Spontaneous mutation frequencies in Salmonella: Enhancement of G/C to A/T transitions and depression of deletion and frameshift mutation frequencies afforded by anoxic incubation

Abstract

Incubation of Salmonella typhimurium under anoxic conditions (0.1% oxygen or less) results in a substantial decrease in small (3-and 6-basepair) deletions in an A/T-rich region of the hisG gene in the hisG428 ochre mutant and also decreases the frequency of minus frameshift mutations in G/C-rich sequences in the his-D3052 and hisC3076 mutants. In contrast, the frequency of G/C-----A/T transition mutations increases substantially during anoxic growth of hisG46. Growth of revertants of strains carrying accessory deletions in the uvrB region of the Salmonella chromosome is drastically impaired on glucose minimal medium when oxygen partial pressures are below 0.1% oxygen.

Spontaneous and mutagen-induced deletions: mechanistic studies in Salmonella tester strain TA102.

“…The frequency of deletions in the lacI gene of E. coli is reduced to 1/25th in a recA mutant (3). Anaerobic growth also results in a preferential reduction in the frequency of deletion revertants of hisG428 (to approximately 1/3), and the frequency is further reduced (to approximately 1/10) in the recA derivative under these conditions (32). This result suggests that at least two independent pathways exist for the generation of the small deletions monitored in this system.…”

Spontaneous mutagenesis and oxidative damage to DNA in Salmonella typhimurium.

“…Studies have shown that oxygen metabolism influences DNA damage in mammals (6, 7) and bacteria. Hartman et al (8) showed that Salmonella typhimurium strains grown under aerobic conditions had increased frequencies of small deletion and frameshift mutations relative to strains grown anaerobically, while the frequency of G-C to AT transitions was depressed under the aerobic conditions. Recently, Farr et al (9) showed that Escherichia coli mutants that lack both the manganese-and iron-containing superoxide dismutases (sodA sodB double mutants) have enhanced spontaneousmutation frequencies compared to wild-type strains during aerobic growth.…”

Mutation spectrum in Salmonella induced by environmental tobacco smoke

“…Sequence analysis of hisG46 revertants has demonstrated that any of five single transitions/transversions (TCC, ACC, GCC, CAC, and CTC) at the first two positions of the hisG46 revertant codon 69 (CCC) can give rise to His ϩ prototrophs [Barnes et al, 1982;Hartman et al, 1984]. Reversions of hisG46 can also occur via extragenic suppression resulting from a T/A 3 G/C transversion within the anticodon of either of two tRNA Thr genes .…”

“…The purified revertants of the hisG46 allele (TA100) were analyzed using the colony hybridization procedure developed by Cebula and Koch [1990] with modifications of Shelton et al [1994] in which six 32 P-labeled probes (5'-GTCGATTCCGGTATT-3', 5'-GTCGATACCGGTATT-3', 5'-GTCGATGCCGGTATT-3', 5'-GTC-GATCACGGTATT-3', 5'-GTCGATCTCGGTATT-3', 5'-GTCGATC-CCGGTATT-3') were used. Six revertant strains containing the six classes of mutations, confirmed by PCR/DNA sequence analysis according to previous sequence information [Hartman et al, 1984], were used as positive controls for the six probes. Two independent hybridizations were performed with each probe in order to confirm the revertant genotype.…”