Low temperature acclimation of electroactive microorganisms may be an effective strategy to enhance the toxicity sensing performance of microbial fuel cell sensors.

Microbial fuel cell (MFC) sensing is a promising method for real-time detection of water biotoxicity, however, the low sensing sensitivity limits its application. This study adopted low temperature acclimation as a strategy to enhance the toxicity sensing performance of MFC biosensor. Two types of MFC biosensors were started up at low (10 °C) or warm (25 °C) temperature, denoted as MFC-Ls and MFC-Ws respectively, using Pb2+ as the toxic substance. MFC-Ls exhibited superior sensing sensitivities towards Pb2+ compared with MFC-Ws at both low (10 °C) and warm (25 °C) operation temperatures. For example, the inhibition rate of voltage of MFC-Ls was 22.81 % with 1 mg/L Pb2+ shock at 10 °C, while that of MFC-Ws was only 5.9 %. The morphological observation showed the anode biofilm of MFC-Ls had appropriate amount of extracellular polymer substances, thinner thickness (28.95 µm for MFC-Ls and 41.58 µm for MFC-Ws) and higher proportion of living cells (90.65 % for MFC-Ls and 86.01 % for MFC-Ws) compared to that of MFC-Ws. Microbial analysis indicated the enrichment of psychrophilic electroactive microorganisms and cold-active enzymes as well as their sensitivity to Pb2+ shock was the foundation for the effective operation and good performance of MFC-Ls biosensors. In conclusion, low temperature acclimation of electroactive microorganisms enhanced not only the sensitivity but also the temperature adaptability of MFC biosensors.

When antibiotics encounter microplastics in aquatic environments: Interaction, combined toxicity, and risk assessments.

Antibiotics and microplastics (MPs), known as emerging pollutants, are bound to coexist in aquatic environments due to their widespread distribution and prolonged persistence. To date, few systematic summaries are available for the interaction between MPs and antibiotics in aquatic ecosystems, and a comprehensive reanalysis of their combined toxicity is also needed. Based on the collected published data, we have analyzed the source and distribution of MPs and antibiotics in global aquatic environments, finding their coexistence occurs in a lot of study sites. Accordingly, the presence of MPs can directly alter the environmental behavior of antibiotics. The main influencing factors of interaction between antibiotics and MPs have been summarized in terms of the characteristics of MPs and antibiotics, as well as the environmental factors. Then, we have conducted a meta-analysis to evaluate the combined toxicity of antibiotics and MPs on aquatic organisms and the related toxicity indicators, suggesting a significant adverse effect on algae, and inapparent on fish and daphnia. Finally, the environmental risk assessments for antibiotics and MPs were discussed, but unfortunately the standardized methodology for the risk assessment of MPs is still challenging, let alone assessment for their combined toxicity. This review provides insights into the interactions and environment risks of antibiotics and MPs in the aquatic environment, and suggests perspectives for future research.

Planktonic/benthic Bathyarchaeota as a "gatekeeper" enhance archaeal nonrandom co-existence and deterministic assembling in the Yangtze River.

Archaea, the third proposed domain of life, mediate carbon and nutrient cycling in global natural habitats. Compared with bacteria, our knowledge about archaeal ecological modes in large freshwater environments subject to varying natural and human factors is limited. By metabarcoding analysis of 303 samples, we provided the first integrate biogeography about archaeal compositions, co-existence networks, and assembling processes within a 6000 km continuum of the Yangtze River. Our study revealed that, among the major phyla, water samples owned a higher proportion of Thaumarchaeota (62.8%), while sediments had higher proportions of Euryarchaeota (33.4%) and Bathyarchaeota (18.8%). A decline of polarization in phylum abundance profile was observed from plateau/mountain/hill to basin/plain areas, which was attributed to the increase of nutrients and metals. Planktonic and benthic Bathyarchaeota tended to co-occur with both major (e.g., methanogens or Thermoplasmata) and minor (e.g., Asgard or DPANN) taxa in the non-random networks, harboring the highest richness and abundances of keystone species and contributing the most positively to edge number, node degree, and nearest neighbor degree. Furthermore, we noted significantly positive contributions of Bathyarchaeota abundance and network complexity to the dominance of deterministic process in archaeal assembly (water: 65.3%; sediments: 92.6%), since higher carbon metabolic versatility of Bathyarchaeota would benefit archaeal symbiotic relations. Stronger deterministic assembling was identified at the lower-reach plain, and higher concentrations of ammonium and aluminum separately functioning as nutrition and agglomerator were the main environmental drivers. We lastly found that the Three Gorges Dam caused a simultaneous drop of benthic Bathyarchaeota abundance, network co-existence, and deterministic effects immediately downstream due to riverbed erosion as a local interference. These findings highlight that Bathyarchaeota are a "gatekeeper" to promote fluvial archaeal diversity, stability, and predictability under varying macroscopic and microscopic factors, expanding our knowledge about microbial ecology in freshwater biogeochemical cycling globally.

Effect of chlorine disinfectant influx on biological sewage treatment process under the COVID-19 pandemic: Performance, mechanisms and implications.

Since the onset of the COVID-19 Pandemic, large amounts of chlorine-containing disinfectants have been used to interrupt the spread of SARS-CoV-2 and residual chlorine eventually entered the hospital or municipal sewage treatment facilities. However, little is known about the effect of chlorine influx on the biological sewage treatment process. Here we investigated the effect of chlorine on the microbiome and the mechanism of microbial chlorine resistance in the activated sludge of the aerobic treatment process, using metagenomic and metatranscriptomic sequencing. We found that chlorine could negatively impact the aerobic treatment performance regarding nitrogen/COD removal with a dose-dependent effect, and the dual effects of chlorine dose and interaction time differentiated the microbial community in activated sludge. The decline of nitrogen/COD removal was attributed to the compressed activity of functional microorganisms, such as the ammonia oxidation bacteria, under chlorinated conditions, and the damage cannot be recovered in a short term. In addition, some microorganisms could survive in chlorinated conditions by up-regulating the chlorine resistance genes (CRGs) expression (approximately 1.5 times) and stimulating new CRGs expression. In particular, species Acinetobacter johnsonii could resist high concentrations of chlorine through various mechanisms, especially the overexpression of efflux pump function encoded by qac genes play a key role. Based on these results, considering the persistence of the epidemic and extensive use of chlorine disinfectants, it cannot be ignored that large amounts of residual chlorine are entering the biological treatment facility, and strictly de-chlorination measures or microbial chlorine resistance regulations before entering should be implemented.

May microbial ecological baseline exist in continental groundwater?

BACKGROUND: Microbes constitute almost the entire biological community in subsurface groundwater and play an important role in ecological evolution and global biogeochemical cycles. Ecological baseline as a fundamental reference with less human interference has been investigated in surface ecosystems such as soils, rivers, and ocean, but the existence of groundwater microbial ecological baseline (GMEB) is still an open question so far. RESULTS: Based on high-throughput sequencing information derived from national monitoring of 733 newly constructed wells, we find that bacterial communities in pristine groundwater exhibit a significant lateral diversity gradient and gradually approach the topsoil microbial latitudinal diversity gradient with decreasing burial depth of phreatic water. Among 74 phyla dominated by Proteobacteria in groundwater, Patescibacteria act as keystone taxa that harmonize microbes in shallower aquifers and accelerate decline in bacterial diversity with increasing well-depth. Decreasing habitat niche breadth with increasing well-depth suggests a general change in the relationship among key microbes from closer cooperation in shallow to stronger competition in deep groundwater. Unlike surface-water microbes, microbial communities in pristine groundwater are predominantly shaped by deterministic processes, potentially associated with nutrient sequestration under dark and anoxic environments in aquifers. CONCLUSIONS: By unveiling the biogeographic patterns and mechanisms controlling the community assembly of microbes in pristine groundwater throughout China, we firstly confirm the existence of GMEB in shallower aquifers and propose Groundwater Microbial Community Index (GMCI) to evaluate anthropogenic impact, which highlights the importance of GMEB in groundwater water security and health diagnosis. Video Abstract.

Interaction of silver nanoparticles with marine/lake snow in early formation stage.

Marine and lake snows play an important ecological role in aquatic systems, and recent researches have also revealed their interactions with various pollutants. In this paper, the interaction of silver nanoparticles (Ag-NPs), a typical nano-pollutant, with marine/lake snow in the early formation stage was investigated by roller table experiments. Results indicated Ag-NPs promoted the accumulation of larger marine snow flocs while inhibited the development of lake snow. The promotion effect of AgNPs might be attributed to their oxidative dissolution into low-toxic silver chloride complexes in seawater, and the subsequent incorporation into marine snow, which would enhance the rigidity and strength of larger flocs and favor the development of biomass. Conversely, Ag-NPs mainly existed in the form of colloidal nanoparticles in lake water and their strong antimicrobial effect suppressed the growths of biomass and lake snow. In addition, Ag-NPs could also affect the microbial community of marine/lake snow, including impact on microbial diversity, and elevation on abundances of extracellular polymeric substances (EPS) synthesis genes and silver resistance genes. This work has deepened our understanding of the fate and ecological effect of Ag-NPs via the interaction with marine/lake snow in aquatic environments.

In situ Nanopore sequencing reveals metabolic characteristics of the Qilian glacier meltwater microbiome.

Nanopore metagenomic sequencing enables rapid annotating microbiological ecosystems, and the previous glacier-related sequencing applications (e.g., targeted ice sheets, ice lake, and cryoconite holes) inspire us to explore high-altitude glacier meltwater at Qilian Mountain, China (3000 to 4000 m above sea level, MASL). Our findings suggest that (1) despite only several hundred meters apart, the microbial communities and functionalities are quite different among vertical alpine distributions; (2) the high-altitude Qilian meltwater microbiome serve several main metabolic functions, including sulfur oxidation, selenite decomposing, photosynthesis, energy production, enzymic, and UV tolerant activities. Meanwhile, our Nanopore metagenomic results indicate that the microbial classifications and functionalities (e.g., chaperones, cold-shock, specific tRNA species, oxidative stress, and resistance to toxic compounds) of Qilian meltwater are highly consistent with the other glacial microbiome, emphasizing that only certain microbial species can survive in the cold environment and the molecular adaptions and lifestyles remain stable all over the world. Besides, we have shown Nanopore metagenomic sequencing can provide reliable prokaryotic classifications within or among studies, which therefore can encourage more applications in the field given faster turnaround time. However, we recommend accumulating at least 400 ng nucleic acids (after extraction) and maximizing Nanopore library preparation efficiency before on-site sequencing to obtain better resolutions.

Is it really safe to replace decabromodiphenyl ether (BDE209) with decabromodiphenyl ethane (DBDPE)?: A perspective from hepatotoxicity.

In this paper, the hepatocytotoxicity and aryl hydrocarbon receptor (AHR) activity of decabromodiphenyl ethane (DBDPE), decabromodiphenyl ether (BDE209) and other 18 analogues were evaluated in vitro using human normal liver cell L02. These dioxin-like compounds showed differential hepatocytotoxicity (EC50  = 0.38-17.87 mg/L) and AHR activity (EROD activity = 4.53-46.35 U/µg). In silico study indicated the distance of π-π bonds between the benzene ring of compounds and residue Phe234 of AHR played a key role in the binding of AHR, and the substituents on the benzene ring also influenced the activity. Combining molecular biology and bioomics, the comprehensive investigations on the hepatotoxic mechanisms have demonstrated the AHR signaling pathway was the key mediation mechanism for the hepatotoxicity of DBDPE/BDE209. The cytochrome P450s (CYP2 family) mediated formation of reactive oxygenated intermediates might be the dominant toxic mechanism, which could produce oxidative stress or cause genotoxicity. Although the experimental toxicity of DBDPE was smaller relative to BDE209, the health risk of DBDPE may be much greater than we expected, due to the high potential to form a variety of dioxin-like intermediates by microbial oxidation of ethyl group. Therefore, whether it is really safe to replace BDE209 with DBDPE is a debatable question, and more ecotoxicological and health data are needed to clarify this issue.

The distinct resistance mechanisms of cyanobacteria and green algae to sulfamethoxazole and its implications for environmental risk assessment.

Cyanobacteria and green algae are the OECD recommended test organisms for environmental toxicity assessments of chemicals. Whether the differences in these two species' responses to the identical chemical affect the assessment outcomes is a question worth investigating. Firstly, we investigated the distinct resistance mechanisms of Synechococcus sp. (cyanobacteria) and R. subcapitata (green algae) to sulfamethoxazole (SMX). The antioxidant system analysis demonstrated that R. subcapitata mainly relies on enhancing the activity of first line defense antioxidants, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), which is the most powerful and efficient response to get rid of ROS, whereas Synechococcus sp. depends upon increasing the activity of glutathione-S-transferase (GST) and GPx to resist oxidative stress. Besides, a total 7 transformation products (TPs) of SMX were identified in R. subcapitata culture medium. The analysis of conjectural transformation pathways and the predicted toxicity indicates that R. subcapitata could relieve SMX toxicity by degrading it to low eco-toxic TPs. Additionally, we summarized numerous exposure data and assessed the environmental risk of various antibiotics, revealing an inconsistent result for the same type of antibiotic by using cyanobacteria and green algae, which is most likely due to the different resistance mechanisms. In the future, modified indicators or comprehensive assessment methods should be considered to improve the rationality of environmental toxicity assessments.

Significant alterations of intestinal symbiotic microbiota induced by intraperitoneal vaccination mediate changes in intestinal metabolism of NEW Genetically Improved Farmed Tilapia (NEW GIFT, Oreochromis niloticus).

BACKGROUND: After millions of years of coevolution, symbiotic microbiota has become an integral part of the host and plays an important role in host immunity, metabolism, and health. Vaccination, as an effective means of preventing infectious diseases, has been playing a vital role in the prevention and control of human and animal diseases for decades. However, so far, minimal is known about the effect of vaccination on fish symbiotic microbiota, especially mucosal microbiota, and its correlation with intestinal metabolism remains unclear. METHODS: Here we reported the effect of an inactivated bivalent Aeromonas hydrophila/Aeromonas veronii vaccine on the symbiotic microbiota and its correlation with the intestinal metabolism of farmed adult Nile tilapia (Oreochromis niloticus) by 16S rRNA gene high-throughput sequencing and gas chromatography-mass spectrometry metabolomics. RESULTS: Results showed that vaccination significantly changed the structure, composition, and predictive function of intestinal mucosal microbiota but did not significantly affect the symbiotic microbiota of other sites including gill mucosae, stomach contents, and stomach mucosae. Moreover, vaccination significantly reduced the relative abundance values of potential opportunistic pathogens such as Aeromonas, Escherichia-Shigella, and Acinetobacter in intestinal mucosae. Combined with the enhancement of immune function after vaccination, inactivated bivalent Aeromonas vaccination had a protective effect against the intestinal pathogen infection of tilapia. In addition, the metabolite differential analysis showed that vaccination significantly increased the concentrations of carbohydrate-related metabolites such as lactic acid, succinic acid, and gluconic acid but significantly decreased the concentrations of multiple lipid-related metabolites in tilapia intestines. Vaccination affected the intestinal metabolism of tilapia, which was further verified by the predictive function of intestinal microbiota. Furthermore, the correlation analyses showed that most of the intestinal differential microorganisms were significantly correlated with intestinal differential metabolites after vaccination, confirming that the effect of vaccination on intestinal metabolism was closely related to the intestinal microbiota. CONCLUSIONS: In conclusion, this paper revealed the microbial and metabolic responses induced by inactivated vaccination, suggesting that intestinal microbiota might mediate the effect of vaccination on the intestinal metabolism of tilapia. It expanded the novel understanding of vaccine protective mechanisms from microbial and metabolic perspectives, providing important implications for the potential influence of vaccination on human intestinal microbiota and metabolism. Video Abstract.

Nanopore-based long-read metagenomics uncover the resistome intrusion by antibiotic resistant bacteria from treated wastewater in receiving water body.

Wastewater treatment plant (WWTP) effluent discharge could induce the resistome enrichment in the receiving water environments. However, because of the general lack of a robust antibiotic-resistant bacteria (ARB) identification method, the driving mechanism for resistome accumulation in receiving environment is unclear. Here, we took advantage of the enhanced ARBs recognition by nanopore long reads to distinguish the indigenous ARBs and the accumulation of WWTP-borne ARBs in the receiving water body of a domestic WWTP. A bioinformatic framework (named ARGpore2: https://github.com/sustc-xylab/ARGpore2) was constructed and evaluate to facilitate antibiotic resistance genes (ARGs) and ARBs identification in nanopore reads. ARGs identification by ARGpore2 showed comparable precision and recall to that of the commonly adopt BLASTP-based method, whereas the spectrum of ARBs doubled that of the assembled Illumina dataset. Totally, we identified 33 ARBs genera carrying 65 ARG subtypes in the receiving seawater, whose concentration was in general 10 times higher than clean seawater's. Notably we report a primary resistome intrusion caused by the revival of residual microbes survived from disinfection treatment. These WWTP-borne ARBs, including several animal/human enteric pathogens, contributed up to 85% of the receiving water resistome. Plasmids and class 1 integrons were reckoned as major vehicles facilitating the persistence and dissemination of ARGs. Moreover, our work demonstrated the importance of extensive carrier identification in determining the driving force of multifactor coupled resistome booming in complicated environmental conditions, thereby paving the way for establishing priority for effective ARGs mitigation strategies.

Assisted Selection of Biomarkers by Linear Discriminant Analysis Effect Size (LEfSe) in Microbiome Data.

There is growing attention toward closed biological genomes in the environment and in health. To explore and reveal the intergroup differences among different samples or environments, it is crucial to discover biomarkers with statistical differences among groups. The application of Linear discriminant analysis Effect Size (LEfSe) can help find good biomarkers. Based on the original genome data, quality control, and quantification of different sequences based on taxa or genes are carried out. First, the Kruskal-Wallis rank test was used to distinguish between specific differences among statistical and biological groups. Then, the Wilcoxon rank test was performed between the two groups obtained in the previous step to assess whether the differences were consistent. Finally, a linear discriminant analysis (LDA) was conducted to evaluate the influence of biomarkers on significantly different groups based on LDA scores. To sum up, LEfSe provided the convenience for identifying genomic biomarkers that characterize statistical differences among biological groups.

Rare biosphere regulates the planktonic and sedimentary bacteria by disparate ecological processes in a large source water reservoir.

The bacteria in the water column and surface sediments are inherently intertwined and inseparable in aquatic ecosystems, yet little is known about the integrated spatiotemporal dynamics and driving mechanisms of both planktonic and sedimentary bacterial communities in reservoirs. By investigating the planktonic and sedimentary bacteria during four seasons from 88 samples of 11 representative sites across the Danjiangkou reservoir, we depicted an integrated biogeographic pattern of bacterial communities in the water source of the world's largest water diversion project. Our study revealed both planktonic (mantel r = 0.502, P = 0.001) and sedimentary (mantel r = 0.131, P = 0.009) bacterial communities were significantly correlated with environmental heterogeneity, but a weak disparity along spatial heterogeneity, and the significant seasonal dynamics of planktonic (mantel r = 0.499, P = 0.001) rather than sedimentary bacteria. Particularly, rare biosphere played a main role in determining the community succession in the reservoir. It not only exhibited a more striking environmental separation than abundant taxa but also was an essential part in mediating spatiotemporal shifts of planktonic bacteria and maintaining the stability of bacterial community. These rare bacteria were respectively mediated by stochastic (62.68%) and selective (79.60%) processes in water and sediments despite abundant taxa being largely determined by stochastic processes (86.88-93.96%). Overall, our study not only fills a gap in understanding the bacterial community dynamics and underlying drivers in source water reservoirs, but also highlights the particular importance of rare bacteria in mediating biogeochemical cycles in world's large reservoir ecosystems.

Effect of Nano-Silver on Formation of Marine Snow and the Underlying Microbial Mechanism.

Roller experiments were conducted to explore the effect of nano-silver on the formation of marine snow and the underlying microbial mechanism. With the increasing concentration of nano-Ag from 1 ng/L to 1 mg/L, the formation and aggregation of marine snow particles were solidly suppressed in a dose-dependent pattern. Moreover, the formed marine snows tended to be thinner fibrous particles with smaller size and increased edge smoothness and compactness in the presence of nano-Ag. The microbial analyses indicated that nano-Ag not only inhibited the development of biomass but also changed the species composition and functional profile of the microbial community. Nano-Ag obviously inhibited most of the abundant species, except for some myxobacteria, which is unfavorable for the microbial community stability. For the microbial functions, some major biological processes including the growth, metabolic, and cellular processes were also inhibited by the high dosage of nano-Ag. The strong microbial inhibition of nano-Ag would contribute to the suppression on the formation of marine snow. Specifically, the function genes of extracellular polymeric substance synthesis and secretion were significantly reduced by nano-Ag, which might be the key and straight microbial factor in suppressing the formation of marine snow.

Enhanced removal efficiency of sulfamethoxazole by acclimated microalgae: Tolerant mechanism, and transformation products and pathways.

This study utilized sulfamethoxazole (SMX) acclimatization to enhance the tolerance and biodegradation capacity of Chlorella vulgaris. Compared to wild C. vulgaris, the growth inhibition and oxidative damage induced by SMX evidently decreased in acclimated C. vulgaris, and meanwhile photosynthetic and antioxidant activities were significantly promoted. The physiological analyses with the aid of principal component analysis revealed the increase of catalase and glutathione reductase activities was the critical tolerant mechanism of acclimated C. vulgaris. As the consequence, the acclimated C. vulgaris exhibited enhanced efficiency and (pseudo-first-order) kinetic rate for removal of SMX. The distribution analysis of residual SMX demonstrated the biodegradation was the major removal mechanism of SMX by C. vulgaris, while bioadsorption and bioaccumulation made pimping contributions. During the degradation process of SMX, nine transformation products (TPs) were identified. Based on the identified TPs, a possible transformation pathway was proposed.

Response of microbial nitrogen transformation processes to antibiotic stress in a drinking water reservoir.

Effects of antibiotics on microbial nitrogen transformation processes in natural aquatic ecosystems are largely unknown. In this study, we utilized the 15N stable isotope tracers and metagenomic sequencing to identify how antibiotics drive nitrogen transformation processes in Danjiangkou Reservoir, which is the largest artificial drinking water reservoir in China. We retrieved 51 nitrogen functional genes, and found that the highest abundances of nitrate reduction and denitrification-related genes occurred in dissimilatory nitrogen transformation pathways. 15N-labelling analysis substantiated that denitrification was the main pathway for nitrogen removal, accounting for 57.1% of nitrogen loss. Nitrogen functional genes and antibiotic resistance genes co-occurred in Danjiangkou Reservoir, and they were mainly carried by the denitrifying bacteria such as Rhodoferax, Polaromonas, Limnohabitans, Pararheinheimera, Desulfobulbus, and Pseudopelobacter. Genome annotation revealed that antibiotic deactivation, Resistance-Nodulation-Division and facilitator superfamily efflux pumps were responsible for the multiple-resistance to antibiotics in these bacteria. Moreover, antibiotics showed non-significant effects on nitrogen transformation processes. It is speculated that denitrifying bacteria harboring ARGs played crucial roles in protecting nitrogen transformation from low-level antibiotics stress in the reservoir. Our results highlight that denitrifying bacteria are important hosts of ARGs, which provides a novel perspective for evaluating the effects of antibiotics on nitrogen cycle in natural aquatic ecosystems.

Influences of petroleum hydrocarbon pyrene on the formation, stability and antibacterial activity of natural Au nanoparticles.

The effect of pyrene on the formation of naturally Au nanoparticles (AuNPs) in the presence of humic acid (HA) under UV irradiation is described. TEM, EDS, FTIR and XPS were carried out to prove the formation of AuNPs and display their morphologies and formation mechanism. There are little differences between size, morphology and function groups of surface coated materials of AuNPs formed with and without pyrene. With the presence of HA, pyrene showed an inhibiting effect on the reduction of Au ion via competition for O2•-, thereby decreasing the production of AuNPs. However, AuNPs formed by HA-pyrene showed higher stability than AuNPs formed by HA with the sedimentation rates of 4.13% and 13.68% respectively after 30-d standing. As for the antibacterial activities against Staphylococcus aureus and Escherichia coli, AuNPs formed by HA-pyrene were more toxic than AuNPs formed by HA. Meanwhile, changes of environmental factors such as temperature, pH and ionic strength exhibited similar influence trend on the formation of AuNPs in the presence and absence of pyrene. The results suggest that the typical petroleum hydrocarbon pyrene contained in spilled oil could influence the formation, fate and ecotoxicity of AuNPs.

Combined Effects of Sulfamethoxazole and Erythromycin on a Freshwater Microalga, Raphidocelis subcapitata: Toxicity and Oxidative Stress.

This study investigated the environmental effects of two familiar emerging contaminants, sulfamethoxazole (SMX) and erythromycin (ERY), and their mixture (10:1 w/w) using a green microalga, R. subcapitata. The cell density, pigment content, and the activities of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) glutathione peroxidase (GSH-Px), and glutathione S-transferase (GST) were analyzed. The calculated EC50 values of SMX, ERY, and their mixture after 96 h were 0.49, 0.044, and 0.06 mg/L, respectively. High concentrations of antibiotics lead to a decrease in chlorophyll a and total carotenoid content, affecting the ability to photosynthesize ROS scavenging capacity. This may be a factor leading to the inhibition of algal growth. When R. subcapitata was exposed to SMX and the mixture, SOD and CAT increased to resist oxidative damage, while the activities of GSH and GST decreased, suggesting that this algae's antioxidant system was unbalanced due to oxidative stress. R. subcapitata reduced the ERY-induced ROS by increasing the activities of SOD, GSH, and GST. The difference in the contents of nonenzymatic antioxidants and enzyme antioxidants in R. subcapitata indicated the antioxidant mechanisms to SMX and ERY were not identical. This study provides insights into the oxidative stress process in R. subcapitata under different antibiotics.

Enhanced degradation of reactive brilliant red X-3B by photocatalysis integrated with micro-electrolysis.

The microwave electrodeless lamp UV photocatalysis (MWUV) integrated with iron carbon micro-electrolysis (ME) was applied to degrade reactive brilliant red X-3B. In the present study, the removal rate of X-3B by MWUV/ME was 95%, which was significantly higher than 56% of MWUV and 62% of ME system. The experiment results demonstrated a synergistic effect in MWUV/ME system, wherein the ME system played an important role in color removal and the formation of ·OH in photocatalysis contributed most for the mineralization of X-3B and its intermediates. The removal efficiency of TOC was 32%, 7.5%, and 59.5% under MWUV, ME, and MWUV/ME processes at the end of the reaction, respectively. The Fe3+ existed in the system was an enhancer of producing ·OH via self-generation of ·OH by UV irradiation or improving the separation of electron-hole in photocatalysis by capturing the electrons. Therefore, the combined treatment of MWUV and ME system has the potential of synergistic effect compared to the separate process. Lowering the initial solution pH and increasing the iron filing dosage and dissolved oxygen were beneficial for the enhancement of degradation efficiency. The inorganic anions showed a diversity influencing the degradation of X-3B. NO3-, CO32-, and SO42- (at higher concentration) promoted the degradation reaction, while Cl- had non-significant effect.