Metagenomic analysis of bacterial populations in soils from the depression area of the R¨ªo Salado

CALELLO E.; COLLAVINO MM; GRASSO DH; AGUILAR O.M

C¨®rdoba, Argentina

Congreso; VI Congreso argentino de microbiolog¨ªa general-SAMIGE; 2009

SAMIGE

Aiming to exploit the genetic potential of soils microorganisms from extreme environments to retrieve salinity tolerance genes, the diversity of saline soil was examined and soil metagenomic DNA was used. Since the estimated size of the cultivable bacterial population ranges between 0.1 and 1%, limited information about the population diversity is available. On the other hand, a metagenomic approach allows to access to knowledge of a broader range, and to be more representative of the microbial communities. In the first step of our study, the biodiversity of two different soils was assessed in soil samples that were collected from sites in the depression area of the R¨ªo Salado (Chascom¨²s, location CH1: S 35 28 12 3 W 58 02 19 6, 40 m height, CH2: S 35 33 11 5, W 57 58 59 3, 14 m height) and have different physical chemistries properties (CH1: elec. cond.: 0.46 mS/cm; pH 1:25 water 6,39; 1.83% organic carbon, 0.18% organic nitrogen, and CH2: elec. cond. 1.6 mS/cm; pH 1:25 water 9.93; 0.67% organic carbon; 0.10% organic nitrogen). Metagenomic DNA from both soil samples was extracted and used to amplify the 16S rRNA gene by using primers deduced from the division bacteria. A library was constructed using the PCR product and clones were randomly sequenced. The collected data was compared against RDP (Ribosomal Database Project II) and Genebank NCBI. Analysis at the level of class, revealed a major representation of Actinobacteria, whereas ¦Á-proteobacteria were represented to a lesser extent. The most represented genera in the library were Conexibacter, followed by Xiphinematobacteriaceae. Furthermore, DGGE (Denaturing Gradient Gel Electrophoresis) technique was used to separate the products of a nested amplification (the variable region of 16S rRNA gene) using bacterial primers, and primers specific for the genera Burkholderia. Different patterns were observed in the two different soils.In addition, some clones from a library constructed with the 16S rRNA PCR product using primers for the genera Arquea were sequenced and a phylogenetic tree was built. Taken these results altogether, we conclude that, microbial community in that environment were found to be represented by highly diverse microorganisms, interestingly most of them seems to be uncultured. Actinobacteria was the most represented genera, which were reported by other authors to be also detected in several environmental niches including those similar to our saline soil