HOMING OF A GROUP-II INTRON FROM LACTOCOCCUS-LACTIS SUBSP LACTIS ML3

Ll.ltrB is a functional group II intron located within a gene (ltrB) e ncoding a conjugative relaxase essential for transfer of the lactococc al element pRS01, In this work, the Ll.ltrB intron was shown to be an independent mobile element capable of inserting into an intronless all ele of the ltrB gene. Ll.ltrB was not observed to insert into a deleti on derivative of the ltrB gene in which the intron splice site was rem oved. In contrast, a second vector containing a 271-nucleotide segment of ltrB spanning the Ll.ltrB splice site was shown to be a proficient recipient of intron insertion. Efficient homing was observed in the a bsence of a functional host homologous recombination system, This work demonstrates that the Ll.ltrB intron is a novel site-specific mobile element in lactococci and that group II intron self-transfer is a mech anism for intron dissemination among bacteria.