TRANSITORY UV RESISTANCE DURING GERMINATION OF UV‐SENSITIVE SPORES PRODUCED BY A MUTANT OF Bacillus cereus 569

Weinberger, Sarah; Evenchik, Z.; Hertman, I.

doi:10.1111/j.1751-1097.1984.tb08858.x

Cited by 2 publications

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“…This stage lasts only 1 to 6 min for individual spores (4). In spores of B. megaterium and B. cereus, this period of high UV resistance is correlated with a low efficiency of formation of spore photoproducts as well as of pyrimidine dimers in DNA (9,13). It was suggested that this was due to a transient change in DNA structure or environment which rendered the DNA photochemically unreactive (9).…”

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“…Second, spores have at least two mechanisms which efficiently repair this spore photoproduct during spore germination, including one which monomerizes the adduct back to two thymines (7,12). Surprisingly, when spores germinate they go through a transient stage of extremely high UV resistance, much higher than that of the dormant spore (3,9,13). This stage lasts only 1 to 6 min for individual spores (4).…”

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Absence of Transient Elevated UV Resistance during Germination of Bacillus subtilis Spores Lacking Small, Acid-Soluble Spore Proteins α and β

Setlow

1988

J Bacteriol

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Germinating spores of Bacillus subtilis mutants which lack small, acid-soluble spore proteins a and I8 did not exhibit the transient elevated UV resistance seen during germination of wild-type spores.Dormant spores of various Bacillus species are much more resistant to UV irradiation than are the corresponding vegetative cells (2). This elevated spore UV resistance appears to have two causes. First, UV irradiation of spores does not produce the pyrimidine dimers formed in vegetative-cell DNA, but rather produces several other photoproducts, the most predominant of which is termed the spore photoproduct, a 5-thyminyl-5,6-dihydrothymine adduct (1, 10). Second, spores have at least two mechanisms which efficiently repair this spore photoproduct during spore germination, including one which monomerizes the adduct back to two thymines (7,12). Surprisingly, when spores germinate they go through a transient stage of extremely high UV resistance, much higher than that of the dormant spore (3,9,13). This stage lasts only 1 to 6 min for individual spores (4). In spores of B. megaterium and B. cereus, this period of high UV resistance is correlated with a low efficiency of formation of spore photoproducts as well as of pyrimidine dimers in DNA (9, 13). It was suggested that this was due to a transient change in DNA structure or environment which rendered the DNA photochemically unreactive (9). In contrast to these results, the transient UV resistance of germinating B. subtilis spores was suggested to be due to a highly active germination repair system which is specific for pyrimidine dimers (11). However, detailed kinetic analysis of changes in UV resistance during B. subtilis spore germination suggested that the UV-resistant stage in this organism was also accompanied by a period of diminished photoreactivity of spore DNA (3,4 (a3--spores), and plated as previously described (5) (Fig. 1). The initiation of spore germination was also measured by following the fall in A6. of the spore suspension (Fig. 1, inset). While most spores had initiated germination by 20 min, some spores were still initiating germination between 20 and 60 min, as was seen by a decrease in the percentage of phase-bright spores in the phase-contrast microscope (data not shown). However, by 60 min ca. 99% of the spores had initiated germination.As found by others (4, 9, 13), germinating wild-type spores showed a transient elevated UV resistance (Fig. 1). The slow decline in elevated resistance was probably due to the slow germination of a small percentage of the spores. Strikingly, at-V spores exhibited no transient elevated UV resistance but only showed the small increase in resistance seen in going from the o-t-dormant spore to the vegetative cell (5) ( Fig. 1; note different doses used). a-spores showed an extremely small transient increase in UV resistance. However, this minute increase may be caused by the small percentage of a-dormant spores which have wild-type UV resistance (data not shown), possibly due to high levels of SASP-P, since there...

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confidence: 99%