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J Bacteriol. 1970 July; 103(1): 9-15
Copyright © 1970 American Society for Microbiology. All Rights Reserved.

Radiation Sensitivity of Haemophilus influenzae: a Composite Response

Biomedical Research Group, Los Alamos Scientific Laboratory, University of California, Los Alamos, New Mexico 87544

ABSTRACT

The survival of ultraviolet (UV)-irradiated cultures of Haemophilus influenzae Rd is determined by at least two responses: (i) excision-repair ability and (ii) UV-induced cell lysis. An UV-resistant mutant, BC200, has the same capabilities as the wild type, Rd, for excising dimers but does not exhibit lysis. Lytic response is dose-dependent. Relative to the wild type, a lower dose of UV causes lysis of a UV-sensitive mutant, BC100, which is incapable of excising thymine dimers. A lytic protein is present in cultures undergoing lysis. Synthesis of this protein is initiated 45 to 60 min after irradiation. Lysis appears to be due to derepression of a defective prophage which codes for an endolysin-like lytic enzyme.