Conférence de Agnès FOUET (Unité Toxines et
Pathogénie Bactérienne - CNRS - URA 2172 Institut
Pasteur, Paris) le vendredi 10 avril 2009 à
11 h 30, IBSM (salle de conférences Jacques Senez), Campus
Joseph Aiguier, Bt IM, CNRS, Marseille : « CodY, the
spoilsport of Bacillus anthracis transition state
regulators ».
Résumé
In Gram-positive bacteria, CodY is an important regulator of genes
whose expression changes upon nutrient limitation. We will discuss
the role of CodY in Bacillus anthracis, the etiologic agent of
anthrax. Global transcriptome analysis of a codY mutant and the
parental strain revealed extensive differences, including reduced
expression of the anthrax toxin genes in the mutant strain.
Interestingly, expression of capsule biosynthesis genes were not
significantly affected in the codY mutant, nor was the expression
of the global virulence regulator gene atxA, as measured using
transcriptional and translational fusions. However, the
accumulation of AtxA protein was strongly reduced, suggesting that
CodY controls toxin gene expression by regulating AtxA
accumulation. By contrast, CodY appeared to control other genes,
such as S-layer genes, directly; CodY bound tightly to the promoter
regions of these genes, which were derepressed in the codY mutant
strain. Disruption of codY completely abolished virulence in a
toxinogenic, non-capsulated strain and resulted in a 1-log higher
LD50 in a non-toxinogenic, capsulated strain, indicating that CodY
influences factors other than toxin synthesis that contribute to
full virulence of B. anthracis.