Detecção quantitativa do gene phzf na biossíntese da fenazina em solos rizosféricos de terra preta da Amazônia

Abstract

The identification of natural antibiotics is of great importance to sustainable agriculture. The phenazine compounds found in the environment may be produced by several species of bacteria that usually are associated with biocontrol activity in plants against phytopathogenic soil organisms. The phenazine is synthesized in seven genes his operon, the gene phzF is a key gene for the production of several natural phenazine. However, there is no study of the frequency of the phenazine genes in rhizosphere of Amazon Dark Earth (ADE). This work was developed according to the proposed goals and split in two studies. In the first study, we evaluated the diversity of sequences and the number of copies of phzF biosynthetic genes in rhizosphere soils (with influence of the roots) and non-rhizosphere (bulk soil) of soybean [Glycine max (L.) Merrill]. For comparison, the number of copies of the 16S rRNA gene was also quantified. For this purpose, an experiment in controlled mesocosm was conducted, with ADE under two environmental conditions: secondary forest and pasture. DNA was extracted from the rhizosphere soil samples, and then subjected to high-throughput sequencing and quantification of the number of gene copies by quantitative PCR. The metagenomic sequences generated were analyzed on the MG-RAST server based on the protein database M5NR, considering sequences belonging to Bacteria Domain. The results indicated eleven taxonomic groups affiliated to phzF gene in soil samples. The qPCR indicated that the number of 16S rRNA and phzF genes was different for rhizosphere and non-rhizosphere soils, as well as for the environments of which were collected. The second study was accomplished to detect and estimate the number of bacterial 16S rRNA and phzF genes by quantitative PCR technique and also to characterize the bacterial community profile in soils under cultivation of cowpea [Vigna unguiculata (L.) Wald]. The quantitative PCR analysis set forth that number of genes was different in both soils. The profile of the bacterial communities of soil samples retrieved by the technique of Polymorphism size of Terminal Restriction Fragment (T-RFLP). It were observed, from the profiles generated by the more homogeneous subgroups analysis, significamemte differentiating structures of bacterial communities between the cowpea rhizosphere and non-rhizosphere soils (bulk).