Large plasmids in an actinomycete

Abstract Using a modified procedure large indigenous plasmids were detected in cells of three strains belonging to a group of phenotypically similar actinomycetes isolated from the rhizoplane and root nodules of Alnus spp. M _r values of the plasmids were estimated to be about 80 · 10⁶ and 120 · 10⁶. The plasmid profiles of different strains of the group were found to be almost identical. This remarkable plasmid similarly is discussed in relation to the common source of isolation.