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THERMAL REACTIVATION OF ULTRAVIOLET‐IRRADIATED ESCHERICHIA COLI : RELATIONSHIP TO RESPIRATION *
Author(s) -
Swenson P. A.,
Boyle J. M.,
Schenley R. L.
Publication year - 1974
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1974.tb06466.x
Subject(s) - incubation , irradiation , strain (injury) , escherichia coli , glycerol , respiration , ultraviolet , chemistry , microbiology and biotechnology , biophysics , biology , biochemistry , materials science , botany , anatomy , physics , optoelectronics , gene , nuclear physics
— The effects of postirradiation incubation at 42°C on respiration and viability were studied in cells of ultraviolet (UV)‐irradiated Escherichia coli strains B/r and B. Prior to UV irradiation (52 J/m 2 at 254 nm), the cells were grown in minimal liquid medium containing glycerol. When incubated in this liquid medium at 37°C, respiration of both strains is known to cease about an hour after UV irradiation, but is found to be continuous upon incubation at 42°C. In both strains, continuance of respiration is accompanied by an early increase in viability (‘liquid thermal reactivation’), but the increase for B/r (30‐fold) is 3 times that for strain B. The kinetic pattern of viability for B/r at 42°C is the same as that previously obtained for B/r and B when respiration is maintained by 5‐fluorouracil (FU) treatment. A different pattern is seen for Strain B at 42°C, but when FU and thermal treatments are given together, the FU type response dominates and the amount of reactivation obtained is about the same as with FU alone. This result suggests that in the absence of FU liquid thermal treatment prevents division of a potentially reactivable group of filaments in this lon ‐ strain. The amount of liquid thermal reactivation (where plates are incubated at 37°C) is about equal to the amount of plate thermal reactivation (where irradiated cells, plated immediately after UV irradiation are incubated at 42°C). We infer that liquid and plate thermal reactivation involves the same group of cells.