PubMed · 1742439
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I D Bross. 1991. Fraudulent statistical methods.. https://pubmed.ncbi.nlm.nih.gov/1742439/
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Bacteria encounter acid stress under a variety of circumstances. Acid stress induces DNA damage and genomic instability, most directly via acid-catalyzed depurination reactions that generate apurinic (abasic, AP) sites on the deoxyribose phosphate backbone. DNA damage responses are important in bacterial resistance to acids. A recent report provided evidence that a DNA repair glycosylase, AlkX, which is capable of initiating the repair of interstrand DNA cross-links (ICLs), contributes to acid resistance by the pulmonary pathogen Acinetobacter baumannii (Kunkle et al. Proc. Nat. Acad. Sci. USA, 2024, 121, e2402422121). This suggested the possibility that AP-derived ICLs might contribute to the acid stress in bacteria. This idea is predicated on earlier work showing that AP sites can generate ICLs via reactions of the ring-opened AP aldehyde with the exocyclic amino groups of nucleobases on the opposing strand of duplex DNA (Price, N. E. J. Am. Chem. Soc. 2014, 136, 3483). However, it was not clear from previous work whether AP-derived ICLs could be generated under conditions of acid stress. The results reported here provide evidence for ICL formation under conditions of acid stress via a sequential process involving acid-catalyzed depurination followed by cross-linking of the resulting AP site with an adenine residue on the opposing strand of duplex DNA. This supports the possibility that AP-derived interstrand cross-links could contribute to the effects of acid stress in bacteria, and proteins involved in the repair of these lesions could be involved in resistance to acid stress.
The effects of heat treated vegetables on mutagenicity were studied using the Salmonella typhimurium system. The mutagens used were 3-amino-1-methyl-5H-pyrido[4,3-b]indole, 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide, 4-nitroquinoline-1-oxide, acridine yellow and 2-aminoanthracene. Most of the heated vegetables unexpectedly showed greater inhibitory activity against the mutagenicity than unheated samples. The activity was increased markedly by heat treatment of water soluble indigestible polysaccharides (IPS). The increase in inhibitory activity due to heat treatment of IPS coincided well with the decrease in their viscosity. Incubating mixtures of mutagens with heated water soluble IPS decreased their affinity for XAD-2 resin. Heating seems to increase the detoxification ability of dietary fibers.
Haploid cells of the yeast Saccharomyces cerevisiae are able to undergo a differentiation-like process: they can switch their mating type between the a and the alpha state. The molecular mechanism of this interconversion of mating types is intrachromosomal gene conversion. It has been shown in a variety of studies that mating type switching in heterothallic strains can be induced by DNA damaging agents, and that different DNA damaging agents differ in the length of incubation after treatment required for induction. Because X-rays induce switching immediately after irradiation and because the DNA double-strand break repair pathway is required for switching, the event initiating heterothallic mating type switching is likely to be a DNA double-strand break. Therefore the assay for heterothallic mating type switching may screen for the induction of DNA double-strand breaks. Several aspects indicating a relationship of mating type switching to mechanisms associated with carcinogenesis are discussed.