Previous Article | Next Article ![]()
J. Bacteriol., 10 1996, 5683-5691, Vol 178, No. 19
HK Hall and JW Foster
The response of Salmonella typhimurium to low pH includes a low-pH
protection system called the acid tolerance response (ATR). The iron-
regulatory protein Fur has been implicated in the ATR since fur mutants are
acid sensitive and cause altered expression of several acid shock proteins
(J. W. Foster, J. Bacteriol. 173:6896-6902, 1991). We have determined that
the acid-sensitive phenotype of fur mutations is indeed due to a defect in
Fur that can be complemented by a fur(+)-containing plasmid. However,
changes in cellular iron status alone did not trigger the ATR. Cells
clearly required exposure to low pH in order to induce acid tolerance. The
role of Fur in acid tolerance was found to extend beyond regulating iron
acquisition. A mutation in fur converting histidine 90 to an arginine
(H90R) eliminated Fur-mediated iron regulation of enterochelin production
and deregulated an iroA-lacZ fusion but had no effect on acid tolerance.
The H90R iron-blind Fur protein also mediated acid shock induction of
several Fur-dependent acid shock proteins and acid control of the hyd
locus. In addition, a Fur superrepressor that constitutively repressed
iron-regulated genes mediated normal Fur-dependent acid tolerance and
pH-controlled gene expression. The results indicate the acid-sensing and
iron-sensing mechanisms of Fur are separable by mutation and reinforce the
concept of Fur as a major global regulator in the cell.
Copyright © 1996, American Society for Microbiology
The role of fur in the acid tolerance response of Salmonella typhimurium is physiologically and genetically separable from its role in iron acquisition
Department of Microbiology and Immunology, College of Medicine, University of South Alabama, Mobile 36688, USA.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»