Mapping of a cloned glucosyltransferase gene in Streptococcus mutans

A cloned glucosyltransferase (gtfA) fragment, inserted adjacent to an erythromycin resistance (Eryr) marker in plasmid pVA891, was used in transformation experiments to determine the genetic location of gftA on the Streptococcus mutans chromosome. Eryr (gftA) cotransformed with a methionine (Met+) marker at a frequency of approximately 23%, whereas cotransfer with a number of other markers was not observed. The number of Met+ transformants was approximately 50-fold greater than the number of Eryr transformants. Furthermore, over 20% of the Eryr transformants were always Met+, whereas less than 1% of the Met+ transformants were Eryr, indicating the extreme asymmetrical cotransfer of these markers. The results indicate that S. mutans genes can be mapped by this procedure.