POSTERS - BLAST X - University of Utah

BLAST X Poster #47
THE ESSENTIAL NATURE OF THE WALK/WALR SIGNAL TRANSDUCTION PATHWAY IS
LINKED TO CELL WALL HYDROLASE ACTIVITY IN STAPHYLOCOCCUS AUREUS
Aurélia Delauné 1 , Olivier Poupel 1 , Adeline Mallet 2 , Sarah Dubrac 1 , and Tarek Msadek 1
Biology of Gram-positive Pathogens 1 , Department of Microbiology, Plateforme de Microscopie
Ultrastructurale 2 , Imagopole, Institut Pasteur, 25 rue du Dr. Roux, 75015 Paris, France
Staphylococcus aureus, a major Gram-positive human pathogen, is a leading cause of
both nosocomial and community infections due to its considerable capacity for adaptation. One
of the principal mechanisms involved in this process are the so-called two-component systems,
bacterial signal transduction pathways with a sensor histidine kinase that is autophosphorylated
in response to specific environmental stimuli and then transfers the phosphoryl group to its
cognate response regulator, which consequently regulates target gene expression. The WalKR
two-component system is well conserved and specific to low G+C Gram-positive bacteria,
including Bacillus subtilis, Staphylococcus aureus and Streptococcus pneumoniae. This system
has been shown to be essential for cell viability.
We have recently demonstrated that the WalKR system positively controls autolytic
activity, and identified ten genes belonging to the WalKR regulon that appear to be involved in
S. aureus cell wall degradation. Reasoning that the essential nature of this signaling pathway
may be related to its role as a master regulatory system for cell wall metabolism, we tested
whether uncoupling autolysin gene expression from WalKR-dependent regulation could
compensate for the essential nature of the system. Several genes from the WalKR regulon were
expressed from a cadmium chloride-inducible promoter in a WalKR-independent manner.
Candidate genes were identified whose expression allowed cells to grow in the absence of
WalKR.
98