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| Author(s): |
Mariana Gomes Germano Silva
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Centro de Energia Nuclear na Agricultura (CENA/STB) |
| Defense date: | 2011-06-17 |
| Examining board members: |
Tsai Siu Mui;
Marli de Fatima Fiore;
Eliana Gertrudes Macedo Lemos;
Gabriel Padilla Maldonado;
Rodrigo Mendes
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| Advisor: | Tsai Siu Mui |
| Abstract | |
Antropogenic Dark Earth or Amazonian Dark Earth soils (ADE) represents one of the most important records of pre-Colombian settlements in Brazilian Amazon region, commonly located along rivers and interfluves. One of the main factors responsible for the singular features of these soils is the presence of high amounts of pirogenic black carbon or biochar, consisting of approximately 35% along anthropogenic surface. The presence of stable organic matter and biological activity are indicative that ADE soils may be hotspots of microbial diversity. The management of organic matter with the aim of conserving and improving soil quality is critical to nutrient cycling and maintenance of sustainable tropical agroecosystems. In this context, the biodegradation processes govern most of the carbon biogeochemical cycle, which quite depends on microbial enzymes such as dioxygenases, which use organic compounds in soil as carbon source and energy. The characterization and isolation of potentially degrader bacteria from ADE soils can generate indicative data of the biological quality of these soils, as well as provide information of the genetic diversity of these microorganisms. Likewise, studies involving diversity of catabolic genes may facilitate the understanding of the role of functional microorganisms present in black carbon in the balance of the fertility of ADE soils, besides the evaluation of their influence on biological communities in these soils. This study assessed the diversity of bacterial communities associated with degradation processes of aromatic compounds in ADE soils and black carbon in Central Amazon through cultivation and molecular techniques. The samples were collected in Caldeirão Experimental Station (Embrapa-CPAA) under secondary forest and manioc culture, along with Costa do Açutuba, Hatahara and Balbina sites. These TPI sites are characterized by distinct ages of occupation by pre-Colombian populations, ranging from 1,200 years ago (Caldeirão sites) to more than 2,000 years, such Costa do Açutuba site. The isolates obtained from enrichment showed great diversity of species and genera, widely described as potentially degraders of a wide range of aromatic substrates, both natural and xenobiotic. The clone libraries containing functional genes showed that the microbial diversity in black carbon was often greater in relation to soil ADE. The vast majority of clusters generated by pyrosequencing (98%) grouped dioxygenases sequences obtained solely in this study. The abundance of catabolic genes was determined by quantitative PCR. The results of this study showed great diversity of genes associated with C cycling, not previously reported in Amazonian anthropogenic soils, proving the essential role of functional microbial communities supporting the fertility of ADE soils (AU) | |