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Root rot is a common disease in soybean (Glycine max) and field pea (Pisum sativum), which restrain increased production in Canada. Sixty-seven isolates of Rhizoctonia were recovered from various diseased plants in Alberta, Canada along with three isolates from diseased soybean plants in Manitoba, Canada. According to their anastomosis behavior, 23 (32.9%) of the isolates were identified as anastomosis group (AG) 4 (AG4), 7 (10.0%) were AG2-1, 10 (14.3%) were AG2-2, 7 (10.0%) were AG5, 3 (4.3%) were AG-E and the AGs of the remaining 20 (28.6%) isolates could not be determined. Isolates belonging to AG4 produced typical symptoms of stem rot and root rot on seedlings of soybean and pea and were more aggressive than the AG2-1, AG2-2, AG5 and AG-E isolates. Selected isolates of AG4, AG2-1, AG2-2, AG5 and AG-E were to some degree able to infect common crops in Alberta, which included barley, canola, corn, faba bean, flax, lupin, lentil, pea, potato, soybean, and wheat. The genetic variability among these isolates was evaluated using phylogenetic analysis based on the rDNA ITS sequences and inter-simple sequence repeat (ISSR) markers. For the ITS sequence analysis, a neighbour-joining tree was constructed using the PAUP program, which clustered the Rhizoctonia isolates into five groups (Groups I to V). However, no correlation was observed between AGs, locations, aggressiveness or host origins. For the ISSR analysis, 54 polymorphic ISSR patterns were identified, indicating a high level of diversity among the isolates.

Chickpea (Cicer arietinum L.) is an important food legume worldwide, providing a source of high-quality protein. Fifteen chickpea samples showing leaf yellowing and root rot were obtained from sout...

Interactions between microorganisms and clay minerals influence the transport and cycling of metal contaminants in both marine and terrestrial environments. The present study was conducted to quantify the adsorption of dissolved cadmium, Cd(II), under seawater-like conditions to the marine cyanobacterium Synechococcus sp. PCC 7002, three common clay minerals (kaolinite, montmorillonite and illite), as well as cell-clay aggregates. We show here that the Synechococcus-only experiments removed the most Cd above pH 5.5, followed in decreasing order by aggregates of 50% cells:50% individual clays, aggregates of cells and all 3 clays, and individual clays. Electron microscope imaging showed that clays associated in a tangential edge-on orientation to the cells in Synechococcus-clay mineral aggregates. A non-electrostatic surface complexation modeling approach was used to fit Cd adsorption onto Synechococcus cells and individual clay minerals. The resulting Cd binding constants were then used in consort with surface functional group pKa values and site concentrations to accurately predict the extent of Cd adsorption onto the Synechococcus-clay mineral aggregates using the component additivity (CA) approach. We observed that the addition of cyanobacterial cells to clay mineral suspensions led to significantly larger mean aggregate sizes of clay minerals, enhancing the clay sedimentation rate. Although specifically focused on Cd, our study indicates that the ratio of bacterial plankton to clay minerals is an important determinant in terms of understanding the rate with which metals are transferred from the water column to the seafloor.

In Canada, clubroot (Plasmodiophora brassicae) disease is managed mainly by planting clubroot resistant (CR) canola (Brassica napus). New pathotypes of P. brassicae have emerged recently, however, which are virulent on most CR canola cultivars. To understand the impact of cultivar rotation on pathotype abundance, greenhouse experiments were conducted in which different canola cultivar rotations were grown in a soil mix containing equal amounts of pathotypes 5X and 3, which are virulent and avirulent, respectively, on CR canola. The rotation treatments included: T1, the same susceptible cultivar planted over four cycles; T2, the same CR cultivar planted over four cycles; and T3, different CR cultivars planted in each cycle. Clubroot severity increased from cycles one to four in all treatments, with the exception of one CR cultivar in T3 that may carry a different source of resistance. Pathogen populations were recovered with a susceptible bait crop and pathotyped on the differentials of Williams plus a CR host (B. napus ‘Mendel’). The percentage of galls classified as pathotype 5X in T1 declined from 50% to 6.7% over the course of the experiment, while galls classified as pathotype 5X increased from 50% to 66.7% in both T2 and T3. Quantitative PCR analysis of the soil with pathotype 5X-specific primers generally confirmed an increase in 5X DNA. The results suggest that continuous planting of CR canola favours a rapid proliferation of virulent pathotypes of P. brassicae, as indicated by the increases in pathotype 5X observed in this study.

Clubroot, caused by Plasmodiophora brassicae, is an important constraint on canola (Brassica napus) production in Canada. Rotations of clubroot-resistant (CR) canola cultivars in various sequences and planting intervals between canola with non-host crops and fallow periods were evaluated to determine their effects on clubroot severity and P. brassicae resting spore populations under field and micro-plot conditions. Under micro-plot conditions, the rotation sequences including CR canola, continuous fallow, and the non-host barley reduced gall weight by 63%–100% and clubroot severity by 34%–100% compared with continuous planting of susceptible canola. No visible clubroot symptoms developed following continuous fallow or the non-host crop. Under field conditions, clubroot severity was very high (78% disease index) in the continuous susceptible canola sequence. Most of the CR canola rotation sequences significantly reduced clubroot severity by 12%–23%, but continuous fallow, continuous barley, and alternating the CR canola cultivars ‘45H29’ or ‘73-47’ with ‘TC72429-10’ reduced clubroot severity by 32%–36%. A comparison of intervals between canola crops and four cropping sequences (continuous susceptible canola, alternating canola with barley or pea, a 2-yr non-host interval between canola crops, and a 3-yr non-host interval between canola crops) was conducted over 5 yr. A 2- or 3-yr non-host interval improved plant height, plant biomass, and seed yield, and reduced gall mass, P. brassicae propagules in the soil, and clubroot severity. A significant yield increase of more than 3600% was observed in a 3-yr non-host interval.

Soybean (Glycine max) acreage on the Canadian Prairies has increased rapidly in recent years. Production has expanded into semiarid regions where irrigation and drainage problems often result in the accumulation of salts in the soil. Fusarium avenaceum and Rhizoctonia solani are the two dominant pathogens in the disease complex that cause root rot and seedling blight of legume crops on the Canadian Prairies. The effects of F. avenaceum or R. solani in combination with soil salinity on soybean root rot were evaluated under greenhouse and mini-plot conditions. As expected, inoculation with F. avenaceum or R. solani consistently reduced seedling emergence and increased root rot severity in soybean. At high soil electrical conductivity values and inoculum densities, seedling emergence decreased and root rot severity increased in soybean in both trials with F. avenaceum and R. solani. Twenty short-season soybean cultivars that were well suited for production in Alberta were evaluated for their reactions to inoculation with F. avenaceum or R. solani in a saline soil (21.1 dS m−1). High seedling emergence was observed for cultivars 900Y61, P002T04R, 900Y01, TH27005RR, P001T34R, and 900Y81 in the non-inoculated control, for P002T04R and 900Y61 in the F. avenaceum treatment, and for 900Y61, 900Y81, and 900Y71 in the R. solani treatment. Root rot severity was low for cultivars NSC Portage and 900Y61 in the non-inoculated control and P002T004R in the F. avenaceum treatment. The cultivar 900Y61 also consistently had lower disease severity over the trials in the mini-plot test.

Soybean (Glycine max (L.) Merr.) has been a commercial oilseed crop in Canada since the 1920s. The production of soybean rapidly increased from 2004 to 2016 in Alberta and Manitoba. Root rot disease caused by the oomycete genus Pythium was observed from 105 fields in 2015 and 2016 in southern Alberta and Manitoba. In the present study, a total of 97 isolates of Pythium were recovered from the root tissues of soybean seedling collected from those fields. Identification of the Pythium species was achieved by examining their morphological features and sequences analysis of internal transcribed spacers (ITS) and cytochrome oxidase subunit 2 gene (Cox II). Nine species of Pythium were identified, with Pythium violae as the predominant species (27 out of 97, 27.8%), followed by P. intermedium (21), P. irregulare (16), P. sylvaticum (12), P. recalcitrans (8), P. ultimum (8), P. heterothallicum (3), P. conidiophorum (1) and P. macrosporum (1). This is the first report of P. conidiophorum, P. recalcitrans and P. violae on soybean in Canada. All the Pythium isolates except three isolates (S2d of P. violae, S29a and S29b of P. heterothallicum) were highly virulent on soybean, causing root rot disease symptoms.

As an important type of typical synthetic azo dyes, the use of sudan I-IV dyes has been of concern worldwide because of their wide applications and illegal addition into various foodstuffs, potentially resulting in water and soil pollution and having adverse effects on human health and ecosystems. However, to date, little has been reported regarding the environmental levels of these dyes and the risks that they pose to human health and ecosystems. Understanding the responses of soil enzymes, functional groups of bacteria and microbial communities to sudan dyes is of great importance to reveal their effect on the soil environment. In this study, we performed a toxicological study on the specific and overall effects of sudan I-IV dyes on the activity of soil enzymes including catalase, urease, and alkaline phosphatase after a 2- and 7-day exposure, functional groups of soil bacteria including nitrogen-fixing, ammonia-oxidizing, and denitrifying bacteria on day 14, and the structure and diversity of soil microbial community compositions on day 30. The results showed that sudan I-IV affected the activity of the soil enzymes, the abundance of the bacterium functional groups, and the structure and diversity of microbial community compositions, and the effects varied by sudan dyes I-IV, the exposure concentration, and the exposure time.

Combined toxicity is a critical issue in risk assessment of contaminants. However, very little is known about the joint effects of graphene oxide (GO, a crucial 2-dimensional carbon material) and hexavalent chromium (Cr6+, a widespread heavy metal), particularly with respect to the critical period of embryogenesis. In this study, the combined toxicity of GO and Cr6+ was evaluated through embryo-larval toxicity test in Danio rerio (zebrafish). Results indicated that the co-exposure of Cr6+ (1 mg/L) and GO (0.01 mg/L) inhibited hatching and spontaneous movement of embryos, but no significant changes were found in the single Cr6+ or GO group. Compared with the single GO or Cr6+ exposure, their co-exposure (GO+Cr6+) significantly enhanced the teratogenicity in a concentration-dependent pattern, and the spinal curvature was observed as the main deformity. GO+Cr6+ changed the protein secondary structures of embryos result of the generation of ROS and oxidative stress. The degradations of vertical myosepta and cartilages were observed in co-exposure group, suggesting that GO+Cr6+ disrupted the development of musculoskeletal system. The genes col11a1a, col2a1a and postnb were down-regulated but the genes acta1b and mmp9 were up-regulated by GO+Cr6+. The interactions between Cr6+ and GO demonstrated that the morphology, structure, and surface properties of GO were modified by Cr6+. The enhanced defects and O-containing groups of GO could trap more β-sheets, induced oxidative stress, disturbed the development of skeletal muscles and cartilages in zebrafish. These data suggested that GO+Cr6+ enhanced their joint toxicity due to the variation of nanoparticle properties. This finding is important for assessing the ecological risk of graphene family nanomaterials in the natural environment.

At present, the uptake and accumulation of nanoplastics by plants have raised particular concerns. However, molecular mechanisms underlying nanoplastic phytotoxicity are still vague and insufficient. To address this scientific gap, we analyzed the transcriptome response of hydroponically grown wheat (Triticum aestivum L.) to polystyrene nanoplastics (PSNPs) (100 nm) by integrating the differentially expressed gene analysis (DEGA) and the weighted gene correlation network analysis (WGCNA). PSNPs could significantly shape the gene expression patterns of wheat in a tissue-specific manner. Four candidate modules and corresponding hub genes associated with plant traits were identified using WGCNA. PSNPs significantly altered carbon metabolism, amino acid biosynthesis, mitogen-activated protein kinase (MAPK) signaling pathway-plant, plant hormone signal transduction, and plant-pathogen interaction Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. In addition, some Gene Ontology (GO) terms associated with the metal ion transport were further screened. These findings shed new light on the phytotoxic mechanism and environmental implication behind the interaction of nanoplastics and crop plants, and advance our understanding of the potential adverse effect induced by the presence of nanoplastics in agricultural systems.

Norfloxacin (NFLX) is a synthetic antibiotic widely used in the treatment of infectious diseases. In this work, the performance of microbial fuel cells (MFCs) toward NFLX degradation, electricity production and the antibiotics resistances genes (ARGs) generation was investigated. NFLX degradation efficiency and COD removal reached 65.5% and 94.5% respectively. The increase in NFLX concentration (128 mg/L) had no significant influence on NFLX degradation efficiency, COD removal and MFCs voltage output while the electricity was successfully generated. The quantitative polymerase chain reaction (qPCR) indicated low absolute abundances of ARGs (mdtk, mdtm, and pmra) compared with the traditional wastewater treatment plants (WWTPs). Anodic bacteria can survive in the presence of high NFLX concentration and sustain its degradation and electricity production. In terms of NFLX degradation, COD removal, diminished ARGs generation and simultaneous energy production, MFC seems to be a promising technology for antibiotics wastewater treatment with a potential to overcome the ARGs challenge.

The increasing production and applications of graphene oxide (GO, a novel carbon nanomaterial) have raised numerous environmental concerns regarding its ecological risks. Triphenyl phosphate (TPhP) disperses in water and poses an increasing hazard to the ecosystem and human health. It is critical to study the environmental responses and molecular mechanisms of GO and TPhP together to assess both chemicals; however, this information is lacking. The present work revealed that GO promoted the bioaccumulation of TPhP in zebrafish larvae by 5.0%-24.3%. The TPhP-induced growth inhibition of embryos (malformation, mortality, heartbeat, and spontaneous movement) at environmentally relevant concentrations was significantly amplified by GO, and these results were supported by the downregulated levels of genes and proteins associated with cytoskeletal construction and cartilage and eye development. TPhP induced negligible alterations in the genes or proteins involved in oxidative stress and apoptosis, but those related proteins were all upregulated by GO. GO and TPhP coexposure activated the mTOR signaling pathway and subsequently promoted apoptosis in zebrafish by potentiating the oxidative stress induced by TPhP, presenting synergistic toxicity. These findings highlight the potential risks and specific molecular mechanisms of combining emerging carbon nanomaterials with coexisting organic contaminants.

Soybean (Glycine max (L.) Merr.) has excellent potential as an alternative crop to canola in southern Alberta farming systems. However, soybean is susceptible to Fusarium root rot, which usually results in the occurrence of dead or dying plants in mid-to-late summer and severe reductions in yield. A total of 102 isolates identified as Fusarium were recovered from diseased soybean root samples collected from central and southern Alberta from 2011 to 2013. Ten species of Fusarium were identified, with F. acuminatum as the predominant species (31 out of 102 isolates, 30.39%), followed by F. equiseti (16.67%), F. culmorum (13.73%), F. avenaceum (10.78%), F. oxysporum (8.82%), F. redolens (7.84%), F. torulosum (4.90%), F. tricinctum (2.94%), F. commune (1.96%) and F. proliferatum (0.98%). This is the first report of F. commune, F. redolens and F. torulosum causing root rot in soybean in Canada. Phylogenetic analyses based on sequence data from the translation elongation factor 1-α (EF-1α) and the internal transcribed spacer (ITS) region were used to evaluate genetic variation and, in conjunction with morphological characters, for species identification. All of the Fusarium isolates were able to infect soybean, although some exhibited varying levels of aggressiveness.

Soil contaminated by aged petroleum hydrocarbons is faced with scarcity of electron acceptors, low activity of functional microbes and inefficient electron transfer, which hinder the bioremediation application. The soil microbial fuel cell (MFC) simultaneously solves these problems with bioelectricity production. In this study, five types of surfactants were introduced to enhance the bioavailability of aged petroleum hydrocarbon in soils. The ampholytic surfactant (lecithos) was optimal due to the highest bioelectricity generation (0.321C d −1 g −1 ) and promoted hydrocarbon degradation (328%), while the nonionic (glyceryl monostearate) and cationic (cetyltrimethylammonium bromide) surfactants were inefficient. The surfactants induced a special microbial enrichment affiliated with Proteobacteria , Firmicutes , Bacteroidetes , Actinobacteria , Chloroflexi , Planctomycetes and Acidobacteria (93%–99% of total) in soil MFCs. The anionic surfactant (sodium dodecyl sulfate) exhibited the strongest selectivity, and α- proteobacteria and γ - proteobacteria abundances decreased while Clostridia increased, much like the result obtained with the biosurfactant β -cyclodextrin. Furthermore, Bacillus abundance was increased in connected soil MFCs, except addition of lecithos in which Clostridium increased to 14.88% from 3.61% in the control. The high correlations among Bacillus , Phenylobacterium , Solibacillus (0.9162–0.9577) and among Alcaligenes , Dysgonomonas , Sedimentibacter (0.9538–0.9966) indicated a metabolic network of microorganisms in the soil bioelectrochemical remediation system.

Root rot is a major constraint on field pea ( Pisum sativum L.) production. Species of Phytophthora can cause seed rot, pre- and post-emergence damping-off, and stem and root rot in many legume crops, but have not been reported in association with pea root rot in Canada. Following a survey of pea fields in Alberta, Canada, in 2015, root tissue with typical symptoms of root rot was plated onto a growth medium, and one isolate was identified as a putative Phytophthora spp. based on its colony characteristics. The isolate was homothallic, producing smooth, thick-walled oospores and both paragynous and amphigynous antheridia on lima bean agar. The sporangia were ovoid or elliptical, non-papillate, and had internal proliferations. Based on these criteria, the isolate was tentatively identified as Phytophthora sansomeana . Sequencing of the internal transcribed spacer (ITS) and Cox II regions revealed 100% identity with the ITS and Cox II sequences of P. sansomeana available in GenBank, confirming this identification. A pathogenicity test indicated that the isolate was pathogenic and caused pre-emergence damping-off, root discoloration, and root rot with brown to dark brown lesions on pea cultivars. This is the first report of P. sansomeana causing root rot in pea in North America.

In Canada, Verticillium wilt of canola (Brassica napus L.), caused by Verticillium longisporum, was first confirmed in Manitoba in 2014. Verticillium dahliae, however, has not been reported to cause this disease. In 2016, a field survey in Alberta revealed canola plants with vascular wilt symptoms. Symptomatic plants were collected and infected stem tissue was cultured on agar medium, with one isolate designated A1-SS05 identified as a putative Verticillium spp. based on its colony characteristics. The colony was off-white in colour with a felt-like surface. On potato dextrose agar, the underside of the colony was dark only in the central area with radiating ridges. On Howell’s medium, only the test isolate exhibited polyphenol oxidase activity. The isolate formed conidiophores with 4–5 verticillate phialides. Mean conidial length was 5.96 µm (range of 4.65–6.64 µm) and mean width was 2.37 µm (range of 1.71–2.79 µm). The isolate also produced irregularly elongated chain-like microsclerotia of vari...

Clubroot, caused by Plasmodiophora brassicae, has become a serious threat to canola (Brassica napus) production in western Canada. Experiments were conducted to evaluate the effect of rate of metam sodium fumigant (dithiocarbamate; sodium N-methyldithiocarbamate; trade name Vapam) and application methods including watering, soil surface covering, and soil incorporation on clubroot of canola. At higher rates (0.4–1.6 mL−1 L soil) metam sodium increased canola seedling emergence and plant health, and reduced root hair infection, gall weight and clubroot severity under greenhouse conditions. Metam sodium application improved subsequent plant growth and reduced clubroot severity, but land preparation and volume of water applied did not affect efficacy. The incorporation of metam sodium into the soil and plastic covering after application improved fumigant efficacy. The study showed that soil fumigation with metam sodium can reduce clubroot severity and improve plant health in the subsequent canola crop.

To mitigate the impact and dissemination of clubroot in western Canada, canola (Brassica napus) producers have relied on clubroot resistance traits. However, in 2013 and 2014, new strains of the clubroot pathogen, Plasmodiophora brassicae, emerged that are virulent on most clubroot-resistant (CR) canola genotypes. Novel strains of the pathogen were inoculated onto two susceptible canola cultivars, one resistant line and six CR cultivars. Although all cultivars/lines showed a susceptible response to inoculation with the new strains of P. brassicae, the severity of disease reaction, root hair infection rates and the amount of P. brassicae DNA present in each canola genotype varied depending on the strain. In addition, the effect of inoculum density on disease severity and gall formation was recorded for one of these new strains on a universally susceptible Chinese cabbage cultivar and one susceptible and 10 resistant canola genotypes. Although root galls were observed at an inoculum density of 103 spores per mL of soil, clear differentiation of susceptible and resistant reactions among canola cultivars/lines was not observed until the inoculum density reached 105 spores mL−1. At a spore density of 106 spores mL−1 and above, all cultivars/lines developed susceptible reactions, although there was some differentiation in the degree of reaction. This study shows the potential to develop a unique disease profile for emergent clubroot pathotypes and shows a useful range of spore densities at which to study new P. brassicae strains.

Soybean [Glycine max (L.) Merr.] has great potential as an alternative crop in western Canada. Root rot is a common constraint in soybean production, and the occurrence of root rot was documented in all 29 fields surveyed in southern Alberta in 2014. Phytophthora spp. cause seed rot, pre- and post-emergence damping-off, and stem and root rot wherever soybean is produced, but it has not been previously reported in association with soybean in Alberta. Following a survey of soybean fields in 2014, root tissue with typical symptoms of root rot was plated onto a selective growth medium, and two isolates were designated as putative Phytophthora spp. based on their colony characteristics. These two isolates were homothallic on lima bean agar, producing smooth, thick-walled oospores and mostly paragynous with some amphigynous antheridia. Based on these criteria, the two isolates were identified as Phytophthora sojae Kaufmann & Gerdemann. Sequencing of the internal transcribed spacer (ITS) region revealed 100% identity with ITS sequences of P. sojae available in GenBank. A pathogenicity test revealed that both isolates of P. sojae were able to cause root rot on soybean and produce typical chocolate brown stem lesions just above the base of the plants. The two isolates were classified as races 4 and 28 of P. sojae based on their virulence on a set of soybean differential cultivars. Race 28 was more virulent than race 4 on the soybean cultivars ‘XBP27005’ and ‘XBP29002’. Regression analysis showed the positive linear relationships of the log of inoculum density with disease severity, and negative linear relationships with seedling emergence, plant height, and plant biomass. This is the first report of Phytophthora spp. causing root rot in soybean in Alberta.

Canola (Brassica napus) is one of the most economically important oilseed crops in Canada. Fusarium seedling blight is a root disease with the potential to cause severe yield reductions in canola. Fusarium spp. are commonly isolated root pathogens from fields in Alberta. Fusarium infection can also cause root rot in adult plants. In this study, 128 isolates identified as Fusarium spp. were recovered from field soils in central Alberta and from the roots of diseased canola plants with typical Fusarium seedling blight symptoms. Six species of Fusarium were identified, with Fusarium acuminatum as the predominant species (57 of 128 isolates, 44.5%). Phylogenetic analyses based on the translation elongation factor 1-α and the internal transcribed spacer sequence data were used for evaluation of genetic variations, and also used for Fusarium spp. identification in combination with morphological characteristics and polymerase chain reaction-based analyses. Based on disease ratings in pathogenicity tests, six isolates of F. avenaceum showed high aggressiveness on canola. Also, the aggressiveness varied within all Fusarium spp. No correlation was observed between aggressiveness and the geographic origin of the isolates.

Decorative ornamental plants have been applied as hyperaccumulators/phytoremediators to a wide spectrum of heavy metal contaminants. In this study, pot culture experiments were conducted to investigate the Sn tolerance and accumulation in Impatiens balsamina L., Mirabilis jalapa L. and Tagetes erecta L., in order to assess the possibility of these three ornamental plants to be used as phytoremediators of Sn-contaminated soil. Results show that all three plants exhibited strong tolerance to Sn contamination, and no significant visual toxicity was observed for all three plants grown under most of the Sn treatments. The amount of Sn accumulated in the three plants was positively correlated with the Sn concentration in the soil. The order of the Sn accumulative capacity was Impatiens balsamina &gt, Mirabilis jalapa &gt, Tagetes erecta. Impatiens balsamina and Tagetes erecta showed a low translocation ability (TF) (&lt, 1), and the roots accumulated the highest Sn concentration, but Impatiens balsamina showed a relatively high bioconcentration factor (BCF, Sn concentration in each part &gt, 100 mg/kg after Sn treatment of 500 mg/kg). Meanwhile, the TF of Mirabilis jalapa was &gt, 1, and the fluorescence accumulated the most Sn. In combination with the adaptation to high concentrations of various heavy metals, these three ornamental plants are potential candidates for Sn mining tailings or contaminated soil.

In the past two decades, more and more attentions have been paid to soil-derived greenhouse gases (GHGs) including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) because there are signs that they have rising negative impacts on the sustainability of the earth surface system. Farmlands, particularly paddy soils, have been regarded as the most important emitter of GHGs (nearly 17%) due to a large influx of fertilization and the abundance in animals, plants and microorganisms. Geobacter, as an electroactive microorganism widely occurred in soil, has been well studied on electron transport mechanisms and the direct interspecies electron transfer. These studies on Geobacter illustrate that it has the ability to be involved in the pathways of soil GHG emissions through redox reactions under anaerobic conditions. In this review, production mechanisms of soil-derived GHGs and the amount of these GHGs produced had been first summarized. The cycling process of CH4 and N2O was described from the view of microorganisms and discussed the co-culture relationships between Geobacter and other microorganisms. Furthermore, the role of Geobacter in the production of soil-derived GHGs is defined by biogeochemical cycling. The complete view on the effect of Geobacter on the emission of soil-derived GHGs has been shed light on, and appeals further investigation.

Flocculants have been used to clarify water for thousands of years. However, the in situ evaluation of flocculant toxicity is difficult because flocculants usually exist as growing complex flocs which is hard to monitor. With alum (KAl(SO4)2·12H2O) as the typical flocculant, a bioelectrochemical sensor is designed to in situ detect its bacterial toxicity. The attenuation ratio of current densities linearly increased with alum concentration (R2 > 0.98) with a slope of 0.0054 A m–2 drop per mg L–1 of alum, indicating a typical toxic response of alum. Turnover and nonturnover cyclic voltammetries (CVs) revealed that the alum inhibited the electrochemical activity of bacteria rather than changing the electron transfer pathways. Alum also hindered the diffusion by flocculation at a concentration larger than 100 mg L–1, which was further confirmed by the linear decrease in viability when biofilm thickness increased. It was revealed that both inactivation of biofilm and influences on diffusion by alum can be det...

Pot experiments were conducted to evaluate the phytoremediation of B[a]P contaminated soil using two ornamental plants (Tagetes patula and Mirabilis jalapa). The results showed that the dry biomass of two plants was increased at low B[a]P contaminated soil and then inhibited with increasing B[a]P concentrations. It exhibited a significantly positive linear relationship between B[a]P absorption in roots, stems, leaves and shoots of the tested plants and the concentration of B[a]P in soils (P

Bioelectrochemical system is an emerging technology for the remediation of soils contaminated by petroleum hydrocarbons. However, performance of such systems can be limited by the inefficient mass transport in soil. Here we report a new method of sand amendment, which significantly increases both oxygen and proton transports, resulting to increased soil porosity (from 44.5% to 51.3%), decreased Ohmic resistance (by 46%), and increased charge output (from 2.5 to 3.5Cg(-1)soil). The degradation rates of petroleum hydrocarbons increased by up to 268% in 135d. The degradation of n-alkanes and polycyclic aromatic hydrocarbons with high molecular weight was accelerated, and denaturing gradient gel electrophoresis showed that the microbial community close to the air-cathode was substantially stimulated by the induced current, especially the hydrocarbon degrading bacteria Alcanivorax. The bioelectrochemical stimulation imposed a selective pressure on the microbial community of anodes, including that far from the cathode. These results suggested that sand amendment can be an effective approach for soil conditioning that will enhances the bioelectrochemical removal of hydrocarbons in contaminated soils.

Graphene oxide (GO), a novel two-dimension carbon nanomaterial, has showed tremendous potential for utilization in intelligent manufacturing and environmental protection. In parallel, tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) is widely distributed in the water environment and represents a great threat to ecosystem health. However, the related knowledge remained absent regarding the impact of GO on the biological risks of TDCIPP. Herein, GO significantly reduced the mortality and malformation rates of zebrafish induced by TDCIPP maximumly by 28.6% and 41.8%, respectively. Decreased mitochondrial respiratory chain (MRC) enzyme and ATP activity induced by TDCIPP were mitigated by GO. Integrating proteomics and metabolomics revealed TDCIPP obviously induced the downregulation of the proteins and metabolites involved in the cytoskeleton, mitochondrial function, carbohydrate and amino acid metabolism, and the TCA cycle, but the alterations were attenuated by GO. GO primarily promoted MRC activity, carbohydrate metabolism, and fatty acid β-oxidation, thus activating the energy metabolism of zebrafish and leading to antagonistic effects on the developmental toxicity of TDCIPP. These results provide a novel view on the co-exposure of GO with other pollutants and promote the reconsideration of the environmental risks of GO.

Bioelectrochemical systems (BESs) are widely investigated as a promising technology to recover bioenergy or synthesize value-added products from wastewaters. The performance of BES depends on the activity of electroactive biofilm (EAB). As the core of BES, it is still unclear how the EAB is formed from mixed inoculum, and how exoelectrogens compete with non-exoelectrogens. Here we confirmed that microbial community composition and the morphology of EAB on the electrode including the thickness and porosity of the biofilm are critical for the performance of BES, and these properties can be simply controlled by the substrate concentration during EAB formation. The EAB formed with 0.1 g/L of acetate (EAB-0.1) exhibited a 90% higher current density than that formed with 1.0 g/L acetate (EAB-1.0). EAB-0.1 had a 50% higher electroactivity per biomass and a 20% thinner thickness than EAB-1.0, which was partly due to the 54% decrease of insulative polysaccharide in biofilm. Limited acetate also imposed a selective pressure to enrich Geobacter up to 88% compared to 72% when acetate was abundant. Our findings demonstrate that a highly active EAB can be formed by limiting substrate concentration, providing a broader understanding of the EAB formation process, the ecology of interspecies competitions and potential applications for bioenergy recovery and trace toxicant detection in the future.

Formaldehyde poses significant threats to the ecosystem and is widely used as a toxicity indicator to obtain electrical signal feedback in electroactive biofilm (EAB)-based sensors. Although many optimizations have been adopted to improve the performance of EAB to formaldehyde, nearly no studies have discussed the toxicity of formaldehyde to EAB. Here, EABs were acclimated with a stable current density (8.9 ± 0.2 A/m2) and then injected with formaldehyde. The current density decreased by 27% and 98% after the injection of 1 and 10 ppm formaldehyde, respectively, compared with that in the control. The ecotoxicity of formaldehyde caused the irreversible loss of current with 3% (1 ppm) and 81% (10 ppm). Confocal laser scanning microscopy and scanning electron microscopy results showed that the redox activity was inhibited by formaldehyde, and the number of dead/broken cells increased from 2% to 40% (1 ppm) and 91% (10 ppm). The contents of the total protein and extracellular polymer substances decreased by more than 28% (1 ppm) and 75% (10 ppm) because of the cleavage reaction caused by formaldehyde. Bacterial community analysis showed that the proportion of Geobacter decreased from 81% to 53% (1 ppm) and 24% (10 ppm). As a result, the current production was significantly impaired, and the irreversible loss increased. Toxicological analysis demonstrated that formaldehyde disturbed the physiological indices of cells, thereby inducing apoptosis. These findings fill the gap of ecotoxicology of toxicants to EAB in a bioelectrochemical system.

Oil spills occur frequently worldwide, resulting in severe damage to water and to human health. Polycyclic aromatic hydrocarbons (PAHs) are the primary toxic components in oil contamination. PAH-degrading microbes have attracted significant attention, but difficulty in their selection and proliferation limits their applications. Graphene oxide quantum dots (GOQDs) improve the proliferation of an indigenous PAH-degrading strain, Bacillus cereus, more effectively than large graphene oxide flakes. Bacillus cereus can metabolize a variety of xenobiotic aromatic compounds as carbon sources and is used in bioremediation. GOQDs contain a variety of aromatic hydrocarbon structures, explaining why the bacteria achieve strong tolerance to PAHs. GOQD-activated cytokinesis increases the secretion of substances important for biofilm formation (extracellular polymeric substances), which further accelerates PAH removal. Proteomic analysis reveals the molecular mechanisms underlying GOQD-induced microbial proliferation. GOQDs induce the overexpression of microbial divisomal proteins associated with division initiation, DNA replication and peptidoglycan hydrolysis/synthesis. Importantly, PAH removal mediated by GOQD-treated Bacillus cereus does not require the addition of GOQDs. The effects of GOQDs on a strain persist for at least 20 generations, suggesting their possible use in low-cost applications. This work proposes a strategy to remove oil contamination using an indigenous bacterial system enhanced by nanomaterials.

The effect of extracellular polymeric substances (EPS), vital organic matters and nutrient elements in the natural environment, on the behavior and toxicology of silver nanoparticles (AgNPs) and ions remains ambiguous. In this study, the role of EPS on the toxicity of AgNPs and dissolved silver ions (from AgNO3) to a green algae Chlorella vulgaris was investigated. After the removal of EPS, algae accumulated more silver, about 7.41- and 1.25-fold of those in the algae with EPS for AgNPs and AgNO3 treatments, respectively. The large amount of accumulated silver was bound to the algal cell surface for AgNPs treatment and was internalized in the algae for AgNO3 treatment, irrespective of the presence of EPS in algae. After exposure to AgNPs, the ruffles in the surfaces of algal cells were filled by AgNPs, and almost invisible. FTIR showed that for both AgNPs and AgNO3, the aldehyde groups on the cell surface were oxidized to carboxyl groups by silver ions, irrespective of the presence of EPS in algal cells, indicating that silver ions were released from the oxidization of AgNPs and reacted with algal cells. The content of chlorophyll showed that AgNPs depressed algal growth more remarkably than did AgNO3, independent of the presence of EPS in algae, suggesting that AgNPs had greater toxic effects on algae than did silver ions. The findings suggest that the barrier effect of EPS gave nanoparticles an extraordinary edge over ions, but EPS had no discerning effect on the interaction of algal cells with the silver ions released from AgNPs and AgNO3, and also on the effect of AgNPs and AgNO3 on algal growth.

In this study, sulfamethoxazole served as the electron donor for microbial electrolysis cells. After 6 months of operation, the removal efficiencies of sulfamethoxazole in three microbial electrolysis cells were 77.60%, 87.55%, and 92.53% for a 3-day period and were directly proportional to the initial added concentrations. However, the removal efficiencies in the microbial electrolysis cells with open circuits and without microorganisms were only 51% and 8%, respectively. Higher sulfamethoxazole concentrations and sustained electrical stimulation caused faster bioelectrochemical reactions, thereby enhancing sulfamethoxazole degradation. Bacterial community analysis revealed that Proteobacteria and Synergistetes, which are the main functional phyla, proliferated with increased antibiotic concentrations. The qPCR results indicated that the copy numbers of antibiotic resistance genes and integrons in microbial electrolysis cell biofilms and effluents were distinctly lower than those in traditional biological treatment systems. Thus, the generation and dissemination of antibiotic resistance genes might be a diminished challenge in microbial electrolysis cells.

The effects of graphene oxide (GO) carbon nanomaterials on ecosystems have been well characterized, but the toxicity of GO at predicted environmental concentrations to living organisms at the protein level remain largely unknown. In the present work, the adverse effects and mechanisms of GO at predicted environmental concentrations were evaluated by integrating proteomics and standard analyses for the first time. The abundances of 243 proteins, including proteins involved in endocytosis (e.g., cltcb, arf6, capzb and dnm1a), oxidative stress (e.g., gpx4b, sod2, and prdx1), cytoskeleton assembly (e.g., krt8, krt94, lmna and vim), mitochondrial function (e.g., ndufa10, ndufa8, cox5aa, and cox6b1), Ca2+ handling (e.g., atp1b2a, atp1b1a, atp6v0a1b and ncx4a) and cardiac function (e.g., tpm4a, tpm2, tnni2a.1 and tnnt3b), were found to be notably altered in response to exposure 100 μg/L GO. The results revealed that GO caused malformation and mortality, likely through the downregulation of proteins related to actin filaments and formation of the cytoskeleton, and induced oxidative stress and mitochondrial disorders by altering the levels of antioxidant enzymes and proteins associated with the mitochondrial membrane respiratory chain. Exposure to GO also increased the heart rate of zebrafish larvae and induced pericardial edema, likely by changing the expression of proteins related to Ca2+ balance and cardiac function. This study provides new proteomic-level insights into GO toxicity against aquatic organisms, which will greatly benefit our understanding of the bio-safety of GO and its toxicity at predicted environmental concentrations.

BACKGROUND: Bioelectrochemical remediation of soils contaminated by petroleum hydrocarbons has received increasing attention as an effective approach to remove pollution with simultaneous electricity generation. RESULTS: Here, glucose was added as a co-substrate in this system. The charge output of soil microbial fuel cells (MFCs) was enhanced by 262%, and the total petroleum hydrocarbon degradation rate increased by 200%. According to the increased dehydrogenase and polyphenol oxidase activities, the exogenetic glucose substantially activated hydrocarbon degradation bacteria (such as Alcanivorax). The Shannon–Wiener Index and richness of soil microbial community decreased after glucose addition, indicating that a selective enrichment of specific communities was imposed by glucose. Correlation analysis showed the biodiversity in soil far from the cathode was mainly determined by the concentration of petroleum hydrocarbons, while that in soil close to the cathode was dominated by the current. CONCLUSION: This study demonstrated that an exogenetic carbon source enhanced the bioelectrochemically assisted degradation of aged petroleum hydrocarbons in saline soils, providing an effective approach to remove contaminations from soil in barren areas or extreme environments. © 2015 Society of Chemical Industry Supporting information may be found in the online version of this article.

Soybean plants showing symptoms of root rot were collected from fields in western Canada to determine the etiology of the disease. Four Fusarium spp., Fusarium avenaceum , Fusarium culmorum , Fusarium oxysporum and Fusarium proliferatum, were identified based on their cultural and morphological characteristics. All of the isolates of these species were pathogenic on soybean. Identification of F. proliferatum was confirmed by PCR analysis with the F. proliferatum -specific primer set CLPRO1/CLPRO2. Amplicons of the target fragments (partial calmodulin (cld) gene, 526 bp) were obtained only from DNA of isolates tentatively identified as F. proliferatum , and sequencing of the amplicon showed it shared 100% identity with the cld gene sequences of F. proliferatum in GenBank. F. proliferatum was the most aggressive of the four Fusarium species identified, causing the greatest root rot severity and reduction of seedling emergence. F. avenaceum was the second most aggressive and caused a greater reduction in seedling numbers than F. culmorum or F. oxysporum . Correlation analysis showed that seedling emergence, shoot dry weight, and seed yield decreased, and root rot severity increased, with the log of inoculum density of F. proliferatum . This is the first report of F. proliferatum causing soybean root rot in Canada.

Clubroot, caused by Plasmodiophora brassicae, is an important disease in canola (Brassica napus) and other crucifers. Experiments were conducted to examine the effectiveness of the prill formulatio...

Developmental toxicity is a critical issue in nanotoxicity. However, very little is known about the effects of graphene oxide (GO, a widely used carbon material) at predicted environmental concentrations on biological development or the specific molecular mechanisms. The present study established that the development of zebrafish embryos exposed to trace concentrations (1-100 μg/L) of GO was impaired because of DNA modification, protein carbonylation and excessive generation of reactive oxygen species (ROS), especially the superoxide radical. Noticeably, there was a nonmonotonic response of zebrafish developmental toxicity to GO at μg/L to mg/L levels. Transcriptomics analysis revealed that disturbing collagen- and matrix metalloproteinase (MMP)-related genes affected the skeletal and cardiac development of zebrafish. Moreover, metabolomics analysis showed that the inhibition of amino acid metabolism and the ratios of unsaturated fatty acids (UFAs) to saturated fatty acids (SFAs) contributed to the above developmental toxicity. The present work verifies the developmental toxicity of GO at trace concentrations and illustrates for the first time the specific molecular mechanisms thereof. Because of the potential developmental toxicity of GO at trace concentrations, government administrators and nanomaterial producers should consider its potential risks prior to the widespread environmental exposure to GO.

Many ecosystems are currently co-contaminated with pesticides and heavy metals, such as chlorpyrifos and cadmium. A promising strategy to remediate mixed chlorpyrifos-cadmium-contaminated sites is the use of chlorpyrifos-degrading bacteria endowed with cadmium removal capabilities. In this work, a gene coding for synthetic phytochelatins (EC20) with high cadmium-binding capacity was introduced into a chlorpyrifos-degrading bacterium, Stenotrophomonas sp. YC-1, resulting in an engineered strain with both cadmium accumulation and chlorpyrifos degradation capabilities. To improve the cadmium-binding efficiency of whole cells, EC20 was displayed on the cell surface of Stenotrophomonas sp. YC-1 using the truncated ice nucleation protein (INPNC) anchor. The surface localization of the INPNC-EC20 fusion protein was demonstrated by cell fractionation, Western blot analysis, and immunofluorescence microscopy. Expression of EC20 on the cell surface not only improved cadmium binding, but also alleviated the cellular toxicity of cadmium. As expected, the chlorpyrifos degradation rate was reduced in the presence of cadmium for cells without EC20 expression. However, expression of EC20 (higher cadmium accumulation) completely restored the level of chlorpyrifos degradation. These results demonstrated that EC20 expression not only enhanced cadmium accumulation, but also reduced the toxic effect of cadmium on chlorpyrifos degradation.

Triclosan (TCS) is released into the terrestrial environment via the application of sewage sludge and reclaimed water to agricultural land. More attention has been paid to its effect on non-target soil organisms. In the present study, chronic toxic effects of TCS on earthworms at a wide range of concentrations were investigated. The reproduction, DNA damage, and expression levels of heat shock protein (Hsp70) gene of earthworms were studied as toxicity endpoints. The results showed that the reproduction of earthworms were significantly reduced (p < 0.05) after exposure to the concentrations ranges from 50 to 300 mg kg(-1), with a half-maximal effective concentration (EC50) of 142.11 mg kg(-1). DNA damage, detected by the comet assay, was observed and there was a clear significant (R(2) = 0.941) relationship between TCS concentrations and DNA damage, with the EC50 value of 8.85 mg kg(-1). The expression levels of Hsp70 gene of earthworms were found to be up-regulated under the experimental conditions. The expression level of hsp70 gene increased, up to about 2.28 folds that in the control at 50 mg kg(-1). The EC50 value based on the Hsp70 biomarker was 1.79 mg kg(-1). Thus, among the three toxicity endpoints, the Hsp70 gene was more sensitive to TCS in soil.

Canola seedling blight, caused by Rhizoctonia solani , and Fusarium spp., can result in large yield losses to canola ( Brassica napus ) at high inoculum pressure. The effect of inoculum density was studied by mixing different amounts of R. solani AG-2-1 and Fusarium avenaceum into a sterilized natural soil and soil-less mix (2:1, v:v) separately, and recording seedling emergence, damping-off and seedling height within ten days after seeding; root rot severity at 12 days after seeding and seed yield at harvest on canola cultivars ‘45H29’ and ‘73-77RR’. Root rot severity increased and emergence, plant height and seed yield decreased with increased inoculum density of both R. solani and F. avenaceum . For quantification of R. solani AG-2-1, a primer and TaqMan probe set (Rs21F/Rs21R/Rs21P) was designed based on the nuclear ribosomal internal transcribed spacer (ITS) region of R. solani AG-2-1. From a conventional PCR amplification, an 88-bp product was amplified from all isolates classified as AG-2-1 with the primers Rs21F and Rs21R. No product was amplified with DNA from isolates belonging to other anastomosis groups of R. solani , other pathogens or the host plant. By using quantitative PCR, DNA amounts as low as 100 fg of R. solani AG-2-1 were detected. The quantity of DNA from soil samples with different inoculum densities estimated using qPCR was highly correlated to the number of colony-forming units (cfu) obtained from the same soil samples for both R . solani AG-2-1 and F . avenaceum .

The twin-arginine translocation (Tat) pathway exports folded proteins across the cytoplasmic membranes of bacteria and archaea. Two parallel Tat pathways (TatAdCd and TatAyCy systems) with distinct substrate specificities have previously been discovered in Bacillus subtilis. In this study, to secrete methyl parathion hydrolase (MPH) into the growth medium, the twin-arginine signal peptide of B. subtilis YwbN was used to target MPH to the Tat pathway of B. subtilis. Western blot analysis and MPH assays demonstrated that active MPH was secreted into the culture supernatant of wild-type cells. No MPH secretion occurred in a total-tat2 mutant, indicating that the observed export in wild-type cells was mediated exclusively by the Tat pathway. Export was fully blocked in a tatAyCy mutant. In contrast, the tatAdCd mutant was still capable of secreting MPH. These results indicated that the MPH secretion directed by the YwbN signal peptide was specifically mediated by the TatAyCy system. The N-terminal sequence of secreted MPH was determined as AAPQVR, demonstrating that the YwbN signal peptide had been processed correctly. This is the first report of functional secretion of a heterologous protein via the B. subtilis TatAyCy system. This study highlights the potential of the TatAyCy system to be used for secretion of other heterologous proteins in B. subtilis.

Clubroot, caused by Plasmodiophora brassicae, has become a serious threat to canola (Brassica napus) production in western Canada. Experiments were conducted under greenhouse and field conditions to assess the effect of Vapam fumigant (dithiocarbamate; sodium N-methyldithiocarbamate) on primary and secondary infection by P. brassicae, clubroot severity, and growth parameters in canola. Preliminary trials showed a 12–16-fold reduction in primary and secondary infection and clubroot severity at all of the Vapam application rates (0·4–1·6 mL L−1 soil) assessed. Vapam was also found to be effective in reducing clubroot severity and improving seed yield of canola under field conditions. Application of Vapam at soil moisture levels in the range of 10–30% (v:v) had a large effect on both disease severity and infection rates and plant growth parameters. The results suggest that Vapam can effectively reduce clubroot severity and may be useful for the treatment of transplant propagation beds in brassica vegetable production, and for the containment of small, localized clubroot infestations in commercial canola crops.

Antibiotics and antibiotic resistance genes (ARGs) in the natural environment have become substantial threats to the ecosystem and public health. Effective strategies to control antibiotics and ARG contaminations are emergent. A novel carbon nanomaterial, graphene oxide (GO), has attracted a substantial amount of attention in environmental fields. This study discovered the inhibition effects of GO on sulfamethoxazole (SMZ) uptake for bacteria and ARG transfer among microorganisms. GO promoted the penetration of SMZ from intracellular to extracellular environments by increasing the cell membrane permeability. In addition, the formation of a GO-SMZ complex reduced the uptake of SMZ in bacteria. Moreover, GO decreased the abundance of the sulI and intI genes by approximately 2-3 orders of magnitude, but the global bacterial activity was not obviously inhibited. A class I integron transfer experiment showed that the transfer frequency was up to 55-fold higher in the control than that of the GO-treated groups. Genetic methylation levels were not significant while sulI gene replication was inhibited. The biological properties of ARGs were altered due to the GO-ARG noncovalent combination, which was confirmed using multiple spectral analyses. This work suggests that GO can potentially be applied for controlling ARG contamination via inhibiting antibiotic uptake and ARG propagation.

In this study, more than 85.1% of sulfamethoxazole (SMX) could be degraded within 60 h. The strengthening of microbial metabolisms and the sustainment of electrical stimulation contributed to the rapid removal of SMX in microbial fuel cells (MFCs). High-performance liquid chromatography identified that SMX could be thoroughly degraded into less harmful alcohols and methane after the MFC processing. In addition, the major role of Shewanella sp. and Geobacteria sp. in power generation, and the promotion of Alcaligenes, Pseudomonas and Achromobacter in SMX degradation have been demonstrated. Moreover, this study further proved that the copy numbers of targeted antibiotic resistance genes and integrons produced in MFCs were much lower than those found in conventional wastewater treatment plants; MFCs seem to be a promising alternative to reduce antibiotics in wastewater treatment and water purification.

Anaerobic digestion (AD) reactors often encounter low pH inhibition during startup and high organic loading periods. The use of a large amount of NaOH in order to raise and buffer the low pH, is reported to be inhibitory to methanogens. In order to address this problem, we acclimatized aceticlastic methanogens to low pH. Methanogens were successfully acclimatized to initial low pH down to 3.5 in a lengthy, five months, acclimatization period. The aceticlastic methanogen, Methanothrix soehngenii which was 96.3% of the total methanogenic population at pH 4.5 and 86.75% at pH 3.5, demonstrated that they were the most tolerant aceticlastic methanogens to low pH. After acclimatization, methane yield at pH 4.5 was comparable to neutral pH. Methanosaeta maintained its dominance over Methanosarcina at an elevated level of acetate (66 mM), and a negative correlation was observed between them. There was a positive correlation between the CH4 content and pH.

Bioelectrochemical systems (BESs) provide an opportunity to detect biological toxicity of water samples. However, the concentration responses of toxins had not been investigated in detail. Using formaldehyde as a toxic substance, the current responses were analyzed over a concentration range from 0.01% to 0.10% in a single chambered BES with 0mV (versus saturated calomel electrode) applied on the anode. The decay percentages of currents increased in proportion with the concentration of formaldehyde after 10000s (∼2.8h), with the peak R(2) of 0.9361 observed at 35,000s (∼9.7h). Fitting results of exponential decay equation showed that the magnification factor (a) closely related with baseline currents and the toxicity factor (b) was in direct proportion to formaldehyde concentration (from 0% to 0.08%) except over the high concentration of 0.10%. These results provide preliminary information about toxin concentration responses in BESs.

Ethylbenzene is classified as a priority pollutant; however, toxicity data, especially those regarding sublethal toxicity, are rarely reported on gastropods. The present work was performed to elucidate the sublethal effects of ethylbenzene using a freshwater snail, Bellamya aeruginosa (Reeve), exposed to ethylbenzene for 21 days followed by a 17-day recovery period. Superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), reduced glutathione (GSH), and malonyldialdehyde (MDA) were used as biomarkers to evaluate oxidative stress in hepatopancreas of snails. In addition, alkaline comet assay was applied to determine the genotoxicity of ethylbenzene in hepatopancreas of snails. These biomarkers and DNA damage exhibited various responses to ethylbenzene in the tested snails. SOD and CAT activities were almost significantly stimulated during the exposure period. As exposure time was prolonged beyond 7 days, CAT activity gradually became significantly increased at higher doses of ethylbenzene. GSH concentration was positively and linearly related with exposure dose. MDA concentration was significantly greater than that in the control only under the lowest treatment after a 7-day exposure. Alkaline comet assay showed that ethylbenzene could significantly induce DNA damage in hepatopancreas of snails, and there was a good dose- and time-response in DNA damage, indicating potential genotoxicity of ethylbenzene on snails. At the end of the recovery period, the repair of DNA damage was not yet completed, showing that DNA repair requires more time. The findings from this study could indicate that SOD, GST, and GSH seem to be effective oxidative biomarkers for snails exposed to ethylbenzene in the short term. CAT proved to be a valuable discriminating biomarker in subchronic exposure to ethylbenzene, but MDA was not a suitable oxidative biomarker for exposure to ethylbenzene in either the short or long term. Alkaline comet assay was efficient tool with which to evaluate the potential genotoxicity of ethylbenzene.

This study aims to evaluate toxic effects of exposure to chlortetracycline (CTC) in soil on reproductive endpoints (juvenile counts and cocoon counts), biochemical responses, and genotoxic potentials of the earthworm Eisenia fetida. Results showed that juvenile counts and cocoon counts of the tested earthworms were reduced after exposure to CTC. The effective concentrations (EC(50) values) for juvenile and cocoon counts were 96.1 and 120.3 mg/kg, respectively. Treatment of earthworms with CTC significantly changed the activity of catalase (CAT), superoxide dismutase (SOD) and glutathione S-transferase (GST). An increase in malondialdehyde (MDA) indicated that CTC could cause cellular lipid peroxidation in the tested earthworms. The percentage of DNA in the tail of single-cell gel electrophoresis of coelomocytes as an indication of DNA damage increased after treatment with different doses of CTC, and a dose-dependent DNA damage of coelomocytes was found. In conclusion, CTC induces physiological responses and genotoxicity on earthworms.

The extreme salinity and high internal resistance of saline-alkali soil contaminated by petroleum hydrocarbons were two key limitations for using the bioelectrochemical remediation. In order to solve two problems, we simply rinsed soil, added carbon fiber to polluted soil. The charge output was enhanced by 110% with increase of the maximum current densities from 81 to 304 mA·m−2 while hydrocarbons degradation rate enhanced by 484%, especially the high molecular weight fractions (C28–C36 of n-alkanes and 4–6 rings of PAHs). These effects were possibly due to the selective enrichment of species belonged to δ-Proteobacteria (Proteobacteria), Flavobacteriia (Bacteroidetes) or Clostridia (Firmicutes), the activities of biological electron transfer and enzymes. As we know, oxygenase gene that directly decided the process of degradation, was surveyed for the first time in soil bioelectrochemical remediation system. The results confirmed that the bio-current stimulated the activities of naphthalene dioxygenase and xylene monooxygenase and thus the hydrocarbons degradation and the electricity generation. Given that electricity generation and the remediation performance are governed by multiple factors, understanding of microbial community and enzyme gene is crucial to promote the power yield and the bioelectrochemical remediation applicability.