Arsenic exposure in northern Mexican women / Exposición a arsénico en mujeres del norte de México

Abstract: Objective: To describe interindividual metabolism variations and sociodemographic characteristics associated to urinary arsenic, and to estimate the arsenic contamination in water from urinary total arsenic (TAs). Materials and methods: Women (n=1 028) from northern Mexico were interviewed about their sociodemographic characteristics and their urinary concentrations of arsenic species were measured by liquid chromatography. Inorganic arsenic (iAs) in water was estimated from urinary TAs. Results: Women were 20-88 years old. TAs in urine ranged from p10=3.41 to p90=56.93 μg/L; 74% of women had levels >6.4 μg/L. iAs in water varied from p10=3.04 to p90=202.12 μg/L; 65% of women had concentrations >10 μg/L, and 41%, concentrations >25 μg/L. Large variations in iAs metabolism were observed. TAs was significantly negatively associated with age and schooling, and positively with the state of residence. Conclusion: Exposure to iAs is an environmental problem in Mexico. Individual variations in metabolism are a challenge to design prevention and control programs.

Resumen: Objetivo: Describir las variaciones interindividuales del metabolismo y las características sociodemográficas asociadas con el arsénico urinario, así como estimar su contaminación en el agua. Material y métodos. Se entrevistó a 1 028 mujeres del norte de México; por cromatografía de líquidos se midieron los metabolitos urinarios de arsénico y, a partir de ellos, se estimó la concentración en agua. Resultados: Las mujeres tuvieron 20-88 años. El arsénico urinario varió de p10=3.41 a p90=56.93 μg/L; 74% de las mujeres tuvieron niveles >6.4 μg/L. El arsénico en agua varió de p10=3.04 a p90=202.12 μg/L; 65% de las mujeres tenían concentraciones >10 μg/L, y 41%, >25 μg/L. Se observaron amplias variaciones en el metabolismo del arsénico. El arsénico urinario se asoció negativamente con la edad y escolaridad, y positivamente con el estado de residencia. Conclusión: La exposición a arsénico es un problema ambiental en México. Las variaciones individuales en su metabolismo son un desafío para diseñar programas de prevención y control.

Possible Metsulfuron Herbicide Detoxification by a Oryza sativa L. Glutathione S-transferase Enzyme

Abstract Rice (Oryza sativa L.) is one of the most important crops in the world, and it is considered the primary source of nutritional layout in developing countries in Asia. The glutathione S-transferases (GSTs) superfamily confers to rice protection against biotic and abiotic stress, and herbicide resistance. However, the three-dimensional structure of a GST Tau class, is unsolved. The objectives of this work were to develop a reliable comparative model for the s-transferase glutathione class Tau 4 from rice, and simulate docking interactions, against herbicides bentazon and metsulfuron. Results showed that the predicted model is reliable and has structural quality. Ramachandran plot set 91.9% of the residues in the most favored regions. All complexes showed negative binding energies values; and metsulfuron docked to the glutathione tripeptide, and it represents a possible insilico evidence of glutathione conjugation with this herbicide.

Producción de enzimas ligninolíticas durante la degradación del herbicida paraquat por hongos de la pudrición blanca / Ligninolytic enzyme production by white rot fungi during paraquat (herbicide) degradation

El paraquat es un herbicida utilizado ampliamente en la agricultura. Debido a su gran distribución y uso inadecuado, representa un problema grave de contaminación del suelo y el agua. Se ha encontrado que los hongos de la podredumbre blanca son capaces de degradar compuestos contaminantes que poseen estructuras similares a la lignina, como es el caso del paraquat. En el presente trabajo se evaluó la degradación de este herbicida y su efecto en la producción de enzimas ligninolíticas por parte de algunos hongos de la podredumbre blanca aislados del sur de México. Seis cepas fúngicas mostraron tolerancia al herbicida durante el cultivo en medio sólido. Tres de las 6 cepas evaluadas, correspondientes a las especies Polyporus tricholoma, Cilindrobasidium laeve y Deconica citrispora, mostraron niveles de degradación del 32, el 26 y el 47%, en ese orden, a los 12 días de cultivo en presencia del xenobiótico. Se detectó un incremento en las actividades de las enzimas lacasa y Mn-peroxidasa en las cepas que presentaron el mayor porcentaje de degradación, probablemente asociado a la disminución del herbicida. Adicionalmente, se realizaron ensayos con extractos enzimáticos procedentes del medio de cultivo extracelular de las 2 cepas que presentaron mayor degradación. Después de 24 h de incubación, se obtuvo una degradación del 49% del paraquat inicial con los extractos de D. citrispora. Los resultados obtenidos indican que la degradación del herbicida estaría asociada a la presencia de enzimas extracelulares en los hongos de la podredumbre blanca. En este trabajo se muestran las primeras evidencias del potencial de biodegradación de diferentes especies de hongos de la pudrición blanca.

Paraquat is a widely used herbicide in agriculture. Its inappropriate use and wide distribution represents a serious pollution problem for soil and water. White rot fungi are capable of degrading pollutants having a similar structure to that of lignin, such as paraquat. This study evaluated the degradation effect of paraquat on the production of ligninolytic enzymes by white rot fungi isolated from the South of Mexico. Six fungal strains showed tolerance to the herbicide in solid culture. Three of the six evaluated strains showed levels of degradation of 32, 26 and 47% (Polyporus tricholoma, Cilindrobasidium laeve and Deconica citrispora, respectively) after twelve days of cultivation in the presence of the xenobiotic. An increase in laccase and manganese peroxidase (MnP) activities was detected in the strains showing the highest percentage of degradation. Experiments were done with enzyme extracts from the extracellular medium with the two strains showing more degradation potential and enzyme production. After 24 hours of incubation, a degradation of 49% of the initial paraquat concentration was observed for D. citrispora. These results suggest that paraquat degradation can be attributed to the presence of extracellular enzymes from white rot fungi. In this work the first evidence of the biodegradation potential of D. citrispora and Cilindrobasidium leave is shown.

Selection, isolation, and identification of fungi for bioherbicide production

Abstract Production of a bioherbicide for biological control of weeds requires a series of steps, from selection of a suitable microbial strain to final formulation. Thus, this study aimed to select fungi for production of secondary metabolites with herbicidal activity using biological resources of the Brazilian Pampa biome. Phytopathogenic fungi were isolated from infected tissues of weeds in the Pampa biome. A liquid synthetic culture medium was used for production of metabolites. The phytotoxicity of fungal metabolites was assessed via biological tests using the plant Cucumis sativus L., and the most promising strain was identified by molecular analysis. Thirty-nine fungi were isolated, and 28 presented some phytotoxic symptoms against the target plant. Fungus VP51 belonging to the genus Diaporthe showed the most pronounced herbicidal activity. The Brazilian Pampa biome is a potential resource for the development of new and sustainable chemical compounds for modern agriculture.

Isolation of an aryloxyphenoxy propanoate (AOPP) herbicide-degrading strain Rhodococcus ruber JPL-2 and the cloning of a novel carboxylesterase gene (feh)

The strain JPL-2, capable of degrading fenoxaprop-P-ethyl (FE), was isolated from the soil of a wheat field and identified as Rhodococcus ruber. This strain could utilize FE as its sole carbon source and degrade 94.6% of 100 mg L−1 FE in 54 h. Strain JPL-2 could also degrade other aryloxyphenoxy propanoate (AOPP) herbicides. The initial step of the degradation pathway is to hydrolyze the carboxylic acid ester bond. A novel esterase gene feh, encoding the FE-hydrolyzing carboxylesterase (FeH) responsible for this initial step, was cloned from strain JPL-2. Its molecular mass was approximately 39 kDa, and the catalytic efficiency of FeH followed the order of FE > quizalofop-P-ethyl > clodinafop-propargyl > cyhalofop-butyl > fluazifop-P-butyl > haloxyfop-P-methyl > diclofop-methy, which indicated that the chain length of the alcohol moiety strongly affected the hydrolysis activity of the FeH toward AOPP herbicides.

Isolation and 2,4-D-degrading characteristics of Cupriavidus campinensis BJ71

An indigenous bacterial strain capable of utilizing 2,4-dichlorophenoxyacetic acid as the sole carbon and energy source was isolated from a soil used for grown wheat with a long-term history of herbicide use in Beijing, China. The strain BJ71 was identified as Cupriavidus campinensis based on its 16S rRNA sequence analysis and morphological, physiological, and biochemical characteristics. The degradation characteristics of strain BJ71 were evaluated. The optimal conditions for 2,4-D degradation were as follows: pH 7.0, 30 °C, 3% (v/v) inoculum size, and an initial 2,4-D concentration of 350 mg L−1. Up to 99.57% of the 2,4-D was degraded under optimal conditions after 6 days of incubation. Strain BJ71 was also able to degrade quizalofop and fluroxypyr. This is the first report of a 2,4-D-degrader containing tfdA gene that can utilize these two herbicides. In a biodegradation experiment, 87.13% and 42.53% of 2,4-D (initial concentration, 350 mg kg−1) was degraded in non-sterile and sterilized soil inoculated with BJ71, respectively, after 14 days. The 2,4-D degradation was more rapid in a soil microcosm including BJ71 than in a soil microcosm without BJ71. These results indicate that strain BJ71 is a potential candidate for the bioremediation of soil contaminated with the herbicide 2,4-D.

Influence of glyphosate in planktonic and biofilm growth of Pseudomonas aeruginosa

This study evaluated the impact of different concentrations of glyphosate (Rondup®) on planktonic and biofilm growth of P. aeruginosa. Aerobic and anaerobic cultures of P. aeruginosa ATCC®15442 inoculated in MHB + glyphosate (0.845 ppm, 1.690 ppm, 8.45 ppm, 16.90 ppm, 84.50 ppm, 169 ppm, 845 ppm, and 1690 ppm) and cultured in normoxia and anoxia, following their OD560nm every hour for 24 h. Biofilms of adapted cells were formed in the presence of glyphosate (0.845 to 1690 ppm) in normoxia and anoxia for 36 h. Glyphosate at concentrations higher than 84.5 ppm reduces the cell density of planktonic aerobic cultures (p < 0.05). However, these same concentrations favor the planktonic anaerobic growth (p < 0.05). On the other hand, the herbicide favors a slight growth of biofilms in a concentration-dependent manner up to 84.5 ppm (p > 0.05), and more pronounced over 169 ppm. Anaerobic biofilms have their growth more readily favored (p < 0.05), regardless of concentration. In a concentration-dependent manner, glyphosate interferes with the growth ability of P. aeruginosa ATCC®15442.

Halotolerance, ligninase production and herbicide degradation ability of basidiomycetes strains

Fungi have been recently recognized as organisms able to grow in presence of high salt concentration with halophilic and halotolerance properties and their ligninolytic enzyme complex have an unspecific action enabling their use to degradation of a number of xenobiotic compounds. In this work, both the effect of salt and polyols on growth of the basidiomycetes strains, on their ability to produce ligninolytic enzyme and diuron degradation were evaluated. Results showed that the presence of NaCl in the culture medium affected fungal specimens in different ways. Seven out of ten tested strains had growth inhibited by salt while Dacryopinax elegans SXS323, Polyporus sp MCA128 and Datronia stereoides MCA167 fungi exhibited higher biomass production in medium containing 0.5 and 0.6 mol.L-1 of NaCl, suggesting to be halotolerant. Polyols such as glycerol and mannitol added into the culture media improved the biomass and ligninases production by D. elegans but the fungus did not reveal consumption of these polyols from media. This fungus degraded diuron in medium control, in presence of NaCl as well as polyols, produced MnP, LiP and laccase.

Effect of 2,4-dichlorophenoxyacetic acid on growth, protein and chlorophyll-a content of Chlorella vulgaris and Spirulina platensis cells.

In this study, effect of different 2,4 -dichlorophenoxyacetic acid (2,4-D) concentrations (0.0, 9.10(-5), 9.10(-4), 9.10(-3) and 9.10(-2) mM) on growth rate, content of protein and chlorophyll-a in Chlorella vulgaris and Spirulina platensis cells was investigated. The most stimulatory effect on growth rate, protein and pigment ratio of C. vulgaris and S. platensis was observed at 9.10(-4) mM concentrations of 2,4-D. The results show that low concentrations of 2,4-D have hormonal effect due to being a synthetic auxin. Cell number protein and pigment rates were inhibited at 9.10(-2) mM concentration in C. vulgaris. Such parameters were inhibited in S. platensis, both at 9.10(-3) and 9.10(-2) mM 2,4-D concentrations. This is due to herbicidal effect of high concentrations of 2,4-D. S. platensis was found to be more sensitive than S. vulgaris to 2,4-D applications. The use of algae as bio-indicators in herbicide contaminated fresh water habitats, was discussed.

Degradation of glyphosate in soil and its effect on fungal population.

Glyphosate application resulted in a decline in soil pH with consequent increase in soil mycoflora suggesting an indirect relationship. Though the composition of mycoflora unchanged, species of aspergilli, fusaria, penicillia and Trichoderma were predominant. HPLC, IR analysis revealed the presence of sarcosine derivative as an intermediary of glyphosate degradation in soil.

Age dependent alterations in photosystem II acceptor side in Cucumis sativus cotyledonary leaf thylakoids: analysis of binding characteristics of herbicide [14C]-atrazine.

Senescence induced temporal changes in photosystems can be conveniently studied in cotyledonary leaves. We monitored the protein, chlorophyll and electron transport activities in Cucumis sativus cv Poinsette cotyledonary leaves and observed that by 20th day, there was a 50%, 41% and 30-33% decline in the chlorophyll, protein and photosystem II activity respectively when compared to 6th day cotyledonary leaves taken as control. We investigated the changes in photosystem II activity (O2 evolution) as a function of light intensity. The photosystem II functional antenna decreased by 27% and the functional photosystem II units decreased by 30% in 20-day old cotyledonary leaf thylakoids. The herbicide [14C]-atrazine binding assay to monitor specific binding of the herbicide to the acceptor side of photosystem II reaction centre protein, D1, showed an increase in the affinity for atrazine towards D1 protein and decrease in the QB binding sites in 20th day leaf thylakoids when compared to 6th day leaf thylakoids. The western blot analysis also suggested a decrease in steady state levels of D1 protein in 20th day cotyledonary leaf thylakoids as compared to 6th day sample which is in agreement with [14C]-atrazine binding assay and light saturation kinetics.