The ROS/SIRT1/STAR axis as a target for melatonin ameliorating atrazine-induced mitochondrial dysfunction and steroid disorders in granulosa cells.

The granulosa cells (GCs) of birds are essential for the reproduction and maintenance of populations in nature. Atrazine (ATR) is a potent endocrine disruptor that can interfere with reproductive function in females and Diaminochlorotriazine (DACT) is the primary metabolite of ATR in the organism. Melatonin (MT) is an endogenous hormone with antioxidant properties that plays a crucial role in development of animal germ cells. However, how ATR causes mitochondrial dysfunction, abnormal secretion of steroid hormones, and whether MT prevents ATR-induced female reproductive toxicity remains unclear. Thus, the purpose of this study is to investigate the protective effect of MT against ATR-induced female reproduction. In the present study, the GCs of quail were divided into 6 groups, as follows: C (Serum-free medium), MT (10 µM MT), A250 (250 µM ATR), MA250 (10 µM MT+250 µM ATR), D200 (200 µM DACT) and MD200 (10 µM MT+200 µM DACT), and were cultured for 24 h. The results revealed that ATR prevented GCs proliferation and decreased cell differentiation. ATR caused oxidative damage and mitochondrial dysfunction, leading to disruption of steroid synthesis, which posed a severe risk to GC's function. However, MT supplements reversed these changes. Mechanistically, our study exhibited that the ROS/SIRT1/STAR axis as a target for MT to ameliorate ATR-induced mitochondrial dysfunction and steroid disorders in GCs, which provides new insights into the role of MT in ATR-induced reproductive capacity and species conservation in birds.

Holistic Assessment Based On Hepatocyte Mitochondria: Lycopene Repairs Oxidized mtDNA to Alleviate Mitochondrial Stress Induced by Atrazine.

Atrazine (ATZ) is a highly persistent herbicide that harms organism health. Lycopene (LYC) is an antioxidant found in plants and fruits. The aim of this study is to investigate the mechanisms of atrazine-induced mitochondrial damage and lycopene antagonism in the liver. The mice were divided into seven groups by randomization: blank control (Con group), vehicle control (Vcon group), 5 mg/kg lycopene (LYC group), 50 mg/kg atrazine (ATZ1 group), ATZ1+LYC group, 200 mg/kg atrazine (ATZ2 group), and ATZ2+LYC group. The present study performed a holistic assessment based on mitochondria to show that ATZ causes the excessive fission of mitochondria and disrupts mitochondrial biogenesis. However, the LYC supplementation reverses these changes. ATZ causes increased mitophagy and exacerbates the production of oxidized mitochondrial DNA (Ox-mtDNA) and mitochondrial stress. This study reveals that LYC could act as an antioxidant to repair Ox-mtDNA and restore the disordered mitochondrial function caused by ATZ.

Zinc Oxide Nanoparticles and Vitamin C Ameliorate Atrazine-Induced Hepatic Apoptosis in Rat via CYP450s/ROS Pathway and Immunomodulation.

Atrazine, as an herbicide, is used widely worldwide. Because of its prolonged persistence in the environment and accumulation in the body, atrazine exposure is a potential threat to human health. The present study evaluated the possible protective effects of zinc oxide nanoparticles and vitamin C against atrazine-induced hepatotoxicity in rats. Atrazine administered to rats orally at a dose of 300 mg/kg for 21 days caused liver oxidative stress as it increased malondialdehyde (MDA) formation and decreased reduced glutathione (GSH) contents. Atrazine induced inflammation accompanied by apoptosis via upregulation of hepatic gene expression levels of NF-κB, TNF-α, BAX, and caspase-3 and downregulation of Bcl-2 gene expression levels. Additionally, it disturbed the metabolic activities of cytochrome P450 as it downregulated hepatic gene expression levels of CYP1A1, CYP1B1, CYP2E1. The liver function biomarkers were greatly affected upon atrazine administration, and the serum levels of AST and ALT were significantly increased, while BWG%, albumin, globulins, and total proteins levels were markedly decreased. As a result of the above-mentioned influences of atrazine, histopathological changes in liver tissue were recorded in our findings. The administration of zinc oxide nanoparticles or vitamin C orally at a dose of 10 mg/kg and 200 mg/kg, respectively, for 30 days prior and along with atrazine, could significantly ameliorate the oxidative stress, inflammation, and apoptosis induced by atrazine and regulated the hepatic cytochrome P450 activities. Furthermore, they improved liver function biomarkers and histopathology. In conclusion, our results revealed that zinc oxide nanoparticles and vitamin C supplementations could effectively protect against atrazine-induced hepatotoxicity.

Actinobacteria bioaugmentation and substrate evaluation for biobeds useful for the treatment of atrazine residues in agricultural fields.

Biopurification systems (BPS) or biobeds are bioprophylaxis systems to prevent pesticide point-source contamination, whose efficiency relies mostly on the pesticide removal capacity of the biomixture, the majority component of a BPS. The adaptation of the components of the biomixtures to local availabilities is a key aspect to ensure the sustainability of the system. In this work, the removal of atrazine (ATZ) was evaluated in biomixtures formulated with three sugarcane by-products as alternative lignocellulosic substrates. Based on the capacity of actinobacteria to tolerate and degrade diverse pesticides, the effect of biomixtures bioaugmentation with actinobacteria was evaluated as a strategy to enhance the depuration capacity of biobeds. Also, the effect of ATZ and/or the bioaugmentation on microbial developments and enzymatic activities were studied. The biomixtures formulated with bagasse, filter cake, or harvest residue, reached pesticide removal values of 37-41% at 28 d of incubation, with t1/2 between 37.9 ± 0.4 d and 52.3 ± 0.4 d. The bioaugmentation with Streptomyces sp. M7 accelerated the dissipation of the pesticide in the biomixtures, reducing ATZ t1/2 3-fold regarding the controls, and achieving up to 72% of ATZ removal. Atrazine did not exert a clear effect on microbial developments, although most of the microbial counts were less in the contaminated biomixtures at the end of the assay. The bioaugmentation improved the development of the microbiota in general, specially actinobacteria and fungi, regarding the non-bioaugmented systems. The inoculation with Streptomyces sp. M7 enhanced acid phosphatase activity and/or reversed a possible effect of the pesticide over this enzymatic activity.

Enhanced biodegradation of atrazine by Arthrobacter sp. DNS10 during co-culture with a phosphorus solubilizing bacteria: Enterobacter sp. P1.

The interaction between pure culture microorganisms has been evaluated allowing for the enhanced biodegradation of various kinds of pollutants. Arthrobacter sp. DNS10 previously enriched in an atrazine-containing soil was capable of utilizing atrazine as the sole nitrogen source for growth, and Enterobacter sp. P1 is a phosphorus-solubilizing bacterium that releases various kinds of organic acids but lacks the ability to degrade atrazine. Whether strain P1 could enhance atrazine biodegradation by the degrader strain DNS10 was investigated in this experiment. Gas chromatography and high-performance liquid chromatography results showed that co-culture of both strains degraded 99.18 ±â€¯1.00% of the atrazine (initial concentration was 100 mg L-1), while the single strain DNS10 only degraded 38.57 ±â€¯7.39% after a 48 h culture, and the resulting concentration of the atrazine final metabolite cyanuric acid were 63.91 ±â€¯3.34 mg L-1 and 26.60 ±â€¯3.87 mg L-1, respectively. In addition, the expression of the atrazine degradation-related genes trzN, atzB and atzC in co-culture treatments was 6.61, 1.81 and 3.09 times that of the single strain DNS10 culture treatment. A substrates utilization test showed that the atrazine-degrading metabolites ethylamine and isopropylamine could serve as the nitrogen source to support strain P1 growth, although strain P1 cannot degrade atrazine or utilize atrazine for growth. Furthermore, the pH of the medium was significantly decreased when strain P1 utilized ethylamine and isopropylamine as the nitrogen source for growth. The results suggest that nondegrader strain P1 could promote the atrazine biodegradation when co-cultured with strain DNS10. This phenomenon is due to metabolite exchange between the two strains. Culturing these two strains together is a new biostimulation strategy to enhance the biodegradation of atrazine by culturing these two strains together.

The MEK/ERK/CREB signaling pathway is involved in atrazine induced hippocampal neurotoxicity in Sprague Dawley rats.

Atrazine (ATR) is a commonly used artificial synthetic herbicide world-wide, which has been implicated as a potential threat to human health. Previous studies have demonstrated that exposure to ATR affects hippocampus-dependent learning and memory in rodents, but the exact molecular mechanism remains to be elucidated. In this study, we investigated the effect of ATR on the hippocampus of postnatal day 35 male Sprague Dawley (SD) rats administered doses of either 10 or 100 mg/kg body weight (BW)/day of ATR for a period of 30 days. A Morris water maze (MWM) test revealed that ATR treatment impaired memory performance in the spatial probe test, especially amongst the high-dose group. Moreover, analysis by electron microscopy showed that hippocampal neuron ultrastructure in the dentate gyrus (DG) and cornu ammonis 1 (CA1) sub-regions was impaired in the ATR-treated groups. Finally, a downregulation in the mRNA and protein expression levels of members of the MEK/ERK/CREB pathway and downstream factors brain-derived neurotrophic factor (BDNF) and Zif268 was observed in hippocampal tissue following ATR treatment. Taken together, these results suggest that developmental exposure to ATR is able to induce functional and morphological lesions in the hippocampus of SD rats, and that the MEK/ERK/CREB signaling pathway may be involved in this process.

From laboratory to environmental conditions: a new approach for chemical's biodegradability assessment.

With thousands of organic chemicals released every day into our environment, Europe and other continents are confronted with increased risk of health and environmental problems. Even if a strict regulation such as REgistration, Authorization and restriction of CHemicals (REACH) is imposed and followed by industry to ensure that they prove the harmlessness of their substances, not all testing procedures are designed to cope with the complexity of the environment. This is especially true for the evaluation of persistence through biodegradability assessment guidelines. Our new approach has been to adapt "in the lab" biodegradability assessment to the environmental conditions and model the probability for a biodegradation test to be positive in the form of a logistic function of both the temperature and the viable cell density. Here, a proof of this new concept is proposed with the establishment of tri-dimensional biodegradability profiles of six chemicals (sodium benzoate, 4-nitrophenol, diethylene glycol, 2,4,5-trichlorophenol, atrazine, and glyphosate) between 4 to 30 °C and 10(4) to 10(8) cells ml(-1) as can be found in environmental compartments in time and space. The results show a significant increase of the predictive power of existing screening lab-scale tests designed for soluble substances. This strategy can be complementary to those current testing strategies with the creation of new indicators to quantify environmental persistence using lab-scale tests.

Atrazine and its metabolites degradation in mineral salts medium and soil using an enrichment culture.

An atrazine-degrading enrichment culture was used to study degradation of atrazine metabolites viz. hydroxyatrazine, deethylatrazine, and deisopropylatrazine in mineral salts medium. Results suggested that the enrichment culture was able to degrade only hydroxyatrazine, and it was used as the sole source of carbon and nitrogen. Hydroxyatrazine degradation slowed down when sucrose and/or ammonium hydrogen phosphate were supplemented as the additional sources of carbon and nitrogen, respectively. The enrichment culture could degrade high concentrations of atrazine (up to 110 µg/mL) in mineral salts medium, and neutral pH was optimum for atrazine degradation. Further, except in an acidic soil, enrichment culture was able to degrade atrazine in three soil types having different physico-chemical properties. Raising the pH of acidic soil to neutral or alkaline enabled the enrichment culture to degrade atrazine suggesting that acidic pH inhibited atrazine-degrading ability. The study suggested that the enrichment culture can be successfully utilized to achieve complete degradation of atrazine and its persistent metabolite hydroxyatrazine in the contaminated soil and water.

Characterization of bacterial diversity in an atrazine degrading enrichment culture and degradation of atrazine, cyanuric acid and biuret in industrial wastewater.

An enrichment culture was used to study atrazine degradation in mineral salt medium (MSM) (T1), MSM+soil extract (1:1, v/v) (T2) and soil extract (T3). Results suggested that enrichment culture required soil extract to degrade atrazine, as after second sequential transfer only partial atrazine degradation was observed in T1 treatment while atrazine was completely degraded in T2 and T3 treatments even after fourth transfer. Culture independent polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) technique confirmed selective enrichment of genus Bacillus along with Pseudomonas and Burkholderia. Degradation of atrazine/metabolites in the industrial wastewater was studied at different initial concentrations of the contaminants [wastewater-water (v/v) ratio: T1, 1:9; T2, 2:8; T3, 3:7; T4, 5:5 and T5, undiluted effluent]. The initial concentrations of atrazine, cyanuric acid and biuret ranged between 5.32 and 53.92 µg mL(-1), 265.6 and 1805.2 µg mL(-1) and 1.85 and 16.12 µg mL(-1), respectively. The enrichment culture was able to completely degrade atrazine, cyanuric acid and biuret up to T4 treatment, while no appreciable degradation of contaminants was observed in the undiluted effluent (T5). Inability of enrichment culture to degrade atrazine/metabolites might be due to high concentrations of cyanuric acid. Therefore, a separate study on cyanuric acid degradation suggested: (i) no appreciable cyanuric acid degradation with accumulation of an unidentified metabolite in the medium where cyanuric acid was supplemented as the sole source of carbon and nitrogen; (ii) partial cyanuric acid degradation with accumulation of unidentified metabolite in the medium containing additional nitrogen source; and (iii) complete cyanuric acid degradation in the medium supplemented with an additional carbon source. This unidentified metabolite observed during cyanuric acid degradation and also detected in the enrichment culture inoculated wastewater samples, however, was degraded up to T4 treatments and was persistent in the T5 treatment. Probably, accumulation of this metabolite inhibited atrazine/cyanuric acid degradation by the enrichment culture in undiluted wastewater.

Reduced salinity increases susceptibility of zooxanthellate jellyfish to herbicide toxicity during a simulated rainfall event.

Accurately predicting how marine biota are likely to respond to changing ocean conditions requires accurate simulation of interacting stressors, exposure regimes and recovery periods. Jellyfish populations have increased in some parts of the world and, despite few direct empirical tests, are hypothesised to be increasing because they are robust to a range of environmental stressors. Here, we investigated the effects of contaminated runoff on a zooxanthellate jellyfish by exposing juvenile Cassiopea sp. medusae to a photosystem II (PSII) herbicide, atrazine and reduced salinity conditions that occur following rainfall. Four levels of atrazine (0ngL(-1), 10ngL(-1), 2µgL(-1), 20µgL(-1)) and three levels of salinity (35 ppt, 25 ppt, 17 ppt) were varied, mimicking the timeline of light, moderate and heavy rainfall events. Normal conditions were then slowly re-established over four days to mimic the recovery of the ecosystem post-rain and the experiment continued for a further 7 days to observe potential recovery of the medusae. Pulse-amplitude modulated (PAM) chlorophyll fluorescence, growth and bell contraction rates of medusae were measured. Medusae exposed to the combination of high atrazine and lowest salinity died. After 3 days of exposure, bell contraction rates were reduced by 88% and medusae were 16% smaller in the lowest salinity treatments. By Day 5 of the experiment, all medusae that survived the initial pulse event began to recover quickly. Although atrazine decreased YII under normal salinity conditions, YII was further reduced when medusae were exposed to both low salinity and atrazine simultaneously. Atrazine breakdown products were more concentrated in jellyfish tissues than atrazine at the end of the experiment, suggesting that although bioaccumulation occurred, atrazine was metabolised. Our results suggest that reduced salinity may increase the susceptibility of medusae to herbicide exposure during heavy rainfall events.

Kinetics of aerobic and anaerobic biomineralization of atrazine in surface and subsurface agricultural soils in Ohio.

The purpose of this study was to assess atrazine mineralization in surface and subsurface samples retrieved from vertical cores of agricultural soils from two farm sites in Ohio. The Defiance site (NW-Ohio) was on soybean-corn rotation and Piketon (S-Ohio) was on continuous corn cultivation. Both sites had a history of atrazine application for at least a couple of decades. The clay fraction increased at the Defiance site and the organic matter and total N content decreased with depth at both sites. Mineralization of atrazine was assessed by measurement of (14)CO2 during incubation of soil samples with [U-ring-(14)C]-atrazine. Abiotic mineralization was negligible in all soil samples. Aerobic mineralization rate constants declined and the corresponding half-lives increased with depth at the Defiance site. Anaerobic mineralization (supplemented with nitrate) was mostly below the detection at the Defiance site. In Piketon samples, the kinetic parameters of aerobic and anaerobic biomineralization of atrazine displayed considerable scatter among replicate cores and duplicate biometers. In general, this study concludes that data especially for anaerobic biomineralization of atrazine can be more variable as compared to aerobic conditions and cannot be extrapolated from one agricultural site to another.

Interactions between atrazine and phosphorus in aquatic systems: effects on phytoplankton and periphyton.

It has been proposed that the herbicide atrazine may increase rates of parasitic trematode infection in amphibians. This effect may occur indirectly as a result of increased biomass of periphyton and augmented populations of aquatic snails, which are the trematode's primary larval host. Evidence has also shown that nutrients alone may induce the same indirect responses. Since both atrazine and nutrients commonly enter surface waters from agricultural run-off, their spatial and temporal co-occurrence are highly probable. In light of recent wide-spread declines in amphibian populations, a better understanding of the role of atrazine in the proposed ecological mechanism is necessary. A microcosm study was conducted to quantify biomass of phytoplankton and periphyton over a range of atrazine and phosphorus concentrations (from 0 to 200 µg L(-1) each) using a central composite rotatable design. Over 10 weeks, biomass and water chemistry were monitored using standard methods. Regression and canonical analyses of the response surfaces for each parameter were conducted. We found significant effects of atrazine and phosphorus on dissolved oxygen, pH, and conductivity throughout the study. Additions of phosphorus mitigated the apparent inhibition of these photosynthetic indicators caused by atrazine. Despite these changes, no consistent treatment-related differences in algal biomass were observed. These results indicate that the indirect impacts of atrazine on total growth of periphyton and likely, subsequent effects on aquatic snails, are not expected to be ecologically significant at the concentrations of atrazine tested (up to 200 µg L(-1)) and over a range of nutrient conditions commonly occurring in agroecosystems.

[Effects of nitrogen and phosphorus fertilizer on atrazine degradation and detoxification by degrading strain HB-5].

An atrazine-degrading strain HB-5 was used as a bacteria for biodegradation. Treatments of soil with nitrogen single, phosphate single and nitrogen phosphate together with HB-5 were carried out for degradation and eco-toxicity test; then, relationship between atrazine degradation rate and soil available nitrogen, available phosphorus were discussed. Atrazine residues were determined by HPLC; available nitrogen was determined with alkaline hydrolysis diffusion method; available phosphorus was determined with 0.5 mol/L-NaHCO3 extraction and molybdenum stibium anti-color method, and toxicity test was carried out with micronucleus test of Vicia faba root tip cells. The results showed that: After separately or together application, nitrogenous and phosphorous fertilizers could significantly accelerate atrazine degradation than soil with HB-5 only. On day 5, the order of atrazine degradation was ANP > AP > AN > A; 7 days later, no statistically significant differences were found between treatments. The available nitrogen and phosphorus level in soil reduced as the degradation rate increased in the soil. The soil of eco-toxicity test results indicated that the eco-toxicity significantly reduced with the degradation of atrazine by HB-5, and the eco-toxicity on treatments of soil with fertilizer were all below the treatments without fertilizer. On day 5, the order of eco-toxicity was ANP < AP < AN < A; 7 days later, all treatments were decreased in control levels. So, adjusting soil nutrient content could not only promote atrazine degradation in soil but also could reduce the soil eco-toxicity effects that atrazine caused. All these results could be keystone of atrazine pollution remediation in contaminated soil in the future.

Field-scale cleanup of atrazine and cyanazine contaminated soil with a combined chemical-biological approach.

A former agrichemical dealership in western Nebraska was suspected of having contaminated soil. Our objective was to characterize and remediate the contaminated site by a combined chemical-biological approach. This was accomplished by creating contour maps of the on-site contamination, placing the top 60 cm of contaminated soil in windrows and mixing with a mechanical high-speed mixer. Homogenized soil containing both atrazine [6-chloro-N-ethyl-N'-isopropyl-1,3,5-triazine-2,4-diamine] and cyanazine {2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl] amino]-2-methylpropanenitrile} was then used in laboratory investigations to determine optimum treatments for pesticide destruction. Iron suspension experiments verified that zerovalent iron (Fe(0)) plus ferrous sulfate (FeSO(4).7H(2)O) removed more than 90% of both atrazine and cyanazine within 14 d. Liquid chromatography/mass spectrometry (LC/MS) analysis of the atrazine solution after treating with Fe(0) and ferrous sulfate identified several degradation products commonly associated with biodegradation (i.e., deethlyatrazine (DEA), deisopropylatrazine (DIA), hydroxyatrazine (HA), and ammelines). Biological treatment evaluated emulsified soybean [Glycine max (L.) Merr.] oil (EOS) as a carbon source to stimulate biodegradation in static soil microcosms. Combining emulsified soybean oil with the chemical amendments resulted in higher destruction efficiencies (80-85%) and reduced the percentage of FeSO(4) needed. This chemical-biological treatment (Fe(0) + FeSO(4) + EOS, EOS Remediation, Raleigh, NC) was then applied with water to 275 m(3) of contaminated soil in the field. Windrows were tightly covered with clear plastic to increase soil temperature and maintain soil water content. Temporal sampling (0-342 d) revealed atrazine and cyanazine concentrations decreased by 79 to 91%. These results provide evidence that a combined chemical-biological approach can be used for on-site, field-scale treatment of pesticide-contaminated soil.

Nitrogen limited biobarriers remove atrazine from contaminated water: laboratory studies.

Atrazine is one of the most frequently used herbicides. This usage coupled with its mobility and recalcitrant nature in deeper soils and aquifers makes it a frequently encountered groundwater contaminant. We formed biobarriers in sand filled columns by coating the sand with soybean oil; after which, we inoculated the barriers with a consortium of atrazine-degrading microorganisms and evaluated the ability of the barriers to remove atrazine from a simulated groundwater containing 1 mg L(-1) atrazine. The soybean oil provided a carbon rich and nitrogen poor substrate to the microbial consortium. Under these nitrogen-limiting conditions it was hypothesized that bacteria capable of using atrazine as a source of nitrogen would remove atrazine from the flowing water. Our hypothesis proved correct and the biobarriers were effective at removing atrazine when the nitrogen content of the influent water was low. Levels of atrazine in the biobarrier effluents declined with time and by the 24th week of the study no detectable atrazine was present (limit of detection<0.005 mg L(-1)). Larger amounts of atrazine were also removed by the biobarriers; when biobarriers were fed 16.3 mg L(-1) atrazine 97% was degraded. When nitrate (5 mg L(-1) N), an alternate source of nitrogen, was added to the influent water the atrazine removal efficiency of the barriers was reduced by almost 60%. This result supports the hypothesis that atrazine was degraded as a source of nitrogen. Poisoning of the biobarriers with mercury chloride resulted in an immediate and large increase in the amount of atrazine in the barrier effluents confirming that biological activity and not abiotic factors were responsible for most of the atrazine degradation. The presence of hydroxyatrazine in the barrier effluents indicated that dehalogenation was one of the pathways of atrazine degradation. Permeable barriers might be formed in-situ by the injection of innocuous vegetable oil emulsions into an aquifer or sandy soil and used to remove atrazine from a contaminated groundwater or to protect groundwater from an atrazine spill.

Degradation of atrazine by an acclimatized soil fungal isolate.

A fungal strain able to use atrazine (2-chloro-4-ethylamino-5-isopropylamino-1,3,5-triazine) as a source of nitrogen was isolated from a corn field soil that has been previously treated with the herbicide. This strain was purified and acclimatized to atrazine at a higher level in the laboratory. A supplemented N was required to trigger the reaction. Atrazine was degraded at a faster rate in inoculated mineral salt medium (MSM) than non-inoculated MSM. Within 20 days, nearly 34% of the atrazine was degraded in inoculated medium while only 2% of the herbicide was degraded in non-inoculated medium. Degradation of atrazine by the isolated fungal strain was also studied in sterile and non-sterile soil to determine the compatibility of the isolated strain with native microorganisms in soil. The degradation of atrazine was found to be more in inoculated sterile soil than in inoculated non-sterile soil. Cell free extract (CFE) of fungal mycelium degraded about 50% of the atrazine in buffer in 96 hours compared to the control. Four atrazine metabolites were isolated and characterized by LCMS. On the basis of morphological parameters the isolate was identified as Penicillium species. Results indicated that the microorganism may be useful for remediation of atrazine-contaminated soil.

Enhancing cell survival of atrazine degrading Rhodococcus erythropolis NI86/21 cells encapsulated in alginate beads.

AIMS: To develop a method to produce beads with encapsulated Rhodococcus erythropolis NI86/21 with high cell density, extended shelf life, ease of handling and good atrazine degradation capabilities in both liquid and in agricultural soil. METHODS AND RESULTS: Our findings show that the supplementary recovery step in nutrient broth media shortly after cell encapsulation facilitates cell survival in both wet and dry beads upon extended storage at 4 degrees C. Air drying has little or no impact on encapsulated R. erythropolis cell's ability to degrade atrazine in liquid or soil. Bead storage for periods extending up to 12 months at 4 degrees C did not affect the capacity of R. erythropolis encapsulated cells to degrade atrazine in either BMN or nonsterile soil extracts. Bentonite-amended beads formulated with 1% skim milk and exposed to the supplementary growth step, outperformed all other bead formats. These beads provided adequate numbers of vigorous R. erythropolis cells in either liquid or soil media to degrade atrazine. CONCLUSIONS: Supplementary growth in nutrient broth media immediately following cell encapsulation greatly enhances R. erythropolis cells survival in both wet and dry beads upon extended storage at 4 degrees C. Wet and dried beads have similar capacity for atrazine degradation, and their usefulness and appeal in agronomic practise will only be known after bioassay evaluation and successful demonstration at field scale using incurred residues. SIGNIFICANCE AND IMPACT OF THE STUDY: R. erythropolis NI86/21 encapsulated cells have the potential to reduce residual atrazine in soil, thereby minimizing the likelihood of off-site transport to ground or river water and reduce the loss of crops because of phytotoxicity of residual herbicide. Owing to their ease of handling, storage and possible compatibilities with pre-existing mechanical equipment, dried bead formats are ideally suited for agricultural and remediational applications.

Effect of corn root exudates on the degradation of atrazine and its chlorinated metabolites in soils.

DIMBOA (3,4-dihydro-2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3-one), a major benzoxazinone of Poaceae plants, was isolated and purified from corn seedlings. The effect of isolated and purified DIMBOA on the degradation of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], and its toxic breakdown products, desethylatrazine [2-chloro-4-amino-6-(isopropylamino)-s-triazine; DEA] and desisopropylatrazine [2-chloro-4-(ethylamino)-6-amino-s-triazine; DIA], was studied in the absence of plants using batch experiments, while the effect of corn root exudates on these compounds was determined in hydroponic experiments. Degradation experiments were performed in the presence and absence of 50 microM, 1 mM, or 5 mM DIMBOA resulting in ratios of DIMBOA to pesticide of 1:1, 20:1, and 100:1. We observed a 100% degradation of atrazine to hydroxyatrazine within 48 h at a ratio of DIMBOA to atrazine of 100:1. DIMBOA had the largest effect on atrazine, while it was about three times less effective on DEA and DIA. Corn (Zea mays L. cv. LG 2185) was exposed to 10 mg L(-1) of either atrazine, DEA, or DIA for 11 d in a growth chamber experiment. Up to 4.3 micromol L(-1) d(-1) of hydroxyatrazine were formed in the nutrient solutions by plants exposed to atrazine, while the formation of hydroxylated metabolites from plants exposed to DEA and DIA was smaller and also delayed. The formation of hydroxylated metabolites increased in the solution with plant age in all atrazine, DEA, and DIA treatments. HMBOA (3,4-dihydro-2-hydroxy-7-methoxy-2H-1,4-benzoxazin-3-one), the lactam precursor of DIMBOA, and a tentatively identified derivative of MBOA (2,3-dihydro-6-methoxy-benzoxazol-2-one) were detected in the corn root exudates. Mass balance calculations revealed that up to 30% of the disappearance of atrazine and DEA, and up to 10% of DIA removal from the solution medium in our study could be explained by the formation of hydroxylated metabolites in the solution itself. Our results show that higher plants such as corn have the potential to promote the hydrolysis of triazine residues in soils by exudation of benzoxazinones.

Riparian deforestation, stream narrowing, and loss of stream ecosystem services.

A study of 16 streams in eastern North America shows that riparian deforestation causes channel narrowing, which reduces the total amount of stream habitat and ecosystem per unit channel length and compromises in-stream processing of pollutants. Wide forest reaches had more macroinvertebrates, total ecosystem processing of organic matter, and nitrogen uptake per unit channel length than contiguous narrow deforested reaches. Stream narrowing nullified any potential advantages of deforestation regarding abundance of fish, quality of dissolved organic matter, and pesticide degradation. These findings show that forested stream channels have a wider and more natural configuration, which significantly affects the total in-stream amount and activity of the ecosystem, including the processing of pollutants. The results reinforce both current policy of the United States that endorses riparian forest buffers as best management practice and federal and state programs that subsidize riparian reforestation for stream restoration and water quality. Not only do forest buffers prevent nonpoint source pollutants from entering small streams, they also enhance the in-stream processing of both nonpoint and point source pollutants, thereby reducing their impact on downstream rivers and estuaries.

Atrazine catabolism by a combined bacterial association (KRA30) under carbon- and nitrogen-limitations in a retentostat.

AIMS: Nutrient-limited atrazine catabolism study in continuous cultures with biomass retention to mimic in situ environmental conditions and thus gain insight of the efficacy of biosupplementation/biostimulation to eliminate reduced herbicide bioavailability. METHODS AND RESULTS: Carbon- and nitrogen-limited retentostat (1 and 5 l) cultivation of a combined atrazine (100 mg l-1)-catabolizing association KRA30 was made. As a nitrogen source, through citrate supplementation, increased herbicide catabolism resulted and was complete in the absence of NH4-N. Co-metabolism of the molecule in the presence of succinate was identified. Population characterization by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) indicated component species numerical dominance shifts in response to changes in nutrient limitation, mineral salts composition and biofilm formation, although the total species complement and catabolic potential were retained. CONCLUSIONS: Biomass and catabolic capacity maintenance, through cost-effective biosupplementation/biostimulation, should promote atrazine bioavailability and so ensure successful amelioration. SIGNIFICANCE AND IMPACT OF THE STUDY: All planning, implementation and monitoring of bioremediation programmes should be underpinned by a combination of molecular and (continuous) culture-based methods.