Cell Envelope Stress Response in Pseudomonas aeruginosa

In memoria of an outstanding microbiologist and friend, Pierre Cornelis

“…These studies led to synthesizing the current knowledge on P. aeruginosa extracytoplasmic function sigma factors (Chevalier et al., 2019 ). Altogether, these studies led to proposing SigX as a new member of the cell envelope stress response (Chevalier et al., 2022 ). Since the envelope forms a barrier between the cell and the environment, several studies have been conducted to deepen the understanding of the molecular mechanisms affecting the outer membrane, in relation to biofilm formation and the production of virulence factors.…”

Transcriptional Regulators Controlling Virulence in Pseudomonas aeruginosa

“…The σ SigX factor regulates the attachment and adherence of P. aeruginosa to host tissues by controlling the swarming and twitching motility of this bacterium [23,165]. It was proposed that σ SigX activity is controlled by a mechanosensing complex involving the antiσ factor CfrX, the outer membrane porin OprF, and the ion channel CmpX [166]. The lack of this σ factor decreases the expression of pilA and flp genes, encoding the pilin subunits of the type IVa and IVb pili, respectively, and the tad operon, encoding the machinery that assembles type IVb pili [23].…”

“…Furthermore, σ SigX regulates the expression of several fatty acid biosynthesis genes, thus playing a crucial role in membrane fluidity and homeostasis [166]. Importantly, many genes of the σ SigX regulon are associated with cell membrane integrity, thus suggesting that σ SigX could regulate the response of P. aeruginosa to membrane-disrupting antimicrobials.…”

“…Several genes encoding pro-inflammatory lipoproteins (i.e., lptA, lptE, and osmE) are induced in mucoid P. aeruginosa strains because their expression is promoted by σ AlgT , which causes excessive inflammation in CF patients [58,172]. Moreover, the genes slyB, encoding a putative porin involved in membrane integrity, osmC, encoding a peroxiredoxin inducible by osmotic stress, and pfpI, encoding a protease that protects against oxidative stress, are differentially expressed in mucoid P. aeruginosa strains in a σ AlgT -dependent manner [46,166,172]. Furthermore, σ AlgT regulates the expression of the heat-shock response σ RpoH factor.…”

cmpX overexpression in Pseudomonas aeruginosa affects biofilm formation and cell morphology in response to shear stress

“…While MscS has been widely studied in Escherichia coli , few data were reported in case of P. aeruginosa . However, nine proteins were predicted to belong to the Msc family in P. aeruginosa, among which one was proposed to belong to the large conductance MscL family, and eight to the MscS family [ 10 , 11 ]. In line with their involvement as sensors of membrane tensions, these proteins were suggested to be part of the cell envelope stress response (CESR) network, since some of them were regulated by the extracytoplasmic function sigma factors (ECFσ) AlgU or SigX [ 11 , 12 ].…”