Toxicity Mechanisms of Nanoplastics on Crop Growth, Interference of Phyllosphere Microbes, and Evidence for Foliar Penetration and Translocation.

Despite the increasing prevalence of atmospheric nanoplastics (NPs), there remains limited research on their phytotoxicity, foliar absorption, and translocation in plants. In this study, we aimed to fill this knowledge gap by investigating the physiological effects of tomato leaves exposed to differently charged NPs and foliar absorption and translocation of NPs. We found that positively charged NPs caused more pronounced physiological effects, including growth inhibition, increased antioxidant enzyme activity, and altered gene expression and metabolite composition and even significantly changed the structure and composition of the phyllosphere microbial community. Also, differently charged NPs exhibited differential foliar absorption and translocation, with the positively charged NPs penetrating more into the leaves and dispersing uniformly within the mesophyll cells. Additionally, NPs absorbed by the leaves were able to translocate to the roots. These findings provide important insights into the interactions between atmospheric NPs and crop plants and demonstrate that NPs' accumulation in crops could negatively impact agricultural production and food safety.

Innovations in chemical degradation technologies for the removal of micro/nano-plastics in water: A comprehensive review.

Micro/nanoplastics (M/NPs) in water have raised global concern due to their potential environmental risks. To reestablish a M/NPs free world, enormous attempts have been made toward employing chemical technologies for their removal in water. This review comprehensively summarizes the advances in chemical degradation approaches for M/NPs elimination. It details and discusses promising techniques, including photo-based technologies, Fenton-based reaction, electrochemical oxidation, and novel micro/nanomotors approaches. Subsequently, critical influence factors, such as properties of M/NPs and operating factors, are analyzed in this review specifically. Finally, it concludes by addressing the current challenges and future perspectives in chemical degradation. This review will provide guidance for scientists to further explore novel strategies and develop feasible chemical methods for the improved control and remediation of M/NPs in the future.

Regulation of ARGs abundance by biofilm colonization on microplastics under selective pressure of antibiotics in river water environment.

Interactions of microplastics (MPs) biofilm with antibiotic resistance genes (ARGs) and antibiotics in aquatic environments have made microplastic biofilm an issue of keen scholarly interest. The process of biofilm formation and the degree of ARGs enrichment in the presence of antibiotic-selective pressure and the impact on the microbial community need to be further investigated. In this paper, the selective pressure of ciprofloxacin (CIP) and illumination conditions were investigated to affect the physicochemical properties, biomass, and extracellular polymer secretion of polyvinyl chloride (PVC) microplastic biofilm. In addition, relative copy numbers of nine ARGs were analyzed by real-time quantitative polymerase chain reaction (qPCR). In the presence of CIP, microorganisms in the water and microplastic biofilm were more inclined to carry associated ARGs (2-3 times higher), which had a contributing effect on ARGs enrichment. The process of pre-microplastic biofilm formation might have an inhibitory effect on ARGs (total relative abundance up to 0.151) transfer and proliferation compared to the surrounding water (total relative abundance up to 0.488). However, in the presence of CIP stress, microplastic biofilm maintained the abundance of ARGs (from 0.151 to 0.149) better compared to the surrounding water (from 0.488 to 0.386). Therefore, microplastic biofilm act as abundance buffer island of ARGs stabilizing the concentration of ARGs. In addition, high-throughput analyses showed the presence of antibiotic-resistant (Pseudomonas) and pathogenic (Vibrio) microorganisms in biofilm under different conditions. The above research deepens our understanding of ARGs enrichment in biofilm and provides important insights into the ecological risks of interactions between ARGs, antibiotics, and microplastic biofilm.

Release Behavior of Liquid Crystal Monomers from Waste Smartphone Screens: Occurrence, Distribution, and Mechanistic Modeling.

Liquid crystal display (LCD) screens can release many organic pollutants into the indoor environment, including liquid crystal monomers (LCMs), which have been proposed as a novel class of emerging pollutants. Knowing the release pathways and mechanisms of LCMs from various components of LCD screens is important to accurately assess the LCM release and reveal their environmental transport behavior and fate in the ambient environment. A total of 47, 43, and 33 out of 64 target LCMs were detected in three disassembled parts of waste smartphone screens, including the LCM layer (LL), light guide plate (LGP), and screen protector (SP), respectively. Correlation analysis confirmed LL was the source of LCMs detected in LGP and SP. The emission factors of LCMs from waste screen, SP, and LGP parts were estimated as 2.38 × 10-3, 1.36 × 10-3, and 1.02 × 10-3, respectively. A mechanism model was developed to describe the release behaviors of LCMs from waste screens, where three characteristics parameters of released LCMs, including average mass proportion (AP), predicted subcooled vapor pressures (PL), and octanol-air partitioning coefficients (Koa), involving coexistence of absorption and adsorption mechanisms, could control the diffusion-partitioning. The released LCMs in LGP could reach diffusion-partition equilibrium more quickly than those in SP, indicating that LCM release could be mainly governed through SP diffusions.

Preferential role of distinct phytochemicals in biosynthesis and antibacterial activity of silver nanoparticles.

Biosynthesis of silver nanoparticles (AgNPs) by plant extracts and its antibacterial utilization has attracted great attention due to the spontaneous reducing and capping capacities of phytochemicals. However, the preferential role and mechanisms of the functional phytochemicals from different plants on AgNPs synthesis, and its catalytic and antibacterial performance remain largely unknown. This study used three widespread arbor species, including Eriobotrya japonica (EJ), Cupressus funebris (CF) and Populus (PL), as the precursors and their leaf extracts as reducing and stabilizing agents for the biosynthesis of AgNPs. A total of 18 phytochemicals in leaf extracts were identified by ultra-high liquid-phase mass spectrometer. For EJ extracts, most kinds of flavonoids participated in the generation of AgNPs by a reduced content of 5∼10%, while for CF extracts, about 15∼40% of the polyphenols were consumed to reduce Ag+ to Ag0. Notably, the more stable and homogeneous spherical AgNPs with smaller size (≈38 nm) and high catalytic capacity on Methylene blue were obtained from EJ extracts rather than CF extracts, and no AgNPs were synthesized from PL extracts, indicating that flavonoids are superior than polyphenols to act as reducer and stabilizer in AgNPs biosynthesis. The antibacterial activities against Gram-positive (Staphylococcus aureus and Bacillus mycoides) and Gram-negative bacteria (Pseudomonas putida and Escherichia coli) were higher in EJ-AgNPs than that in CF-AgNPs, which confirmed the synergistic antibacterial effects of flavonoids combined with AgNPs in EJ-AgNPs. This study provides a significant reference on the biosynthesis of AgNPs with efficient antibacterial utilization underlying effect of abundant flavonoids in plant extracts.

Phytotoxicity of polystyrene, polyethylene and polypropylene microplastics on tomato (Lycopersicon esculentum L.).

Despite the fact that microplastic pollution in terrestrial ecosystems has received increasing attention, there are few studies on the potential effects of different microplastics on terrestrial plants. In this study, the toxicity of polystyrene (PS), polyethylene (PE) and polypropylene (PP) microplastics with different concentrations (0, 10, 100, 500 and 1000 mg/L) to tomato (Lycopersicon esculentum L.) were studied by a hydroponic experiment. The results showed that the three microplastics had inhibitory effects on seed germination when the concentration was less than or equal to 500 mg/L, and the inhibition rate ranged from 10.1% to 23.6%. Interestingly, the inhibition effect was alleviated under 1000 mg/L microplastic treatment. Generally, PE was more toxic to seedling growth than PS and PP. Additionally, it was confirmed that microplastics could cause oxidative stress in plants, and PP was relatively less toxic to antioxidant enzymes than PS and PE. These results can provide a theoretical basis and data support for further investigation on the toxicity of microplastics to tomatoes, and contribute to understanding the type specificity of microplastics' toxic effects on plants.

Enhanced microbial reduction of aqueous hexavalent chromium by Shewanella oneidensis MR-1 with biochar as electron shuttle.

Biochar, carbonaceous material produced from biomass pyrolysis, has been demonstrated to have electron transfer property (associated with redox active groups and multi condensed aromatic moiety), and to be also involved in biogeochemical redox reactions. In this study, the enhanced removal of Cr(VI) by Shewanella oneidensis MR-1(MR-1) in the presence of biochars with different pyrolysis temperatures (300 to 800 °C) was investigated to understand how biochar interacts with Cr(VI) reducing bacteria under anaerobic condition. The promotion effects of biochar (as high as 1.07~1.47 fold) were discovered in this process, of which the synergistic effect of BMBC700(ball milled biochar) and BMBC800 with MR-1 was noticeable, in contrast, the synergistic effect of BMBCs (300-600 °C) with MR-1 was not recognized. The more enhanced removal effect was observed with the increase of BMBC dosage for BMBC700+MR-1 group. The conductivity and conjugated O-containing functional groups of BMBC700 particles themselves has been proposed to become a dominant factor for the synergistic action with this strain. And, the smallest negative Zeta potential of BMBC700 and BMBC800 is thought to favor decreasing the distance from microbe than other BMBCs. The results are expected to provide some technical considerations and scientific insight for the optimization of bioreduction by useful microbes combining with biochar composites to be newly developed.

Study of the effects of ultrafine carbon black on the structure and function of trypsin.

Due to the rapid development of industrial society, air pollution is becoming a serious problem which has being a huge threat to human health. Ultrafine particles (UFPs), one of the major air pollutants, are often the culprits of human diseases. At present, most of the toxicological studies of UFPs focus on their biological effects on lung cells and tissues, but there are less researches taking aim at the negative effects on functional proteins within the body. Therefore, we experimentally explored the effects of ultrafine carbon black (UFCB) on the structure and function of trypsin. After a short-term exposure to UFCB, the trypsin aromatic amino acid microenvironment, protein backbone and secondary structure were changed significantly, and the enzyme activity showed a trend that rose at first, then dropped. In addition, UFCB interacts with trypsin in the form of a complex. These studies demonstrated the negative effects of UFCB on trypsin, evidencing potential effects on animals and humans.

Combined cytotoxicity of polystyrene nanoplastics and phthalate esters on human lung epithelial A549 cells and its mechanism.

Awareness of risks posed by widespread presence of nanoplastics (NPs) and bioavailability and potential to interact with organic pollutants has been increasing. Inhalation is one of the more important pathways of exposure of humans to NPs. In this study, combined toxicity of concentrations of polystyrene NPs and various phthalate esters (PAEs), some of the most common plasticizers, including dibutyl phthalate (DBP) and di-(2-ethyl hexyl) phthalate (DEHP) on human lung epithelial A549 cells were investigated. When co-exposed, 20 µg NPs/mL increased viabilities of cells exposed to either DBP or DEHP and the modulation of toxic potency of DEHP was greater than that of DBP, while the 200 µg NPs/mL resulted in lesser viability of cells. PAEs sorbed to NPs decreased free phase concentrations (Cfree) of PAEs, which resulted in a corresponding lesser bioavailability and joint toxicity at the lesser concentration of NPs. The opposite effect was observed at the greater concentration of NPs, which may result from the dominated role of NPs in the combined toxicity. Furthermore, our data showed that oxidative stress and inflammatory reactions were mechanisms for combined cytotoxicities of PAEs and NPs on A549 cells. Results of this study emphasized the combined toxic effects and mechanisms on human lung cells, which are helpful for assessing the risk of the co-exposure of NPs and organic contaminants in humans.

Sorption of brilliant green dye using soybean straw-derived biochar: characterization, kinetics, thermodynamics and toxicity studies.

The present study was aimed to investigate brilliant green (BG) dye sorption onto soybean straw biochar (SSB) prepared at 800 °C and further understanding the sorption mechanism. Sorption kinetic models such as pseudo-first and pseudo-second order were executed for demonstrating sorption mechanism between the dye and biochar. Results of kinetics study were fitted well to pseudo-second-order kinetic model (R2 0.997) indicating that the reaction followed chemisorption mechanism. Furthermore, the effect of various parameters like sorbent dose, dye concentration, incubation time, pH and temperature on dye sorption was also studied. The maximum dye removal percentage and sorption capacity for SSB (800 °C) within 60 min were found to be 99.73% and 73.50 mg g- 1, respectively, at pH 8 and 60 °C temperature, whereas adsorption isotherm studies showed a higher correlation coefficient values for Freundlich model (R2 0.990-0.996) followed by Langmuir model suggesting that sorption process was multilayer. The characterization of biomass and biochar was performed with the aid of analytical techniques like scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) theory, X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA). FTIR analysis showed active groups on biochar surface. BET study revealed higher surface area of biochar (194.7 m2/g) than the biomass (12.84 m2/g). Besides, phyto- and cytogenotoxic studies revealed significant decrease in the toxicity of dye containing water after treating with SSB. Therefore, this study has proved the sorption potential of soybean straw biochar for BG dye and could be further considered as sustainable cost-effective strategy for treating the textile dye-contaminated wastewater.

Graphitic carbon nitride/biochar composite synthesized by a facile ball-milling method for the adsorption and photocatalytic degradation of enrofloxacin.

In order to enhance the removal performance of graphitic carbon nitride (g-C3N4) on organic pollutant, a simultaneous process of adsorption and photocatalysis was achieved via the compounding of biochar and g-C3N4. In this study, g-C3N4 was obtained by a condensation reaction of melamine at 550°C. Then the g-C3N4/biochar composites were synthesized by ball milling biochar and g-C3N4 together, which was considered as a simple, economical, and green strategy. The characterization of resulting g-C3N4/biochar suggested that biochar and g-C3N4 achieved effective linkage. The adsorption and photocatalytic performance of the composites were evaluated with enrofloxacin (EFA) as a model pollutant. The result showed that all the g-C3N4/biochar composites displayed higher adsorption and photocatalytic performance to EFA than that of pure g-C3N4. The 50% g-C3N4/biochar performed best and removed 45.2% and 81.1% of EFA (10 mg/L) under darkness and light with a dosage of 1 mg/mL, while g-C3N4 were 19.0% and 27.3%, respectively. Besides, 50% g-C3N4/biochar showed the highest total organic carbon (TOC) removal efficiency (65.9%). Radical trapping experiments suggested that superoxide radical (•O2-) and hole (h+) were the main active species in the photocatalytic process. After 4 cycles, the composite still exhibited activity for catalytic removal of EFA.

High pyrolysis temperature biochar reduced the transport of petroleum degradation bacteria Corynebacterium variabile HRJ4 in porous media.

Biochar has been widely applied for the remediation of petroleum-contaminated soil. However, the effect of biochar on the transport of petroleum degradation bacteria has not been studied. A typical Gram-positive petroleum degradation bacteria-Corynebacterium variabile HRJ4 was used to study the effect of different biochars on bacterial transport and retention. Results indicated that the addition of biochar in sand was effective for reducing the transport of bacteria and poplar sawdust biochar (PSBC) had a stronger hinder effect than corn straw biochar (CSBC). The hindrance was more evident with pyrolysis temperature of biochar raised from 300°C to 600°C, which was attributed to the increase of specific surface area (309 times). The hindrance effect also enhanced with higher application rate of biochar. Furthermore, the reduction of HRJ4 transport was more obvious in higher (25 mmol/L) concentration of NaCl solution owing to electrostatic attraction enhancement. The adsorption of biochar to HRJ4 was defined to contribute to the hindrance of HRJ4 transport mainly. Combining the influence of feedstocks and pyrolysis temperature on HRJ4 transport, it suggested that specific surface area had the greatest effect on HRJ4 transport, and pore-filling, electrostatic force also contributed to HRJ4 retained in quartz sand column. At last, phenol transportation experiment indicated that the restriction of biochar on HRJ4 enhanced the phenol removal rate in the column. This study provides a theoretical basis for the interaction of biochar and bacteria, which is vital for the remediation of oil-contaminated soil and groundwater in the field.

Toxicity assessment of Fluoranthene, Benz(a)anthracene and its mixed pollution in soil: Studies at the molecular and animal levels.

An increasing amount of Fluoranthene (Fla) and Benz(a)anthracene (BaA) is being produced and used, eventually entering the soil sediments. The accumulation of Fla and BaA will cause poisoning to typical enzymes (α-Amylase) and organisms (Eisenia fetida) in soil. However, the studies about exploring and comparing the different effects of Fla, BaA and their joint effect at different levels are rarely reported. In this paper, the different effects of Fla, BaA and their mixed pollutant on α-Amylase were evaluated and compared at the molecular level, and the effect of Fla-BaA to the antioxidant system of earthworm (Eisenia fetida) was investigated from the aspects of concentration and exposure time at the animal level. The results showed that Fla-BaA had the greatest influence on the skeleton structure and the microenvironment of amino acid residue of α-Amylase compared to Fla and BaA, and in the mixed pollutant system, the joint effect mode was additive mode. The inhibitory effect of Fla-BaA on the activity of α-Amylase was also stronger than that of the system alone. The assays at the animal level showed that low concentrations (below 5 mg/kg) of Fla-BaA increased the activity of GSH-Px and SOD while high concentrations inhibited their activity. The POD that was activated throughout the experiment period suggested its key role in the earthworm antioxidant system. Changes in T-AOC and MDA showed that long-term and high-dose of Fla-BaA exposure inhibited the antioxidant capacity of Eisenia fetida, causing lipid peroxidation and damage to cells.

Effects of four disaccharides on nucleation and growth of ice crystals in concentrated glycerol aqueous solution.

Devitrification has been determined to be one of the major causes of cell death in cryopreservation by vitrification method. Reliable quantification of the nucleation and growth of ice crystals of devitrification is of great importance for the optimization of the vitrification solutions. In the present study, cryomicroscopy was used to investigate the nucleation and growth of ice crystals in concentrated glycerol aqueous solution (60 wt%) in the presence of sucrose, trehalose, maltose and lactose. Results showed that sucrose rather than trehalose seems to be the most effective one to inhibit the nucleation and ice growth, despite the excellent inhibitory ability of trehalose on ice growth that has been confirmed in many researches. Hence, for ice inhibition, sucrose was a more effective disaccharide additive to suppress nucleation and growth of ice crystals that occurred during devitrification in concentrated glycerol solutions.

Perfluorodecanoic acid-induced oxidative stress and DNA damage investigated at the cellular and molecular levels.

Perfluorodecanoic acid (PFDA) has been widely used in production of many daily necessities because of its special nature. Althoughtoxic effects of PFDA to organisms have been reported, there is little research on the genotoxicity induced by oxidative stress of PFDA on the cellular and molecular levels simultaneously. Thus, we investigated the DNA oxidative damage caused by PFDA in mouse hepatocytes. On the cellular level, an increase in ROS content indicated that PFDA caused oxidative stress in mouse hepatocytes. In addition, after PFDA exposure, the comet assay confirmed DNA strand breaks and an increased 8-OHdG content demonstrated DNA oxidative damage. On the molecular level, the microenvironment of aromatic amino acids, skeleton and secondary structure of catalase (CAT) were varied after PFDA exposure and the enzyme activity was reduced because PFDA bound near the heme groups of CAT. Moreover, PFDA was shown to interact with DNA molecule by groove binding. This study suggests that PFDA can cause genotoxicity by inducing oxidative stress both on the cellular and molecular levels.

A comparative analysis of ball-milled biochar, graphene oxide, and multi-walled carbon nanotubes with respect to toxicity induction in Streptomyces.

Ball-milled biochar has recently attracted a lot of attention due to the simplicity of its preparation and low cost. However, it is unknown if the biochar is environmentally safe. Here, the toxic effect of ball-milled biochar on Streptomyces was compared to that of pristine biochar and two other carbon nanomaterials of different shapes-graphene oxide and multi-walled carbon nanotubes. The effect of these different materials on antibiotic production was characterized. The results showed that even at concentrations of up to 10 mg/L, pristine biochar had a negligible effect on toxicity and antibiotic production in Streptomyces. However, after ball milling, the physical and chemical properties of biochar changed dramatically. Cells were severely damaged, and there was a significant increase in antibiotic production after the addition of ball-milled biochar. Exposure to 10 mg/L of ball-milled biochar caused massive cell disruption; the survival rate of Streptomyces coelicolor M145 cells was only 68.2% as compared to 90% after treatment with 10 mg/L graphene oxide and multi-walled carbon nanotubes. The secretion of the antibiotics- the red intracellular pigment undecylprodigiosin (RED) and blue diffusible pigment actinorhodin (ACT) was enhanced with the highest level in treatment with ball milled biochar, as compared to that with the other two carbon nanomaterials. This effect can be attributed to increased expression of pathway-specific regulatory genes redD, redZ and actⅡ-ORF4. Ball-milled biochar can be developed as an effective additive to increase antibiotic yield. However, we should restrict the large-scale use of ball-milled biochar before fully understanding its impact on the environment and human health.

Characterization of ultraviolet-modified biochar from different feedstocks for enhanced removal of hexavalent chromium from water.

Biochars produced from different feedstocks via pyrolytic carbonization and ultraviolet (UV) modification were used as alternative adsorbents for aqueous hexavalent chromium (Cr(VI)) remediation. Structural and morphological analysis showed that UV irradiation increased the surface area of biochar and added a large amount of oxygen-containing functional groups on the biochar's surface, resulting in about 2-5 times increase of Cr(VI) removing capacity (14.39-20.04 mg/g) compared to that of unmodified biochars (3.60-8.43 mg/g). The sorption ability among different feedstocks after modification was as follows: corn stack > sawdust > wheat straw. The adsorption kinetics and adsorption isotherm data agreed well with the pseudo-second-order model and Freundlich model, respectively. Experimental and modeling results suggested that the oxygen-containing functional groups and surface areas of biochars were notably increased after UV irradiation, which was mainly governed by surface complexation. X-ray photoelectron spectroscopy analysis showed that reduction occurred during Cr(VI) adsorption. In addition, UV irradiation significantly increased the concentration of dissolved organic matter (DOM) in biochars. The collected outcomes showed that UV-modified biochar was a good material for the removal of hexavalent chromium from aqueous medium. The excellent adsorption capacity, environmental-friendly and low cost properties made the novel material an auspicious candidate for environmental remediation.

Combination of rhamnolipid and biochar in assisting phytoremediation of petroleum hydrocarbon contaminated soil using Spartina anglica.

Biochar (BC) and rhamnolipid (RL) is used in bioremediation of petroleum hydrocarbons, however, the combined effect of BC and RL in phytoremediation has not been studied until now. In this paper, the phytoremediation of petroleum hydrocarbon-contaminated soil using novel plant Spartina anglica was enhanced by the combination of biochar (BC) and rhamnolipid (RL). Samples of petroleum-contaminated soil (10, 30 and 50 g/kg) were amended by BC, BC+ RL and rhamnolipid modified biochar (RMB), respectively. After 60 day's cultivation, the removal rate of total petroleum hydrocarbons (TPHs) for unplanted soil (UP), planted soil (P), planted soil with BC addition (P-BC), planted soil with BC and RL addition (P-BC + RL) and planted soil with addition of RMB (P-RMB) were 8.6%, 19.1%, 27.7%, 32.4% and 35.1% in soil with TPHs concentration of 30 g/kg, respectively. Compared with UP, the plantation of Spartina anglica significantly decreased the concentration of C8-14 and tricyclic PAHs. Furthermore, the application of BC and RMB alleviated the toxicity of petroleum hydrocarbons to Spartina anglica via improving plant growth with increasing plant height, root vitality and total chlorophyll content. High-throughput sequencing result indicated that rhizosphere microbial community of Spartina anglica was regulated by the application of BC and RMB, with increase of bacteria and plant mycorrhizal symbiotic fungus in biochar and RMB amended soil.

Vertical response of microbial community and degrading genes to petroleum hydrocarbon contamination in saline alkaline soil.

A column microcosm was conducted by amending crude oil into Dagang Oilfield soil to simulate the bioremediation process. The dynamic change of microbial communities and metabolic genes in vertical depth soil from 0 to 80 cm were characterized to evaluate the petroleum degradation potential of indigenous microorganism. The influence of environmental variables on the microbial responds to petroleum contamination were analyzed. Degradation extent of 42.45% of n-alkanes (C8-C40) and 34.61% of 16ΣPAH were reached after 22 weeks. Relative abundance of alkB, nah, and phe gene showed about 10-fold increment in different depth of soil layers. Result of HTS profiles demonstrated that Pseudomonas, Marinobacter and Lactococcus were the major petroleum-degrading bacteria in 0-30 and 30-60 cm depth of soils. Fusarium and Aspergillus were the dominant oil-degrading fungi in the 0-60 cm depth of soils. In 60-80 cm deep soil, anaerobic bacteria such as Bacteroidetes, Lactococcus, and Alcanivorax played important roles in petroleum degradation. Redundancy analysis (RDA) and correlation analysis demonstrated that petroleum hydrocarbons (PHs) as well as soil salinity, clay content, and anaerobic conditions were the dominant effect factors on microbial community compositions in 0-30, 30-60, and 60-80 cm depth of soils, respectively.

Mechanisms of oxidative stress caused by CuO nanoparticles to membranes of the bacterium Streptomyces coelicolor M145.

Toxic effects of widely used CuO nanoparticles (NPs) on the genus Streptomyces has been seldom studied. This work investigated toxicities of several sizes of CuO nanoparticles (NPs) to Streptomyces coelicolor M145 (S. coelicolor M145). Compared with NPs, toxicity of micrometer-sized CuO on M145 was trivial. In 0.9% NaCl, when the concentration of CuO NPs was 100 mg/L, survival of bacteria increased from 18.3% in 20 nm particles to 31.1% in 100 nm particles. With increasing concentrations of CuO, the level of ROS gradually increased and there were significant differences (p ＜ 0.05) in ROS exposed to 20, 40 and 100 nm (80 nm) CuO NPs. In TSBY medium, toxicity of CuO NPs was less and mainly attributed to release of Cu2+, analysis by confocal laser scanning microscope (CLSM) showed that size of the mycelium did not change although some individual bacteria died. This was likely due to Cu2+ released from NPs entering cells through the membrane, while in 0.9% NaCl, lesions on membranes was caused by NPs outside the bacteria. This research indicated that toxicity of CuO NPs to S. coelicolor, is related to both size of NPs and is dependent on characteristics of the medium. CAPSULE: This is the first time to measure the toxicity of nano materials to Streptomyces, and toxic CuO NPs to Streptomyces have been shown to differ depending on medium.