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J. Bacteriol., Aug 1995, 4451-4456, Vol 177, No. 15
C Yanofsky and V Horn
The growth-inhibiting drug bicyclomycin, known to be an inhibitor of Rho
factor activity in Escherichia coli, was shown to increase basal level
expression of the tryptophanase (tna) operon and to allow growth of a
tryptophan auxotroph on indole. The drug also relieved polarity in the trp
operon and permitted growth of a trp double nonsense mutant on indole. Nine
bicyclomycin-resistant mutants were isolated and partially characterized.
Recombination data and genetic and biochemical complementation analyses
suggest that five have mutations that affect rho, three have mutations that
affect rpoB, and one has a mutation that affects a third locus, near rpoB.
Individual mutants showed decreased, normal, or increased basal-level
expression of the tna operon. All but one of the resistant mutants
displayed greatly increased tna operon expression when grown in the
presence of bicyclomycin. The tna operon of the wild-type drug-sensitive
parent was also shown to be highly expressed during growth with
noninhibitory concentrations of bicyclomycin. These findings demonstrate
that resistance to this drug may be required by mutations at any one of
three loci, two of which appear to be rho and rpoB.
Copyright © 1995, American Society for Microbiology
Bicyclomycin sensitivity and resistance affect Rho factor-mediated transcription termination in the tna operon of Escherichia coli
Department of Biological Sciences, Stanford University, California 94305-5020, USA.
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