Sylvie Chevalier
University of Rouen, France
Title: Cell wall stress response in Pseudomonas aeruginosa: Involvement of the ECF sigma factor SigX
Biography
Biography: Sylvie Chevalier
Abstract
The bacterial cell envelope is the fi rst line of defense against environmental threats. Cell envelope stress responses (CESRs)
detect cell wall integrity alterations and reprogram gene expression to ensure bacterial survival. Pathogens need CESRs
to survive inside the host, where their envelopes face host immune system eff ectors and antimicrobials. Th e underlying signal
transduction can be mediated by extracytoplasmic function (ECF) σ factors. P. aeruginosa displays two CESR ECF σ factors,
AlgU and the recently described SigX. Using complementary approaches including OMICs, qRT-PCR, CLSM, anisotropy,
FAME and phenotypic analyses, we have shown that i) SigX regulates directly or indirectly more than 300 genes being involved
in numerous cellular processes (virulence, motility, adhesion, biofi lm formation); ii) membrane fl uidity alterations originating
from a sigX mutation result in strong dysregulations of CbrA/B, Crc and Hfq networks, linking SigX to the metabolic pathways;
iii) expression and activity of SigX are increased in response to numerous conditions (high sucrose or tobramycine sub-lethal
concentrations, low osmolarity, cold shock); suggesting that SigX responds to envelope perturbations. ECF factors activity is
usually regulated via sequestration by their cognate anti sigma factors. In sigX near vicinity, the cfrX-cmpX operonic structure
is transcribed at least partly from a SigX-dependent promoter. Based on molecular tools and in silico analyses, we have shown
that the hypothetical protein CfrX and the predicted mechanosensitive channel CmpX are involved in SigX activity. Future
challenges will now put emphasise on the interactions linking SigX, CfrX and CmpX to get further insights into CESR in P.
aeruginosa.