Dynamics,Diversity and Function of Endophytic Siderophore-Producing Bacteria in Rice |
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Authors: | Inés Loaces Lucía Ferrando Ana Fernández Scavino |
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Institution: | 1.Cátedra de Microbiología, Facultad de Química y Facultad de Ciencias,Universidad de la República,Montevideo,Uruguay |
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Abstract: | Siderophore production confers to bacteria competitive advantages to colonize plant tissues and to exclude other microorganisms
from the same ecological niche. This work shows that the community of endophytic siderophore-producing bacteria (SPB) associated
to Oryza sativa cultivated in Uruguayan soils is dynamic and diverse. These bacteria were present in grains, roots, and leaves, and their
density fluctuated between log10 3.44 and log10 5.52 cfu g−1 fresh weight (fw) during the plant growth. Less than 10% of the heterotrophic bacteria produced siderophores in roots and
leaves of young plants, but most of the heterotrophic bacteria were siderophore-producers in mature plants. According to their
amplified restriction DNA ribosomal analysis (ARDRA) pattern, 54 of the 109 endophytic SPB isolated from different plant tissues
or growth stages from replicate plots, were unique. Bacteria belonging to the genera Sphingomonas, Pseudomonas, Burkholderia, and Enterobacter alternated during plant growth, but the genus Pantoea was predominant in roots at tillering and in leaves at subsequent stages. Pantoea ananatis was the SPB permanently associated to any of the plant tissues, but the genetic diversity within this species—revealed by
BOX-PCR fingerprinting- showed that different strains were randomly distributed along time and plant tissue, suggesting that
a common trait of the species P. ananatis determined the interaction with the rice plant. Several isolates were stronger IAA producers than Azospirillum brasilense or Herbaspirillum seropedicae. In vitro inhibition assays showed that SPB of the genus Burkholderia were good antagonists of pathogenic fungi and that only one SPB isolate of the genus Pseudomonas was able to inhibit A. brasilense and H. seropedicae. These results denoted that SPB were selected into the rice plant. P. ananatis was the permanent and dominant associated species which was unable to inhibit two of the relevant plant growth-promoting
bacteria. |
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