Intein-mediated expression of cecropin in escherichia coli

Different strategies have been used to overcome the difficulties to produce antimicrobial peptides. Here we used Intein Mediated Purification with an Affinity Chitin-binding Tag (IMPACT-System, New England Biolabs) for the expression of the antimicrobial peptide cecropin to reduce its sensitivity to intracellular proteases and use its inducible self-cleaving capability to remove the carrier. Cecropin was cloned into suitable expression vector pTYB11, and expression induced by IPTG in Escherichia coli ER2566. The use of 22ºC induction allowed the expression of cecropin with its intein carrier in soluble form. Cell extracts were purified by chitin affinity chromatography and intein-mediated splicing of the target protein was achieved by thiol addition, obtaining a final yield of 2.5 mg cecropin/l. Cecropin cleaved from the intein had its proper biologically active form, showing a micromolar antimicrobial activity against Vibrio ordalii, Vibrio alginolyticus and Escherichia coli.

Design and expression of a retro doublet of cecropin with enhanced activity

Novel doublet molecules of cecropin A from Drosophila melanogaster were designed and constructed combining the regular (CECdir) with the inverted (CECret) coding sequence of the standard CEC A1 gene resulting in the following configurations: CECdir-CECret and CECret-CECdir. These two recombinant molecules were generated using a three-primer driven PCR reaction yielding composite single functional aminoacidic molecules with the coding sequences of CECdir linked in frame with the coding sequence of CECret and vice versa. In order to obtain these constructions, a retropeptide DNA-coding sequence was chemically synthesized to match the expected polarity of the newly generated CECret sequence. Both doublet antimicrobial peptides (drAMPs) were cloned in the T7 promoter driven expression plasmid pET27b+ and expressed in E. coli BL21 without any fusion protein. Only the former recombinant peptide was expressed and purified from cell extracts and its specific activity against two different bacteria showed to be higher than those displayed by their monomer parental counterparts.

Protective effect of an antimicrobial peptide from Mytilus edulis chilensis expressed in Nicotiana tabacum L

A "defensin-like" antibacterial peptide from Mytilus edulis chilensis, was sub-cloned into a binary vector for expression in plant tissues. The resulting new clone was electroporated into A. tumefaciens to transform tobacco plants. The presence of the construct in transgenic tobacco lines was demonstrated through RT-PCR, Northern and Western blots. Transformed positive plants were selected and grown for challenging. Tobacco leaves were infiltrated with Pseudomonassyringae pv. syringae and visual lesions determined at different times post-exposure. Of seven plants exposed, four gave variable protection up to seven days post-infection while one of them appears to be fully protected. These results suggest that defensin-like antimicrobial peptides from molluscs are a good source to provide resistance of tobacco plants to Pseudomonassyringae pv. syringae.

Gill tissues of the mussel Mytilus edulis chilensis: a new source for antimicrobial peptides

Antimicrobial peptides are small-sized, cationic and amphipathic molecules able to neutralize pathogenic microorganisms. Their antimicrobial effects tie them to mechanisms of immune defense, which is why they have been normally purified from immune cells. We describe an apparently new group of antimicrobial peptides from gill tissues of the mussel Mytilus edulis chilensis. 20 specimens yielded 40 g of gills which produced 16 mg of an enriched fraction with antimicrobial activity as low as 0.045 µg/µl over reference strains. Considering the chemical nature of these molecules we used an acid extraction procedure followed by consecutive cationic exchange and hydrophobic interaction chromatography steps for peptide enrichment. The resulting post Sep-pak C-18® 20 percent acetonitrile (ACN) eluate was fractionated by reverse phase HPLC and all resulting fractions were the source for in vitro antimicrobial activity evaluation. Active fractions were characterized by SDS-containing protein gel electrophoresis. All fractions were particularly enriched with low molecular weight peptides displaying neutralizing growth activity against Gram positive and Gram negative bacteria and 10 times more efficient over fungal pathogens. Active fractions resulted to be thermostable and non cytotoxic to eukaryotic cells. Considering these results, industrial waste gills of bivalves arise as a new source for antimicrobial molecules.

La enfermería en Colombia y la reforma del sector salud / Nursing in Colombia and the health reform

Se analiza la práctica de la enfermería en Colombia por medio de una investigación cualitativa que busca comprender el valor social del cuidado de enfermería. la información se obtuvo mediante entrevistas a profesionales y auxiliares que trabajaban en instituciones de salud con mayor desarrollo en el proceso de implementación de la reforma. Se expone la experiencia d enfermería desde la subjetividad de los actores entrevistados frente a lo que hacen, lo que saben, las cosas que hacen y el contexto en que trabajan. La naturaleza del estudio no permite generalizaciones, pero sí identifica tendencias de la práctica de la enfermería. Se constató que las condiciones de trabajo son precarias: existe distanciamiento del cuidador profesional con el sujeto de atención, idealización de roles, dilemas éticos, vacíos conceptuales para precisar la esencia de su quehacer, sufrimiento psíquico y burocratización de los servicios. Constituye un estudio de caso dentro de un trabajo multicéntrico orientado por la OPS realizado en Argentina, Colombia, Brasil, México y Estados Unidos donde se estudia, además, la regulación y la educación en enfermería.