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PubMed2006

Effects of in ovo exposure to imazalil and atrazine on sexual differentiation in chick gonads.

We examined the effects of atrazine and imazalil, 2 commonly used pesticides, on sexual differentiation in chickens. Atrazine and imazalil were injected into fertile eggs on d 0. At hatching, sex genotype and phenotype were determined. Gonads were stereomicroscopically and histologically observed. In ovo exposure of atrazine (0.01 to 3 mg/egg) did not influence hatchability, whereas imazalil exposure (2 mg/egg) inhibited hatchability. The sex genotype matched the sex phenotype in controls, atrazine, and imazalil-exposed groups. In control females, the right gonad was regressed at hatching. Regression of the right gonad, however, was inhibited following atrazine and imazalil exposure. In atrazine-exposed female chicks, the left gonads had normal ovary structures, and the remaining right gonads had ovary medulla-like structures. In imazalil-exposed females, some left gonads had an ovary medulla-like structure without the cortex as well as tubules, and the right gonad had testis-like structures. There was no change in male gonads at hatching following atrazine and imazalil exposure. Aromatase activity of the left gonad from female chicks was not changed by any concentration of atrazine exposure. These results suggest that atrazine and imazalil inhibit regression of the right gonad in female chicks, although it is not clear whether the remaining right gonad has aromatase activity. In ovo exposure to atrazine influences sexual differentiation of the ovary by different mechanisms from imazalil, possibly by the induction of aromatase in the right gonad, whereas it is confirmed that imazalil inhibits in vitro aromatase activity in the chick ovary. The results indicated that in ovo exposure to imazalil inhibits sexual differentiation of the ovary by inhibiting aromatase activity.

Animals↗

PubMed2000

Characterization of an atrazine-degrading Pseudaminobacter sp. isolated from Canadian and French agricultural soils.

Atrazine, a herbicide widely used in corn production, is a frequently detected groundwater contaminant. Fourteen bacterial strains able to use this herbicide as a sole source of nitrogen were isolated from soils obtained from two farms in Canada and two farms in France. These strains were indistinguishable from each other based on repetitive extragenic palindromic PCR genomic fingerprinting performed with primers ERIC1R, ERIC2, and BOXA1R. Based on 16S rRNA sequence analysis of one representative isolate, strain C147, the isolates belong to the genus Pseudaminobacter in the family Rhizobiaceae. Strain C147 did not form nodules on the legumes alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), red clover (Trifolium pratense L.), chickpea (Cicer arietinum L.), and soybean (Glycine max L.). A number of chloro-substituted s-triazine herbicides were degraded, but methylthio-substituted s-triazine herbicides were not degraded. Based on metabolite identification data, the fact that oxygen was not required, and hybridization of genomic DNA to the atzABC genes, atrazine degradation occurred via a series of hydrolytic reactions initiated by dechlorination and followed by dealkylation. Most strains could mineralize [ring-U-(14)C]atrazine, and those that could not mineralize atrazine lacked atzB or atzBC. The atzABC genes, which were plasmid borne in every atrazine-degrading isolate examined, were unstable and were not always clustered together on the same plasmid. Loss of atzB was accompanied by loss of a copy of IS1071. Our results indicate that an atrazine-degrading Pseudaminobacter sp. with remarkably little diversity is widely distributed in agricultural soils and that genes of the atrazine degradation pathway carried by independent isolates of this organism are not clustered, can be independently lost, and may be associated with a catabolic transposon. We propose that the widespread distribution of the atrazine-degrading Pseudaminobacter sp. in agricultural soils exposed to atrazine is due to the characteristic ability of this organism to utilize alkylamines, and therefore atrazine, as sole sources of carbon when the atzABC genes are acquired.

Agriculture↗

PubMed2002

Novel psbA1 gene from a naturally occurring atrazine-resistant cyanobacterial isolate.

A naturally occurring atrazine-resistant cyanobacterial isolate, strain SG2, was isolated from an atrazine-containing wastewater treatment system at the Syngenta atrazine production facility in St. Gabriel, La. Strain SG2 was resistant to 1,000 microg of atrazine per ml but showed relatively low resistance to diuron [3-(3,4-dichlorophenyl)-1,1-dimethyl urea]. Analyses of 16S ribosomal DNA indicated that strain SG2 falls into the Synechocystis/Pleurocapsa/Microcystis group. Photosynthetically driven oxygen evolution in strain SG2 was only slightly inhibited (about 10%) by 2,000 microg of atrazine per ml, whereas in the control strain Synechocystis 6803, oxygen evolution was inhibited 90% by 1,000 microg of atrazine per ml. No atrazine accretion, mineralization, or metabolites were detected when strain SG2 was grown with [(14)C]atrazine. Strain SG2 contained three copies of the psbA gene, which encodes the D(1) protein of the photosystem II reaction center. Nucleotide sequence analyses indicated that the psbA2 and psbA3 genes encoded predicted proteins with the same amino acid sequence. However, the psbA1 gene product contained five extra amino acids, which were not found in PsbA proteins from five other cyanobacteria. Moreover, the PsbA1 protein from strain SG2 had an additional 13 amino acid changes compared to the PsbA2/PsbA3 proteins and contained 10 amino acid alterations compared to conserved residues found in other cyanobacteria. Reverse transcriptase PCR analysis indicated that the psbA1 gene and the psbA2/psbA3 gene(s) were expressed in photosynthetically grown cells in the presence of atrazine. These results suggest that strong selection pressure conferred by the continual input of atrazine has contributed to the evolution of a herbicide-resistant, yet photosynthetically efficient, psbA gene in a cyanobacterium.

Amino Acid Sequence↗

PubMed1992

[Rainbow trout and zebrafish, two models for continuous toxicity tests: relative sensitivity, species and organ specificity in cytopathologic reaction of liver and intestines to atrazine].

In order to elucidate cytopathological alterations in hepatic and intestinal cells, immature rainbow trout (Oncorhynchus mykiss) were exposed for five weeks to 10, 20, 40, and 160 micrograms/l of the herbicide atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine; model 1). For comparison, ultrastructural changes in female zebra fish (Brachydanio rerio) liver were studied after exposure to 100, 1,000 and 10,000 micrograms/l atrazine for three months (exposure from egg stage to sexual maturation; model 2). Neither epithelial nor glandular cells in the gastrointestinal tract of rainbow trout reveal cytological modifications following exposure to atrazine. In contrast, hepatocytes of rainbow trout and zebra fish clearly display dose-dependent and species-specific cytopathological effects at 40 and 1000 micrograms/l, respectively. In rainbow trout (model 1), rough endoplasmic reticulum (RER) appears of particular diagnostic value for the effects of atrazine, since it already shows a full spectrum of cytological alterations after 40 micrograms/l, and since in cells without RER modifications no further cytopathological symptoms can be revealed. At 40 micrograms/l atrazine, further changes include disturbance of the intracellular compartmentation, increased heterogeneity of mitochondria (longitudinally arranged cristae, branching, size), formation of myelinated bodies as well as immigration of macrophages and granulocytes along the biliary system and the space of Disse. The separation of peripheral storage areas from the central organelle-containing cytoplasm is no longer evident at 80 micrograms/l, and the phagocytic activity of invading macrophages is drastically increased. Following exposure to 160 micrograms/l atrazine, additional pathological changes comprise clubshaped deformation of mitochondria, formation of myelinated bodies in the intermembranous space of mitochondria, increase of degranulated ER cisternae and lysosomes, as well as perisinusoidal accumulation of lipid droplets. Deformation of the nuclear envelope, elevated mitotic activity and an increased number of nuclei with two or more nucleoli indicate interactions between atrazine and the nucleus. In the liver of female zebra fish (model 2), atrazine-induced alterations are limited to increased parenchymal variability, disturbance of the intracellular compartmentation, partial RER fractionation and vesiculation, club-shaped deformation of mitochondria and an increase in the number of lysosomes, myelinated bodies and invading macrophages at 1000 micrograms/l atrazine. After three months at 10,000 micrograms/l, mortality of zebra fish is increased to 100%. According to cytopathological alterations of hepatocytes following long-term exposure, susceptibility of the test model rainbow trout to atrazine appears higher than that of the model zebra fish.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2005

Sorption of dissolved organic matter and its effects on the atrazine sorption on soils.

The dissolved organic matter (DOM), water soluble organic matter derived from sewage sludge was separated into hydrophobic fraction (Ho) and hydrophilic fraction (Hi). The sorption of DOM and its fractions on soils and the effects of DOM sorption on a nonionic pesticide (atrazine(2-chloro-4-ethylamino-6-isopropylamino-1,3,5-trazine)) distribution between soil and water were investigated using a batch equilibrium technique. The total DOM sorption on soils described by the Langmuir equation reached saturation as the DOM concentration increased. The sorption of Ho fit the Freundlich model. In contrast, a negative retention evidently occurred as adding Hi at higher level in tested soils. The sorption of Ho dominated the total DOM sorption and the release of soil organic matter (SOM). Effects of DOM on the atrazine sorption by soils were DOM-concentration dependent and dominated by the interaction of atrazine, DOM, and soil solids. Generally, the presence of DOM with lower concentration promoted atrazine sorption on soils, namely the apparent partitioning constant (Kd) for atrazine sorption in the presence of DOM was larger than the distribution constant (Kd) without DOM; whereas the presence of DOM with higher concentration inhibited atrazine sorption (i.e., Kd < Kd). The overall effects of DOM on atrazine sorption in soils might be related to the DOM sorption and the release of soil intrinsic organic matter into aqueous solution. The sorption of Ho on soils promoted the atrazine sorption on soil, while the release of SOM by Hi and the competitive sorption between Hi and atrazine on soil surface led to a decrease of atrazine sorption. Information provided in this work may contribute to a better understanding of the DOM sorption and its impacts on the contaminant soil-water distribution.

Adsorption↗

PubMed2003

Atrazine sensor based on molecularly imprinted polymer-modified gold electrode.

Molecularly imprinted polymers (MIP) have been elucidated to work as artificial receptors. In our present study, a MIP was applied as a molecular recognition element to a chemical sensor. We have constructed an atrazine sensor based on a MIP layer selective for atrazine and its electrochemical reduction on gold electrode. The atrazine sensor was fabricated by directly polymerizing the atrazine-imprinted polymer composed from methacrylic acid and ethylene glycol dimethacrylate onto the surface of a gold electrode. By introducing LiCl into the MIP, atrazine was reduced below -800 mV vs Ag/AgCl reference electrode, at pH 3. The cathodic current of atrazine depended on the concentration of atrazine at the range of 1-10 microM. The sensor exhibited a selective response to atrazine. A nonimprinted polymer-modified electrode did not show selective response to atrazine, thus implying that the imprinted polymer acts as recognition element of atrazine sensor.

Journal Article↗

PubMed2005

Degradation and sorption of atrazine, hexazinone and procymidone in coastal sand aquifer media.

The degradation, sorption and transport of atrazine, hexazinone and procymidone in saturated coastal sand aquifer media were investigated in batch and column experiments. The pesticides were incubated with sterilised and non-sterilised groundwater or a mixture of groundwater and the aquifer material in the dark at 15 degrees C for 120 days. The estimated half-lives of the pesticides (and their ranges) in the mixture of groundwater and aquifer sand were 36 (31-40), 54 (40-77) and 84 (46-260) days for atrazine, procymidone and hexazinone, respectively. Compared with the relevant results for the groundwater-sand mixture phase, the estimated half-life of pesticides in the groundwater phase alone was shorter for procymidone (21 days) but longer for hexazinone (134 days); atrazine was not degraded in the groundwater phase. Chemical degradation appeared to have played the predominant role in the degradation of hexazinone and procymidone in the aquifer system, while both chemical and biological processes seemed to be important for the degradation of atrazine. Batch isothermal experiments were carried out at pH 4.6-4.7 to obtain sorption coefficients under equilibrium conditions. The isothermal data of the pesticides fitted well with the non-linear Freundlich function with an exponent of sorption coefficient that was greater than one. Contrary to reports in the literature, sorption of atrazine was the greatest, and procymidone was slightly more sorbed than hexazinone. A column experiment was conducted at a typical field-flow velocity of 0.5 m day(-1) over 60 days to study pesticide attenuation and transport in flow dynamic conditions. Retardation factors, R, derived from a two-site sorption/desorption model were 8.22, 1.76 and 1.63 for atrazine, procymidone and hexazinone, respectively. Atrazine displayed the lowest mobility and the mobility of procymidone was only slightly less than that of hexazinone, which is consistent with observations in the batch experiment. A possible explanation for these observations is that ionic atrazine is bound to oppositely charged ionic oxides, and ionic oxides have less effect on the sorption of the non-ionic procymidone. The significant tailing in the pesticide breakthrough curves (BTCs) in comparison with the bromide BTC, together with model-simulated results, suggests that the transport of the pesticides was under chemical non-equilibrium conditions with R values that were less than their equivalent values predicted using the batch equilibrium isothermal data. As a result of non-linear kinetic sorption, retardation factors of the pesticides in groundwater systems would not be constant and will decrease with decreasing pesticide concentrations and increasing flow velocities. Hence, the use of equilibrium isotherm data will probably over-predict the sorption of pesticides in groundwater systems. Rhodamine WT, a commonly used groundwater tracer, was significantly retarded (R = 5.48) and its BTC was much more spread out than the bromide BTC. Therefore, it would not be a good tracer for the indication of groundwater flow velocity and dispersion for the coastal sand aquifer system. In contrast to some aquifer media, the dye tracer was unsuitable as a marker of the appearance of atrazine in a coastal sand aquifer system.

Adsorption↗

PubMed2002

Comparision of atrazine and metolachlor affinity for bermudagrass ( Cynodon dactylon L.) and two soils.

Given that bermudagrass is being used as one of the grasses of choice in grass filter strip plantings as an acceptable grass to reduce off-target losses of herbicides, laboratory experiments were conducted to determine and compare the relative affinity of bermudagrass, a Weswood soil, and a Houston Black soil for atrazine (6-chloro- N-ethyl- N-isopropyl-1,3,5-triazine-2,4-diamine) and metolachlor (2-chloro- N-(2-ethyl-6-methylphenyl)- N-(2-methoxy-1-methyethyl) acetamide). Experiments were also conducted to determine if the presence of one herbicide affects the relative affinity of the other compound to these sorbents. The experiments were carried out using radiolabeled atrazine and metolachlor. Results were reported in disintegrations min(-1) (dpms) and converted to K(d) to determine and compare relative affinity. Both K(d) values for relative affinity of atrazine (86.2) and metolachlor (131.5) to bermudagrass were significantly greater than those of the two soils, Weswood (atrazine, 20.0 and metolachlor, 28.4) and Houston Black (atrazine, 35.8 and metolachlor, 33.5). The two compounds were also mixed together to mimic the common practice of applying atrazine and metolachlor simultaneously as a tank mix. Relative affinity of atrazine to any of the sorbents was not affected by the presence of metolachlor. Similarly, when comparing the affinity of metolachlor alone to that of metolachlor with atrazine present in the solution, no significant differences were observed for bermudagrass or the Weswood soil. However, on the Houston Black soil, the presence of atrazine significantly increased the soil's affinity for metolachlor.

Acetamides↗

PubMed2006

In ovo exposure to a triazine herbicide: effects of atrazine on circulating reproductive hormones and gonadal histology in young Japanese quail.

The triazine herbicide, atrazine, has come under scrutiny for its reported feminizing effects in amphibians. To date, there is little information concerning the effects of atrazine on reproduction in avian species. The current study examined the putative reproductive toxicity of atrazine after exposure in ovo. Atrazine at 504, 246, and 123 microg/kg was administered to Japanese quail eggs before incubation. The eggs were hatched and the birds raised to 14 days of age. Indices of hatchability, sex ratios, and growth were determined. Furthermore, circulating concentrations of reproductive hormones (estradiol, progesterone, and testosterone) and gonadal histology were examined. Atrazine at 504 microg/kg decreased 14-day hatchling weight by 13.1% versus controls. However, no detrimental effects on hatchability or sex ratios were observed. In female birds, atrazine at 504 microg/kg decreased ovarian weights and circulating concentrations of progesterone to 48.3% and 73.3%, respectively, versus control. However, concentrations of estradiol and testosterone did not differ from controls. In male quail, at all doses tested, atrazine had no effect on gonadal weights or circulating concentrations of estradiol, testosterone, or progesterone. Moreover, no incidences of left ovotestis formation were observed. In contrast, 10 ng/kg ethinylestradiol (a positive control) induced the formation of a left ovotestis in four of eight birds analyzed. The current results may suggest that exposure to atrazine in ovo at concentrations above ecologic relevance exerts effects on the reproductive system of young Japanese quail. However, no evidence is presented that atrazine induces feminization of the testis in male quail.

Animals↗

PubMed2003

Microbial community responses to atrazine exposure and nutrient availability: linking degradation capacity to community structure.

Repeated pesticide exposure may enhance biodegradation through selective enrichment of pesticide-metabolizing microorganisms, particularly when the compound is used as a C and energy source. The relationship between pesticide application history and degradation rate is unclear when the chemical is utilized as a nutrient source other than C. Atrazine, a poor source of C and energy, was chosen as a model compound because it can serve as an N source for some microorganisms. Soils with (H-soil) and without (NH-soil) prior s-triazine treatment history were repeatedly exposed to atrazine and a variety of C and N source amendments. Exposure to atrazine and inorganic-N availability were the dominant factors leading to the development of microbial communities with an enhanced capacity to degrade atrazine. The density of the atrazine-degrading microorganisms increased immediately, up to 1000-fold, with atrazine exposure in the H-soil, but comparable increases were not observed in the NH-soil until 12 weeks following laboratory acclimation, despite high rates of atrazine mineralization in these soils immediately following the acclimation period. Whole-soil fatty acid methyl ester (FAME) analysis showed that the application of alternative C and N sources in addition to atrazine resulted in a microbial community composition that was distinctly different from that in either the atrazinealone treatment or water controls for both the H- and NH-soils. These data suggest that the microbial communities in both soils were altered differently in response to the treatments but developed a similar enhanced capacity to mineralize atrazine.

Atrazine↗

PubMed2005

Environmental levels of atrazine and its degradation products impair survival skills and growth of red drum larvae.

Red drum larvae (Sciaenops ocellatus) were exposed to environmentally realistic and sublethal levels of the herbicide atrazine (2-chloro-4-ethylamin-6-isopropylamino-S-triazine) to evaluate its effects on ecologically critical traits: growth, behavior, survival potential, and resting respiration rate. Settlement size larvae (7 mm total length) were given an acute exposure of atrazine at 0, 40, and 80 microg l(-1) for 4 days. Tests of 96 h survival confirmed that these naturally occurring concentrations were sublethal for red drum larvae. Growth, routine swimming, antipredator responses to artificial and actual predators, and resting respiration rate were monitored 1 and 3 days after onset of exposure. Atrazine exposure significantly reduced growth rate. Atrazine-exposed larvae also exhibited significantly higher routine swimming speeds, swam in more convoluted paths, and were hyperactive. Responses to artificial and actual predators were not affected by atrazine exposure nor were resting respiration rates. The higher rate of travel (86% higher in atrazine-treated larvae) resulted in higher predicted encounter rates with prey (up to 71%) and slow moving predators (up to 63%). However, hyperactivity and faster active swimming speeds of exposed larvae indicated that naturally occurring sublethal levels of atrazine will result in an elevated rate of energy utilization (doubling the total metabolic rate), which is likely to increase the risk of death by starvation. Moreover, atrazine effects on growth will prolong the larval period, which could reduce the juvenile population by as much as 24%. We conclude that environmentally realistic levels of atrazine induce behavioral and physiological effects on fish larvae that would compromise their survival expectations.

Animals↗

PubMed2004

Laboratory assessment of atrazine and fluometuron degradation in soils from a constructed wetland.

Constructed wetlands offer promise for removal of nonpoint source contaminants such as herbicides from agricultural runoff. Laboratory studies assessed the potential of soils to degrade and sorb atrazine and fluometuron within a recently constructed wetland. The surface 3 cm of soil was sampled from two cells of a Mississippi Delta constructed wetland; one shallow area disturbed only hydrologically, and the second excavated to provide greater water-holding capacity. The excavated area was more acidic on average (pH 4.85 versus 5.21), but otherwise the physical properties and general microbial enzyme activities in the two areas were similar. Soils were treated with 84 and 68 microg kg(-1) soil (14)C-ring labeled atrazine and fluometuron, respectively, and incubated under either saturated (88% moisture, w:w) or flooded (1cm standing water) conditions. Soils were sampled over 32 days and extracted for herbicide and metabolite analysis. Under saturated conditions, fluometuron metabolized to desmethylfluometuron (DMF) with a half-life equal 25-27 days. However, under flooded conditions, the half-life of fluometuron was more than 175 days. Atrazine dissipated rapidly in saturated and flooded soil with a half-life of approximately 23 days, but only 10% of atrazine was mineralized to CO(2). The overall atrazine and fluometuron dissipation rates were similar between the two cells, but each area had a different pattern of metabolite accumulation. The major route of atrazine dissipation was incorporation of atrazine residues into methanol-nonextractable (soil-bound) components, with minimal extractable metabolite accumulation. A mixed-mode extractant (potassium phosphate:acetonitrile) recovered greater amounts of (14)C-residues from atrazine-treated soils, suggesting that hydrolysis of atrazine to hydroxylated metabolites was a major component of the bound residues. These studies indicate the potential for herbicide dissipation in wetland soils and a differential effect of flooding on the fate of these herbicides.

Atrazine↗

PubMed2005

Induction of atrazine tolerance in a natural soil assemblage of microalgae reared in the laboratory.

We investigated the occurrence of tolerance to atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) in soil microalgae by means of the pollution-induced community tolerance methodology. To this end, a natural soil assemblage of microalgae, reared under laboratory conditions, was used as experimental model. Experimental cultures were exposed to 0.46, 0.93, 1.85, 2.70, and 5.40 mg atrazine/L medium for 40 days. After this chronic exposure, both untreated and atrazine-pretreated cultures were subjected to a short-term dose-effect study with atrazine using average growth rate as endpoint. Results showed that chronic exposure to atrazine induced significant changes at the community level, increasing its atrazine tolerance. In addition, atrazine-pretreated assemblages seemed to display, on average, a reduced growth rate compared with untreated assemblages in the absence of atrazine. Response to the presence of atrazine could thus be achieved with some fitness cost. This suggests that the soil microalgal productivity could be diminished after exposure to atrazine.

Atrazine↗

PubMed2004

Characterization of Arthrobacter nicotinovorans HIM, an atrazine-degrading bacterium, from agricultural soil New Zealand.

Arthrobacter nicotinovorans HIM was isolated directly from an agricultural sandy dune soil 6 months after a single application of atrazine. It grew in minimal medium with atrazine as sole nitrogen source but was unable to mineralize 14C-ring-labelled atrazine. Atrazine was degraded to cyanuric acid. In addition to atrazine the bacterium degraded simazine, terbuthylazine, propazine, cyanazine and prometryn but was unable to grow on terbumeton. When added to soil, A. nicotinovorans HIM did enhance mineralization of 14C-ring-labelled atrazine and simazine, in combination with naturally occurring cyanuric acid degrading microbes resident in the soil. Using PCR, the atrazine-degradation genes atzABC were identified in A. nicotinovorans HIM. Cloning of the atzABC genes revealed significant homology (>99%) with the atrazine degradation genes of Pseudomonas sp. strain ADP. The atrazine degradation genes were held on a 96 kbp plasmid.

Agriculture↗

PubMed2004

Real-time reverse transcription PCR analysis of expression of atrazine catabolism genes in two bacterial strains isolated from soil.

The level of expression of highly conserved, plasmid-borne, and widely dispersed atrazine catabolic genes (atz) was studied by RT-qPCR in two telluric atrazine-degrading microbes. RT-qPCR assays, based on the use of real-time PCR, were developed in order to quantify atzABCDEF mRNAs in Pseudomonas sp. ADP and atzABC mRNAs in Chelatobacter heintzii. atz gene expression was expressed as mRNA copy number per 10(6) 16S rRNA. In Pseudomonas sp. ADP, atz genes were basally expressed. It confirmed atrazine-degrading kinetics indicating that catabolic activity starts immediately after adding the herbicide. atz gene expression increased transitorily in response to atrazine treatment. This increase was only observed while low amount of atrazine remained in the medium. In C. heintzii, only atzA was basally expressed. atzA and atzB expression levels were similarly and significantly increased in response to atrazine treatment. atzC was not expressed even in the presence of high amounts of atrazine. This study showed that atz genes are basally expressed and up-regulated in response to atrazine treatment. atz gene expression patterns are different in Pseudomonas ADP and C. heintzii suggesting that the host may influence the expression of plasmid-borne atrazine-catabolic potential.

Atrazine↗

PubMed2004

Atrazine degradation in anaerobic environment by a mixed microbial consortium.

Atrazine degradation by anaerobic mixed culture microorganism in co-metabolic process and in absence of external carbon and nitrogen source was studied at influent atrazine concentration range of 0.5-15 mg/l. Wastewater of desired characteristic was prepared by the addition of various constituents in distilled water spiked with atrazine. In co-metabolic process, dextrose of various concentrations (150-2000 mg/l) was supplied as external carbon source. The reactors were operated in sequential batch mode in which 20% of treated effluent was replaced by the same amount of fresh wastewater everyday, thus maintaining a hydraulic retention time (HRT) equal to 5 days. In co-metabolic process, 40-50% of influent atrazine degradation was observed. First-order atrazine degradation rate (expressed in day(-1)) was better in co-metabolic process (5.5 x 10(-4)) than in absence of external carbon source (2.5 x 10(-5)) or carbon and nitrogen source (1.67 x 10(-5)). In presence of 2000 mg/l of dextrose, atrazine degradation was between 8% and 15% only. Maximum atrazine degradation was observed from wastewater containing 300 mg/l of dextrose and 5mg/l of atrazine. Influent atrazine concentration did not have much effect on the methanogenic bacteria which was clear from methane gas production and specific methanogenic activity (SMA).

Atrazine↗

PubMed2003

Inoculation of an atrazine-degrading strain, Chelatobacter heintzii Cit1, in four different soils: effects of different inoculum densities.

The possibility to improve atrazine degradation in soils by bioaugmentation was studied. The atrazine-mineralizing strain, Chelatobacter heintzii Cit1, was inoculated in four sterile and four non-sterile soils, at varying inoculum densities. Two soils, which had shown enhanced atrazine mineralization, were used to determine which inoculum density was capable of restoring their original mineralizing capacity after sterilization. The two other soils, with intermediate and low capacity to mineralize atrazine, were used in order to demonstrate that atrazine mineralization in such soils could be improved by inoculation. Mineralization kinetics were fitted using the Gompertz model. In the case of soils adapted to atrazine mineralization, inoculation of C. heintzii did not accelerate the rate of atrazine mineralization, which was essentially performed by the indigenous microflora. However, with soils that did not mineralize atrazine, the introduction of 10(4) cfug(-1) resulted in a 3-fold increase of atrazine mineralization capacity.

Atrazine↗

PubMed2003

Lack of modifying effects of atrazine and/or tamoxifen on thyroid carcinogenesis in rats pretreated with N-bis(2-hydroxypropyl)nitrosamine (DHPN).

The modifying effects of atrazine, and/or tamoxifen, on thyroid carcinogenesis were investigated in a rat two-stage carcinogenesis model following N-bis(2-hydroxypropyl)nitrosamine (DHPN) initiation. Five-week-old male F344 rats were given a single subcutaneous injection of DHPN (2800 mg/kg, body weight) or vehicle alone. Starting 1 week later, the animals were fed a diet supplemented with 0, 5, 50 or 500 ppm of atrazine, 500 ppm atrazine plus 5 ppm tamoxifen, or 5 ppm tamoxifen in the DHPN-treated groups, and 0 or 500 ppm of atrazine in the DHPN-untreated groups for 24 weeks. At autopsy major organs, including the thyroid, pituitary, liver, kidney, testis, epididymis, and brain, were collected and histopathologically examined. Body weights were significantly (P<0.05) decreased by the high doses of atrazine or tamoxifen, the effect being enhanced in combination. Relative thyroid weights were significantly increased (P<0.05) only in the tamoxifen-treated group and pituitary weights were elevated with 500 ppm atrazine plus tamoxifen (P<0.05). Relative liver weights were increased by the high dose of atrazine. However, the atrazine and/or tamoxifen treatments did not induce significant histopathological changes in the major organs, including the thyroid, nor cause significant changes in serum TSH levels. These results suggest that neither atrazine nor tamoxifen may promote thyroid carcinogenesis, alone as well as in combination.

Animals↗