Isolation and characterization of Bradyrhizobium elkanii as a root nodule symbiont of red sword bean Canavalia gladiata var. gladiata
Isolation and characterization of Bradyrhizobium elkanii as a root nodule symbiont of red sword bean Canavalia gladiata var. gladiata
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DOI：
10.1080/00380768.2022.2078645
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发表时间：
2022-05
影响因子：
2
通讯作者：
Wataru Masuda;Yusuke Hatanaka;A. Mochizuki;Shin Okazaki;B. Nanzai;A. Saito
中科院分区：
文献类型：
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作者：
Wataru Masuda;Yusuke Hatanaka;A. Mochizuki;Shin Okazaki;B. Nanzai;A. Saito
摘要从红刀豆（Canavalia gladiata var.剑兰），以阐明共生体的分类学。根据16S rRNA基因的核苷酸序列，在52株细菌分离物中，28株被鉴定为慢生根瘤菌属，10株被鉴定为根瘤菌属。从28个慢生根瘤菌菌株中筛选出9个菌株，其ITS区核苷酸序列与已知的B同源性分别为99.9%和100%。elkanii菌株这9个菌株与B的相似性在70%以上。DNA-DNA杂交分析表明，该菌株为B型。elkanii。在使用用氯化汞溶液处理的红剑豆种子的根瘤形成实验中，所有用每种B. elkanii菌株（分离株TI 06或MI 08，或模式株USDA 76 T）形成圆形根瘤（每株植物234 - 664个根瘤），而在不使用根瘤菌菌株培养的对照植物中没有观察到根瘤。从获得的根瘤中分离的细菌菌株显示出与相应接种菌株相同的ITS区的核苷酸序列。实验中形成的根瘤具有乙炔还原活性，表明根瘤具有固氮活性。因此，我们得出结论，B。elkanii是红刀豆的根瘤共生体。
ABSTRACT Bacterial strains were isolated from root nodules of red sword bean (Canavalia gladiata var. gladiata) cultivated in Shizuoka, Japan, in order to elucidate the taxonomy of the symbionts. Of the 52 bacterial isolates, 28 strains were identified as the genus Bradyrhizobium and 10 as Rhizobium, based on the nucleotide sequences of 16S rRNA genes. Nine Bradyrhizobium isolates, which were phylogenetically selected from the 28 strains, exhibited nucleotide sequences of ITS regions that were 99.9% or 100% identical with known B. elkanii strains. These nine strains shared more than 70% similarity with B. elkanii USDA 76 T or USDA 94 in DNA-DNA hybridization analysis, indicating that the strains are B. elkanii. In a nodule formation experiment using red sword bean seeds treated with mercury chloride solution, all of the plants which were inoculated with each of the B. elkanii strains (the isolate TI06 or MI08, or the type strain USDA 76 T) formed round-type root nodules (234–664 nodules per plant), while no nodules were observed in control plants that were cultivated without inoculating bacterial strains. The bacterial strains, which were isolated from the obtained nodules, exhibited nucleotide sequences of the ITS regions that were identical to those of the corresponding inoculated strains. The root nodules formed in the experiment exhibited acetylene-reducing activity, suggesting the nitrogen-fixation activity of the nodules. We thus conclude that B. elkanii is a root nodule symbiont of red sword bean.