Acidobacteria have been described as one of the most abundant and ubiquitous bacterial phyla in soil. However, factors contributing to this ecological success are not well elucidated mainly due to difficulties in bacterial isolation. Acidobacteria may be able to survive for long periods in soil due to protection provided by secreted extracellular polymeric substances that include exopolysaccharides (EPSs). Here we present the first study to characterize EPSs derived from two strains of Acidobacteria from subdivision 1 belonging to Granulicella sp. EPS are unique heteropolysaccharides containing mannose, glucose, galactose and xylose as major components, and are modified with carboxyl and methoxyl functional groups that we characterized by Fourier transform infrared (FTIR) spectroscopy. Both EPS compounds we identified can efficiently emulsify various oils (sunflower seed, diesel, and liquid paraffin) and hydrocarbons (toluene and hexane). Moreover, the emulsions are more thermostable over time than those of commercialized xanthan. Acidobacterial EPS can now be explored as a source of biopolymers that may be attractive and valuable for industrial applications due to their natural origin, sustainability, biodegradability and low toxicity.

RESUMOEstudos sobre a atividade microbiológica que ocorre na rizosfera de diversos vegetais levaram ao descobrimento de grupos de microrganismos importantes para o desenvolvimento vegetal. Dentre eles estão as rizobactérias que são capazes de colonizar as raízes, estimulando-a diretamente ou beneficiando o crescimento e o desenvolvimento de diversas plantas. Estas bactérias são chamadas Rizobactérias Promotoras de Crescimento em Plantas (RPCP). Este trabalho teve o objetivo de isolar, identificar, testar a capacidade da solubilização de fosfato e a produção de ácido indol acético (AIA) de bactérias que habitam a rizosfera de plantas de milho. A análise parcial do gene 16S rRNA dos 58 isolados possibilitou a identificação dos gêneros, Bacillus, Burkholderia e Azospirillum, sendo os mais frequentes totalizando 68% dos isolados, seguidos de Sphingomonas, Pseudomonas, Herbaspirillum, Pantoea , Bosea. Desses, 27 apresentaram a capacidade de solubilização do fosfato e 18 foram positivos no teste colorimétrico para detecção de produção do AIA. A partir destes resultados, selecionou-se um organismo pertencente ao gênero Sphingomonas para ser testado em casa de vegetação como promotor de crescimento com as estirpes de Azospirillum brasilense (AbV5 e AbV6). As plantas foram avaliadas quanto à altura aos vinte e setenta dias após a germinação e a massa seca da parte aérea (MSPA)e parte radicular (MSPR) foi quantificada após setenta dias no encerramento do experimento. Os resultados das análises do isolado pertencente ao gênero Sphingomonas foram estatisticamente semelhantes às estirpes AbV5 e AbV6 na planta de milho indicando que este microrganismo possui potencial para ser utilizado como RPCP. Palavras-chaves: RPCP, ácido indol acético, solubilização de fosfato, Sphingomonas spp. ABSTRACT IDENTIFICATION AND EVALUATION OF BACTERIA ISOLATED FROM ROOTS OF MAIZEResearches about microbiological activity on many plants rizosphere led to the discovery of groups of important microrganisms for plants development. Among them there are the rizobacteria able to colonize the roots, stimulating directly or benefiting many plants. These bacteria are called Growth Promoting Rizobacteria or GPR. In view of this, the present study was performed, aiming to isolate, identify and test phosphate solubilization and acetic indol acid (AIA) production in bacteria that lives in maize roots. The partial analysis of the 16S rRNA gene of the 58 isolates enabled the identification of the genres Bacillus, Burkholderia and Azospirillum, and the most frequent totaling 86% of the isolates, followed by Sphingomonas, Pseudomonas, Herbaspirillum, Pantoea and Bosea. Out of the 58 isolates, 27 showed the capacity of phosphate solubilization and 18 were positive to the AIA production colorimetric detection test. From these results was chosen an organism belonging to the genre Sphingomonas to be tested at greenhouse as growth promoter with the strains Azospirillum brasiliense (AbV5 e AbV6). The plants were assessed twenty and seventy days after germination. Dry ...

The members of subdivision 1 Acidobacterium were grown at different pH values in a new medium formulation named PSYL 5 includes sucrose, as a carbon source and other compounds (such as KHPO and MgSO7HO). Growth rate was nearly constant at pH 5 and declined at pH 3-4 and 6-7. However, it was found that the effects involving good C/N ratios and pH on the growth of members of subdivision 1 Acidobacterium were significant, and the strongest effect was given by this conditions at pH 5. In additional, incubation results of 48, 72, 96 and 120 h were relatively shorter as compared to other media earlier described for members of subdivision 1 of the phylum Acidobacteria on solid laboratory media.

Exopolysaccharide (EPS) are produced by a diverse of rhizobia species and has been demonstrated to be a bioemulsifier with potential applications in the degradation of hydrocarbons. In the present study, attempts were made to obtain the new exopolysaccharide production by Rhizobium tropici (SEMIA 4080 and MUTZC3) strains during growth on hydrocarbon substrate. Under the different cultivation conditions, the high molecular weight exopolysaccharides from Rhizobium tropici strains cultivated for 96h mainly consisted of carbohydrates (79-85%) and a low percentage of protein. The EPSC3-D differed from the others, with only 60% of carbohydrate. However, all strains produced polymers with distinct rheology properties, such as viscosity of each EPS sample, suitable for different applications. In addition, RP-HPLC, FTIR and NMR studies revealed EPS produced by rhizobia strains were similar indicating minimal difference between EPS compositions.

Xylella fastidiosa is the etiologic agent of diseases in a wide range of economically important crops including citrus variegated chlorosis, a major threat to the Brazilian citrus industry. The genomes of several strains of this phytopathogen have been completely sequenced enabling large-scale functional studies. In this work we used whole-genome DNA microarrays to investigate the transcription profile of X. fastidiosa grown in defined media with different glucose concentrations. Our analysis revealed that while transcripts related to fastidian gum production were unaffected, colicin-V-like and fimbria precursors were induced in high glucose medium. Based on these results, we suggest a model for colicin-defense mechanism in X. fastidiosa.