RESUMEN
Despite the importance of nitrous oxide (N2O) in the global radiative balance and atmospheric ozone chemistry, its sources and sinks within the Earth's system are still poorly understood. In the ocean, N2O is produced by microbiological processes such as nitrification and partial denitrification, which account for about a third of global emissions. Conversely, complete denitrification (the dissimilative reduction of N2O to N2) under suboxic/anoxic conditions is the only known pathway accountable for N2O consumption in the ocean. In this work, it is demonstrated that the biological assimilation of N2O could be a significant pathway capable of directly transforming this gas into particulate organic nitrogen (PON). N2O is shown to be biologically fixed within the subtropical and tropical waters of the eastern South Pacific Ocean, under a wide range of oceanographic conditions and at rates ranging from 2 pmol N L(-1) d(-) to 14.8 nmol N L(-1) d(-1) (mean ± SE of 0.522 ± 1.06 nmol N L(-1) d(-1), n = 93). Additional assays revealed that cultured cyanobacterial strains of Trichodesmium (H-9 and IMS 101), and Crocosphaera (W-8501) have the capacity to directly fix N2O under laboratory conditions; suggesting that marine photoautotrophic diazotrophs could be using N2O as a substrate. This metabolic capacity however was absent in Synechococcus (RCC 1029). The findings presented here indicate that assimilative N2O fixation takes place under extreme environmental conditions (i.e., light, nutrient, oxygen) where both autotrophic (including cyanobacteria) and heterotrophic microbes appear to be involved. This process could provide a globally significant sink for atmospheric N2O which in turn affects the oceanic N2O inventory and may also represent a yet unexplored global oceanic source of fixed N.
Asunto(s)
Fijación del Nitrógeno , Óxido Nitroso/metabolismo , Synechococcus/metabolismo , Organismos Acuáticos/metabolismo , Chile , Cianobacterias/metabolismo , Cinética , Nitrificación , Oxígeno/metabolismo , Océano Pacífico , PerúRESUMEN
Se expone el estudio realizado con un panel entrenado, cuya finalidad fue determinar si las modificaciones que ocurren en la etapa de almacenamiento de pollos faenados, causan diferencias organolépticas significativas, detectables por el consumidor. Los productos correspondían a pollos faenados en tres fechas consecutivas, almacenados a 20-C hasta el momento de su evaluación. Se investigaron aspectos de calidad en el producto crudo por test numérico como sigue: para color (amplitud 3), apariencia general (amplitud 5), y para presencia de defectos (amplitud 5), representando la calidad óptima, 13 puntos. Los juicios se analizaron por varianza y test de Duncan. Para estimar cambios de sabor se usó paralelamente el test triangular en carne grasa y magra. Estadísticamente, se estableció homogeneidad del conjunto de juicios en cuanto a los dos tipos de carne (P = 0.05). Los resultados obtenidos indican que a nivel de 0.1% dos productos eran idénticos y uno diferente, cuya calidad era significativamente superior al nivel del 5%. El grado de diferencia, de leve a moderado, se debió al sabor