Chromosomal Amplification of the Escherichia coli lipB Region Confers High-Level Resistance to Selenolipoic Acid

One of the mutants (slr7 mutant) of a wild-type Escherichia coli strain resistant to selenolipoic acid reported previously (K. E. Reed, T. W. Morris, and J. E. Cronan, Jr., Proc. Natl. Acad. Sci. USA 91:3720-3724, 1994) unexpectedly grew on minimal medium following transductional introduction of a lipA null mutation. We report that the slr7 strain carries a duplication of the lip chromosomal region that causes the phenotype of the mutant strain.