不动杆菌PSB-K解磷促生能力及全基因组测序分析

Phosphate-solublizing and plant growth-promoting effects and whole genome sequencing of Acinetobacter baumannii PSB-K

摘要:

【背景】土壤中的磷元素普遍以难溶性磷酸盐形式存在，限制了植物对其直接吸收利用。解磷细菌能够将环境中难溶性磷酸盐转化为植物可吸收利用的磷形态，对改善土壤磷素营养具有重要意义。【目的】分离并鉴定一株高效解磷细菌，探究其解磷能力、促生效果及相关基因，以期为解磷菌肥的研发提供优良的菌株资源及理论支持。【方法】从土壤中分离筛选具有明显解磷效果的解磷细菌，通过生理生化特性和分子生物学技术对其进行鉴定。通过透明圈法和钼锑抗比色法评估其解磷能力；通过单因素试验分析不同种类碳源、氮源及难溶性磷酸盐对菌株解磷效果的影响。进一步，通过二代测序平台对菌株进行全基因组测序，解析其基因组中与解磷及铁载体合成运输相关的基因组成情况。最后，通过水培试验验证该菌株对植物的促生作用。【结果】经鉴定，高效解磷细菌PSB-K为鲍曼不动杆菌(Acinetobacter baumannii)，其解磷指数达到2.58。在碳源为葡萄糖、氮源为硝酸钾和难溶性磷酸盐为磷酸三钙时，菌株展现出最佳解磷性能，发酵液中可溶性磷含量高达560.35 μg/mL。全基因组测序结果显示，菌株PSB-K基因组全长为3 983 883 bp，包含3 849个编码基因，其中涵盖了多种有机酸合成、磷酸盐转运及铁载体合成运输相关基因。水培试验结果表明，施加菌株PSB-K对油菜幼苗叶片面积、植株鲜重和根系长度具有显著的促生作用，最好的菌液浓度分别为2.50×10⁷、2.50×10⁷、1.25×10⁷ CFU/mL，分别较对照组提高了72.15%、72.08%、197.81%。【结论】菌株PSB-K表现出对多种难溶性磷酸盐均有溶解能力，并且其解磷性能受碳氮源种类显著影响。该菌株对油菜生长具有显著的促生作用，为微生物菌肥的开发提供了菌种资源。此外，全基因组数据为深入探究解磷菌的解磷机制及功能基因挖掘提供了重要参考。

Abstract:

[Background] Phosphorus in soil generally exists in the form of insoluble phosphate, which limits the direct absorption and utilization by plants. Phosphate-solubilizing bacteria can convert the insoluble phosphate in the environment into phosphorus that can be absorbed and utilized by plants. [Objective] To isolate and identify a highly efficient phosphate-solubilizing bacterial strain, and explore its phosphate-solubilizing capacity, plant growth-promoting effect, and related genes, so as to provide elite strain resources and theoretical support for the research and development of phosphate-solubilizing bacterial fertilizer. [Methods] The strain with significant phosphate-solubilizing effects was isolated from soil and identified based on physiological and biochemical characteristics as well as molecular evidence. The phosphate-solubilizing capability of the strain was determined by the transparent circle method and the Mo-Sb colorimetric method. Single-factor experiments were carried out to study the effects of different carbon sources, nitrogen sources, and insoluble phosphates on the phosphate-solubilizing capability of the strain. Further, the whole genome of the strain was sequenced by the next-generation sequencing platform, and the genes related to phosphate solubilizing and siderophore synthesis and transport in the genome were mined. Finally, the plant growth-promoting effect of the strain was assessed by the hydroponic experiment. [Results] Strain PSB-K was identified as Acinetobacter baumannii, with a phosphate-solubilizing index of 2.58. Strain PSB-K exhibited the highest phosphate-solubilizing capability in the case of glucose as the carbon source, potassium nitrate as the nitrogen source, and tricalcium phosphate as the insoluble phosphate, under which the soluble phosphorus concentration in the fermentation liquid reached 560.35 μg/mL. The whole genome of strain PSB-K was 3 983 883 bp in length, containing 3 849 coding genes, including various genes involved in organic acid synthesis, phosphate transport, and siderophore synthesis and transport. The results of the hydroponic experiment showed that strain PSB-K applied at 2.50×10⁷, 2.50×10⁷, and 1.25×10⁷ CFU/mL demonstrated the strongest promoting effects on the leaf area, fresh weight, and root length of oilseed rape seedlings, which were increased by 72.15%, 72.08%, and 197.81%, respectively, compared with the control. [Conclusion] Strain PSB-K possessed the capability to solubilize a variety of insoluble phosphates, and carbon and nitrogen sources directly influenced the phosphate-solubilizing performance of the strain. With a growth-promoting effect on oilseed rape plants, this strain serves as a candidate for the development of microbial fertilizer. In addition, the whole-genome data provides a reference for understanding the phosphate-solubilizing mechanisms and mining functional genes of phosphate-solubilizing bacteria.