Assessment of potential biotoxicity induced by biochar-derived dissolved organic matters to biological fermentative H2 production.

Biochar is a widely used antecedent for improving bio­hydrogen production. However, little is known about the impact of biochar-derived dissolved organic matter (DOM) on the performance of fermentative bio-H2 production. Herein, we evaluated the impact of biochar-derived DOM on the fermentation performance of hydrogen-producing microflora. The pyrolysis temperature of biochar affected the DOM composition, with lower pyrolysis temperatures showing more serious inhibition on H2 accumulation. When biochar was pyrolyzed at 500 °C, DOM prolonged the fermentation period and decreased H2 production from 1330.41 mL L-1 to 1177.05 mL L-1 compared to the control group. The xylose utilization in mixed substrate decreased from 29.72% to 26.41%, which is not favorable for practical applications where lignocellulosic biomass is used as a substrate. Otherwise, DOM caused a 6% reduction in microbial biomass accumulation and less soluble metabolites formation. The potential mechanism of DOM inhibiting bio­hydrogen production was verified by identifying an increase in reactive oxygen species (ROS) level (178.2%) and the microbial community shifted to containing fewer hydrogen-producing strains. The finding prompts a more precise design of biochar applications in fermentation systems to alleviate the potential hazards and maximum the fermentation performance, not limited to fermentative hydrogen production system.

Responses of nitrogen removal under microplastics versus nanoplastics stress in SBR: Toxicity, microbial community and functional genes.

Microplastics (MPs) and nanoplastics (NPs), as emerging pollutants, are frequently detected in wastewater treatment plants. However, studies comparing the effects of MPs versus NPs on nitrogen removal by activated sludge are rarely reported. Here, the responses of nitrogen removal performance, microbial community and functional genes to MPs and NPs in sequencing batch reactors were investigated. Results revealed that MPs (10 and 1000 µg/L) had no effects on nitrogen removal. While upon exposure to NPs, although low concentration (10 µg/L) of NPs showed no remarkable influence on nitrogen removal, high level (1000 µg/L) of NPs decreased NH4+-N removal efficiency by 24.48% and caused accumulation of NO3--N and NO2--N. These inhibitory probably due to the acute toxicity of NPs to activated sludge, which was reflected by the increasing reactive oxygen species generation and lactate dehydrogenase release. The toxic effects of NPs further declined the relative abundance of nitrifiers (e.g., Nitrospira) and denitrifiers (e.g., Dechloromonas). These negative effects, accompanied by a decrease in abundance of amoA and nxrA genes related to nitrification (30.01% and 65.24% of control) and narG, nirK and nirS genes associated with denitrification (78.59%, 61.39%, and 86.17% of control), directly illustrated the attenuate phenomenon observed in nitrogen removal.

(Micro) nanoplastics promote the risk of antibiotic resistance gene propagation in biological phosphorus removal system.

Microplastics (MPs), nanoplastics (NPs) and antibiotic resistance genes (ARGs), as emerging pollutants, have been frequently detected in wastewater treatment plants. However, the behavior of phosphorus and ARGs under MP and NP (MP/NP) pressure in biological phosphorus removal (BPR) system is still unknown. This study investigated the effects of MP/NPs on phosphorus removal and ARGs propagation in BPR system. Results showed that MP/NPs had no influence on phosphorus removal, but significantly promoted the amplification of tetracycline resistance genes (TRGs). Moreover, the TRG abundance were more facilitated by MPs than NPs, and the TRGs of efflux pump and enzymatic modification mechanism were mainly enriched. Meanwhile, MP/NPs increased the transmission risk of multiple resistance genes and mobile gene elements (MGEs). Microbial communities demonstrated the main polyphosphate accumulating organisms shifted from Acinetobacter to unclassified_Gammaproteobacteria, which explained why phosphorus removal efficiency was unaffected with MP/NP addition. Correlation analysis revealed there was no significant correlation between ARGs and MGEs (intI1 and intI2), but the abundances of potential hosts of ARGs were significantly increased with MP/NP addition, implying microbial community structure changes rather than gene horizontal transfer was the main factor promoting ARG propagation under MP/NP pressure.

Immunohistochemical Analysis of Histone H3 Modification in Newt Tail Tissue Cells following Amputation.

BACKGROUND: Newts have impressive regenerative capabilities, but it remains unclear about the role of epigenetic regulation in regeneration process. We herein investigated histone modifications in newt tail tissue cells following amputation. METHODS AND RESULTS: Iberian ribbed male newts (6-8 months old) were suffered to about 1.5 cm length of amputation of their tails for initiating regeneration process, and the residual stump of tail tissues was collected for immunohistochemical analysis 3 days later. Compared to the tissue cells of intact tails, c-kit-positive stem cells and PCNA-positive proliferating cells were significantly higher in tails suffered to amputation (P < 0.001). Amputation also significantly induced the acetylation of H3K9, H3K14, and H3K27 in cells of the tails with amputation (P < 0.001), but did not significantly change the methylation of H3K27 (P = 0.063). CONCLUSION: These results suggest that epigenetic regulation likely involves in newt tail regeneration following amputation.

Removal of antibiotic resistant bacteria and antibiotic resistance genes in wastewater effluent by UV-activated persulfate.

The emerging antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are increasingly appreciated to be as important as microbial contaminants. This paper focused on UV-activated persulfate (UV/PS), an advanced oxidation process, in removing ARB and ARGs from secondary wastewater effluent. Results showed that the inactivation efficiency of macrolides-resistant bacteria (MRB), sulfonamides-resistant bacteria (SRB), tetracyclines-resistant bacteria (TRB) and quinolones-resistant bacteria (QRB) by UV/PS reached 96.6 %, 94.7 %, 98.0 % and 99.9 % in 10 min, respectively. UV/PS also showed significant removal efficiency on ARGs. The reduction of total ARGs reached 3.84 orders of magnitude in UV/PS which is more than that in UV by 0.56 log. Particularly, the removal of mobile genetic elements (MGE) which might favor the horizontal gene transfer of ARGs among different microbial achieved 76.09 % by UV/PS. High-throughput sequencing revealed that UV/PS changed the microbial community. The proportions of Proteobacteria and Actinobacteria that pose human health risks were 4.25 % and 1.6 % less than UV, respectively. Co-occurrence analyzes indicated that ARGs were differentially contributed by bacterial taxa. In UV/PS system, hydroxyl radical and sulfate radical contributed to the removal of bacteria and ARGs. Our study provided a new method of UV/PS to remove ARGs and ARB for wastewater treatment.

Fate and removal of antibiotic resistance genes in heavy metals and dye co-contaminated wastewater treatment system amended with ß-cyclodextrin functionalized biochar.

Biochar has been received increasing concerns regarding its environmental effect, which is promising in wastewater treatment. In this study, the performance of ß-cyclodextrin functionalized biochar (ß-BC) on the removal of antibiotic resistance genes (ARGs) in wastewater treatment under the co-stresses of heavy metals and dye is evaluated. Results show that when 20 mg/L heavy metals (HMs) and 150 mg/L methyl orange (MO) are present in daily fed influent, only 0.05 mg/L HMs residual and 96.79%-98.84% MO removal efficiency achieved in ß-BC additive group, compare to 0.16 mg/L and 87.92%-94.11% of that in control, respectively, indicating that ß-BC can benefits the performance of contaminants removal. To evaluate the role of ß-BC plays on ARGs in multi-contaminants stressed system, tet W, tet M, sul-1, sul-2, blaTEM, oxa-1, qnr-S, erm-B and intI-1 are identified. The relative abundance of all identified ARGs are decreased when ß-BC presence compared to the corresponding groups without ß-BC additive. The diversity and composition of microbial community are explored and the reduction of potential antibiotic-resistant bacteria is speculated as a driver of ARGs removal. In conclusion, our study demonstrates that ß-BC possesses the ability to promote the removal of ARGs during continuous wastewater treatment under HMs-MO co-contaminant.