Conjugal transfer of plasmid DNA between streptococci immobilized in calcium alginate gel beads.

A rapid and simple technique was developed for conjugation between group N and group D streptococci by using cells entrapped within calcium alginate gel beads. With this method, the frequencies of transfer of lactose metabolism from Streptococcus lactis ME2 to S. lactis LM2302 were comparable to those achieved with agar surface matings. Conjugal transfer of the chloramphenicol and erythromycin resistance plasmid pVA797::Tn917 from S. faecalis V1229 to S. faecalis V1102 in alginate beads occurred at frequencies comparable to those achieved with filter matings. The results demonstrated efficient conjugal transfer of plasmid DNA among alginate-immobilized streptococcal cells and suggested that this method could be used as an alternative to conventional solid-surface and filter matings with these organisms.