ANDREOTE, F. D.

KAVAMURA, V. N.

MELO, I. S. de

SANTOS, S. N.

TAKETANI, R. G.

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(P4.14 Bulk and rhizosphere bacterial communities of the Caatinga vegetation: ~~\'drought effects 'IV.N. Kovamuro'", S.N. Santos':', F.D. Andreote', R.G. Taketan/ and /.5. Mel021 Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Piracicaba, SP, Brasil2 Laboratório de Microbiologia Ambiental - Embrapa Meio Ambiente, Jaguariúna, SP, BrasilCorresponding mail: VanessaNessnerKavamura.vannessner@yahoo.com.brThe semi-arid climate of Brazilian Northeast is characterized by low precipitation, hightemperatures and a typical vegetation called Caatinga. It presents plants such as cacti that havedeveloped adaptive structures to this environment. Bacteria have also evolved some mechanismsto live along with these plants. There are few studies about microorganisms inhabiting theCaatinga biome as well as microorganisms associated to the cacti. Cereus jamacaru, a typicalcactus from this biome, is commonly found and it maintains its characteristics ali over the year.Therefore, the aim of this study is to analyze the spatial distribution of soil and Cereus jamacarurhizosphere bacterial community using cultivation-independent approaches and to evaluate howdrought affects these organisms. Soil and cacti rhizosphere were collected from five samplingpoints throughout the Caatinga. Each of these samples had their DNA extracted and PCRamplifiedto obtain 165 rRNA gene fragments which were visualized by DGGE analysis. The DGGEfingerprints showed seasonal shifts for the non-rhizosphere soil samples, while for rhizospheresamples, it is not possible to observe such difference in band patterns, thus indicating a possibleadaptation from the rhizosphere communities to the rainy and dry season. For the rainy season,itis possible to see a greater variation of the different sampling points for rhizosphere samples thanfor bulk soil. On the other hand, for the dry season, that variation is not 50 clear, and the DGGEprofile seems to be more uniform. The difference observed in rainy season rhizosphere samplesmight be due to soil physical and chemical characteristics, which are important features that couldalso design the structure of soil communities. Further use of Principal Component Analysis (PCA)will allow the identification and correlation of bands with different soil types. Canonic CorrelationAnalysis (CCA) will enable the recognition of the main factors influencing bacterial communitycomposition. This work will provide a baseline for the understanding of soil and rhizospherebacterial community structure in Caatinga vegetation of semi-arid climate.194

Bulk and rhizosphere bacterial communities of the Caatinga vegetation: drought effects.

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