heavy metals on sediment ecosystems under different sediment conditions. [Display omitted] • Effects on enzyme activities varied with MPs types and sediment conditions. • 10 % PLA MPs significantly increased the bioavailability of Pb in sediment. • MPs reduced the complexity and stability of bacterial co-occurrence networks. • Co-exposure PLA MPs and Pb exhibited stronger negative impact on wheatgrass growth. • The bacterial structures were mainly driven by sediment enzyme activities. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are able to interact with diverse contaminants in sediments. However, the impacts of MPs on sediment properties and bacterial community structure in heavy metal-contaminated sediments remain unclear. In this study, we investigated the adsorption of Pb(II) by sediment-MPs mixtures and the effects of different concentration MPs on sediment enzyme activities, DOM fractions, and Pb bioavailability in riverine sediments, and further explored the response of sediment microbial community to Pb in the presence of MPs. The results indicated that the addition of MPs significantly decreased the adsorption amount of Pb(II) by sediments, especially decreased by 12.6% at 10% MPs treatment. Besides, the changes in enzyme activities, DOM fractions exhibited dose-dependent effects of MPs. The higher level of MPs (5% and 10%) tends to transform Pb into more bioavailable fractions in sediments. Also, MPs amendment was observed to alter sediment bacterial community structures, and community differences were evident in the uncontaminated and lead-contaminated sediments. Therein, significant increase of Bacteroidota , Proteobacteria and decrease of Firmicutes abundance in Pb-contaminated sediment at the phylum level were observed. These findings are expected to provide comprehensive information for assessing the combined ecological risks of heavy metals and MPs in riverine sediments. [Display omitted] • The adsorption capacity of sediment for Pb(II) decreased with the content of MPs. • The changes in sediment enzyme activities and DOC structures varied with MPs concentration. • High doses of MPs increased the bioavailability of Pb in sediments. • MPs had a greater impact on bacterial community in Pb-contaminated sediments. [ABSTRACT FROM AUTHOR]

Due to the mass production and daily use of plastic products, the potential toxicity of microplastics to the water environment has attracted worldwide attention. In this work, the effect of typical microplastics (PET) on the performance of activated sludge from membrane bioreactors (MBR) was evaluated. The impacts on biological removal efficiency were unconspicuous with continuous dosing of 60 particles/L. However, further investigations revealed that PET particle accumulation caused adverse impacts on settleability and dewaterability. The SVI value increased from 53.3 ml/g MLSS to 69.9 ml/g MLSS and the CST in the PET reactor increased by 22%. Nevertheless, hydrophobicity was reduced by 49.2%. Mechanism studies exposed that the PET microplastics accumulation improved extracellular polymeric substances (EPS) from 116.96 mg/L to 138.70 mg/L and caused cell membrane damage. The abundance and diversity of microbial community reduced in activated sludge in PET reactor compared with control reactor. These phenomena revealed a possible hypothesis that the microplastic particles increased EPS and cytotoxicity of activated sludge. However, the rate of transmembrane pressure (TMP) build-up was significantly mitigated in PET-MBR compared to that in a control-MBR (1.27 folds), which attributes that physical scour of particles may still alleviate membrane contamination in MBR. • Membrane biofouling was alleviated due to physical scouring of PET particles. • The physicochemical properties of sludge were changed after long-term PET exposure. • Accumulation of PET particles caused EPS secretion and cell membrane damage. • Long-term exposure to PET changed the microbial community of MBR system. [ABSTRACT FROM AUTHOR]

Agriculture practices, such as fertilization and cultivation, inevitably modify the soil ecological environment by altering the soil microbial community structure and the nitrogen (N) metabolism processes. The influences of rainfall combined with agriculture practices on microbial community structure and soil N metabolism were not well understood. It is important to investigate the combined effects of rainfall and agriculture practices on the soil N metabolism in varied soil layers for better agriculture management. In this paper, the effects of fertilization, cultivation as well as rainfall on N metabolism related microorganisms and key functional genes at various depths in a vegetable field were investigated. Results showed that Soil microbial community structure of 30 cm depth is more sensitive to soil properties change. Nitrogen-fixing bacteria (NFB) was promoted (from 0.07% to 1.43%) after fertilization, and cultivation shifted the dominance of NFB from Ensifer to Bacillus in 20–30 cm soil layer. Denitrifier Pseudomonas in 20 cm (from 0.93 to 5.01%) and comammox Nitrospira in 30 cm (from 3.3% to 3.82%) were promoted after rainfall. Soil C/N is a major determinant of soil N metabolism-related microorganisms. Fertilization before rainfall and cultivation at 30 cm is recommended. The findings in this paper could provide the scientific basis for better agriculture management practices. • Cultivation changed the genus of nitrogen-fixing bacteria in 20–30 cm soil layer. • Pseudomonas in 20 cm and Nitrospira in 30 cm were promoted after rainfall. • Rainfall had a great influence on the microbial communities across each soil layer. • Soil C/N is a major determinant of soil nitrogen metabolism-related microorganisms. • N fertilization before rainfall and agricultural activity is recommended. [ABSTRACT FROM AUTHOR]

Quorum sensing (QS) is a process widely exist in bacteria, which refers to the cell-cell communication through secretion and sensing the specific chemical signal molecules named autoinducers. This review demonstrated recent research progresses on the specific impacts of signal molecules in the granular sludge reactors, such corresponding exogenous strategies contained the addition of QS signal molecules, QS-related enzymes and bacteria associated with QS process. Accordingly, the correlation between QS signaling molecule content and sludge granulation (including the formation and stability) was assumed, the comprehensive conclusion elucidated that some QS signals (acyl-homoserine lactone and Autoinducer 2) can accelerate the growth of particle diameter, the production of extracellular polymeric substance (EPS), microbial adhesion and change the microbiome structure. But diffusable signal factor (DSF) acted as a significant disincentive to the formation and stability of GS. As a result, it deserved serious attention on the value and role of QS signals in the GS. This review attempts to illuminate the potential method for addressing the main bottleneck: to accelerate the formation of granules and keep the high stability of GS for a long-term reactor. Therefore, review discussed the possible trends of GS: QS and intercellular/intracellular signaling which can lay a theoretical foundation for mechanism of GS formation and stability, would be of practical significance for further application in the future. Image 10514 • Particle diameter in the granules were relative to the variety of signal molecules. • The production of EPS was enhanced by AHLs and AI-2 and reduced by DSF. • Augmentation of signal molecules changed the microbial community in the granules. • Mechanism of signal molecules functioned in granules could be effectively applied. [ABSTRACT FROM AUTHOR]

In this paper, sediment microbial fuel cell (SMFC) with nano‐Fe2O3 modified anode was investigated to enhance in‐situ remediation. Results showed that the modification led to higher removal of total organic matter (TOC) after 50 days. Anodic microbial community was further analyzed. It was found that the decrease of relative abundance of exoelectrogens and the suppression of methanogens led to the reduction of the power generation in SMFC with modified anode. Longilinea was one of key bacteria regarding TOC degradation. Besides, potential environmental effects resulting from SMFC and nano‐Fe2O3 modification were also discussed. The competition of exoelectrogens with methanogens for nutrient potentially resulted in the reduction of methane emission. The SMFC system could inhibit the growth of fecal bacteria and the nano‐Fe2O3 modified anode had stronger inhibitory effect, which further reduce the risks induced by fecal bacteria to human health. The modification could further maintain the biodiversity of eucaryon and achieve higher ecosystem stability. [ABSTRACT FROM AUTHOR]

• Microbial community dynamics are analyzed under the condition of exogenous QQ. • The change of sludge's biofouling propensity is investigated when adding exogenous QQ. • Exogenous QQ can reduce the species diversities of MBRs, especially in the short term. • Exogenous QQ can enhance biofouling propensity of sludge itself in the short term. • The enhancing of biofouling propensity of sludge depends on the dynamics of situ QS and QQ bacteria. Recently, bacterial quorum quenching (QQ) has been proven as a novel approach for biofouling mitigation in membrane bioreactors (MBRs). The information about microbial community is vital for the development of QQ strategies. Also, the change of microbial community may affect the biofouling propensity of sludge. In this study, the effects of exogenous QQ on microbial community dynamics in MBRs were investigated, along with biofouling propensity of activated sludge. QQ MBR dosed with exogenous QQ bacteria exhibited a better anti-biofouling, whereas the wastewater treatment performance was almost no difference compared with control MBR. As for the microbial community, exogenous QQ had an impact on both the bacterial diversities and community composition, especially for the quorum sensing (QS) and QQ bacteria in situ. The addition of exogenous QQ could reduce the QQ ability of sludge itself in the short term, and enhance its biofouling propensity. These findings provided new insights for the development of QQ strategies. [ABSTRACT FROM AUTHOR]

• The microbial community in wastewater play an important role in current generation. • The presence of aerobic bacteria in the sample reduces the current generation. • The anode needs to be cultured by the same source of water a prior measurement. • Pretreatment of bacteria before testing may improve the accuracy and reliability. • Two ways to reduce the systemic error in testing wastewater were firstly proposed. Microbial fuel cells (MFCs) based sensors had been studied in measuring biochemical oxygen demand (BOD) or the equivalent chemical oxygen demand (COD) recently. Limited attention has been paid to the effect of the microbial communities in wastewater on the responses of these sensors. This study systematically evaluated, for the first time, the effect of wastewater samples from a variety of sources on the electrical response of a micro-fabricated double-chamber MFC device. It was found that the response of the MFC is positively correlated with the bacterial composition, in particular electroactive bacteria. The presence of aerobic bacteria in the sample reduces the current generation. These findings indicated that the bacterial content of the water sample could be a significant interference source and must be considered in the use of µMFC-based sensors. Filtering samples may be effective in improving the reliability of these microsensors. [ABSTRACT FROM AUTHOR]