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.
Highlights
Pseudomonas aeruginosa is a ubiquitous Gram-negative γ proteobacterium that thrives in different environments, including soils, water, nematodes, plants and mammals [1,2]
The Pf4 variant isolated in the current study was able to induce lysis on its host lawns (Figure 1C) and affected the growth of its host since the generation time was increased from 37 min for dH103 to 57 min for dH103Pf4+ (Figure 1D)
Since it has been previously shown that biofilm architecture was closely related to the EPS produced by P. aeruginosa [70], we evaluated the expression of the three EPS-encoding operons by RT-qPCR
Summary
Pseudomonas aeruginosa is a ubiquitous Gram-negative γ proteobacterium that thrives in different environments, including soils, water, nematodes, plants and mammals [1,2]. This opportunistic pathogen is responsible for a wide range of infections in the lungs, urinary tract, and burn wounds [3]. Filamentous phages (Inoviridae) are widespread in the microbial world. They have a long and thin filamentous shape and contain a single-stranded circular DNA genome [7,8]. P. aeruginosa strains integrate in their genome several filamentous bacteriophages designated as Pf phages. Bacteriophages Pf1 and Pf4 use as receptors type IV pili (TFP) from PAK [11] and PAO1 [12,13], respectively, while Pf3 of strain PAO binds to the RP4 conjugative pilus [11]
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