Transfer of foreign Genes into the Bradyrhizobium japonicum and their Inoculation Effects on Soybean Plants

Bradyrhizobium japonicum에 외부유전자(外部遺傳子)의 도입(導入)과 대두(大豆)에 대한 접종효과

The fate of inoculum strain of Bradyrhizobium japonicum was studied by using genetically marked strain. RJB6 $str^rnal^rneo^r$. A spontaneous mutant of B. japonicum isolated from nodules was made to have antibiotic resistance against streptomycin and nalidixic acid. In order to make genetically marked strain, neomycine resistant gene(Tn5) was introduced into this spontaneous mutant by conjugation with E. coli containing pSUP2021. The southern hybridization was carried out to confirm the plasmid insertion. Hybridization of chromosome DNA using pSUP2021(Tn5) as a probe showed that Tn5 was located on the 4.9kb fragment of chromosome. Soybean seeds were planted into a soil previously cultivated with soybean and inoculated with different cell densities of marked strain. Fourty days after planting, the inoculation effects on nodule number, nodule fresh weight, plant height and nitrogen content in the plot inoculated with heavy cell suspension was a little better than those in the plot with low inoculation. The recovery percentage of the marked strains was about 12% in the plot inoculated with heavy density cell suspension, while 5% in the plot inoculated with low cell suspension.

접종근류균(接種根瘤菌)의 소장(消長)을 유전공학적(遺傳工學的)으로 조제(調劑)한 Bradyrhizobium japonicum RJB6 $str^rnal^rneo^r$을 이용(利用)하여 연구(硏究)하였다. 전남(全南)일대로 부터 분리(分離) 동정한 균(菌)에 먼저 streptomycin과 nalidixic acid에 저항성(抵抗性)을 갖는 spontaneous mutant를 유도하고 이어 pSUP2021를 함유(含有)하고 있는 E. coli와 conjugation하여 neomycin 저항성(抵抗性) gene(Tn5)을 도입(導入)하였다. Southern hybridization한 결과(結果) 4.9kb상에서 Tn5를 확인(確認)했다. 서로 다른 균밀도(菌密度)로 파종(播種)한 40일후, 크로로필을 제외한 근류수(根瘤數), 근류신선중(根瘤新鮮重), 간장 및 질소함량이 low cell suspension 처리구보다 heavy cell suspension 처리구에서 약간 높았다. 표식균주(標識菌株)의 회수율(回收率)은 heavy cell suspension 처리구에서 12%인 반면, low cell suspension 처리구에서는 5%에 지나지 않았다.