Integration of plasmid DNA coding for beta-lactamase production in the Haemophilus influenzae chromosome

Of beta-lactamase-producing strains of Haemophilus influenzae, 65% do not contain extrachromosomal plasmid DNA. These strains, however, conjugally transfer beta-lactamase production to a recipient strain from which a 30-megadalton plasmid can be isolated. Restriction enzyme analysis and Southern transfer of DNA from both donor and recipient strains revealed that chromosomal integration of plasmid sequences occurred in all donor strains examined.