Journal of Bacteriology, September 2000, p. 5036-5045, Vol. 182, No. 18
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
B Factor from Bacillus anthracis and Its Role
in Virulence
andToxines et Pathogénie Bactériennes (URA 1858, CNRS), Institut Pasteur, Paris, France
Received 3 April 2000/Accepted 19 June 2000
The operon encoding the general stress transcription factor
B and two proteins of its regulatory network, RsbV and
RsbW, was cloned from the gram-positive bacterium Bacillus
anthracis by PCR amplification of chromosomal DNA with degenerate
primers, by inverse PCR, and by direct cloning. The gene cluster was
very similar to the Bacillus subtilis sigB operon
both in the primary sequences of the gene products and in the order of
its three genes. However, the deduced products of sequences upstream
and downstream from this operon showed no similarity to other
proteins encoded by the B. subtilis sigB operon.
Therefore, the B. anthracis sigB operon contains
three genes rather than eight as in B. subtilis. The
B. anthracis operon is preceded by a
B-like promoter sequence, the expression of which
depends on an intact
B transcription factor in B. subtilis. It is followed by another open reading frame that is
also preceded by a promoter sequence similarly dependent on B. subtilis
B. We found that in B. anthracis, both these promoters were induced during the
stationary phase and induction required an intact sigB gene. The sigB operon was induced by heat shock.
Mutants from which sigB was deleted were constructed in a
toxinogenic and a plasmidless strain. These mutants differed from the
parental strains in terms of morphology. The toxinogenic
sigB mutant strain was also less virulent than the parental
strain in the mouse model. B. anthracis
B
may therefore be a minor virulence factor.
Present address: Institut de Génétique et
Microbiologie, CNRS UMR 8621, Laboratoire de Génétique
Moléculaire de la Traduction, Université Paris-Sud, 91405 Orsay cedex, France.
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