Although new studies describe the use of PGPR (Plant Growth-Promoting Rhizobacteria) in Brazil, they rarely evaluate the natural existence of these bacterial species in the soil. The objective of this study was to evaluate PGPR in two samples under different use types, one with native forest and the other with eucalyptus, through construction and sequencing of a metagenomic DNA library. Using specific probes from the internally transcribed region of 16S-23S rRNA genes, fragments of PCR products were inserted into the vector and cloned. The library generated 495 clones, which were sequenced and identified using Blast software. A greater number of PGPR was found in the soil under eucalyptus than under forest. Actinobacteria and Proteobacteria phyla were more abundant in Eucalyptus sp soil, and the phylum Firmicutes was not found in forest soil. Only eight different species were detected: Bacillus subtilis, Bacillus megaterium, Bradyrhizobium japonicum, Bradyrhizobium elkanii, Bradyrhizobium sp., Frankia sp., Pseudomonas fluorescens and Pseudomonas gladioli. This study provided valuable information about PGPR in soils under forest species and their possible used in reforestation, as well as for a more detailed understanding of these microorganisms in Brazilian soils.
PGPR; microbial ecology; Eucalyptus sp.; ITS
