A single nucleotide polymorphism between Escherichia coli strains K12 and B is known to alter the mechanism by which the arginine repressor regulates arginine biosynthesis, from a regulated system in E. coli K12 to a deregulated system in E. coli B. Laboratory experiments have demonstrated that the different regulatory strategies are selectively favored under different environmental conditions. In this study we analyzed 537 E. coli strains and show that the argR allele in E. coli B, which causes deregulation, is rare in isolates obtained from natural sources. Moreover, sequence analysis of 85 strains shows no evidence of selection at the arginine repressor locus. This illustrates that analysis of sequence data is insufficient to detect selection of uncommon alleles in rare environments.
Bibliographical noteFunding Information:
We are grateful to Amy Suiter and the members of the Dean lab for their reviews and insights. The authors gratefully acknowledge the support of the National Science Foundation Graduate Research Fellowship Program, National Institutes of Health, University of Minnesota, and the United States Department of Agriculture for funding.
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- Arginine repressor
- Haploid polymorphism
- Regulatory polymorphism