Biosynthesis of selenium-containing small molecules in diverse microorganisms.

Selenium is an essential micronutrient in diverse organisms. Two routes are known for its insertion into proteins and nucleic acids, via selenocysteine and 2-selenouridine, respectively1. However, despite its importance, pathways for specific incorporation of selenium into small molecules have remained elusive. Here we use a genome-mining strategy in various microorganisms to uncover a widespread three-gene cluster that encodes a dedicated pathway for producing selenoneine, the selenium analogue of the multifunctional molecule ergothioneine2,3. We elucidate the reactions of all three proteins and uncover two novel selenium-carbon bond-forming enzymes and the biosynthetic pathway for production of a selenosugar, which is an unexpected intermediate en route to the final product. Our findings expand the scope of biological selenium utilization, suggest that the selenometabolome is more diverse than previously thought, and set the stage for the discovery of other selenium-containing natural products.

Efecto de nutrientes sobre la producción de biomasa del hongo medicinal Ganoderma lucidum / Effect of nutrients in the biomass production of the medicinal mushroom Ganoderma lucidum

El hongo Ganoderma lucidum, en los constituyentes de su biomasa, tiene compuestos con propiedades benéficas para la salud; es por esto que el conocimiento de las condiciones nutricionales adecuadas para su crecimiento permitirá su producción industrial y a bajo costo. En este trabajo se evaluó a nivel de matraz el efecto de la relación C/N, y la presencia de diferentes fuentes de carbono, nitrógeno y micronutrientes sobre la producción de biomasa. Empleando glucosa y peptona como fuentes de carbono y nitrógeno, respectivamente, se encontró una relación C/N óptima de 16,7:1 para la cual la máxima producción de biomasa fue de 25 g/L. Manteniendo esta relación C/N, y sustituyendo la glucosa por lactosa o harina de cebada y la peptona por extracto de levadura, la producción de biomasa se incrementó a 35 g/L. En presencia de harina de cebada la adición al medio de cultivo de sales de Mg y K, y de tiamina, no generó un mayor incremento en la producción de biomasa. La producción de biomasa de G. lucidum se ve favorecida por la presencia en el medio de cultivo de relaciones C/N cercanas a las reportadas conforme a la composición típica de los hongos, así como por la presencia de sustratos complejos como la harina de cebada que le aportan además de la fuente de carbono micronutrientes necesarios para su desarrollo.

Ganoderma lucidum fungus has some biomass components with beneficial health properties. The knowledge about its nutritionals requirements for growing will favor its industrial production at lower cost. In this work, the effect of C/N ratio, the presence of different carbon, nitrogen and micronutrients sources, on fungal biomass production, were evaluated. Using glucose and peptone as carbon and nitrogen sources, respectively, an optimal C/N ratio of 16,7:1 was found, for which the maximal biomass production was 25 g/L. Replacing glucose by lactose or barley flour and peptone by yeast extract at the same C/N ratio, the biomass production was enhanced to 35 g/L. With barley flour in the culture medium, the presence of Mg and K salts and thiamine did not turn out into a major increase of biomass. The G. lucidum biomass production is promoted by C/N ratios in the culture medium nearly equivalent to that found in the fungus, as well as the presence of complex substrates as barley flour which, additionally, contributes with important micronutrients along with the carbon source.

Effects of Zn rates and application forms on protein and some micronutrients accumulation in common bean (Phaseolus vulgaris L.).

In order to investigation the effects of Zn rates and application forms on protein and element contents (Fe, Cu, Mn, N and Zn) in bean plant, an experiment was conducted as a factorial based on completely randomized design at greenhouse conditions during 2006. Treatments were included zinc rates in 4 levels (10, 20, 30 and 40 mg Zn kg(-1) soil(-1) in ZnSO4 source) and 3 application forms (soil application, seed pelleting and foliar spraying). Results showed that Zn rates had significant effect on accumulation of Zn, Cu, Mn and N in bean leaves. Nitrogen accumulation in leaves reduced with increasing of zinc in the soil. Among Zn application forms, spray application had the highest accumulation of Fe, Zn and Mn in leaves (423.17, 282.89 and 88.17 mg kg(-1), respectively). The highest Zn content in seed was observed in 20 and 40 mg Zn kg(-1) soil(-1) levels (46.39 and 45.62 mg kg(-1), respectively). Meanwhile, all treatments of Zn (both rate and application) had not significant effects on Cu and Mn accumulation in bean seeds. According to interaction effects between Zn rates and application forms, the highest Fe content in seed was observed when 40 mg kg(-1) soil(-1) of Zn was applied as foliar spraying. The seed protein content nearly was stable while Zn levels was increased from 20 to 40 mg Zn kg(-1) soil(-1). Grain yield had significant correlation to zinc and Cu of leaves but, biomass had significant and negative correlation to Zn content of leaves at p < 0.05% probability levels.