Microbial communities in boron soils from Salta

MORAGA, NORMA; RAJAL, VERONICA; CRUZ, MERCEDES CECILIA; WUERTZ, STEFAN

Congreso; XIII Congreso Argentino de Microbiologia General; 2018

SAMIGE

Salta Province, in the northwest of Argentina, is the main worldwide producer of hydroboracite and leads in exports of boron mineral and its derivatives in Latin America. This intense industrial development has an important environmental impact on water and soils. In addition to the natural presence of boron in flat-salts and riverbanks, there are others contaminated soils caused by boron mining industry, proximate to urbanized areas.Here we report the microbial community assembly of soils, natural and anthropogenically contaminated with boron, using next-generation sequencing techniques. We collected soils from three sites: 1) Tincalayu, one of the main deposit extraction flat salts; 2) Animaná, a riverbank with natural boron compounds; 3) Baradero, an urban burden from a former processing factory. Three samples were collected from each site, two exposed to high boron concentration and one control. Soil physicochemical analysis included humidity, organic matter, pH, B2O3, and total boron. We used the 16S ribosomal RNA gene, targeting the V4-V5 hypervariable region, and following the QIIME pipeline with SILVA database, we obtained the meta-barcoded microbial profiling. Multivariate statistical analyses were used to assess the microbial community and its relationships with environmental data.Microbial community analysis showed variability of richness and α-diversity indices among samples. Taxonomic classification revealed that, at the phylum level, Actinobacteria was the most abundant in the natural boron-soil samples from Tincalayu and Animaná (43.5% ± 2.5 and 27.9% ± 3.4, respectively). Meanwhile, Firmicutes was predominant in Baradero-soils (20.5 to 55.7%) and had very low relative abundance in the flat-salt soils (2.6% ± 1.1). Proteobacteria was the third most abundant phylum (17.0% of total) with higher numbers in Animaná (25.7% ± 8.5) and similar abundance in Tincalayu and Baradero (12.9% ± 9.2 and 11.4% ± 6.4, respectively). The genus level analysis revealed that Bacillus sp. was the highest taxonomic group in Baradero and Animana. On the other side, an uncultured bacteria of order Gaiellales (Thermoleophilia class) was the most abundant OTU within Actinobacteria in Tincalayu. DistLM-dbRDA analysis indicated that edaphic properties: pH, humidity, and B2O3 concentration shape the microbial assemblies. Microbial community ordination analysis by means of Hierarchical Clustering and nMDS plots showed that exposed-samples from Tincalayu and Baradero formed two distinctive groups (natural vs anthropogenic contaminated soil), and all samples from Animaná grouped together with the control samples from the other two sites.To the best of our knowledge, this is the first study showing microbial communities of boron associated soils in Argentina. It provides a better understanding of soil-borne microbiome assemblies and valuable information for contaminated sites management.