土壤产铁载体细菌的筛选及其对铁氧化物的活化与利用

Screening of soil siderophore-producing bacteria and their activation and utilization of iron oxide

摘要:

【背景】土壤中铁主要以难溶态铁氧化物的形式存在，有效性较低，产铁载体细菌对铁氧化物的活化是提高铁利用效率的有效途径。【目的】从林木土壤筛选产铁载体细菌，并观察菌株对难溶性铁氧化物的利用效应，可为土壤微生物资源开发及其在养分调控中的作用提供理论依据。【方法】通过CAS检测法从林木根系附近表层土壤中分离产铁载体细菌，借助生物培养实验分析温度和pH对微生物生长和铁载体产生的影响，通过振荡平衡实验，探究细菌产铁载体对铁氧化物的活化效应。【结果】通过CAS检测法从林木根系附近表层土壤中分离得到12株产铁载体细菌，16S rRNA基因扩增子测序初步鉴定结果显示筛选细菌均为假单胞菌属。选取铁载体产生能力和生长活性较高的两株细菌ARSB02和CNRSB01作为重点研究对象，结果显示，不同条件下CNRSB01的生物量和铁载体产量均高于菌株ARSB02，22 h时菌株ARSB02和CNRSB01的铁载体活性单位分别达到67.07%和84.60%。pH 5.0-8.0的范围内两株细菌可以保持较好的铁载体产生能力，菌株ARSB02和CNRSB01在pH 7.0时铁载体产生能力最强，铁载体活性单位分别达到38.98%和48.77%。铁载体产生最适温度为25-30 ℃，菌株ARSB02和CNRSB01在30 ℃时铁载体产生能力最强，铁载体活性单位分别达到42.35%和56.06%。在针铁矿悬液中ARSB02和CNRSB01均能较好地生长，菌株ARSB02在铁氧化物比例为0.03 g/L时生物量最高，OD₄₂₀值为0.75，菌株CNRSB01在铁氧化物比例为0.015 g/L时生物量最高，OD₄₂₀值为1.11。而且细菌铁载体对铁氧化物有一定的活化效应，144 h时菌株ARSB02和CNRSB01对针铁矿的活化量分别达到12.99 μmol/L和 16.50 μmol/L。【结论】从林木根系附近表层土壤中分离得到的产铁载体细菌均属于假单胞菌，产铁载体细菌对铁氧化物有一定的活化能力，研究结果在林木土壤微生物资源开发和应用中具有重要的意义。

Abstract:

[Background] Iron in soil mainly exists in the form of insoluble iron oxide with low availability. The activation of iron oxide by siderophore-producing bacteria is an effective way to improve the iron utilization efficiency. [Objective] To observe the utilization of insoluble iron oxide by the siderophore-producing bacterial strains isolated from woodland soil and provide a theoretical basis for the development of microbial resources and the research on its role in nutrient regulation. [Methods] Siderophore-producing bacteria were isolated from surface soil near the tree roots by CAS detection method. The effects of temperature and pH on the growth and siderophore production of the isolates were analyzed by plate culture method. The activation effect of siderophore-producing bacteria on iron oxide was explored via oscillation balance experiments. [Results] Twelve siderophore-producing bacterial strains were isolated from surface soil near the tree roots. The results from 16S rRNA gene amplicon sequencing showed that the isolates were Pseudomonas. We selected two strains ARSB02 and CNRSB01 and analyzed their siderophore production and growth. The biomass and siderophore production of CNRSB01 were higher than those of ARSB02 under different conditions. At the time point of 22 h, the siderophore activity of ARSB02 and CNRSB01 reached 67.07% and 84.60%, respectively. The two strains could maintain good siderophore production within the range of pH 5.0-8.0 and the strongest siderophore production capacity (38.98% and 48.77%, respectively) at pH 7.0. The strains showed good siderophore production performance at 25-30℃ and the strongest siderophore production capacity (42.35% and 56.06%, respectively) at 30 ℃. Both ARSB02 and CNRSB01 grew well in goethite suspension. Strain ARSB02 had the highest biomass (OD₄₂₀value of 0.75) in the suspension with the iron oxide ratio of 0.03 g/L and strain CNRSB01 had the highest biomass (OD₄₂₀ value of 1.11) in the suspension with the iron oxide ratio of 0.015 g/L. The siderophore produced by the two strains could activate goethite. At the time point of 144 h, the activation of goethite by ARSB02 and CNRSB01 reached 12.99 μmol/L and 16.50 μmol/L, respectively. [Conclusion] The siderophore-producing bacteria isolated from surface soil near the tree roots all belong to Pseudomonas and have the ability to activate iron oxide. The results are of significance for the development and application of microbial resources in woodland soil.