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Media type:
E-Article
Title:
Interplay between Iron Homeostasis and the Osmotic Stress Response in the Halophilic Bacterium Chromohalobacter salexigens
Contributor:
Argandoña, Montserrat;
Nieto, Joaquín J.;
Iglesias-Guerra, Fernando;
Calderón, Maria Isabel;
García-Estepa, Raúl;
Vargas, Carmen
imprint:
American Society for Microbiology, 2010
Published in:Applied and Environmental Microbiology
Language:
English
DOI:
10.1128/aem.03136-09
ISSN:
0099-2240;
1098-5336
Origination:
Footnote:
Description:
<jats:title>ABSTRACT</jats:title>
<jats:p>
In this study, the connection between iron homeostasis and the osmostress response in the halophile
<jats:italic>Chromohalobacter salexigens</jats:italic>
was investigated. A decrease in the requirement for both iron and histidine and a lower level of siderophore synthesis were observed at high salinity, and these findings were correlated with a lower protein content in salt-stressed cells. A six-gene operon (
<jats:italic>cfuABC</jats:italic>
-
<jats:italic>fur</jats:italic>
-
<jats:italic>hisI</jats:italic>
-
<jats:italic>orf6</jats:italic>
operon) located downstream of the
<jats:italic>ectABC</jats:italic>
ectoine synthesis genes was characterized. A
<jats:italic>fur</jats:italic>
strain (in which the ferric iron uptake regulator Fur was affected) had the Mn resistance phenotype typical of
<jats:italic>fur</jats:italic>
mutants, was deregulated for siderophore production, and displayed delayed growth under iron limitation conditions, indicating that
<jats:italic>fur</jats:italic>
encodes a functional iron regulator.
<jats:italic>hisI</jats:italic>
was essential for histidine synthesis, which in turn was necessary for siderophore production. Fur boxes were found in the promoters of the
<jats:italic>cfuABC</jats:italic>
-
<jats:italic>fur</jats:italic>
-
<jats:italic>hisI</jats:italic>
-
<jats:italic>orf6</jats:italic>
and
<jats:italic>ectABC</jats:italic>
operons, suggesting that Fur directly interacts with DNA in these regions. Fur mediated the osmoregulated inhibition of
<jats:italic>cfuABC</jats:italic>
-
<jats:italic>fur</jats:italic>
-
<jats:italic>hisI</jats:italic>
-
<jats:italic>orf6</jats:italic>
operon expression by iron and functioned as a positive regulator of the
<jats:italic>ectABC</jats:italic>
genes under high-salinity conditions, linking the salt stress response with iron homeostasis. Excess iron led to a higher cytoplasmic hydroxyectoine content, suggesting that hydroxyectoine protects against the oxidative stress caused by iron better than ectoine. This study provides the first evidence of involvement of the iron homeostasis regulator Fur as part of the complex circuit that controls the response to osmotic stress in halophilic bacteria.
</jats:p>