Plasmids of Selenomonas ruminantium and development of host-vector system

A high frequency of plasmids was detected in the rumen bacterium Selenomona s ruminantium. Plasmids 0.9-20 kb in size were detected in more than 50 % t ested strains. Densitometric analysis indicated that plasmid DNA could repr esents more than 25 % of total cellular DNA. Up to six plasmids were detect ed in strain S. ruminantium 18. Two smallest cryptic plasmids pSRD181 and p SRD182 from this strain were cloned into Escherichia coh vector pBluescript SK(+) and partially characterized. The plasmid pSRD181 is 1.4 kb and pSRD18 2 is 2.0 kb. While computer analysis of pSRD181 sequence data showed high h omology with replication protein of Staphylococcus aureus plasmids, the pSR D182 sequence showed no significant homology in GenBank data, Strain S. rum inantium 28 was successfully transformed with pJW1 derived plasmid pJIB1 us ing ampicillin resistance gene as marker This is the first report on transf ormation of selenomonads with foreign DNA.