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Molecular characterization of nitrogen-fixing bacteria isolated from brazilian agricultural plants at São Paulo state Caracterização molecular de bactérias fixadoras de nitrogênio isoladas de plantas brasileiras no estado de São Paulo

By Érica. L. Reinhardt, Patrícia L. Ramos, Gilson P. Manfio, Heloiza R. Barbosa, Crodowaldo Pavan and Carlos A. Moreira-Filho

Abstract

Fourteen strains of nitrogen-fixing bacteria were isolated from different agricultural plant species, including cassava, maize and sugarcane, using nitrogen-deprived selective isolation conditions. Ability to fix nitrogen was verified by the acetylene reduction assay. All potentially nitrogen-fixing strains tested showed positive hybridization signals with a nifH probe derived from Azospirillum brasilense. The strains were characterized by RAPD, ARDRA and 16S rDNA sequence analysis. RAPD analyses revealed 8 unique genotypes, the remaining 6 strains clustered into 3 RAPD groups, suggesting a clonal origin. ARDRA and 16S rDNA sequence analyses allowed the assignment of 13 strains to known groups of nitrogen-fixing bacteria, including organisms from the genera Azospirillum, Herbaspirillum, Pseudomonas and Enterobacteriaceae. Two strains were classified as Stenotrophomonas ssp. Molecular identification results from 16S rDNA analyses were also corroborated by morphological and biochemical data.<br>Quatorze linhagens de bactérias fixadoras de nitrogênio foram isoladas de diferentes espécies de plantas, incluindo cassava, milho e cana-de-açúcar, usando condições seletivas desprovidas de nitrogênio. A capacidade de fixar nitrogênio foi verificada por ensaio de redução de acetileno. Todas as linhagens fixadoras de nitrogênio testadas apresentaram hibridização positiva com sonda de gene nifH derivada de Azospirillum brasilense. As linhagens foram caracterizadas por RAPD, ARDRA e sequenciamento do gene 16S rDNA. As análises de RAPD revelaram 8 genótipos, as 6 linhagens restantes foram agrupadas em 3 grupos de RAPD, sugerindo uma origem clonal. ARDRA e seqüências de 16S rDNA foram alocadas em 13 grupos conhecidos de bactérias fixadoras de nitrogênio, incluindo organismos dos gêneros Azospirillum, Herbaspirillum, Pseudomonas e Enterobacteriaceae. Duas linhagens foram classificadas como Stenotrophomonas ssp. Os resultados da identificação molecular baseados em sequencias de 16S rDNA corroboram com dados obtidos em testes morfológicos e bioquímicos

Topics: bactéria endofítica, diazotróficas, isolamento seletivo, sistemática molecular, endophytic bacteria, diazotrophs, selective isolation, molecular systematics, Microbiology, QR1-502, Science, Q, DOAJ:Microbiology, DOAJ:Biology, DOAJ:Biology and Life Sciences
Publisher: Sociedade Brasileira de Microbiologia
Year: 2008
DOI identifier: 10.1590/S1517-83822008000300002
OAI identifier: oai:doaj.org/article:08a8c32a95f945a289d56b604706b547
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