TRANSFORMATION BY PLASMID AND CHROMOSOMAL DNAS IN HAEMOPHILUS-PARAINFLUENZAE

An efficient procedure for transformation of H. parainfluenzae by plasmid DNA is described. The procedure involved a new technique for preparation of competent cells that increased the transforming efficiency of a chromosomal strr marker about 20 fold and that of the plasmid ampr about 100 fold. The addition of either Mg2+ or Ca2+ promoted the stimulation of plasmid ampr by another factor of 50, however, the chromosomal strr marker was not further affected. The total stimulation of plasmid transformation was a factor of 5000 and the final ratio of ampr to strr activity was 1 to 100. These results suggested that plasmid and chromosomal DNAs have different specific requirements for transformation. © 1979.