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紫云英根瘤菌CH203含有3条质粒(pRHa,97MI);pRHb,168MD;pRHc,251MD为共生质粒),用带蔗糖敏感基因Tn5-sacB进行菌株质粒消除和质粒缺失突变株筛选,获得一系列突变株。与野生型菌相比,质粒pRHa的丢失导致菌株结无效根瘤,质粒pRHb的丢失使菌株失去共生能力,在TY培养基平板上菌落变得粗糙,失去了脂多糖(LPSI)。质粒pRHc(共生质粒)的丢失显然失去其菌株的共生能力,同时使菌株抗酸性明显减弱。质粒回复能恢复突变株的表现特征和共生能力。此外,紫云英根瘤菌CH205含有5条大小不同的质粒(分子量42MD～230MD),该菌株某些质粒的消除能显著增强菌株的结瘤固氮能力。研究结果也表明除共生质粒外,紫云英根瘤菌其它质粒明显影响菌株的共生效应。
The results showed that there were three plasmids (pRHa, 97MI); pRHb, 168MD; pRHc and 251MD were symbiotic plasmids), and the strain Tn5-sacB with sucrose-sensitive gene was used to eliminate the plasmid and delete the plasmid- Mutant strains. The loss of plasmid pRHa led to ineffective nodulation of the strain compared to the wild-type strain, and the loss of the plasmid pRHb caused the strain to lose symbiotic ability. On the TY medium plate, the colonies became rough with loss of lipopolysaccharide (LPSI). The loss of plasmid pRHc (symbiotic plasmid) apparently loses its symbiotic ability of the strain while significantly reducing the acid resistance of the strain. Plasmid recovery can restore the mutant phenotype and symbiotic ability. In addition, Rhizobium japonicum CH205 contains five different size plasmids (molecular weight of 42MD ~ 230MD), the elimination of certain strains of this strain can significantly enhance the ability of the strains nodulation and nitrogen fixation. The results also show that, except for the symbiotic plasmids, other plasmids of Rhizobium japonicum obviously affect the symbiotic effect of the strains.