Enrique Sánchez-Salinas

Removal of two organophosphate pesticides by a bacterial consortium immobilized in alginate or tezontle.

In order to remove methyl-parathion (MP) and tetrachlorvinphos (TCF), a bacterial consortium was immobilized with two supports consisting of alginate beads or stones of tezontle colonized by biofilm. Removal kinetics were recorded for suspended and immobilized consortium using a mineral salt medium supplemented with MP and TCF at 25mg/L and with 0.1% (w/v) glucose as a co-substrate. The viability of the consortium cultivated in suspension was maintained for 6 days, whereas the viability of the consortium immobilized in alginate and tezontle supports was maintained for up to 11 and 13 days, respectively. Growth was enhanced when using glucose as a co-substrate. The percentage of MP removed was significantly higher (alpha=0.05) when consortium was immobilized in alginate beads and biofilm on tezontle as compared to suspension culture.

Pesticides in the Environment: Impacts and its Biodegradation as a Strategy for Residues Treatment

A vast number of pollutants and waste materials including heavy metals are disposed into the environment per annum. Approximately 6 x 106 chemical compounds have been synthesized, with 1,000 new chemicals being synthesized annually. Almost 60,000 to 95,000 chemicals are in commercial use. According to Third World Network reports, more than one billion pounds (450 million kilograms) of toxins are released globally in air and water. The contaminants causing ecological problems leading to imbalance in nature is of global concern. The environmentalists around the world are trying to overcome this by several means. However, although they are raising their voices at international platforms regarding the depletion of natural resources; little attention is given to their words and many substances are still used without caring of the adverse consequences (Shukla et al., 2010). Among these chemicals we can find pesticides, which are defined as any substance or mixture of substances which are used to control destructive pests such as insects, plant disease organisms and weeds, including many other living organisms such as nematodes, arthropods other than insects, and vertebrates that endanger our food supply, health, or comfort. In particular, the term pesticide refers to chemical substances that alter biological processes of living organisms deemed to be pests, whether these are insects, mould or fungi, weeds or noxious plants. Pesticides are widely used in most areas of crop production to minimize infestations by pests and thus protect crops from potential yield losses and reduction of product quality (Damalas, 2009). These pests potentially cause damage or interfere in any other way in the production, elaboration, storage, transport, or commercialization of food, agricultural products and wood products or animal food. Pesticides may be given to animals to prevent insects, arachnids or other plagues in or over their bodies (FAO, 2002). Certainly, pesticides have improved longevity and quality of life, chiefly in the area of public health. Insect control programs have saved millions of lives by combating diseases such as malaria, yellow fever and typhus. In addition, the use of pesticides constitutes an important aspect of modern agriculture, as they are absolutely necessary for economical pest management (Gouma, 2009). The most promising opportunity for maximizing benefits and minimizing risks is to invest time, money, and effort into developing a diverse toolbox of

Optimization of methyl parathion biodegradation and detoxification by cells in suspension or immobilized on tezontle expressing the opd gene

The goal of this study was to optimize methyl parathion (O,O-dimethyl-O-4-p-nitrophenyl phosphorothioate) degradation using a strain of Escherichia coli DH5α expressing the opd gene. Our results indicate that this strain had lower enzymatic activity compared to the Flavobacterium sp. ATCC 27551 strain from which the opd gene was derived. Both strains were assessed for their ability to degrade methyl parathion (MP) in a mineral salt medium with or without the addition of glucose either as suspended cells or immobilized on tezontle, a volcanic rock. MP was degraded by both strains with similar efficiencies, but immobilized cells degraded MP more efficiently than cells in suspension. However, the viability of E. coli cells was much higher than that of the Flavobacterium sp. We confirmed the decrease in toxicity from the treated effluents through acetylcholinesterase activity tests, indicating the potential of this method for the treatment of solutions containing MP.

Pesticide Biodegradation: Mechanisms, Genetics and Strategies to Enhance the Process

As a result of human activities, currently a large number of pollutants and waste are eliminated to the environment. Worldwide, more than one billion pounds of toxins are released into the air and water. Approximately 6x106 chemical compounds have been produced; annually 1,000 new products are synthetized and between 60,000 and 95,000 chemicals are commercially used [1]. Among these substances are chemical pesticides, which are used extensively in most areas of crop production in order to minimize pest infestations, to protect the crop yield losses and to avoid reducing the product quality.

Draft Genome Sequence of the Organophosphorus Compound-Degrading Burkholderia zhejiangensis Strain CEIB S4-3

ABSTRACT Burkholderia species are widely distributed in the environment. A Burkholderia zhejiangensis strain was isolated from pesticide-contaminated soil from an agricultural field in Mexico and identified as an organophosphorus compound-degrading bacterium. In this study, we report the draft genome sequence of Burkholderia zhejiangensis strain CEIB S4-3.

Enhancing methyl parathion degradation by the immobilization of Burkholderia sp. isolated from agricultural soils

Organophosphate pesticides are of great interest for research because they are currently the most commonly used pesticides. In this study, a bacterial strain capable of completely degrading methyl parathion (MP) was isolated from agricultural soils in central Mexico. This strain was designated strain S5‐2 and was identified as Burkholderia cenocepacia. To increase degradation yields, cells were immobilized on three different supports: powdered zeolite and Opuntia sp. and Agave sp. fibers. The results indicated a significant increase in MP hydrolysis and p‐nitrophenol (PNP) degradation with immobilized cells compared to free cell cultures. Furthermore, immobilized cells were capable of withstanding and degrading higher concentrations of PNP compared to cell suspension cultures. The cell viability in the free cell cultures, as well as PNP degradation, was affected at concentrations greater than 25 mg/L. In contrast, cells immobilized on Opuntia sp. and Agave sp. fibers completely degraded PNP at concentrations of 100 mg/L. To verify that MP solution toxicity was decreased by B. cenocepacia strain S5‐2 via pesticide degradation, we measured the acetylcholinesterase activity, both before and after treatment with bacteria. The results demonstrate that the activity of acetylcholinesterase was unaffected after MP degradation by bacteria.

Burkholderia cenocepacia Strain CEIB S5-1, a Rhizosphere-Inhabiting Bacterium with Potential in Bioremediation

ABSTRACT Burkholderia cenocepacia is considered an opportunistic pathogen from humans and may cause disease in plants. A bioprospection from a plaguicide-contaminated agricultural field in Mexico identified several methyl parathion-degrading bacteria. Here, we report the draft genome sequence of B. cenocepacia strain CEIB S5-1, which gave us clues into ecological biodiversity.

Greenhouse gas emissions in the state of Morelos, Mexico: A first approximation for establishing mitigation strategies

In this study, the authors report the first greenhouse gas emission inventory of Morelos, a state in central Mexico, in which the emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) have been identified using the Intergovernmental Panel on Climate Change (IPCC) methodology. Greenhouse gas (GHG) emissions were estimated as CO2 equivalents (CO2 eq) for the years 2005, 2007, and 2009, with 2005 being treated as the base year. The percentage contributions from each category to the CO2 eq emissions in the base year were as follows: 38% from energy, 30% from industrial processes, 23% from waste, 5% from agriculture, and 4% from land use/land use change and forestry (LULUCF). As observed in other state inventories in Mexico, road transportation is the main source of CO2 emissions, wastewater handling and solid waste disposal are the main sources of CH4 emissions, and agricultural soils are the source of the most significant N2O emissions. The information reported in this inventory identifies the main emission sources. Based on these results, the government can propose public policies specifically designed for the state of Morelos to establish GHG mitigation strategies in the near future. Implications: In this paper, the emissions of greenhouse gases that are generated in the state of Morelos in central Mexico were calculated. The authors calculated carbon dioxide, methane, and nitrous oxide gases emitted from the categories energy, waste, industrial processes, agriculture, and LULUCF. These emissions correspond to 1.24% of the total issued nationwide. These first results will be the basis for mitigation and adaptation strategies against climate change, as well as for establishing public policies in the study area.

Response of Zea mays to multimetal contaminated soils: a multibiomarker approach

Heavy metals present in mine tailings pollute agroecosystems, put the integrity of the environment at risk and become a major route of exposure to humans. The present study was carried out in Taxco, Guerrero, Mexico, where millions of tons of mine tailings have been deposited. Soils from this region are used for agricultural activities. Maize (Zea mays) was selected as a test plant, because it is one of the most common and important cereal crops in Mexico and worldwide. Thirteen metals were selected and their bioaccumulation in roots, leaves and fruits were measured in plants cultivated in soils contaminated with mine tailings and those cultivated in non-contaminated soils. The effect of metal bioaccumulation on: macro and micromorphology, size, biomass, coloration leaf patterns and on DNA damage levels in different structures were determined. The bioaccumulation pattern was: root > leaf > fruit, being only Mn and Cr bioaccumulated in all three structures and V in the roots and leaves. A significant effect of metal bioaccumulation on 50% of the size and leaf shape and 55% of the biomass characters in Z. mays exposed plants was detected. Regarding micromorphological characters, a significant effect of metal bioaccumulation on 67% of the leaf characters and on 100% of the color basal leaf characters was noted. The effect of metal bioaccumulation on the induction of DNA damage (leaf > fruit > root) was detected employing single cell gel electrophoresis analysis. An approach, in which multi endpoints are used is necessary to estimate the extent of the detrimental effects of metal pollution on agroecosystem integrity contaminated with mine tailings.

Draft Genome Sequence of Burkholderia cenocepacia Strain CEIB S5-2, a Methyl Parathion- and p-Nitrophenol-Degrading Bacterium, Isolated from Agricultural Soils in Morelos, Mexico

ABSTRACT Burkholderia cenocepacia is an opportunistic pathogen that belongs to Burkholderia cepacia complex (BCC). Burkholderia cenocepacia strain CEIB S5-2 was isolated from agricultural soils in Morelos, Mexico, and previously has shown its abilities for bioremediation. In this study, we report the draft genome sequence of Burkholderia cenocepacia strain CEIB S5-2.