We have demonstrated the possibility of hybrid plasmid pSPA044 conjugative transfer from E. coli cells into different Rhizobium species. The bireplicon plasmid, constructed earlier in our laboratory, consisting of pBR325 and HindIII fragment 13 of the nopaline plasmid pTiC58 was mobilized for transfer by the helper plasmid pRK2013 with the frequency about 10(-4). We conclude the hybrid plasmid pSPA044 to be able to replicate stably in Rhizobiaceae cells.