%0 Journal Article
%T Stationary phase expression of the arginine biosynthetic operon argCBH in Escherichia coli
%A Jeevaka P Weerasinghe
%A Tao Dong
%A Michael R Schertzberg
%A Mark G Kirchhof
%A Yuan Sun
%A Herb E Schellhorn
%J BMC Microbiology
%D 2006
%I BioMed Central
%R 10.1186/1471-2180-6-14
%X In this study, we report that expression of the argCBH operon is induced in stationary phase cultures and is reduced in strains possessing a mutation in rpoS, which encodes an alternative sigma factor. Using strains carrying defined argR, and rpoS mutations, we evaluated the relative contributions of these two regulators to the expression of argH using operon-lacZ fusions. While ArgR was the main factor responsible for modulating expression of argCBH, RpoS was also required for full expression of this biosynthetic operon at low arginine concentrations (below 60 ¦ÌM L-arginine), a level at which growth of an arginine auxotroph was limited by arginine. When the argCBH operon was fully de-repressed (arginine limited), levels of expression were only one third of those observed in ¦¤argR mutants, indicating that the argCBH operon is partially repressed by ArgR even in the absence of arginine. In addition, argCBH expression was 30-fold higher in ¦¤argR mutants relative to levels found in wild type, fully-repressed strains, and this expression was independent of RpoS.The results of this study indicate that both derepression and positive control by RpoS are required for full control of arginine biosynthesis in stationary phase cultures of E. coli.The biosynthesis and/or scavenging of arginine are important during host colonization by uropathogenic Escherichia coli. In urine, expression of the E. coli argCBH operon and artJ, encoding a periplasmic transporter, increases more than 10 fold [1] and 18 fold [2], respectively. Synthesis of arginine is likely required during infection as the concentration of arginine found in urine is below that necessary to support maximal growth of E. coli [1]. Consistent with these data, infection challenge in a murine model with E. coli strains carrying mutations in the argC gene results in impaired proliferation in the kidney [1]. In enteropathogenic E. coli [3] arginine synthesis and transport, together with arginine decarboxylase (encoded by a
%U http://www.biomedcentral.com/1471-2180/6/14