Dados do Trabalho

Título

MICROBIAL REACTIVE OXYGEN SPECIES AS OXIDIZING AGENT OF METALS AND ORGANIC MATTER IN RAINFOREST SOILS

Resumo

Redox cycles in temperate forest soils in southern Chile are influenced by high organic matter content (SOM), fine textures, and extensive rainfall. This causes cyclical fluctuations in dissolved oxygen content due to displacement generated by water saturation (biotic and abiotic cycles). In this context, reactive oxygen species (ROS) play an important role as biotic and abiotic catalysts in the oxidation of SOM and metal oxidation in the soil. However, the origin of ROS is associated with abiotic mechanisms such as water photolysis, anaerobic reactions (e.g. Fenton), and limited biotic sources (e.g. anaerobic decomposition fungi). Nonetheless, microbial ROS in oxic environments have not been attributed relevant functions in the soil. In this study we hypothesize that aerobic soil bacteria produce ROS as oxidation agents of SOM and redoximorphic metals [Fe(II) and Mn(II)] as a secondary mechanism to the oxidation mediated by oxidoreductase enzymes. The contribution to the oxidation of SOM, Fe and Mn by biotic (b) and abiotic (ab) ROS sources in soils from Tolhuaca (TNP) and Nahuelbuta (NNP) National Park were studied in microcosms incubations at 360h. ROS production in both groups was stimulated by the Haber-Weiss reaction using Xanthine-Xanthine oxidases (HB). A control (C) was included to determine the native levels. The stimulated-biotic group (bHB) showed a higher rate of CO2 efflux, as well as the content of oxidized Mn and Fe; followed by biotic control (bC), stimulated-abiotic group (abHB) and abiotic soil (abC). Hydrogen peroxide and hydroxyl radicals correlate with the content of oxidized Mn and Fe, and oxidized SOM. ATP production and respiratory rates correlate with endogenous ROS production in stimulated (bHB) and unstimulated (bC) soils, concluding that ROS is released by soil bacteria contributing to the oxidation processes of SOM, Fe/Mn redox cycles and microbial component in rainforest ecosystem.  

Instituição financiadora

FONDECYT 3200758 AND FONDECYT 11230807