Loss of genetic accuracy in mutants of the thermoacidophile Sulfolobus acidocaldarius
GREG D. BELL 1 and DENNIS W. GROGAN 1,2
1 Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006, USA
2 Author to whom correspondence should be addresssed ([email protected])
Received July 24, 2001; accepted October 2, 2001; published online October 30, 2001
To investigate how hyperthermophilic archaea can propagate their genomes accurately, we isolated Sulfolobus acidocaldarius mutants exhibiting abnormally high rates of spontaneous mutation. Our isolation strategy involved enrichment for mutator lineages via alternating selections, followed by screening for the production of spontaneous, 5-fluoro-orotate-resistant mutants in micro-colonies. Several candidates were evaluated and found to have high frequencies of pyrE and pyrF mutation and reversion. Neither an increased efficiency of plating of mutants on selective medium, nor the creation of a genetically unstable pyrE allele, could be implicated as the cause of these high frequencies. The strains had elevated frequencies of other mutations, and exhibited certain phenotypic differences among themselves. A large increase in sensitivity to DNA-damaging agents was not observed, however. These properties generally resemble those of bacterial mutator mutants and suggest loss of functions specific to genetic accuracy.
5-fluoro-orotic acid, hyperthermophilic archaea, mismatch repair, mutator mutants, spontaneous mutation.