苏打盐碱地水稻内生鲍曼不动杆菌J-7的分离、全基因组分析及促生作用

Isolation, whole genome analysis, and plant growth-promoting effect evaluation of endophytic Acinetobacter baumannii J-7 from rice grown in soda saline-alkaline soil

摘要:

目的 从黑龙江省大庆市苏打盐碱地种植的水稻茎内筛选并鉴定一株对水稻生长具有促进作用的内生菌，探究其促生能力及相关基因，以期丰富并利用水稻内生微生物资源。方法 采用稀释涂布法从水稻茎内分离出一株内生菌，通过形态、生理生化试验及16S rRNA基因测序进行菌株鉴定；基于二代Illumina全基因组测序技术解析菌株促生功能机制；利用antiSMASH预测次级代谢产物基因簇；通过促生性能试验、水稻种子萌发与育苗试验评估菌株促生性能。结果 分离的一株水稻内生细菌编号为J-7，基于全基因组测序及平均核苷酸一致性分析(average nucleotide identity analysis, ANI)初步鉴定菌株为鲍曼不动杆菌(Acinetobacter baumannii)。菌株为中温菌，在pH 10.5条件下OD₆₀₀值为0.679，说明其具有一定耐碱性；在1.0 mol/L NaCl浓度下OD₆₀₀值为0.293，说明其有一定耐盐性。促生特性鉴定结果显示菌株具有溶解无机磷及有机磷的能力，溶无机磷量为(179.54±1.21) mg/L，溶有机磷量为(65.57±1.07) mg/L；同时具备产铁载体及利用铁铵盐的特性。菌株基因组(国家微生物科学数据中心登录号NMDC60154488)全长3 666 630 bp，G+C含量为39%，共编码3 432个基因，含有8个潜在的次生代谢产物编码基因簇；施加1×10⁷ CFU/mL菌悬液的水稻种子萌发试验组较对照组胚根长、茎基宽分别显著提高了13.02%和17.68%；施加2×10⁹ CFU/mL菌悬液的水稻育苗试验组较对照组株高、根长分别显著提升了32.69%和36.55%。结论 菌株J-7对水稻具有良好促生作用，作为微生物菌种资源在农业中具有一定的应用潜力。全基因组测序为深入研究鲍曼不动杆菌促生机制提供了理论依据。

Abstract:

Objective To screen and identify an endophytic bacterial strain with plant growth-promoting effects on rice from the stem of rice grown in the soda saline-alkaline soil in Daqing City, Heilongjiang Province and explore its plant growth-promoting effects and related genes, with a view to enriching and utilizing the endophytic microbial resources of rice.Methods An endophytic bacterial strain was isolated from rice stems via the dilution coating method, and the strain was identified by morphological observation, physiological and biochemical tests, and 16S rRNA gene sequencing. The mechanisms underlying the plant growth-promoting effects of the strain were deciphered by Illumina sequencing of the whole genome. antiSMASH was used to predict the synthetic gene clusters of secondary metabolites. The plant growth-promoting performance of the strain was evaluated by promotion performance, rice seed germination, and seedling cultivation tests.Results An isolated endophytic bacterial strain of rice was designated as J-7, and the strain was identified as Acinetobacter baumannii by whole genome sequencing and ANI analysis. The strain was a mesophilic bacterium with an OD₆₀₀ value of 0.679 at pH 10.5, showcasing alkaline tolerance. The strain had an OD₆₀₀ value of 0.293 in the presence of 1.0 mol/L NaCl, exhibiting salt tolerance. The strain had the ability to solubilize inorganic and organic phosphorus, with the amounts of inorganic and organic phosphorus solubilized being (179.54±1.21) mg/L and (65.57±1.07) mg/L, respectively. In addition, the strain had the ability to produce siderophores and utilize ferric ammonium salts. The strain genome (national microbiology data center accession number: NMDC60154488) was 3 666 630 bp in length, with the G+C content of 39% and a total of 3 432 genes (including 8 potential synthetic gene clusters of secondary metabolites). The rice seed germination test results showed that the application of 1×10⁷ CFU/mL suspension of the strain significantly increased the radicle length and stem base width by 13.02% and 17.68%, respectively, compared with the control group. The rice seedling cultivation test results showed that the application of 2×10⁹ CFU/mL suspension of the strain significantly increased the plant height and root length by 32.69% and 36.55%, respectively, compared with the control group.Conclusion Strain J-7 has a good growth-promoting effect on rice, showing application potential in agriculture as a microbial strain resource. Whole genome sequencing provides a theoretical basis for in-depth study of the plant growth-promoting mechanism of A. baumannii.