Abstract
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.
Highlights
Soil bacterial communities carry genes with yet unknown functions that could possibly be important concerning biotechnological applications
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 Amazonian Dark Earth (ADE) rhizospheric and bulk soil sampled in the forest, and in the agriculture managed soil, being subsequently cultivated with caupi bean
The gene copy number of the bacterial 16S rRNA in the forest soil determined by qPCR was 3.85×109 copies/g of soil in rhizospheric soils and 3.94×109 copies/g of soil in 372±42.9a 4.3±0.57b 0.73±0.057b 158±16.7a
Summary
Soil bacterial communities carry genes with yet unknown functions that could possibly be important concerning biotechnological applications. Molecular techniques make possible to identify and characterize these microorganisms, functional bacterial communities associated to plants In this way, the Amazonian Dark Earth, known as Amazonian Black Soil or “Terra Preta” (ADE), de Souza et al. Represents a kind of soil that is colonized by bacterial communities with potential biotechnological contribution (Lehmann et al, 2003; Lima et al, 2002) These soils are characterized by a dark coloration due to the high charcoal concentration, originated from traditional burnings, utilized by the Amazonian ancient populations. It is found in diverse sites in the amazon biome, exhibiting elevated pH values, fertility and microbiological diversity (Navarrete et al, 2010). The detection of secondary compounds in the environment produced by prokaryotic cells has been increasing in face of the improvement of molecular tools that make possible their application in biocontrol of plant pathogens in commercial crops
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