Originally published as Genetics Published Articles Ahead of Print on August 24, 2008.

Genetics, Vol. 180, 17-25, September 2008, Copyright © 2008
doi:10.1534/genetics.108.089086

The Rate and Character of Spontaneous Mutation in Thermus thermophilus

Reena R. Mackwan^*,1, Geraldine T. Carver^,1, Grace E. Kissling, John W. Drake and Dennis W. Grogan^*,2

^* Department of Biological Sciences, University of Cincinnati, Cincinnati, Ohio 45221-0006 and Laboratory of Molecular Genetics and Biostatistics Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709-2233

² Corresponding author: Department of Biological Sciences, 614 Rieveschl Hall (ML 0006), Clifton Court, Cincinnati, OH 45221-0006.
E-mail: grogandw{at}email.uc.edu

Selection of spontaneous, loss-of-function mutations at two chromosomal loci (pyrF and pyrE) enabled the first molecular-level analysis of replication fidelity in the extremely thermophilic bacterium Thermus thermophilus. Two different methods yielded similar mutation rates, and mutational spectra determined by sequencing of independent mutants revealed a variety of replication errors distributed throughout the target genes. The genomic mutation rate estimated from these targets, 0.00097 ± 0.00052 per replication, was lower than corresponding estimates from mesophilic microorganisms, primarily because of a low rate of base substitution. However, both the rate and spectrum of spontaneous mutations in T. thermophilus resembled those of the thermoacidophilic archaeon Sulfolobus acidocaldarius, despite important molecular differences between these two thermophiles and their genomes.

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