Affiliation:
1. Department of Plant and Environmental Sciences, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
Abstract
ABSTRACT
The
yjbEFGH
operon is implicated in the production of an exopolysaccharide of an unknown function and is induced by osmotic stress and negatively regulated by the general stress response sigma factor RpoS. Despite the obvious importance of RpoS, negative selection for
rpoS
has been reported to take place in starved cultures, suggesting an adaptive occurrence allowing the overexpression of RpoD-dependent uptake and nutrient-scavenging systems. The trade-off of the RpoS-dependent functions for improved nutrient utilization abilities makes the bacterium more sensitive to environmental stressors, e.g., osmotic stress. In this work, we addressed the hypothesis that overinduction of genes in
rpoS
-deficient strains indicates their essentiality. Using DNA microarrays, real-time PCR, and transcriptional fusions, we show that genes of the
wca
operon, implicated in the production of the colanic acid exopolysaccharide, previously shown to be induced by osmotic stress, are also negatively controlled by RpoS. Both exopolysaccharides in the synthesis of which
yjb
and
wca
are involved are overproduced in an
rpoS
mutant during osmotic stress. We also show that both operons are essential in an
rpoS
-deficient strain but not in the wild type; promoters of both operons are constitutively active in
yjb rpoS
mutants; this strain produces extremely mucoid colonies, forms long filaments, and exhibits a reduced growth capability. In addition, the
wca rpoS
mutant's growth is inhibited by osmotic stress. These results indicate that although induced in the wild type, both operons are much more valuable for an
rpoS
-deficient strain, suggesting that the overproduction of both exopolysaccharides is an adaptive action.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Reference66 articles.
1. Functional Heterogeneity of RpoS in Stress Tolerance of Enterohemorrhagic
Escherichia coli
Strains
2. Bi, E. F., and J. Lutkenhaus. 1991. FtsZ ring structure associated with division in Escherichia coli. Nature354:161-164.
3. Carballes, F., C. Bertrand, J. P. Bouche, and K. Cam. 1999. Regulation of Escherichia coli cell division genes ftsA and ftsZ by the two-component system rcsC-rcsB. Mol. Microbiol.34:442-450.
4. Charette, M., G. W. Henderson, and A. Markovitz. 1981. ATP hydrolysis-dependent activity of the lon(capR) protein of E. coli K12. Proc. Natl. Acad. Sci. USA78:4728-4732.
5. Chen, G., C. L. Patten, and H. E. Schellhorn. 2004. Positive selection for loss of RpoS function in Escherichia coli. Mutat. Res.455:193-203.
Cited by
70 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献