Restriction and modification systems of ruminal bacteria

A high frequency of type II restriction endonuclease activities was detecte d in Selenomonas ruminantium but not In other rumen bacteria tested Eight d ifferent restriction endonucleases were characterized in 17 strains coming from genetically homogeneous local population, Chromosomal DNA isolated fro m S. ruminantium strains was found to be refractory to cleavage by various restriction enzymes, implying the pre- sence of methylase activities additi onal to those required for protection against the cellular endonucleases Th e presence of Dam methylation was detected in S ruminantium strains as well as in several other species belonging to the Sporomusa subbranch of low G + C Gram-positive bacteria (Megasphaera elsdenii, Mitsuokella multiacidus).