RESUMO

The marine archaeon Methanosarcina acetivorans contains a putative NAD + -independent d-lactate dehydrogenase (D-iLDH/glycolate oxidase) encoded by the MA4631 gene, belonging to the FAD-oxidase C superfamily. Nucleotide sequences similar to MA4631 gene, were identified in other methanogens and Firmicutes with >90 and 35-40% identity, respectively. Therefore, the lactate metabolism in M. acetivorans is reported here. Cells subjected to intermittent pulses of oxygen (air-adapted; AA-Ma cells) consumed lactate only in combination with acetate, increasing methane production and biomass yield. In AA-Ma cells incubated with d-lactate plus [14C]-l-lactate, the radioactive label was found in methane, CO2 and glycogen, indicating that lactate metabolism fed both methanogenesis and gluconeogenesis. Moreover, d-lactate oxidation was coupled to O2-consumption which was sensitive to HQNO; also, AA-Ma cells showed high transcript levels of gene dld and those encoding subunits A (MA1006) and B (MA1007) of a putative cytochrome bd quinol oxidase, compared to anaerobic control cells. An E. coli mutant deficient in dld complemented with the MA4631 gene, grew with d-lactate as carbon source and showed membrane-bound d-lactate:quinone oxidoreductase activity. The product of the MA4631 gene is a FAD-containing monomer showing activity of iLDH with preference to d-lactate. The results suggested that air adapted M. acetivorans is able to co-metabolize lactate and acetate with associated oxygen consumption by triggering the transcription and synthesis of the D-iLDH and a putative cytochrome bd: methanophenazine (quinol) oxidoreductase. Biomass generation and O2 consumption, suggest a potentially new oxygen detoxification mechanism coupled to energy conservation in this methanogen.

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RESUMO

Corn and common bean have been cultivated together in Mesoamerica for thousands of years in an intercropping system called "milpa," where the roots are intermingled, favoring the exchange of their microbiota, including symbionts such as rhizobia. In this work, we studied the genomic expression of Rhizobium phaseoli Ch24-10 (by RNA-seq) after a 2-h treatment in the presence of root exudates of maize and bean grown in monoculture and milpa system under hydroponic conditions. In bean exudates, rhizobial genes for nodulation and degradation of aromatic compounds were induced; while in maize, a response of genes for degradation of mucilage and ferulic acid was observed, as well as those for the transport of sugars, dicarboxylic acids and iron. Ch24-10 transcriptomes in milpa resembled those of beans because they both showed high expression of nodulation genes; some genes that were expressed in corn exudates were also induced by the intercropping system, especially those for the degradation of ferulic acid and pectin. Beans grown in milpa system formed nitrogen-fixing nodules similar to monocultured beans; therefore, the presence of maize did not interfere with Rhizobium-bean symbiosis. Genes for the metabolism of sugars and amino acids, flavonoid and phytoalexin tolerance, and a T3SS were expressed in both monocultures and milpa system, which reveals the adaptive capacity of rhizobia to colonize both legumes and cereals. Transcriptional fusions of the putA gene, which participates in proline metabolism, and of a gene encoding a polygalacturonase were used to validate their participation in plant-microbe interactions. We determined the enzymatic activity of carbonic anhydrase whose gene was also overexpressed in response to root exudates.

RESUMO

The European continent is inhabited by medically important venomous Viperinae snakes. Vipera ammodytes, Vipera berus, and Vipera aspis cause the greatest public health problems in Europe, but there are other equally significant snakes in specific regions of the continent. Immunotherapy is indicated for patients with systemic envenoming, of which there are approximately 4000 annual cases in Europe, and was suggested as an indication for young children and pregnant women, even if they do not have systemic symptoms. In the present study, the safety and venom-neutralizing efficacy of Inoserp Europe-a new F(ab')2 polyvalent antivenom, designed to treat envenoming by snakes in the Eurasian region-were evaluated. In accordance with World Health Organization recommendations, several quality control parameters were applied to evaluate the safety of this antivenom. The venom-neutralizing efficacy of the antivenom was evaluated in mice and the results showed it had appropriate neutralizing potency against the venoms of several species of Vipera, Montivipera, and Macrovipera. Paraspecificity of the antivenom was demonstrated as well, since it neutralized venoms of species not included in the immunization schemes and contains satisfactory levels of total proteins and F(ab')2 fragment concentration. Therefore, this new polyvalent antivenom could be effective in the treatment of snake envenoming in Europe, including Western Russia and Turkey.

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RESUMO

Se evaluaron los dos métodos para la determinación de nitritos, que solicita la normatividad mexicana, en alimentos infantiles cárnicos con verduras. Se determinó el contenido de nitritos a los alimentos infantiles, materias primas y productos intermedios del proceso de elaboración; en cada corrida analítica se incluyeron un blanco de reactivos y una muestra testigo; además se determinó la sensibilidad, porcentaje de recuperación y precisión de las metodologías. Los resultados en los alimentos infantiles indicaron una importante diferencia en los contenidos de nitritos obtenidos entre las metodologías, debido a la persistente presencia de turbidez en los extractos. Se propusieron diferentes tratamientos físicos para eliminarla, pero únicamente la redujeron; tal turbidez se atribuyó a los hidratos de carbono; las concentraciones de nitritos informadas presentaron una dispersión grande y estuvieron por debajo del límite de cuantificación de ambos métodos, por lo que no es recomendable la aplicación de estas técnicas para alimentos que se sospechan contienen trazas de nitritos.

Evaluation of the methods for the determination of nitrites in baby foods according Mexican legislation. We evaluated the two methods accepted by the Mexican norm for the determination of nitritesin infant meatbased food with vegetables. We determined the content of nitrites in the infant food, raw materials as well as products from the intermediate stages of production. A reagent blank and a reference sample were included at each analytical run. In addition, we determined the sensitivity, recovery percentage and accuracy of each methodology. Infant food results indicated an important difference in the nitrite content determined under each methodology, due to the persistent presence of turbidity in the extracts. Different treatments were proposed to eliminate the turbidity, but these only managed to reduce it. The turbidity was attributed to carbohydrates which disclosed concentration exhibit a wide dispersion and were below the quantifiable limit under both methodologies; therefore it is not recommended to apply these techniques with food suspected to contain traces of nitrites.

Assuntos

RESUMO

We evaluated the two methods accepted by the Mexican norm for the determination of nitritesin infant meat-based food with vegetables. We determined the content of nitrites in the infant food, raw materials as well as products from the intermediate stages of production. A reagent blank and a reference sample were included at each analytical run. In addition, we determined the sensitivity, recovery percentage and accuracy of each methodology. Infant food results indicated an important difference in the nitrite content determined under each methodology, due to the persistent presence of turbidity in the extracts. Different treatments were proposed to eliminate the turbidity, but these only managed to reduce it. The turbidity was attributed to carbohydrates which disclosed concentration exhibit a wide dispersion and were below the quantifiable limit under both methodologies; therefore it is not recommended to apply these techniques with food suspected to contain traces of nitrites.

Assuntos