Department of Soil Science, Agriculture & Natural Resources Campus, Faculty of Agricultural Engineering & Technology, University of Tehran, Daneshkadeh Ave., Karaj, Tehran, 31587-77871, Iran.
Agriculture Biotechnology Research Institute of Iran (ABRII), Agriculture Research, Education and Extension Organization (AREEO), Karaj, Iran.
Int Microbiol. 2020 Aug;23(3):415-427. doi: 10.1007/s10123-019-00115-y. Epub 2020 Jan 2.
Saline area may tend to be a productive land; however, many of salt-affected soils have nitrogen limitation and depend on plant-associated diazotrophs as their source of 'new' nitrogen. Herein, a total of 316 salinity tolerant nitrogen-fixing endophytic bacteria were isolated from roots of the halophyte Suaeda sp. sampled from 22 different areas of Iran to prepare the collection of nitrogen-fixing bacterial endophytes and evaluate the plant growth-promoting effect of effective isolates on growth of the halophyte Suaeda maritima. All of the identified nitrogen-fixing endophytes were classified to Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes phylum while we did not detect common nitrogen-fixing endophyte of glycophytes like Azospirillum. The genera Pseudomonas and Microbacterium were both encountered in high abundance in all samples, indicating that they might play an advanced role in the micro-ecosystem of the halophyte Suaeda. In addition, the results also showed that not only soil salinity can affect halophyte endophytic composition but also other factors such as geographical location, plant species, and other soil properties may be involved. Interestingly, only Zhihengliuella halotolerans and Brachybacterium sp. belonging to Actinobacteria could grow in semi-solid N-free (NFb) medium supplemented with 6% NaCl and highly enhanced growth of S. maritima in vitro. Overall, this study offers useful new resources for nitrogen-fixing endophytic bacteria which may be utilized to improve approaches for providing bio-fertilizer useful in saline-based agriculture.
盐渍地区可能倾向于成为生产力较高的土地；然而，许多盐渍土壤存在氮素限制，依赖于植物相关的固氮生物作为其“新”氮源。在此，从伊朗 22 个不同地区采集的盐生植物碱蓬根部分离出了 316 株耐盐固氮内生细菌，以制备固氮细菌内生菌集合，并评估有效分离株对盐生植物滨藜生长的促生作用。所有鉴定出的固氮内生菌均被分类为变形菌门、放线菌门、厚壁菌门和拟杆菌门，而我们没有检测到常见的盐生植物糖质植物的固氮内生菌，如固氮螺菌。假单胞菌属和微杆菌属在所有样本中都大量存在，表明它们可能在盐生植物滨藜的微生态系统中发挥着重要作用。此外，研究结果还表明，不仅土壤盐度会影响盐生植物内生菌的组成，地理位置、植物种类和其他土壤特性等其他因素也可能参与其中。有趣的是，只有耐盐 Zhihengliuella halotolerans 和属于放线菌的 Brachybacterium sp. 能够在添加 6%NaCl 的半固体无氮（NFb）培养基中生长，并在体外显著促进滨藜的生长。总的来说，本研究为固氮内生菌提供了有用的新资源，可用于改进提供基于盐的农业中有用的生物肥料的方法。
