Microorganisms drive the biogeochemical cycling of elements on Earth. Despite their importance and large diversity involved in specific processes, studies are usually restricted to a small fraction of the microbiota that can be isolated and cultivated. Little is known about the microorganisms that act on the carbon cycle in soils under tropical environment, known as methanotrophs. These organisms participate in the oxidation of methane (CH4), playing an important role in controlling the emission of greenhouse gas into the atmosphere.Amazonian Dark Earth (ADE) is important ecosystem in the Amazonian region and contains organic amendments, such as charcoal (biochar), that were incorporated into ADE in pre-Columbian times. This has resulted in soils prized for their sustained fertility. ADE soils exhibit approximately three times more organic matter, 70 times more biochar and higher microbial diversity compared to their adjacent soils. Therefore, functional diversity analysis in ADE can provide information on how adaptive microorganisms may influence the fertility of soils and their involvement in the C-biogeochemical cycle. It is believed that the structure and function of microbial communities within these soils, with emphasis on charcoal microsite, present different composition of adjacent soil with mineral origin, with possibility of occurrence of specific taxa with highly functional activities. Methane-oxidizing bacteria (methanotrophs) in this ecosystem may serve as a methane filter and limit methane emissions. Yet little is known about the diversity and identity of the methanotrophs present in TPA. A stable isotope probing (SIP) approach will be used to study aerobic methane-oxidizing bacteria (methanotrophs) in ADE and its charcoal. 16S rRNA and the pmoA gene, which encodes a subunit of the methane monooxygenase enzyme, will be analyzed following the incubation of ADE with 13CH4 and the separation of 13C-labelled DNA and RNA from unlabeled nucleic acids.
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