侵染3株模式豆科根瘤菌的噬菌体生物学特性

豆科作物根瘤菌被噬菌体浸染后,在一定程度上会引起根瘤菌数目和结瘤量的降低,进而导致共生固氮作用弱化和作物产量的显著下降.然而,目前关于根瘤菌噬菌体的相关研究报道较少.本研究以3株模式根瘤菌,即慢生型大豆根瘤菌、中华大豆根瘤菌和中华苜蓿根瘤菌为宿主,于黑土农田土壤中采用双层平板培养法从每个宿主细菌分离3株噬菌体,共分离获得9株根瘤菌噬菌体,对其形态结构及生物学特征进行综合分析.结果表明:侵染苜蓿根瘤菌噬菌体(SMM)和慢生型根瘤菌噬菌体(BDM)属于肌尾噬菌体科,而侵染中华根瘤菌噬菌体(SSS)隶属于长尾噬菌体科.9株噬菌体的最佳感染复数均在0.001~1.0的变化范围内.一步生长曲线结果显示,BDM的潜伏期和爆发期明显长于SMM和SSS,但获得的裂解量最小.根瘤菌噬菌体在30~40℃和中性pH条件下侵染活性最大.对比发现,侵染同一宿主的噬菌体生物学特征虽存在一定差异,但分异度远小于不同宿主噬菌体间的差异.

Biological characteristics of bacteriophages infecting three typic rhizobia of legume

Bacteriophages infecting rhizobia of legume leads to a significant decrease in the number of rhizobia in soil and nodulation in legume, which finally affects nitrogen fixation and remarkably reduces crop yield. However, limited studies have focused on bacteriophages of rhizobia. In this study, three typic rhizobium strains of Bradyrhizobium diazoefficiens USDA110^T, Sinorhizobium sojae CCBAU05684^T and Sinorhizobium meliloti USDA1002^T were used as the host bacteria. From each host, three rhizobiophages were isolated from an agricultural black soil with double-layer plate method. We isolated nine rhizobiophages and investigated their morphological feature and biological characteristics. The results showed that the phages of SMM (infecting Sinorhizobium meliloti USDA1002^T) and BDM (infecting Bradyrhizobium diazoefficiens USDA110^T) belonged to Myoviridae family, while phages of SSS (infecting Sinorhizobium sojae CCBAU05684^T) belonged to Siphoviridae family. The optimal multiplicity of infection for nine phages ranged from 0.001 to 1.0. The one-step growth curve showed that the latent and rising periods of BDM were remarkably longer than that of SMM and SSS, but the bust size was minimal. Nine phages had the strongest infecting activity at 30-40 ℃ and at neutral pH condition. Comparative analysis showed that the biological characteristics of phages infected with the same host were different, with the differentiation being smaller than that of phages infected with different hosts.