Radioresistance of Micrococcus radiodurans during the growth cycle.
Micrococcus radiodurans, irradiated aerobically in phosphate buffer, exhibits a phasic response to x-irradiation during its growth cycle. The culture progresses from a relatively sensitive state during the exponential portion of the growth cycle to a highly resistant state during the stationary phase. The shift in resistance is characterized by a marked extension of the shoulder of the survival curve and a threefold increase in the LD99 from 250 kR to over 700 kR. The resistant state appears to be a metastable condition, readily induced in exponential-phase cultures and easily reversed in stationary-phase cultures. Similar variations are not elicited in response to ultraviolet irradiation. The phasic response does not appear to be the result of a low-molecular-weight extractable sulfhydryl radioprotective agent.
Serianni
R W
RW
Biology Department, State University of New York at Buffalo, Buffalo, New York, USA.
Bruce
A K
AK
D049109:Cell Proliferation / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D008837:Micrococcus / Q000166:cytology / Q000254:growth & development* / Q000528:radiation effects*; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000502:physiology* / Q000528:radiation effects