Search

Cell surface hydrophobicity (CSH) dominates the interactions between rhizobacteria and pollutants at the soil‐water interface, which is critical for understanding the dissipation of pollutants in the rhizosphere microzone of rice. Herein, we explored the effects of self‐adaptive CSH of Sphingomonas sp. strain PAH02 on the translocation and biotransformation behaviour of cadmium‐phenanthrene (Cd‐Phe) co‐pollutant in rice and rhizosphere microbiome. We evidenced that strain PAH02 reduced the adsorption of Cd‐Phe co‐pollutant on the rice root surface while enhancing the degradation of Phe and adsorption of Cd via its self‐adaptive CSH in the hydroponic experiment. The significant upregulation of key protein expression levels such as MerR, ARHDs and enoyl‐CoA hydratase/isomerase, ensures self‐adaptive CSH to cope with the stress of Cd‐Phe co‐pollutant. Consistently, the bioaugmentation of strain PAH02 promoted the formation of core microbiota in the rhizosphere soil of rice (Oryza sativa L.), such as Bradyrhizobium and Streptomyces and induced gene enrichment of CusA and PobA that are strongly associated with pollutant transformation. Consequently, the contents of Cd and Phe in rice grains at maturity decreased by 17.2% ± 0.2% and 65.7% ± 0.3%, respectively, after the bioaugmentation of strain PAH02. These findings present new opportunities for the implementation of rhizosphere bioremediation strategies of co‐contaminants in paddy fields. [ABSTRACT FROM AUTHOR]

• Bio-Cd and bio-As in rhizosphere soil increased before the heading stage. • Content of ΣPAHs showed a decreased trend during whole growth period of rice. • Massilia and Sphingomonas were dominant rhizobacteria in HM-PAH contaminated soil. • Rhizobacteria interacted with pollutants intensely at tillering and heading stage. • Bio-Cd and ΣPAHs were key factors influenced community structure of rhizobacteria. This study investigated the transformations of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) in rhizosphere soils and adaptive responses of rhizobacterial community under the real field conditions during four growth stages (e.g., greening, tillering, heading, and maturity) of early rice (Zhongjiazao 17) and late rice (Zhongyou 9918) in Jiangshe village (JSV) and Yangji village (YJV). Results showed that rhizosphere soils of YJV were mildly polluted by Cd and PAHs compared to that of JSV. The relative abundance of bioavailable Cd (bio-Cd) and bioavailable As (bio-As) in rhizosphere soil increased before the heading stage but decreased at the subsequent growth stage, but the content of ΣPAHs in rhizosphere soil decreased gradually during whole growth period. The dominant rhizobacteria genera at YJV (e.g., Bacillus, Massilia, Sphingomonas , and Geobacter) increased at an abundance level from the tillering to heading stage. Rhizobacteria interacted with the above co-pollutant more intensely at the tillering and heading stage, where genes involved in HM-resistance and PAH-degradation appeared to have a significant enhancement. The contents of bio-Cd and bio-As in rhizosphere soil of early rice were higher than that of late rice at each growth stage, especially at the heading stage. Bio-Cd, ΣPAHs, and organic matter were key factors influencing the community structure of rhizobacteria. Results of this study provide valuable insights about the interactions between HM-PAH co-pollutant and rhizobacterial community under real field conditions and thus develop in-situ rhizosphere remediation techniques for contaminated paddy fields. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • HDS can effectively enrich chloramphenicol, rifampicin, and MLS resistance genes. • Bacillus , Rhizobium , and Rossellomorea are the hosts for ARGs that HDS enriched. • Abundances of cat , macB , and rpoB in soil were reduced by 36–85.7% after HDS enrichment. • HDS induced upregulation of chemotaxis genes in ARGs carriers. • HDS can accelerate the biofilm formation of ARGs carriers. Pathogenic microorganisms with antibiotic resistance genes (ARGs) pose a serious threat to public health and soil ecology. Although new drugs and available antibacterial materials can kill ARG carriers but accidentally kill beneficial microorganisms. Therefore, the rapid enrichment and separation of ARGs and their carriers from soil is becoming an important strategy for controlling the diffusion of ARGs. Hydroxamate siderophore (HDS) has gained widespread attentions for its involvement in trace element transfer among microorganisms in the soil environment, we thus explored an in-situ trapping-enrichment method for ARGs and their carriers via a small molecular HDS secreted by Pseudomonas fluorescens HMP01. In this study, we demonstrate that HDS significantly in-situ traps and enriches certain ARGs, including chloramphenicol, MLS, rifamycin, and tetracycline resistance genes in the soil environment. The enrichment efficiencies were 1473-fold, 38-fold, 17-fold, and 5-fold, respectively, higher than those in the control group. Specifically, the primary enriched ARGs were rpoB , mphL , catB 2, and tetA (60), and Bacillus , Rhizobium , Rossellomorea , and Agrobacterium were hosts for these ARGs. This enrichment was caused by the upregulation of chemotaxis genes (e.g., cheW , cheC , and cheD) and rapid biofilm formation within the enriched bacterial population. Notably, representative ARGs such as cat , macB , and rpoB were significantly reduced by 36%, 85.7%, and 72%, respectively, in the paddy soil after HDS enrichment. Our research sheds light on the potential application of siderophore as a rapping agent for the eco-friendly reduction of ARGs and their carriers in soil environments. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the learning abilities of linear recurrent neural networks (RNNs) trained using Gradient Descent. We present a theoretical guarantee demonstrating that these linear RNNs can effectively learn any stable linear dynamical system with polynomial complexity. Importantly, our derived generalization error bound is independent of the episode length. For any stable linear system with a transition matrix C characterized by a parameter ρ C related to the spectral radius, we prove that despite the non-convexity of the parameter optimization loss, a linear RNN can learn the system with polynomial sample and time complexity in 1 1 - ρ C , provided that the RNN has sufficient width. Notably, the required width of the hidden layers does not depend on the length of the input sequence. This work provides the first rigorous theoretical foundation for learning linear RNNs. Our findings suggest that linear RNNs are capable of efficiently learning complex dynamical systems, paving the way for further research into the learning capabilities of more general RNN architectures. [ABSTRACT FROM AUTHOR]

Exploring a novel green efficient bioeluant is a golden key to unlock the ex-situ scale remediation of soil contaminated with heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs). Hydroxamate siderophore (HDS) produced by Pseudomonas fluorescens HMP01, with certain hydrophobicity and strong coordination because of its special chemical structure (e.g., hydroxamic acid and dihydroxy quinoline chromophore), was used to investigate the bioleaching efficiency of HMs and PAHs from actual contaminated soils and underlying mechanisms. Results showed that leaching efficiency for HMs and PAHs from the co-contaminated soil was higher than that of single contaminated soil due to the cation-π interaction and coordination, which was closely related to the spacial configuration changes of the complex. HDS not only increased the bioleaching efficiency of cationic HMs by chelation (the leaching amount of Cd2+, Pb2+, Hg2+, Cu2+, Zn2+, and Ni2+ achieved 27.5, 110.4, 6.9, 477.7, 10,606.9, and 137.4 mg/kg HDS, respectively) but also enhanced the bioleaching amount of PAHs by solubilization (the leaching amount of phenanthrene reached 90.2 mg/kg HDS. Also, the residual HDS in soils caused no significant ecological risk. As expected, HDS is a desirable bioeluant to promote the scale application of the ex-situ remediation of soil contaminated with HMs and PAHs. [Display omitted] • Hydroxamate siderophore (HDS) produced by Pseudomonas fluorescens HMP01. • Cationic HMs and PAHs in co-contaminated soils can be effectively leached by HDS. • Cation-π and chelation dominated the synergistic leaching of HMs and PAHs by HDS. • All leached soils preserved quality, functions, and no ecological risk. [ABSTRACT FROM AUTHOR]

An arable land shortage is emerging due to soil pollution and a growing population, with many cultivated areas experiencing high-intensity utilisation. Uncultivated arable land (UAL) represents a potential resource, essential for safeguarding future food supply. However, the contamination characteristics and risks of heavy metals (HMs) in UAL remain unclear, hindering safe crop production when UAL is activated for farming. A total of 52 soil samples of UAL were collected in the Dongting Lake Basin, China, to assess contamination levels and potential risks of HMs. The study found that Cd (1.11 mg⋅kg−1) and As (43.48 mg⋅kg−1) were the primary pollutants responsible for ecological and occupational health risks in UAL of the Dongting Lake Basin, which were derived from industrial and agricultural sources, respectively. Should these UAL be reclaimed for rice production, dietary exposure to HMs would pose significant non-carcinogenic and unacceptable carcinogenic risks based on predictive models utilising the bioavailable HM content in the soil. According to the predicted content of HMs in rice and the total amount of HMs in soil, UAL was categorized into four groups (reclamation, reclamation after restoration, ecological remediation, and strict control). To ensure the safety of rice production, it is suggested that UAL in the west and south of Dongting Lake Basin could be reclaimed after ecological monitoring and restoration, while UAL in the east of the study area was classified as requiring strict control. This study provides support for reasonable reclamation and risk assessment of UAL. [Display omitted] • Cd and As were the primary pollutants caused ecological risks and soil degradation. • Health risks assessed by the total amount of soil HMs overestimated actual risks. • The bioavailable HMs in soil posed health risks via direct and dietary exposures. • Prediction models of HM content in rice were proposed as bioavailable HMs in soil. • An applicable risk classification and management scheme for UAL was proposed. [ABSTRACT FROM AUTHOR]

Despite effective mining environmental regulations, residual metal pollution persists, leading to significant ecological harm and posing substantial risks to human well-being. This study employed multiple-criteria methods to investigate the ecological and health risks caused by metals in multiple environmental media (e.g., arable soil, indoor dust, PM 10 , homegrown vegetables, and rice) around abandoned mine areas (MA) in central south China. The study also aimed to identify predominant risk factors and the main exposure pathway. The findings revealed that metal levels and risks in the environmental media surrounding the MA were significantly higher than those in the control areas (away from abandoned mines, CA). This indicates that the accumulation of metals in the environmental media surrounding the MA was attributed to the previous mining activities. Variations in metal content were observed among different environmental media in MA, with Cd from mining source being the primary pollutant in arable soil, indoor dust, PM 10 , and vegetables, while As from agricultural source was the main pollutant in rice. Additionally, the consumption of Cd-contaminated vegetables and As-contaminated rice emerged as the primary routes of health hazards for the local population, leading to significant non-carcinogenic and carcinogenic risks. Consequently, it is imperative for the government and mining companies to promptly establish risk control and remedial strategies for mitigating residual metal levels in multiple environmental media surrounding the MA. [Display omitted] • Mining causes residual metal accumulation in multiple environments around the area. • Residual metals from mining pose an ecological risk to the surrounding environment. • Cd and As were the primary pollutants in the multiple environments surrounding mines. • Dietary exposure was the major source of health hazards for local populations. • Mining and agricultural sources were the priority control sources in the study area. [ABSTRACT FROM AUTHOR]

Soils contaminated with heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) have been becoming a worldwide concerned environmental problem because of threatening public healthy via food chain exposure. Thus soils polluted by HMs and PAHs need to be remediated urgently. Physical and chemical remediation methods usually have some disadvantages, e.g., cost-expensiveness and incomplete removal, easily causing secondary pollution, which are hence not environmental-friendly. Conventional microbial approaches are mostly used to treat a single contaminant in soils and lack high efficiency and specificity for combined contaminants. Genetically engineered microorganisms (GEMs) have emerged as a desired requirement of higher bioremediation efficiency for soils polluted with HMs and PAHs and environmental sustainability, which can provide a more eco-friendly and cost-effective strategy in comparison with some conventional techniques. This review comments the recent advances about successful bioremediation techniques and approaches for soil contaminated with HMs and/or PAHs by GEMs, and discusses some challenges in the simultaneous removal of HMs and PAHs from soil by designing multi-functional genetic engineering microorganisms (MFGEMs), such as improvement of higher efficiency, strict environmental conditions, and possible ecological risks. Also, the modern biotechnological techniques and approaches in improving the ability of microbial enzymes to effectively degrade combined contaminants at a faster rate are introduced, such as reasonable gene editing, metabolic pathway modification, and protoplast fusion. Although MFGEMs are more potent than the native microbes and can quickly adapt to combined contaminants in soils, the ecological risk of MFGEMs needs to be evaluated under a regulatory, safety, or costs benefit-driving system in a way of stratified regulation. Nevertheless, the innovation of genetic engineering to produce MFGEMs should be inspired for the welfare of successful bioremediation for soils contaminated with HMs and PAHs but it must be supervised by the public, authorities, and laws. [Display omitted] • This review highlights the removal of different types of HMs or PAHs by GEMs. • There are some challenges in constructing MFGEMs to remove HMs and PAHs compound pollution in soil. • Some reasonable strategies are provided to remove HMs and PAHs compound pollution by MFGEMs. • The implementation of GEMs should be stratified and be supervised under the permission of government and public forever. [ABSTRACT FROM AUTHOR]

This study investigated the diffusion and enrichment of antibiotic resistance genes (ARGs) and pathogens via the transmission chain (mulberry leaves - silkworm guts - silkworm feces - soil) near a manganese mine restoration area (RA) and control area (CA, away from RA). Horizontal gene transfer (HGT) of ARGs was testified by an IncP a-type broad host range plasmid RP4 harboring ARGs (tetA) and conjugative genes (e.g., korB , trbA , and trbB) as an indicator. Compared to leaves, the abundances of ARGs and pathogens in feces after silkworms ingested leaves from RA increased by 10.8% and 52.3%, respectively, whereas their abundance in feces from CA dropped by 17.1% and 97.7%, respectively. The predominant ARG types in feces involved the resistances to β-lactam, quinolone, multidrug, peptide, and rifamycin. Therein, several high-risk ARGs (e.g., qnrB , oqxA , and rpoB) carried by pathogens were more enriched in feces. However, HGT mediated by plasmid RP4 in this transmission chain was not a main factor to promote the enrichment of ARGs due to the harsh survival environment of silkworm guts for the plasmid RP4 host E. coli. Notably, Zn, Mn, and As in feces and guts promoted the enrichment of qnrB and oqxA. Worriedly, the abundance of qnrB and oqxA in soil increased by over 4-fold after feces from RA were added into soil for 30 days regardless of feces with or without E. coli RP4. Overall, ARGs and pathogens could diffuse and enrich in environment via the sericulture transmission chain developed at RA, especially some high-risk ARGs carried by pathogens. Thus, greater attentions should be paid to dispel such high-risk ARGs to support benign development of sericulture industry in the safe utilization of some RAs. [Display omitted] • ARGs and pathogens were more enriched in feces after silkworms ingested leaves from RA. • QnrB , oqxA , and rpoB enriched in feces were carried by some pathogens. • HMs in the transmission chain promoted enrichment of qnrB and oqxA in feces and soil. • The diffusion risk of ARGs in sericulture industry in mining area needs attention. [ABSTRACT FROM AUTHOR]