High frequency of conjugation in Lactobacillus mediated by an aggregation-promoting

Lactobacillus plantarum strain 4B2, which exhibits a strong autoaggregating phenotype, receives the broad-host-range plasmid pAMPl with conjugation efficiencies as high as transconjugants per donor using solid matings; broth matings also occur, but at low transfer frequencies. Filter-sterilized spent supernatant of this strain contains a 32 kDa protein that promotes aggregation, and consequently a high frequency of conjugation, in lactic acid bacteria containing a-l,2-glucose-substituted lipoteichoic or teichoic acids. It appears, therefore, that the substituted lipoteichoic or teichoic acids act as receptors for the aggregation-promoting protein