title: Induction and repair of DNA strand breaks in Bacteroides fragilis.
abstract: Alkaline sucrose gradient sedimentation was used to establish whether strand breakage and repair take place in the DNA of UV-irradiated Bacteroides fragilis during the removal of pyrimidine dimers. A B. fragilis wild-type strain and two of its repair mutants, a mitomycin C sensitive mutant (MTC25) having wild-type levels of UV survival, and a UV-sensitive, mitomycin C sensitive mutant (UVS9), were investigated. Under anaerobic conditions, far-UV irradiation induced metabolically regulated strand breakage and resynthesis in the wild-type strain, but this was markedly reduced in both the MTC25 and UVS9 mutants. Approximately half of the strand breaks generated by the various strains were rejoined during further holding in buffer. Under replicating conditions, complete repair of strand breaks in the wild type was observed. Caffeine treatment under anaerobic conditions caused direct DNA strand breakage in B. fragilis cells but did not inhibit UV-induced breakage or repair.
authors.affiliation: Department of Microbiology, University of Cape Town, Rondebosch, South Africa.
authors.forename: V R
authors.initials: VR
authors.lastname: Abratt
authors.forename: M J
authors.initials: MJ
authors.lastname: Peak
authors.forename: J G
authors.initials: JG
authors.lastname: Peak
authors.forename: J D
authors.initials: JD
authors.lastname: Santangelo
authors.forename: D R
authors.initials: DR
authors.lastname: Woods
mesh_terms: D000693:Anaerobiosis; D001441:Bacteroides fragilis / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D002110:Caffeine / Q000494:pharmacology; D002499:Centrifugation, Density Gradient; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects / Q000528:radiation effects; D004269:DNA, Bacterial / Q000187:drug effects / Q000528:radiation effects; D009154:Mutation; D011740:Pyrimidine Dimers / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial; D011740:Pyrimidine Dimers; D002110:Caffeine