超慢生型大豆根瘤菌的生理生化和共生特性的研究

A STUDY ON PHYSIOLOGICAL,BIOCHEMICAL AND SYMBIOTIC CHARACTERISTICS OF EXTRA-SLOW-GROWING SOYBEAN RHIZOBIUM

超慢生型大豆根瘤菌(ESG,extra-slow-growing soybean rhizobium)是不同于大豆另两类共生体——慢生型大豆根瘤菌(Bradyrhizobium japonicum)和快生型大豆根瘤菌(Sin-orhizobium fredii)的新类群。它们在生长速率和生理学特性等方面均表现出较大的差异。根瘤类菌体的扫描结果表明,ESG 的类菌体形态为杆状,与另外两群相近,但发现有'Y'形类菌体。ESG 利用碳源范围较窄,抗生素自然耐受性比慢生型低,在柠檬酸盐培养基上不生长;代时超长,已测定的7个菌株代时为23.3—41.9h。细胞成分 N,c 分析结果表明,ESG 在三个类群中 N 含量最高,C 含量最低。温室盆栽试验证明 ESG 中大部分菌株的固氮酶活性和植株含氮量与生产用菌株相当。ESG 菌株可以在绿豆上结瘤并有固氮酶活性。

Extra-slow-growing soybean rhizobium(ESG)is a new group which is differentiatedfrom the other two groups of symbionts ofsoybean(Bradyrhizobium japonicum & Sinor-hizobium fredii)by growth rate,and physio-logical and biochemical characteristics.Scan-ning micrograph showed that almost all bac-teroids in the nodules of soybean inoculatedwith ESG strains were rod-shaped,although'Y'-shaped ones were also found.ESGstrains were able to utilize fewer carbon sou-rces and have lower antibiotic resistance thanB.japonicum strains.Seven strains testedhad generation times ranging from 23.3 to41.9 hours,indicating that ESG had extra-long generation times.Cell component(N,C)analysis showed that ESG had the highestnitrogen content but the lowest carbon con-tent among the three groups.Pot culture as-say in the greenhouse demonstrated that ESGstrains and the strains applied to soybeanproduction had very similar nitrogenase acti-vity and total nitrogen accumulation.Fur-thermore,ESG strains were able to nodulatePhaseolus aureus and had a detectable nitro-genase activity.