The conjugation mechanism of IncP plasmids may be employed to mobilize small non-conjugative plasmids from Escherichia coli to a wide range of different organisms. This strategy has been adapted for use with the Gram-positive anaerobe, Clostridium acetobutylicum NCIB 8052. Several shuttle vectors containing replicons from pAM beta 1 (Enterococcus faecalis), pCB101 (Clostridium butyricum) or pWV01 (Streptococcus cremoris), together with the cis-acting oriT region of RK2, have been constructed, and transferred to and established in this organism. One of the vectors apparently contains a hot spot for insertion of IS1. Conjugative mobilization of plasmids from E. coli will provide a useful alternative to electroporation for effecting gene transfer to this industrially important anaerobe.