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Cyanobacteria of biological soil crusts from Brazilian dry tropical forest (caatinga) and southern grasslands (Pampa): metagenomics, taxonomic characterization and relationships with physical and chemical parameters


Studies focusing composition and structure of biological soil crusts (BSCs, biocrusts) occurring in Brazilian territory are still at early stage. In a previous project, our team evaluate the cyanobacterial composition of BSCs from savannah (cerrado) areas at southeastern Brazil using traditional (direct observation and isolation in culture) and new generation sequencing (NGS) approaches. Results reveal a very particular composition for each studied locality with several unrecognized records of taxonomic entities, suggesting the existence of a reasonable number of unknown taxa. In a co-authored work with researchers of Arizona State University, we observed deep differences in taxonomic composition of cyanobacterial assemblages between crusts from Brazilian savannah and from North American desert evaluated by the same methods. These indicatives point to an important role of the environment in determining the structure of biological crusts. Thus, the present proposal aims to advance in the studies of this biological component, which plays important ecological roles in the areas where it occurs, increasing the knowledge of part of its composition and structure and searching for possible relations of occurrence with the environmental determinants. The project proposes to focus on BSCs occurring in two other national biomes: the caatinga and the southern fields (or pampa). In these two types of environments, the crust establishment conditions are favorable, although they are shaped by different ways. In caatinga areas, scarce rainfall and little water retained in the little weathered soils result in the occurrence of a poorly developed and sparsely distributed arboreal-shrub vegetation, which favors the establishment of BSCs. In southern fields areas, although there is no restriction of humidity, the presence of fragile and relatively poor soils, the occurrence of strong and constant winds and the low temperatures limit the occurrence of larger vegetation and, consequently, make the existence of biological crusts possible. The expected results will allow to compare the biota found in the different studied environments and to characterize the occurrence of the different species and assemblages according to environmental parameters. Fieldwork will be carried out in the region of the city of Cabaceiras (Paraíba State), chosen as the representative of caatinga biome, and in the region of the city of Alegrete (Rio Grande do Sul State), area of occurrence of the pampa biome. In each area, two sampling sites will be selected, looking for distinct conditions within the range of occurrence of each biome (e.g., drier vs. wetter site or associated vegetation with different characteristics between two sites). The crusts will be collected, according to the standard methodology, along transects of 200 m, where 10 samples will be collected at each site. Soil portions will also be collected for the analysis of physical and chemical parameters, such as granulometry, total nitrogen and fractions, total phosphorus, orthophosphate, organic matter and pH. Temperature, relative humidity and irradiance will be measured directly in the field. Morphological analyzes will be performed for the populations of cyanobacteria found directly on the crusts or from isolates in culture. Molecular analyzes will be conducted in two ways. In the first, DNA extraction and amplification and sequencing of the molecular marker (16S rRNA gene) will be done from cultured material. In the second, we will conduct massive sequencing through NGS technology. The results generated by the second analysis, besides the compositional information of the assemblages, will allow the investigation of possible relationships between cyanobacteria distribution and environmental factors. (AU)

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
MACHADO DE LIMA, NATHALI MARIA; MUNOZ-ROJAS, MIRIAM; VAZQUEZ-CAMPOS, XABIER; ZANINI BRANCO, LUIS HENRIQUE. Biocrust cyanobacterial composition, diversity, and environmental drivers in two contrasting climatic regions in Brazil. Geoderma, v. 386, . (17/11126-6)
MACHADO DE LIMA, NATHALI MARIA; BRANCO, LUIS H. Z.. Biological soil crusts: new genera and species of Cyanobacteria from Brazilian semi-arid regions. PHYTOTAXA, v. 470, n. 4, p. 263-281, . (17/11126-6)

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