Effect of Chromosome Homology of Plasmid Transformation and Plasmid Conjugal Transfer in Haemophilus Influenzae

Abstract

Homology between a resident plasmid in H. influenzae and a plasmid entering the cell has been shown to be very important for the acquisition by the cell of genetic markers from the incoming plasmid. For example, the frequency of transformation of recombination-proficient H. influenzae by two 51-kbp plasmids increases by more than 3 orders of magnitude when the recipient cells contain a partially homologous plasmid (1). This increase is not simply the result of increased uptake of plasmid DNA into the cell, since no transformation could be observed with Rec⁻ recipients which take up DNA as well as the wild type. Furthermore, one of the plasmids has been shown to contain the DNA uptake sites necessary for efficient uptake into competent H. influenzae cells (Setlow and Albritton, unpublished experiments), and the data suggest that the other plasmid also contains such sites. Thus, the plasmids are able to transform Rec cells containing homologous DNA at a higher frequency because of events occurring following DNA uptake.