Fourteen recombinant plasmids were constructed by inserting fragments of pSAS, a naturally occurring plasmid of Methylophilus spp. KISRI-5, into the multiple cloning sites of pUC19. Six recombinants and three known Escherichia coli plasmids were used to transform three thermotolerant methylotrophic KUSRI strains by use of an optimized protocol of electroporation. Analysis of transformants for plasmid DNA showed that all plasmids were stable in the methylotrophic hosts. These studies offer opportunities to develop Methylophilus spp. as host-vector systems.