Purification and PCR amplification procedures for DNA extracted from environmental samples (soil, compost, and river sediment) were improved by introducing three modifications: precipitation of DNA with 5% polyethylene glycol 8000 (PEG) and 0.6 M NaCl; filtration with a Sepharose 4B-polyvinylpolypyrrolidone (PVPP) spin column; and addition of skim milk (0.3% w/v) to the PCR reaction solution. Humic substances' concentration after precipitation with 5% PEG was 2.57-, 5.3-, and 78.9-fold lower than precipitation with 7.5% PEG, 10% PEG, and isopropanol, respectively. After PEG precipitation, Sepharose, PVPP and the combined (Sepharose-PVPP) column removed 92.3%, 89.5%, and 98%, respectively, of the remaining humic materials. Each of the above-mentioned modifications improved PCR amplification of the 16S rRNA gene. DNA extracted by the proposed protocol is cleaner than DNA extracted by a commercial kit. Nevertheless, the improvement of DNA purification did not improve the detection limit of atrazine degradation gene atzA.

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The following study evaluated the diversity and biogeography of 83 new atrazine-degrading bacteria and the composition of their atrazine degradation genes. These strains were isolated from 13 agricultural soils and grouped according to rep-PCR genomic fingerprinting into 11 major clusters, which showed biogeographic patterns. Three clusters (54 strains) belonged to the genus Arthrobacter, seven clusters (28 strains) were similar to the genus Nocardioides and only one strain was a gram-negative from the genus Ancylobacter. PCR assays for the detection of the genes atzA, B, C, D, E, F and trzN conducted with each of the 83 strains revealed that 82 strains (all gram positive) possessed trzN, 74 of them possessed the combination of trzN, atzB and atzC, while only the gram-negative strain had atzA. A similar PCR assay for the two analogous genes, atzA and trzN, responsible for the first step of atrazine degradation, was performed with DNA extracted directly from the enrichment cultures and microcosms spiked with atrazine. In these assays, the gene trzN was detected in each culture, while atzA was detected in only six out of 13 soils. These results raise an interesting hypothesis on the evolutionary ecology of the two atrazine chlorohydrolase genes (i.e. atzA and trzN) and about the biogeography of atrazine-degrading bacteria.

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We studied the mineralization and sorption of 14 C-glyphosate in samples of three soil types from El Espinal municipality (Tolima) with different land use history: (1) soil subjected to pesticide use and sowing of annual crops (mainly rice) during 30 years; (2) soil in rest for five years with sown grassland, and (3) secondary semidry forest soil without record of pesticide use. The 14 C-glyphosate mineralization in the soil samples was effected in biometers. One hundred and six days after the incubation with the herbicide, 53%, 38% and 23% of the glyphosate was mineralized in the forest, grass and rice-crop soil samples, respectively. The glyphosate sorption phenomenon (adsorption-desorption) was adjusted to the Freundlich model. The Kd des values for forest, grassland and rice-crop soil samples were 17.00, 1.83 and 3.10, respectively. The low rate of glyphosate mineralization allowed us to infer that the glyphosate can become an environmental pollution problem due to its high persistence in the soil.Key words: Herbicides, microorganisms, radiomarked, pollution, rice. Mineralización y adsorción del 14 C-glifosato en muestras de tres tipos de suelo provenientes de El Espinal, Colombia ResumenSe estudió la adsorción y la mineralización de 14 C-glifosato en muestras de tres tipos de suelo provenientes del municipio de El Espinal, Tolima, con diferente historia de uso: (1) un suelo con historia de uso de pesticidas durante 30 años y cultivos anuales (principalmente arroz); (2) un suelo en receso de 5 años con pasto de corte, y (3) un suelo de bosque secundario semiseco sin registro de uso de plaguicidas. La mineralización del 14 C-glifosato en los suelos se efectuó en biómetros. A los 106 días de la incubación con el herbicida, 53 %, 38 % y 23 % del glifosato estaba mineralizado en los suelos de bosque, de pasto de corte y cultivo de arroz, respectivamente. El fenómeno de adsorción del glifosato (adsorción-desorción) se ajustó al modelo de Freundlich. Los valores Kd des para los suelos de bosque, pasto de corte y cultivo de arroz fueron 17,00, 1,83 y 3,10, respectivamente. La baja tasa de mineralización del glifosato permite inferir que este puede convertirse en un problema de contaminación del medio ambiente debido a su alta persistencia en el suelo.

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The aim of the present study was to develop an alternative method to the traditional curing process using water vapour permeable bags to obtain a dry-cured pork loin product. The dry-cured pork loins obtained by this mew process showed an adequate hygienic quality and good sensory acceptance. The salting-curing process using water permeable bags requires less manipulation, reduces waste generation and allows greater control during processing. This technique could be an interesting alternative to the traditional processes, improving the hygienic quality of the products and minimizing the environmental impact.