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J. Bacteriol., 03 1996, 1394-1400, Vol 178, No. 5
NN Rao and A Kornberg
The Escherichia coli mutant (ppk) lacking the enzyme polyphosphate kinase,
which makes long chains of inorganic polyphosphate (poly P), is deficient
in functions expressed in the stationary phase of growth. After 2 days of
growth in a medium limited in carbon sources, only 7% of the mutants
survived compared with nearly 100% of the wild type; the loss in viability
of the mutant was even more pronounced in a rich medium. The mutant showed
a greater sensitivity to heat, to an oxidant (H2O2), to a redox-cycling
agent (menadione), and to an osmotic challenge with 2.5 M NaCl. After a
week or so in the stationary phase, mutant survivors were far fewer in
number and were replaced by an outgrowth of a small-colony-size variant
with a stable genotype and with improved viability and resistance to heat
and H2O2; neither polyphosphate kinase nor long-chain poly P was restored.
Suppression of the ppk feature of heat sensitivity by extra copies of rpoS,
the gene encoding the RNA polymerase sigma factor that regulates some 50
stationary-phase genes, further implicates poly P in promoting survival in
the stationary phase.
Copyright © 1996, American Society for Microbiology
Inorganic polyphosphate supports resistance and survival of stationary- phase Escherichia coli
Department of Biochemistry, Stanford University School of Medicine, California 94305-5307, USA.
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