苜蓿中华根瘤菌nifA基因在共生固氮过程中担负着调控功能,nifA突变株Rm1354在宿主植物的根部诱导白色无效根瘤。本文报道Rm1354在自生状态下的表型变化。nifA的突变导致根瘤菌在半固体培养基上泳动变慢,胞外蛋白含量降低。有趣的是,Rm1354在延宕期间高丝氨酸内酯含量比野生型低,在指数期和静止期却比野生型高。另外,突变株Rm1354的竞争结瘤能力也大大减弱。这些结果揭示了苜蓿中华根瘤菌nifA基因对许多细胞学过程都有调控作用。 Alfalfa Sinorhizobium nifA gene plays a regulatory role in symbiotic nitrogen fixation. The nifA mutant Rm1354 induces white null roots in the roots of host plants. This article reports the phenotypic changes of Rm1354 in a spontaneous state. The mutation of nifA resulted in rhizobia swimming slowly in the semi-solid medium, the extracellular protein content decreased. Interestingly, the homoserine lactone content of Rm1354 was lower than that of wild type during prolonged periods and higher than that of wild type during exponential and quiescent periods. In addition, the competing nodulation ability of mutant Rm1354 was also greatly reduced. These results reveal that the S. meliloti nifA gene regulates many cytological processes.