RESUMO
Sugarcane is an economically important culture in Brazil. Endophytic bacteria live inside plants, and can provide many benefits to the plant host. We analyzed the bacterial diversity of sugarcane cultivar RB-72454 by cultivation-independent techniques. Total DNA from sugarcane stems from a commercial plantation located in Paraná State was extracted. Partial 16S rRNA genes were amplified and sequenced for library construction. Of 152 sequences obtained, 52% were similar to 16S rRNA from Pseudomonas sp, and 35.5% to Enterobacter sp. The genera Pantoea, Serratia, Citrobacter, and Klebsiella were also represented. The endophytic communities in these sugarcane samples were dominated by the families Enterobacteriaceae and Pseudomonadaceae (class Gammaproteobacteria).
Assuntos
Endófitos/genética , Enterobacteriaceae/genética , Pseudomonadaceae/genética , Saccharum/microbiologia , Técnicas de Cultura , Tipagem Molecular , Filogenia , RNA Bacteriano/genética , RNA Ribossômico 16S/genéticaRESUMO
Endophytic and epiphytic bacteria were isolated from two soybean cultivars (Foscarin and Cristalina). Significant differences were observed in bacterial population densities in relation to season of isolation, soybean growth phase and the tissues from which the isolates were obtained. The isolates were identified by partial 16S rDNA sequence analysis, with most of the isolates belonging to the Pseudomonaceae, Burkholderiacea and Enterobacteriaceae groups. The potential of the isolates for plant growth promotion was evaluated by screening for indoleacetic acid (IAA) production and mineral phosphate solubilization; 34% of endophytic bacteria produced IAA and 49% were able to solubilize mineral phosphate whereas only 21% of epiphytic bacteria produced IAA although 52% were able to solubilize mineral phosphate. A high frequency of IAA producing isolates occurred in the early ripening Foscarin cultivar whereas a high percentage of phosphate solubilizing isolates were obtained from plants in the initial development stage (V6). We also found that 60% of endophytic and 69% of epiphytic isolates that produced IAA and solubilized mineral phosphate were also able to fix nitrogen in vitro. The soybean-associated bacteria showing characteristics related to plant growth promotion were identified as belonging to the genera Pseudomonas, Ralstonia, Enterobacter, Pantoea and Acinetobacter.
Assuntos
Bactérias/classificação , Bactérias/metabolismo , Biodiversidade , Glycine max/crescimento & desenvolvimento , Glycine max/microbiologia , Ácidos Indolacéticos/metabolismo , Bactérias/genética , Bactérias/isolamento & purificação , Burkholderiaceae/classificação , Burkholderiaceae/genética , Burkholderiaceae/isolamento & purificação , DNA Bacteriano/química , DNA Bacteriano/isolamento & purificação , DNA Ribossômico/química , DNA Ribossômico/isolamento & purificação , Enterobacteriaceae/classificação , Enterobacteriaceae/genética , Enterobacteriaceae/isolamento & purificação , Microbiologia Ambiental , Genes de RNAr , Dados de Sequência Molecular , Fixação de Nitrogênio , Fosfatos/metabolismo , Filogenia , Pseudomonadaceae/classificação , Pseudomonadaceae/genética , Pseudomonadaceae/isolamento & purificação , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
Xylella fastidiosa strains are responsible for several plant diseases and since such isolates display a broad host range and complex biological behavior, genomic comparisons employing microarray hybridizations may provide an effective method to compare them. Thus, we performed a thorough validation of this type of approach using two recently sequenced strains of this phytopathogen. By matching microarray hybridization results to direct sequence comparisons, we were able to establish precise cutoff ratios for common and exclusive sequences, allowing the identification of exclusive genes involved in important biological traits. This validation will enable the use of microarray-based comparisons across a wide variety of microorganisms
Assuntos
Genoma Bacteriano , Doenças das Plantas/microbiologia , Pseudomonadaceae/genética , Hibridização de Ácido Nucleico , Análise de Sequência com Séries de Oligonucleotídeos , Fases de Leitura Aberta , Homologia de SequênciaRESUMO
Xylella fastidiosa is a fastidious, xylem-limited bacterium that causes a range of economically important plant diseases. Here we report the complete genome sequence of X. fastidiosa clone 9a5c, which causes citrus variegated chlorosis--a serious disease of orange trees. The genome comprises a 52.7% GC-rich 2,679,305-base-pair (bp) circular chromosome and two plasmids of 51,158 bp and 1,285 bp. We can assign putative functions to 47% of the 2,904 predicted coding regions. Efficient metabolic functions are predicted, with sugars as the principal energy and carbon source, supporting existence in the nutrient-poor xylem sap. The mechanisms associated with pathogenicity and virulence involve toxins, antibiotics and ion sequestration systems, as well as bacterium-bacterium and bacterium-host interactions mediated by a range of proteins. Orthologues of some of these proteins have only been identified in animal and human pathogens; their presence in X. fastidiosa indicates that the molecular basis for bacterial pathogenicity is both conserved and independent of host. At least 83 genes are bacteriophage-derived and include virulence-associated genes from other bacteria, providing direct evidence of phage-mediated horizontal gene transfer.
Assuntos
Genoma Bacteriano , Plantas/microbiologia , Pseudomonadaceae/genética , Análise de Sequência de DNA , Aderência Bacteriana , Proteínas de Bactérias/metabolismo , Transporte Biológico , Mapeamento Cromossômico , Citrus/microbiologia , Reparo do DNA , DNA Bacteriano , Metabolismo Energético , Dados de Sequência Molecular , Plantas Tóxicas , Biossíntese de Proteínas , Pseudomonadaceae/metabolismo , Pseudomonadaceae/patogenicidade , Nicotiana/microbiologia , Transcrição Gênica , Virulência/genéticaRESUMO
Data are presented which indicate that plasmid pRD1 can be transferred from Escherichia coli to strains of Azospirillum brasilense with a frequency of about 10(-7). The reverse was also possible; in this case the frequency of transfer appeared to be much higher, about 5 x 10(-1). Transfer of the plasmid was also obtained between strains of A. brasilense; in this cross the transfer frequency was very high (about 10(-1)). Moreover the pRD1 plasmid seems very stable in A. brasilense cells.