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J. Bacteriol., Nov 1997, 6831-6836, Vol 179, No. 21
HM Steinman, F Fareed and L Weinstein
Caulobacter crescentus is an obligate aerobe which is exposed to high
concentrations of photosynthetic oxygen and low levels of nutrients in its
aquatic environment. Physiological studies of oxidative and starvation
stresses in C. crescentus were undertaken through a study of lacZ fusion
and null mutant strains constructed from the cloned 5' end of katG,
encoding a catalase-peroxidase. The katG gene was shown to be solely
responsible for catalase and peroxidase activity in C. crescentus. Like the
katG of Escherichia coli, C. crescentus katG is induced by hydrogen
peroxide and is important in sustaining the exponential growth rate.
However, dramatic differences are seen in growth stage induction. E. coli
KatE catalase and KatG catalase- peroxidase activities are induced 15- to
20-fold during exponential growth and then approximately halved in the
stationary phase. In contrast, C. crescentus KatG activity is constant
throughout exponential growth and is induced 50-fold in the stationary
phase. Moreover, the survival of a C. crescentus katG null mutant is
reduced by more than 3 orders of magnitude after 24 h in stationary phase
and more than 6 orders of magnitude after 48 h, a phenotype not seen for E.
coli katE and katG null mutants. These results indicate a major role for C.
crescentus catalase-peroxidase in stationary-phase survival and raise
questions about whether the peroxidatic activity as well as the protective
catalatic activity of the dual-function enzyme is important in the response
to starvation stress.
Copyright © 1997, American Society for Microbiology
Catalase-peroxidase of Caulobacter crescentus: function and role in stationary-phase survival
Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461-1602, USA. steinman@aecom.yu.edu
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