Activation of the Cell Wall Stress Response in Pseudomonas aeruginosa Infected by a Pf4 Phage Variant

Abstract

Pseudomonas aeruginosa PAO1 has an integrated Pf4 prophage in its genome, encoding a relatively well-characterized filamentous phage, which contributes to the bacterial biofilm organization and maturation. Pf4 variants are considered as superinfectives when they can re-infect and kill the prophage-carrying host. Herein, the response of P. aeruginosa H103 to Pf4 variant infection was investigated. This phage variant caused partial lysis of the bacterial population and modulated H103 physiology. We show by confocal laser scanning microscopy that a Pf4 variant-infection altered P. aeruginosa H103 biofilm architecture either in static or dynamic conditions. Interestingly, in the latter condition, numerous cells displayed a filamentous morphology, suggesting a link between this phenotype and flow-related forces. In addition, Pf4 variant-infection resulted in cell envelope stress response, mostly mediated by the AlgU and SigX extracytoplasmic function sigma factors (ECFσ). AlgU and SigX involvement may account, at least partly, for the enhanced expression level of genes involved in the biosynthesis pathways of two matrix exopolysaccharides (Pel and alginates) and bis-(3’-5’)-cyclic dimeric guanosine monophosphate (c-di-GMP) metabolism.

Filamentous Pseudomonas Phage Pf4 in the Context of Therapy-Inducibility, Infectivity, Lysogenic Conversion, and Potential Application

“…The enhanced cell surface hydrophobicity and swimming motility also contributed to cells' better interaction with surface, and the established biofilms were probably further more intensively developed, as numerous phage particles contributed to the biofilm matrix structure. The role of Pf4 in biofilm matrix structure [13,16], as well as in biofilm volume and thickness [64] were previously documented for PAO1 strain. Cell lysis by Pf4 phage may additionally contribute to better biofilm production, and this phenomenon was confirmed in the original host PAO1 [15].…”

Pf4 Phage Variant Infection Reduces Virulence-Associated Traits in Pseudomonas aeruginosa

“…In a previous study, we identified a transposon mutant derived from P. aeruginosa H103 (dH103Pf4 + PAO1 strain) overproducing superinfective Pf4 phages termed Pf4* ( 31 ). Pf4* displayed characteristics of a superinfective variant, i.e., it was able to induce cell lysis on its wild-type host.…”

“…We have shown that P. aeruginosa exposure to Pf4* resulted in altered biofilm architecture with increased matrix-encoded gene expression and c-di-GMP production. In addition, in flow cell dynamic conditions, numerous sessile bacteria were displaying a filamentous morphology ( 31 ). Noticeably, the cell envelope stress response (CESR) that is mediated by two extracytoplasmic function (ECF) sigma factors, AlgU and SigX, was strongly activated in response to Pf4* infection, suggesting a link between the regulation of the cell shape and the reorganization of cytoskeleton-like structures ( 31 ).…”

“…In addition, in flow cell dynamic conditions, numerous sessile bacteria were displaying a filamentous morphology ( 31 ). Noticeably, the cell envelope stress response (CESR) that is mediated by two extracytoplasmic function (ECF) sigma factors, AlgU and SigX, was strongly activated in response to Pf4* infection, suggesting a link between the regulation of the cell shape and the reorganization of cytoskeleton-like structures ( 31 ). Here, we conducted a transcriptome sequencing (RNA-seq)-based study to get further insights into the response of P. aeruginosa upon Pf4* phage infection.…”

Impact of Carbon Source Supplementations on Pseudomonas aeruginosa Physiology

“…Noticeably, the extracytoplasmic function sigma factor SigX was shown to control membrane fluidity homeostasis − probably by regulating the expression of de novo fatty acid biosynthesis. , A sigX mutant was shown to display an increased membrane stiffness, while a strain overproducing SigX possessed a more fluid membrane . In addition, Fléchard et al demonstrated that SigX is indirectly involved in carbon catabolite repression regulation (via Crc and CrcZ), probably partly because of its enhanced stiffness and consequent loss of integrity and functionality .…”