Our results have indicated that S.griseus No. 45 (donor),a streptomycin producer,involves two plasmids,pSGl (19X106 dalton) and pSG2 (2.3X106 dalton),while the other,S.

• 45(给体)中存在两个质粒pSG1(19×10~6道尔顿)和pSG2(2.；3×10~6道尔顿)。