Background: Members of the genus Rhodococcus are frequently found in soil and other natural environments and are highly resistant to stresses common in those environments. The accumulation of storage compounds permits cells to survive and metabolically adapt during fluctuating environmental conditions. The purpose of this study was to perform a genome-wide bioinformatic analysis of key genes encoding metabolism of diverse storage compounds by Rhodococcus jostii RHA1 and to examine its ability to synthesize and accumulate triacylglycerols (TAG), wax esters, polyhydroxyalkanoates (PHA), glycogen and polyphosphate (PolyP). Results: We identified in the RHA1 genome: 14 genes encoding putative wax ester synthase/acyl-CoA: diacylglycerol acyltransferase enzymes (WS/DGATs) likely involved in TAG and wax esters biosynthesis; a total of 54 genes coding for putative lipase/esterase enzymes possibly involved in TAG and wax ester degradation; 3 sets of genes encoding PHA synthases and PHA depolymerases; 6 genes encoding key enzymes for glycogen metabolism, one gene coding for a putative polyphosphate kinase and 3 putative exopolyphosphatase genes. Where possible, key amino acid residues in the above proteins (generally in active sites, effectors binding sites or substrate binding sites) were identified in order to support gene identification. RHA1 cells grown under N-limiting conditions, accumulated TAG as the main storage compounds plus wax esters, PHA (with 3-hydroxybutyrate and 3-hydroxyvalerate monomers), glycogen and PolyP. Rhodococcus members were previously known to accumulate TAG, wax esters, PHAs and polyP, but this is the first report of glycogen accumulation in this genus.

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SUMMARY:The fish processing operations in Patagonia produce large amounts of waste. The main fishery resource in Argentina is the Argentine hake (Merluccius hubbsi). The ports of the province of Chubut (the most important of which are Puerto Madryn, Rawson and Comodoro Rivadavia), together with Caleta Paula Port (province of Santa Cruz), in the Argentine Patagonia, capture more than 82,000 tons of hake annualy, 80% of which are of M. hubbsi, which is mostly converted into fillets. From this capture, about 2,296 tons of liver would be available for the extraction of oil. To promote the recovery and industrial use of fish oil, in the present study, we determined the variation in the proximate composition and fatty acid profile of Argentine hake waste from the ports mentioned above at different catch times. Proximate composition was determined according of the Official Methods of Analysis (AOAC). Fatty acid profile was analyzed by gas chromatography of the fatty acid methyl esters (FAMEs). A standard mixture of FAMEs was run under identical conditions to identify the compounds on the basis of their retention times. Fatty acids were quantified using heptadecanoic acid (C17:0) as internal standard. The highest lipid recovery (27.0 to 41.8% of total lipids) was obtained from the liver fraction. Palmitic acid (C16:0), oleic acid (18:1 n9), docosahexaenoic acid (22:6 n3), eicosapentaenoic acid (20:5 n3) and palmitoleic acid (16:1) were the main constituents. Protein levels in viscera without livers (V-L) were higher than those in the liver. The extraction of marine fish oil and the production of fish offal meal from waste from fish factories would contribute to the sustainability of the regional industry, because it would also decrease the volume of waste, with benefits to the environment. KEYWORDS: Liver oil; Merluccius hubbsi; Proximate compositionRESUMEN: Variación en la composición proximal y perfil de ácidos grasos recuperados a partir de residuos del procesamiento de merluza argentina (Merluccius hubbsi) en Patagonia. El procesamiento de pescados en Patagonia produce gran cantidad de residuos. El recurso de pesca más importante en la Argentina es la merluza argentina (Merluccius hubbsi). En Patagonia, los puertos de la provincia del Chubut (de los cuales los más importantes son Puerto Madryn, Rawson y Comodoro Rivadavia), y Caleta Paula (provincia de Santa Cruz), capturan más de 82.000 t anuales de merluza, de las cuales el 80% corresponden a M. hubbsi. La misma es en su mayoría convertida en filetes. De esta captura, aproximadamente 2.296 toneladas de hígados estarían disponibles para la extracción de aceites. Para promover la recuperación y el uso industrial del aceite de pescado, se ha determinado la variación en la composición proximal de los residuos y el perfil de ácidos grasos de híga-dos de merluza argentina capturada en diferentes épocas en los puertos mencionados arriba. La variación en composición proximal fue determinada según la metodología propuesta por los Official Methods of Analysis (AOAC). El per...

Resumen: Contenido de nutrientes de especies leñosas en la estepa patagónica, Argentina. Las plantas leñosas constituyen una reserva vital de alimentos para herbívoros que habitan la estepa patagónica. Estudios preliminares mostraron alto contenido en materia soluble en éter (FAT) en varias de ellas. Para conocer si la baja disponibilidad de nitrógeno de los suelos conduce a una baja calidad de forraje y si el alto contenido en FAT se corresponde con una alta cantidad de ácidos grasos (FA), se analizaron parámetros químicos de calidad del forraje de partes aéreas de trece especies nativas patagónicas. Las plantas mostraron un contenido en proteínas crudo (CP) moderado a bajo. Independientemente de su contenido en FAT, todas las muestras presentaron aproximadamente el mismo contenido en FA totales con un promedio del 1% en materia seca. El mayor contenido en CP fue en las partes aéreas de Atriplex lampa (13%), Atriplex sagittifolia (10%), Adesmia salamancensis (10%) y en las semillas de Retanilla patagonica (22%). Este parámetro y los valores de digestibilidad (DMD) definen a estas cuatro especies como las de mejor calidad forrajera. A excepción de A. lampa y Berberis microphylla, las cuales han sido previamente estudiadas en otras regiones de Argentina, éste constituye el primer reporte sobre calidad nutricional de partes aéreas de especies leñosas patagónicas. Palabras clave: Ácidos grasos, análisis proximal, plantas leñosas.Summary: Woody plants constitute a vital food reserve for the herbivores inhabiting the Patagonian steppe. In a preliminary study, some of these plants showed a high content of ether extract (FAT). To determine whether the low availability of nitrogen in soils leads to low forage quality and whether a high FAT content correlates with a high amount of nutritive lipids, namely fatty acids (FA), chemical parameters of forage quality of aerial parts of thirteen woody plants from this steppe were analyzed. Plants showed moderate or low crude protein (CP) content, and, independently of the FAT content, all samples had approximately the same total content of FA (TFA), with an average of 1% of dry matter. The highest CP content was found in aerial parts of Atriplex lampa (13%), Atriplex sagittifolia (10%), Adesmia salamancensis (10%) and seeds of Retanilla patagonica (22%). This parameter and the values of digestibility (DMD) defined these four species as those with best forage quality. Except for A. lampa and Berberis microphylla, which have been previously studied in other regions of Argentina, this is the first report on the nutritional quality of woody species from the Patagonian steppe.