de Campos Samanta Bolzan, Roesch Luiz Fernando Wurdig, Zanettini Maria Helena Bodanese, Passaglia Luciane Maria Pereira
Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, CP, Brazil.
Curr Microbiol. 2006 Jul;53(1):43-7. doi: 10.1007/s00284-005-0191-y. Epub 2006 Jun 6.
In this work, we further analyzed an Azospirillum brasilense Sp7 mutant (Sp7::Tn5-33) showing a pleiotrophic phenotype due to a Tn5 insertion into an open reading frame of 840 bp (orf280). The deduced amino acid sequence of this region has high similarity to a family of universal stress proteins. Because the most interesting property exhibited by the Sp7::Tn5-33 mutant was an enhanced in vitro nitrogen fixation activity, we addressed the question of whether it could benefit the host plant. We found that the increased nitrogenase activity at the free-living state of the mutant bacterium was correlated with an increased production of the nitrogenase reductase protein (NifH), in amounts approximately 1.5 times higher than the wild type. The mutant strain exhibited the same level of auxin production and the same colonization pattern of wheat roots as the wild type. We also observed that Sp7::Tn5-33 increased the total plant dry weight, although the N content did not differ significantly between wheat plants inoculated with mutant or wild-type strains.
在这项研究中，我们进一步分析了巴西固氮螺菌Sp7突变体（Sp7::Tn5-33），该突变体由于Tn5插入到一个840 bp的开放阅读框（orf280）中而表现出多效性表型。该区域推导的氨基酸序列与一类通用应激蛋白家族具有高度相似性。由于Sp7::Tn5-33突变体表现出的最有趣特性是体外固氮活性增强，我们探讨了它是否能使宿主植物受益这一问题。我们发现，突变细菌自由生活状态下增加的固氮酶活性与固氮酶还原蛋白（NifH）产量的增加相关，其产量比野生型高约1.5倍。突变菌株与野生型表现出相同水平的生长素产生和相同的小麦根定殖模式。我们还观察到，尽管接种突变体或野生型菌株的小麦植株之间的氮含量没有显著差异，但Sp7::Tn5-33增加了植株的总干重。
