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利用转座子Tn5随机插入突变法，从毛萼田菁茎瘤菌（Azorhizobiumcaulinodans）中筛选得到两株吸氢活性缺陷突变株（Hup-）R－49和R－309，其固氮酶活性也大大降低，约为野生型固氮酶活性的6％～8％。以带有Bradyrhizobiumjaponicum的5．9kb的hup基因的质粒pHR11为探针与A．caulinodansORS571和B.japonicum122DES（Hup＋）的总DNA进行分子杂交，放射自显影表明，A．coulinodans基因组含有与B.japonicum的hup基因同源的DNA片段，将携带B．japonicumhup基因的嵌合质粒pHR11与A.caulinodansHup-突变株进行体内遗传互补，接合转移子吸氢酶活性可以恢复至野生型的60％，同时固氮酶的活性亦有所提高。
Two nitrogen-absorbing mutant strains (Hup-) R-49 and R-309 were screened from Azorhizobium caulinodans using transposon Tn5 random insertion mutagenesis. The nitrogenase activity was also greatly reduced, About 6% to 8% of wild-type nitrogenase activity. The plasmid pHR11 with a 5.9 kb hup gene of Bradyrhizobium japonicum was used as a probe and A. The total DNA of caulinodansORS571 and B.japonicum122DES (Hup +) was subjected to molecular hybridization and autoradiography indicated that The coulinodans genome contains a DNA fragment homologous to the hup gene of B. japonicum that will carry B. The chimeric plasmids pHR11 and A.caulinodans Hup-mutant of japonicum hup gene were complemented in vivo, and the activity of the conjugate transferor hydrogenase could be recovered to 60% of the wild type, and the activity of nitrogenase was also increased.