Natural genetic transformation in the rumen bacterium Streptococcus bovis JB1

Natural transformation of Streptococcus bovis JB1 was demonstrated after de velopment of competence in normal culture medium. Transformation efficienci es were not significantly increased when heat-inactivated horse serum was a dded to the medium before growth. This is the first time that a resident ru men bacterial species has been shown to be naturally transformable. Transfo rmation allowed the acquisition of plasmids or integration of sequences int o the chromosome. No transformation was observed in the presence of undilut ed autoclaved or filter-sterilised ovine rumen fluid or filter-sterilised o vine saliva, suggesting that transformation in the ruminant digestive tract is a rare event, although transformation was observed in the presence of 1 % and 0.5% filter-sterilised rumen fluid. The use of natural transformation of S. bovis should facilitate Further molecular biological studies on this species. (C) 1999 Federation of European Microbiological Societies. Publis hed by Elsevier Science B.V. All rights reserved.