Global systems of symbiotic nitrogen-fixing bradyrhizobia by comparative genomics of phylogenetic super-neighbors

通过系统发育超邻体的比较基因组学对全球共生固氮慢生根瘤菌进行了研究。土生型慢生根瘤菌菌株S23321缺乏与日本根瘤菌USDA110高度共生性的共生岛，提示为共生慢生型根瘤菌的祖先型基因组。另一方面，基因组分析表明，土壤中的寡养农单胞菌是一种固氮共生菌。事实上，所有营养不良的文库菌株都能通过共生固氮来结瘤。此外，日本血吸虫III型蛋白分泌系统(T3SS)的rhcJ和TTSI突变体获得了对Rj2大豆结瘤的能力，这表明T3SS分泌的效应物引发了这两个伙伴之间的不亲和性。

Global systems of symbiotic nitrogen-fixing bradyrhizobia were conducted by comparative genomics of phylogenetic super-neighbors of the bacteria. Soil-dwelling Bradyrhizobium sp. strain S23321 lacked symbiosis island with high genomic co-linearity with B. japonicum USDA110, suggesting an ancestral-type genome of symbiotic bradyrhizobia. On the other hand, the genome analysis suggested soil-dwelling Agromonas oligotrophica (Bradyrhizobium oligotrophicum) is a nitrogen-fixing symbiont of Aechynomeny indica. Indeed, all texted strains of A. oligotrophica are able to nodulate A. indica with symbiotic nitrogen fixation. In addition, the rhcJ and ttsI mutants of B. japonicum for the type III protein secretion system (T3SS) gained the ability to nodulate Rj2 soybean, suggesting the effectors secreted via T3SS trigger incompatibility between these two partners.