jdoliver at MBIO.MBIO.NCSU.EDU ("James D. Oliver") wrote:
>Can anyone tell me anything about the mutability of rpoS (katF)? Is
>it a hypermutable gene?
Interesting question. There seems to be a growing and puzzling
literature on mutations in rpoS. These papers you may have already seen:
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Nucleic Acids Res 20: 5479-80 (1992)[93065224]
DNA base sequence variability in katF (putative sigma
factor) gene of Escherichia coli.
A. Ivanova, M. Renshaw, R. V. Guntaka & A. Eisenstark
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Science 259: 1757-60 (1993)[93206120]
Microbial competition: Escherichia coli mutants that
take over stationary phase cultures.
M. M. Zambrano, D. A. Siegele, M. Almiron, A. Tormo & R. Kolter
Department of Microbiology and Molecular Genetics, Harvard Medical
School, Boston, MA
02115.
Many microorganisms, including Escherichia coli, can survive extended
periods of starvation. The
properties of cells that survived prolonged incubation in stationary
phase were studied by mixture
of 10-day-old (aged) cultures with 1-day-old (young) cultures of the
same strain of Escherichia
coli. Mutants from the aged cultures that could grow eventually took
over the population, which
resulted in the death of the cells from the young cultures. This
phenotype was conferred by
mutations in rpoS, which encodes a putative stationary phase-specific
sigma factor. These rapid
population shifts have implications for the studies of microbial
evolution and ecology.
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FEMS Microbiol Lett 126: 171-176 (1995)[95220644]
The live oral typhoid vaccine Ty21a is a rpoS mutant
and is susceptible to various environmental stresses.
V. Robbe-Saule, C. Coynault & F. Norel
Institut Pasteur, Unite des Enterobacteries, INSERM U389, Paris, France.
The rpoS (katF) gene, which encodes a RNA polymerase sigma factor (sigma
s), regulates the
virulence of Salmonella typhimurium in mice. In the present study, we
show that rpoS mutants can
be frequently found among laboratory strains of Salmonella. In addition,
a rpoS mutation was
identified in the S. typhi live oral vaccine Ty21a. Introduction of a
wild-type rpoS gene in Ty21a
allowed the bacteria to survive better under starvation conditions and
increased their resistance to
other stresses. These results contribute to a better understanding of
the genetic background of the
live typhoid oral vaccine Ty21a and suggest that the rpoS mutation may
contribute to the safety of
this strain in humans.
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In addition to this, I gather from a brief glimpse at the ASM meeting
abstracts that the lab strain of salmonella of LT2 is also an rpoS
mutant and this underlies its low pathogenicity.
So, it looks as if mutants in rpoS are commonly selected for, for
whatever reason?!
Why are you interested in rpoS?
Mark
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Dr Mark Pallen, Senior Lecturer in Medical Microbiology,
St Bartholomew's Hospital Medical College, London, EC1A 7BE
currently on a Research Leave Fellowship at Imperial College
Rm 502, Dept of Biochem, Imperial College, London, SW7 2AY
email:m.pallen at ic.ac.uk WWW: http://www.qmw.ac.uk/~rhbm001/mpallen.html
phone: day ++44(0)1715945254, eves ++44(0)1815057937, FAX
++44(0)1715945255
Author, Microbial Underground: http://www.qmw.ac.uk/~rhbm001
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"Presume not mice to scan, the proper study of mankind is man"
(not) Alexander Pope
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