Among the PGPB, the genus Azospirillum—with an emphasis on A. brasilense—is likely the most studied microorganism for mitigation of plant stress. Here, we report the investigation of functional mutants HM053, ipdC and FP10 of A. brasilense to understand how the biological functions of these microorganisms can affect host Zn uptake. HM053 is a Nif⁺ constitutively expressed strain that hyper-fixes N₂ and produces high levels of the plant’s relevant hormone auxin. FP10 is a Nif^- strain deficient in N₂-fixation. ipdC is a strain that is deficient in auxin production but fixes N₂. Zn uptake was measured in laboratory-based studies of 3-week-old plants using radioactive ⁶⁵Zn²⁺ (t_½ 244 days). Principal Component Analysis was applied to draw out correlations between microbial functions and host ⁶⁵Zn²⁺ accumulation. Additionally, statistical correlations were made to our prior data on plant uptake of radioactive ⁵⁹Fe³⁺ and ⁵⁹Fe²⁺. These correlations showed that low microbial auxin-producing capacity resulted in the greatest accumulation of ⁶⁵Zn. Just the opposite effect was noted for ⁵⁹Fe where high microbial auxin-producing capacity resulted in the greatest accumulation of that tracer.

中文翻译：

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促进植物生长的细菌可影响玉米中锌的吸收：使用巴西偶氮螺旋菌功能突变体的作用机理研究

在PGPB中，假单胞菌属（Azospirillum）（重点是巴西曲霉）可能是研究最多的缓解植物胁迫的微生物。在这里，我们报告调查功能突变体HM053，ipdC和A. brasilense的FP10，以了解这些微生物的生物学功能如何影响宿主对锌的吸收。HM053是Nif ⁺组成型表达的菌株，可高度固定N ₂并产生高水平的植物相关激素生长素。FP10是硝苯地平^-在N-应变缺陷₂ -fixation。ipdC是一种生长素缺乏的菌株，但可以固定N₂。在3周龄植物的实验室研究中，使用放射性⁶⁵ Zn ²⁺（_t½244天）测量了锌的吸收。应用主成分分析法得出微生物功能与宿主⁶⁵ Zn ²⁺积累之间的相关性。另外，与我们先前关于植物吸收放射性⁵⁹ Fe ³⁺和⁵⁹ Fe ^2+的数据进行了统计相关性。这些相关性表明，低的微生物生长素生产能力导致⁶⁵ Zn的最大积累。注意到相反的效果是⁵⁹高微生物生长素生产能力的铁导致该示踪剂的最大积累。