Microbial diversity in the phyllosfhere and soil of the Atlantic Forest

Abstract

In a previous work, we have observed that the phyllosphere of different plant species select for distinct bacterial communities, and that each phyllosphere may harbor a substantial number of unknown bacterial species. Our estimates point to 2 to 13 million of new bacterial species only in the canopy of the Atlantic Forest In another work developed in a 10 ha permanent plot at the Carlos Botelho State Park, we have observed that the bacterial communities in the phylIosphere of plants phylogeneticalIy cIoser were more similar to each other than in the phyllosphere of plants phylogeneticalIy more distant. Also relevant is the fact that even considering the spatial variability of the bacterial community structure in the phyllosphere of plants of the same species at different geographical positions, such variation is smaller than that observed among individuals of different species. Our data suggest that the bacterial populations in the phyllosphere are select by the plant species, and that each plant species harbor a unique bacterial community in its phyllosphere. The analyses of the bacterial community associated to the bark of the same plant species reveled low bacterial species richness, with dominance of few genera, as compared to the phylIosphere, and community structures defined by the plant species as well. In contrast, the soil under the canopy of the tree species sampled showed bacterial communities with higher species richness, as compared to phylIosphere and bark, with lower spatial variability and less dependency on the plant species. In general, our data points to a new paradigm in microbial ecology: the microbial diversity associated to the plant surfaces may be as high as the diversity in the soil, considered the environment with the highest microbial diversity known. Understanding the functional roles of these microorganisms in the phyIIosphere and soil of the Atlantic Forest is not a trivial task, even though the advances in the analytical techniques have significantly contributed for that Hence, establishing a relationship between phylogeny and metabolic function is crucial for determining which microbial groups are essential for ecosystem sustainability, in particular for the C and N cycles. In the proposed project, we aim to evaluate the bacterial and fungi diversity in the phylIosphere and soil, respectively, in four 10 ha permanent plots of the Biota program, at Parque Estadual da Ilha do Cardoso (High Restinga Forest), Parque Estadual de Carlos Botelho (Dense Ombrophylous Forest) e Estação Ecológica de Assis (Cerradão), and their possible relationships with biochemical processes relevant for the functionality of forest ecosystems, using metaproteomics. In addition, we aim to quantify the biological nitrogen fixation and the diversity of diazothrophs in 1 ha permanent plots of a Dense Ombrophylous Forest at the Serra do Mar State Park. (AU)