Applied and Environmental Microbiology, May 1999, p. 2065-2071, Vol. 65, No. 5
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
andDepartment of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612
Received 6 November 1998/Accepted 12 February 1999
Pseudomonas aeruginosa accumulates polyphosphates in
response to nutrient limitations. To elucidate the function of
polyphosphate in this microorganism, we have investigated polyphosphate
metabolism by isolating from P. aeruginosa 8830 the genes
encoding polyphosphate kinase (PPK) and exopolyphosphatase (PPX), which
are involved in polyphosphate synthesis and degradation, respectively.
The 690- and 506-amino-acid polypeptides encoded by the two genes have
been expressed in Escherichia coli and purified, and their activities have been tested in vitro. Gene replacement was used to
construct a PPK-negative strain of P. aeruginosa 8830. Low residual PPK activity in the ppk mutant suggests a possible
alternative pathway of polyphosphate synthesis in this microorganism.
Primer extension analysis indicated that ppk is transcribed
from a
E-dependent promoter, which could be responsive
to environmental stresses. However, no coregulation between
ppk and ppx promoters has been demonstrated in
response to osmotic shock or oxidative stress.
Present address: Howard Hughes Medical Institute, University of
Chicago, Chicago, IL 60637.
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