Analysis of a bacterial community structure and the diversity of phzF gene in samples of the Amazonian Dark Earths cultivated with cowpea [Vigna unguiculata (L.) Wald]

It is important to understand the Amazonian Dark Earth (ADE) diversified microbial communities which colonize agricultural soils and interact with plants, allowing a more sustainable way of soil utilization. Genomic prospection of biotechnological interest, such as the phenazine biosynthesis genes, was carried out by the characterization of the bacterial community structure through the analysis of the 16S rRNA gene in ADE rhizospheric and bulk soil sampled in the forest, and in the agriculture managed soil, being subsequently cultivated with caupi bean. Additionally, the phzF gene coding for a key enzyme in the phenazine biosynthesis was detected and quantified. Gene polymophism (Terminal Restriction Fragment Length Polymorphism, T-RFLP) analysis revealed differences in the bacterial community structure between colonized rhizospheric and bulk soil, but there were no differences concerning the 16S rRNA gene copy number. Besides, the phzF gene copy number was higher in the rhizospheric than in the bulk soil, without any difference between forest and agricultural soils. This work confirms that the type of soil and the interaction between plants and microorganisms are key factors that shape the structure and diversity of bacterial communities and represent a biotechnological potential, with the possibility of finding natural compounds for use in biological control. Key words: Amazonian Dark Earth, rhizosphere, quantitative polymerase chain reaction (PCR), terminal restriction fragment length polymorphism (T-RFLP), microbial diversity.