Caracterização molecular da comunidade bacteriana associada à crosta biológica do solo no bioma Caatinga

Abstract

In recent years, many researchers have sought to identify and establish who are the main microscopic organisms present in soil biological crusts (CBS) around the world. Arid and semi-arid environments, such as the Caatinga biome, are the most favorable environment to the CBS formation, mainly due to the scarcity of vegetation cover, the incidence of direct light in the soil and the low levels of precipitation. However, studies on CBS in the Caatinga biome are poorly understood, even though this is proving to be a favorable environment for the development and establishment of CBS. Thus, our aim was to study the bacterial composition presents in CBS of the Caatinga biome inserted in the desertification nucleus of Irauçuba (CE). We collected CBS in grazed Caatinga areas. In order to compare the structure of the communities in different treatments, soil samples from three different soil treatments (i.e., native Caatinga vegetation, natural recovery and grazed) were also analyzed. The total DNA of the samples was extracted and, subsequently, the sequencing of the 16S rRNA gene was performed on the Illumina Miseq platform (primers 515F / 806R). The data were grouped into Operational Taxonomic Units (OTUs), which were classified taxonomically using the SILVA database (132) and QIIME (1.9) software. In CBS, the OTUs were attributed to the 38 phyla, 91 classes, 225 orders, 428 families and 879 bacterial genera. There was a higher abundance of the phylum Cyanobacteria, Proteobacteria and Planctomycetes in CBS, deferring to the other soil managements. The most abundant class and order in the CBS were Oxyphotobacteria and Nostocales, respectively. For the diversity indexes (Shannon and richness), the CBS show a lower value than the other treatments (except for grazed), showing the influence of environmental conditions and anthropic activity on their stability. Samples of CBS showed high taxa of shared OTUs with grazed Caatinga management, suggesting the participation of these soils in the formation of the bacterial community associated with CBS. Understanding the main components of the CBS of degraded areas in the Caatinga biome, as well as their respective role, can represent fundamental knowledge for the development of future research focusing on the recovery of degraded areas.