Transformation between Haemophilus influenzae and Haemophilus parainfluenzae.

Heterospecific transformation between Haemophilus influenzae and H. parainfluenzae is from one to more than six orders of magnitude lower than homospecific transformation, depending on the marker assayed. However, the physical integration of deoxyribonucleic acid (DNA) in heterospecific compared with homospecific transformation is only slightly decreased. Measurement of integration of ultraviolet-irradiated heterospecific transforming DNA suggests that compared with homospecific DNA a longer piece of heterospecific transforming DNA must undergo pairing for integration to occur. Heterospecific transforming DNA behaves towards ultraviolet inactivation of biological activity as though it had undergone some previous inactivation. The efficiency of heterospecific transformation can be improved by light sonic treatment of the DNA or by the use of DNA containing markers which originated from the heterospecific recipient. The presence of an excision mechanism in the recipient cell does not affect killing or marker efficiency in heterospecific transformation. The data indicate that the low frequency of transformation between H. influenzae and H. parainfluenzae results mostly from lethality. It is proposed that integration of heterospecific transforming DNA results in alterations in the base sequence of the recipient genome which cannot be repaired. Transcription and translation of the altered DNA could result in synthesis of nonfunctional essential proteins.