ABSTRACT

Biological soil crusts (BSC) are commonly found in soils in the drylands regions, which can influence stabilization, water retention, nutrient cycling (particularly carbon (C) and nitrogen (N) dynamics), and several ecological processes. However, the composition of BSC in Brazilian soils undergoing the desertification process remains poorly understood. This study aimed to characterize the bacterial community in BSC formed in a Brazilian semiarid region under the desertification process. Thus, a highly desertified region was selected from which 34 BSC samples were collected. The total DNA of the BSC was extracted from 0.5 g samples, and the bacterial community was sequenced by a Next Generation Sequencing (NGS) platform (Miseq – Illumina®) using universal primers (515F and 806R). Bioinformatic analysis was carried out in QIIME (v.1.9), and the Operational Taxonomic Units (OTU) table was constructed following the Sumaclust methodology. The pH of BSC, C, N, and phosphorus contents was analyzed. Our study identified a diverse bacterial community in the BSCs. Cyanobacteria, Chloroflexi, and Proteobacteria phyla presented the greatest relative abundance (%) across the samples. Cyanobacteria were dominated by the orders Nostocales and Leptolyngbyales. The prediction of the putative functions found that mostf OTU were related to phototrophy, photosynthetic cyanobacteria, and photoautotrophy. The study found correlations between bacterial phyla and BSC properties, with Cyanobacteria positively related to C. Chloroflexi, Armatimonadetes, and WPS-2 were negatively correlated with C and N contents. These results suggest the critical roles bacteria communities play in BSCs from the Caatinga biome and highlight the potential impact of environmental factors on their diversity and functions.

Caatinga; cyanobacteria; drylands; microbial ecology; biofilms