Ultraviolet sensitivity and photoproducts in spore-like bodies of an excision-repair-deficient and dipicolinic-acid-less strain of Bacillus subtilis

A simple convenient biological dosimeter for monitoring solar UV-B radiation

The use of dry Bacillus subtilis spores as a biological dosimeter for the monitoring of solar UV-B (290-330 nm) radiation was described. Our field tests had supported the utility of this dosimeter as a reproducible and reliable sunlight dosimeter.

Involvement of calcium and dipicolinic acid in the resistance of Bacillus cereus BIS-59 spores to u.v. and gamma radiations

The role of dipicolinic acid (DPA) in determining the resistance of Bacillus cereus spores to u.v. and gamma radiation was investigated. B. cereus BIS-59 spores containing varying amounts of DPA were prepared by appropriate compositional adjustments in the secondary media. Compared with spores containing 6 per cent DPA (dry weight) those containing 0.8 per cent DPA were far more sensitive to u.v. radiation. Similar u.v. radiation sensitivity was also found in respect of a DPA-less mutant of B. cereus T 6A 1. Pre-treatment of DPA deficient spores (of wild type or mutant B. cereus) with DPA or the presence of DPA during irradiation resulted in increased resistance of these spores to u.v. radiation. In the range 0.2 to 1 per cent DPA content of spores of B. cereus BIS-59, a striking inverse relationship could be discerned between the DPA content and the number of spore photo-products (5-thymidyl, 5,6-dihydrothymine) formed in DNA and spore viability. The resistance of B. cereus spores to gamma radiation did not seem to be influenced by their DPA content.

A comparison of UV induced DNA photoproducts from isolated and non-isolated developing bacterial forespores

UV-induced photoproduct formation has been compared in non-isolated and isolated developing forespores. We have found that levels of spore type photoproducts are greatly affected by mother cell DNA. We have also observed the presence of the photoproduct 6-4'-(pyrimidin-2'-one)-thymine in developing forespores. We conclude from these and other data in the literature that the degree of hydration around the forespore DNA is reduced by the presence of dipicolinic acid which influences photoproduct formation without causing a change in conformational state.

Transitory germinative excision repair in Bacillus subtilis

Bacillus subtilis strains UVSSP-42-1 (hcr42 ssp1) and UVSSP-1-1 (hcr1 ssp1) are ultraviolet (UV) radiation sensitive both as dormant spores and as vegetative cells. These strains are unable to excise cyclobutane-type dimers from the deoxyribonucleic acid (DNA) of irradiated vegetative cells and fail to remove spore photoproduct from the DNA of irradiated spores either by excision (controlled by gene hcr) or by spore repair (controlled by gene ssp1). When irradiated soon after spore germination, these strains excise dimers, but not spore photoproduct, from their DNA. This process, termed germinative excision repair, functions only transiently in the germination phase and is responsible for the high UV resistance of germinated spores and for their temporary capacity to host cell reactivate irradiated phages infecting them. The recA1 mutation confers higher UV sensitivity to the germinated spores, but does not interfere with dimer removal by germinative excision repair.