Cátedra de Microbiología, Facultad de Química y Facultad de Ciencias, Universidad de la República, Montevideo, Casilla de Correo, Uruguay.
Microb Ecol. 2011 Apr;61(3):606-18. doi: 10.1007/s00248-010-9780-9. Epub 2010 Dec 3.
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 log(10) 3.44 and log(10) 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.
铁载体生产使细菌具有在植物组织中定殖和排除同一生态位中其他微生物的竞争优势。本研究表明，与在乌拉圭土壤中种植的水稻相关的内生铁载体生产菌（SPB）群落是动态和多样的。这些细菌存在于谷物、根和叶中，其密度在植物生长过程中在 log(10) 3.44 到 log(10) 5.52 cfu g(-1) 新鲜重量（fw）之间波动。在幼株的根和叶中，不到 10%的异养菌产生铁载体，但在成熟植株中，大多数异养菌都是铁载体生产者。根据扩增限制性 DNA 核糖体分析（ARDRA）模式，从不同植物组织或不同重复样地的不同生长阶段分离的 109 株内生 SPB 中，有 54 株是独特的。在植物生长过程中，属 Sphingomonas、Pseudomonas、Burkholderia 和 Enterobacter 的细菌交替出现，但在分蘖期的根和后续阶段的叶中，属 Pantoea 占优势。Pantoea ananatis 是与任何植物组织都永久相关的 SPB，但通过 BOX-PCR 指纹分析揭示的该物种内的遗传多样性表明，不同的菌株是随机分布在时间和植物组织中的，这表明该物种 Pantoea ananatis 的一个共同特征决定了与水稻的相互作用。一些分离株比 Azospirillum brasilense 或 Herbaspirillum seropedicae 产生更强的 IAA。体外抑制试验表明，属 Burkholderia 的 SPB 是病原菌真菌的良好拮抗剂，而属 Pseudomonas 的只有一株 SPB 分离株能够抑制 A. brasilense 和 H. seropedicae。这些结果表明 SPB 是被选择进入水稻植株的。Pantoea ananatis 是永久和主要相关的物种，它不能抑制两种相关的植物促生菌。
