The emergence of resistance genes is a global phenomenon that poses a significant threat to both animals and humans. Lakes are important reservoirs of genes that confer resistant to antibiotics and metals. In this study, we investigated the distribution and diversity of antibiotic resistance genes (ARGs) and metal resistance genes (MRGs) in the sediment of Daihai Lake using high-throughput sequencing and metagenomic analysis. The results indicated that all sampling sites had similar bacterial community structures, with Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes being the most abundant. A total of 16 ARG types containing 111 ARG subtypes were deposited in the sediment. Among the resistance genes to bacitracin, multidrug, macrolide-lincosamide-streptogramin (MLS), tetracycline, beta-lactam, and sulfonamide were the dominant ARG types, accounting for 89.9–94.3% of the total ARGs. Additionally, 15 MRG types consisting of 146 MRG subtypes were identified. In all samples, MRGs of the same type presented resistance to Pb, Ni, Hg, W, Zn, Ag, Cr, Fe, As, Cu, and multimetals. Overall, the distribution and diversity of antibiotic and metal resistance genes showed no significant differences in the samples. Plasmids (91.03–91.82%) were the most dominant mobile genetic elements in the sediments of Daihai Lake. Network analysis indicated that the target ARGs and MRGs were significantly positively correlated with the microorganisms. Potential hosts for various ARGs and MRGs include Proteobacteria, Euryarchaeota, Actinobacteria, Chloroflexi, and Bacteroidetes.

Various microplastics (MPs) are found in the environment and organisms. MP residues in organisms can affect health; however, their impacts on metabolism in aquatic organisms remain unclear. In this study, zebrafish embryos were exposed to polyethylene MPs with sizes ranging from 1 to 4 μm at concentrations of 0, 10, 100, and 1000 μg/L for 7 days. Through qPCR technology, the results indicated that zebrafish exposed to polyethylene MPs exhibited significant change in microbes of the phyla Firmicutes, Bacteroidetes, Proteobacteria, and Verrucomicrobia, etc. Moreover, 16S RNA gene sequencing revealed that there was a significant difference in alpha diversity between the control and 1000 μg/L MP-treated groups. At the genus level, the abundance of Aeromonas, Shewanella, Microbacterium, Nevskia and Methyloversatilis have increased remarkably. Conversely, the abundance of Pseudomonas, Ralstonia and Stenotrophomonas were significant reduction after MPs exposure. In addition, the levels of TG (triglyceride), TCHO (total cholesterol), NEFA (nonesterified fatty acid), TBA (total bile acid), GLU (glucose) and pyruvic acid significantly changed in MP-treated larval zebrafish, indicating that their metabolism was disturbed by MPs. Transcriptional levels of glucose and lipid metabolism-related genes showed a decreasing trend. Furthermore, LC/MS-based nontargeted metabolomics analysis demonstrated that a total of 59 phospholipid-related substances exhibited significant changes in larval fish treated with 1000 μg/L MPs. The mRNA levels of phospholipid metabolism-related genes were also obviously changed. Pearson correlation analysis indicated that the abundance of Aeromonas, Shewanella and Chitinibacter bacteria showed a negative correlation with most phospholipids, while Nevskia, Parvibacter and Lysobacter showed a positive correlation with most phospholipids. Based on these results, it is suggested that 1–4 μm PE-MPs could impact the microbiome and metabolism of larval zebrafish. All of these results indicated that the health risk of MPs cannot be ignored.

Large amounts of antibiotics/disinfectants are used in the farming of ornamental fish so as to prevent and treat bacterial infection. This may exert considerable selection pressures on the prevalence and propagation of antibiotic resistance genes (ARGs). However, the levels of ARGs and their potential prevalence mechanism in the wastewater of the ornamental fish industry remains unclear. In this work, wastewater is collected from a representative ornamental fish market (OFM) that is located at the northern China to study the occurrence and abundance of 21 ARGs and 2 integrase genes. Results indicated that 15 different ARGs and 2 integrase genes are existent and prevalent in the wastewater of OFM, whereby concentrations range from 2.01 to 10.34 copies/L. Proteobacteria, Bacteroidetes, Verrucomicrobia, and Firmicutes are the predominant phyla in the wastewater samples. 17 species of human opportunistic pathogens are present with relative abundance of up to 0.01%, which suggests a considerable risk of pathogens acquiring and disseminating ARGs. Moreover, oxytetracycline, ciprofloxacin, norfloxacin, sulfadiazine, and chloramphenicol are most frequently detected in wastewater, with concentrations of up to 1150, 877, 514, 1970, and 1700 ng/L, respectively. Notably, good correlations have been determined among ARGs and antibiotics, non-antibiotic environmental factors in wastewater of OFM. This current study reveals, for the first time, that OFM is a previously unperceived reservoir for ARG prevalence in aquatic environment and water environmental factors (particularly antibiotics), and their induced shifts in the microbial communities are the key factors for distribution of ARGs in OFM.

Anaerobic digestion, a promising technology for waste utilization and bioenergy generation, is a suitable approach to convert the shrimp waste to biomethane, reducing its environmental impact. In this study, shrimp chaff (SC) was co-digested corn straw (CS), wheat straw (WS), and sugarcane bagasse (SB). In co-digestion, SC enhanced biomethane production of CS by 8.47-fold, followed by SC + WS (5.67-folds), and SC + SB (3.37-folds). SC addition to agricultural biomass digestion also promoted the volatile solids removal up to 85%. Microbial community analysis of SC and CS co-digestion presented the dominance of phylum Bacteroidetes, Firmicutes, Proteobacteria, and Euryarchaeota. Proteolytic bacteria were dominant (18.02%) during co-digestion of SC and CS, with Proteiniphilum as major bacterial genera (14%) that converts complex proteinaceous substrates to organic acids. Among the archaeal community, Methanosarcina responsible for conversion of acetate and hydrogen to biomethane, increased up to 70.77% in SC and CS digestion. Addition of SC to the digestion of agricultural wastes can significantly improve the biomethane production along with its effective management to reduce environmental risks.

Composting is an effective technology to recycle organic solid waste as a green resource. However, pharmaceutical fermentation residue (PFR) contains a variety of pollutants, such as residual drug and antibiotic resistance genes (ARGs), which limits the green cycle of using PFR as a resource. To promote the green recycling of PFR, this study evaluated the characteristics of abundance and the response relationship of ARGs during the process of rapid composting. Different rapid composting samples were collected, and DNA was extracted from each sample. The absolute abundance of ARGs was quantified using quantitative PCR, and the microbial community structure was identified using high-throughput sequencing. The results showed that ermB, ermF, tetM and tetQ were reduced by 89.55%, 15.10%, 89.55%, and 82.30% respectively, and only sul2 increased by approximately 5-fold. Mobile genetic elements (MGEs) directly affected the changes in abundance of ARGs. As typical MGEs, intl1 and intl2 decreased by 3.40% and 54.32%, respectively. Potential host microorganisms important factors that affected ARGs and MGEs. A network analysis indicated that the potential host microorganisms were primarily distributed in Firmicutes and Proteobacteria at the phylum level. The pH and content of water-extractable sulfur were physicochemical parameters that substantially affected the abundance of potential host microorganisms through redundancy analysis. Industrial-scale rapid composting could reduce the number of ARGs and shorten the composting cycle, which merits its popularization and application.

Landfill mining and reclamation is a new strategy for addressing the lack of space available for new landfills and realizing the sustainable development of landfills. A gas-water joint bioreactor landfill is regulated by injecting water and/or recirculating leachate, and a blasting aeration system to optimize waste stabilization. In this study, four landfill reactors were constructed to investigate the effects of ventilation methods, including continuous (20 h d⁻¹) and intermittent aeration (4 h d⁻¹ in continuous or 2-h aeration per 12 h, twice a day), on the degradation of organic matter and volatile organic compound (VOC) emissions in comparison with traditional landfills. A total of 62 VOCs were detected in the landfill reactors. Among them, halogenated compounds had the highest abundance (39.8–65.4 %), followed by oxygenated compounds, alkanes and alkenes, and aromatic compounds. Both intermittent and continuous aeration could accelerate the degradation of landfilled waste and increase the volatilization rate of VOCs. Compared with intermittent aeration, the degradation of landfilled waste was more quickly in the landfill reactor with continuous aeration. However, intermittent aeration could create anaerobic-anoxic-aerobic conditions, which were conducive to the growth and metabolism of anaerobic and aerobic microorganisms in landfills and thereby reduced more than 63.4 % of total VOC emissions from the landfill reactor with continuous aeration. Moreover, intermittent aeration could reduce the ventilation rate and decrease the cost of aeration by 80 % relative to continuous aeration. Firmicutes, Bacteroidetes, Proteobacteria and Tenericutes predominated in the landfill reactors. The environmental variables including organic matter and VOCs concentrations had significant influences on microbial community structure in the landfilled waste. These findings indicated that intermittent aeration was an effective way to accelerate the stabilization of landfilled waste and reduce the cost and environmental risks in bioreactor landfills with gas-water joint regulation.

Combining hydrothermal treatment and composting is an effective method to dispose of penicillin fermentation residue (PFR), but the safety and related mechanism are still unclear. In this study, penicillin solution was hydrothermally treated to decipher its degradation mechanism, and then hydrothermally treated PFR (HT-PFR) was mixed with bulking agents at ratios of 2:0 (CK), 2:1.5 (T1), and 2:5 (T2) to determine the absolute abundance of antibiotic resistance genes (ARGs) and the succession of bacterial community. Results showed that penicillin was degraded to several new compounds without the initial lactam structure after hydrothermal treatment. During composting, temperature and pH of the composts increased with the raising of HT-PFR proportion, except the pH at days 2. After 52 days of composting, the absolute copies of ARGs (blaTEM, blaCMY2, and blaSFO) and the relative abundance of bacteria related to pathogens were reduced significantly (P < 0.05). Especially, the total amount of ARGs in the samples of CK and T1 were decreased to equal level (around 5 log₁₀ copies/g), which indicated that more ARGs were degraded in the latter by the composting process. In the CK samples, Bacteroidetes and Proteobacteria accounted for ~69.8% of the total bacteria, but they were gradually replaced by Firmicutes with increasing proportions of HT-PFR, which can be caused by the high protein content in PFR. Consisting with bacterial community, more gram-positive bacteria were observed in T1 and T2, and most of them are related to manganese oxidation and chitinolysis. As composting proceeded, bacteria having symbiotic or pathogenic relationships with animals and plants were reduced, but those related to ureolysis and cellulolysis were enriched. Above all, hydrothermal treatment is effective in destroying the lactam structure of penicillin, which makes that most ARGs and pathogenic bacteria are eliminated in the subsequent composting.

Growing evidence suggests that metallic oxide nanoparticles can pose a severe risk to the health of invertebrates. Previous attention has been mostly paid to the effects of metallic oxide nanoparticles on the survival, growth and physiology of animals. In comparison, the effects on gut microbiota and incidence of antibiotic resistance genes (ARGs) in soil fauna remain poorly understood. We conducted a microcosm study to explore the responses of the non-target soil invertebrate Enchytraeus crypticus gut microbiota and resistomes to copper oxide nanoparticles (CuO NPs) and copper nitrate by using bacterial 16S rRNA gene amplicons sequencing and high throughput quantitative PCR. The results showed that exposure to Cu2+ resulted in higher bioaccumulation (P < 0.05) and lower body weight and reproduction (P < 0.05) of Enchytraeus crypticus than exposure to CuO NPs. Nevertheless, exposure to CuO NPs for 21 days markedly increased the alpha-diversity of the gut microbiota of Enchytraeus crypticus (P < 0.05) and shifted the gut microbial communities, with a significant decline in the relative abundance of the phylum Planctomycetes (from 37.26% to 19.80%, P < 0.05) and a significant elevation in the relative abundance of the phyla Bacteroidetes, Firmicutes and Acidobacteria (P < 0.05). The number of detected ARGs in the Enchytraeus crypticus gut significantly decreased from 45 in the Control treatment to 16 in the Cu(NO3)2 treatment and 20 in the CuO NPs treatment. The abundance of ARGs in the Enchytraeus crypticus gut were also significantly decreased to 38.48% when exposure to Cu(NO3)2 and 44.90% when exposure to CuO NPs (P < 0.05) compared with the controls. These results extend our understanding of the effects of metallic oxide nanoparticles on the gut microbiota and resistome of soil invertebrates.

Soil antibiotic resistome and the nitrogen cycle are affected by florfenicol addition to manured soils but their interactions have not been fully described. In the present study, antibiotic resistance genes (ARGs) and nitrogen cycle genes possessed by soil bacteria were characterized using real-time fluorescence quantification PCR (qPCR) and metagenomic sequencing in a short-term (30 d) soil model experiment. Florfenicol significantly changed in the abundance of genes conferring resistance to aminoglycosides, β-lactams, tetracyclines and macrolides. And the abundance of Sphingomonadaceae, the protein metabolic and nitrogen metabolic functions, as well as NO reductase, nitrate reductase, nitrite reductase and N₂O reductase can also be affected by florfenicol. In this way, ARG types of genes conferring resistance to aminoglycosides, β-lactamases, tetracyclines, colistin, fosfomycin, phenicols and trimethoprim were closely associated with multiple nitrogen cycle genes. Actinobacteria, Chlorobi, Firmicutes, Gemmatimonadetes, Nitrospirae, Proteobacteria and Verrucomicrobia played an important role in spreading of ARGs. Moreover, soil physicochemical properties were important factors affecting the distribution of soil flora. This study provides a theoretical basis for further exploration of the transmission regularity and interference mechanism of ARGs in soil bacteria responsible for nitrogen cycle.

Heavy metals (HMs) in an aquatic environment mainly affects fish, and thus, fish are convenient pollution bio-indicators. In this study, the toxic effects of HM mixture (chromium (Cr), cadmium (Cd), copper (Cu)) in 0 mg/L to 3.2 mg/L concentration range was investigated in Cyprinus carpio (28 days). HM accumulation, histopathology, oxidative stress, and gut microbial changes were evaluated. HMs accumulated in the order of Cr > Cu > Cd, primarily in the kidneys and finally scales. Reactive oxygen species generation increased in all exposure groups up to day 14, with maximum generation at 3.2 mg/L mixture, which later decreased on day 28 in all. Malondialdehydeand and superoxide dismutase levels increased from day 7 to 28 with increased HM concentrations, while total protein showed an inverse trend. Gill histopathology showed major changes such as uplifted and disintegrated primary lamella, and secondary lamella shortening. The kidneys were characterized by glomerular necrosis, Bowman’s capsule expansion, and tubular space dilatation. Proteobacteria and Firmicutes abundance increased up to 59.4% and 99.16% in 0.8 mg/L and 3.2 mg/L treatment groups, respectively. This study provided a better understanding on the physiology and gut microbiota alteration in C. carpio under multiple HM stress.