POSTERS - BLAST X - University of Utah

BLAST X Mon. Morning Session
THE ROLE OF SIGNAL TRANSDUCTION IN CELL WALL METABOLISM IN BACILLUS
SUBTILIS
Paola Bisicchia, David, Noone, Efthimia Lioliou and Kevin M Devine.
Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2. Ireland.
The cell wall of Gram positive bacteria is an extracellular structure, physically removed
from the biosynthesis of the precursors used in its synthesis. Peptidoglycan and teichoic acid
precursors are synthesized within the cytoplasm and transported across the cytoplasmic
membrane where they are incorporated into the cell wall during growth and cell division. The
spatial separation of these processes implies bidirectional signaling between the cell wall and
cytoplasmic compartments, that recent work has begun to elucidate. We have shown that the
essential YycFG two-component signal transduction system of Bacillus subtilis controls cell wall
metabolism – during exponential growth, it activates expression of the YocH, YvcE and LytE
autolysins and represses expression of YoeB (IseA), an inhibitor of autolysin activity, and YjeA a
peptidoglycan deacetylase whose activity on peptidoglycan modulates its susceptibility to
autolysin digestion (Howell et al., 2003; Bisicchia et al., 2007; Salzberg and Helmann, 2007;
Yamomoto et al., 2008). Thus we propose that YycG senses some aspect(s) of the cell wall
externally, perhaps the Lipid II intermediate, and transduces this information into the cytoplasm
so that the cell wall synthetic activities in these two compartments are coordinated (Dubrac et
al., 2008). We have also demonstrated a close connection between YycFG and the PhoPR
two-component system that controls one of the phosphate limitation responses in B. subtilis
(Hulett, 2002). YycFG and PhoPR are closely related phylogenetically - hybrid YycF’-‘PhoP and
PhoP’-‘YycF response regulators are functional and there are similarities in the YycF and PhoP
DNA binding sequences. We have also shown (i) that while YycG can phosphorylate only its
cognate response regulator YycF, PhoR can phosphorylate both PhoP and YycF and (ii) that
cells depleted for YycFG cannot mount a normal PhoPR-mediated phosphate limitation
response. From these observations, we postulated that the roles of YycFG and PhoPR might
be linked during cell wall metabolism and phosphate limitation.
In this talk we will present the results of further analysis on the relationships between the
YycFG and PhoPR two-component systems and their roles in cell wall metabolism during
growth and phosphate limitation.
References:
Bisicchia et al., (2007) Molecular Microbiology 65: 180-200.
Dubrac et al., (2008) Molecular Microbiology In Press
Howell et al., (2003) Molecular Microbiology 49: 1639-1655.
Howell et al., (2006) Molecular Microbiology 59:1199-1215.
Hulett, (2002) The Pho regulon. in ‘B. subtilis and is closest relatives’ ASM Press.
Salzberg and Helmann (2007) J. Bacteriology 189: 4671-4680.
Yamamoto et al., (2008) Molecular Microbiology 70: 168-182.
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