Differential Modulation of Quorum Sensing Signaling through QslA in Pseudomonas aeruginosa Strains PAO1 and PA14

• Published in: Journal of bacteriology 2019-11, Vol.201 (21)
• Main Authors: Sana, T G, Lomas, R, Gimenez, M R, Laubier, A, Soscia, C, Chauvet, C, Conesa, A, Voulhoux, R, Ize, B, Bleves, S
• Format: Article
• Language: English
• Subjects: Bacteriology; Biofilms; Clinical isolates; Cytotoxicity; Gene deletion; Gene expression; Gene sequencing; Genes; Laboratories; Macrophages; Pathogens; Phenotypes; Pseudomonas aeruginosa; Pyocyanin; Quorum sensing; Ribonucleic acid; RNA; Secretion; Toxicity; Virulence; Virulence factors
• ISSN: 0021-9193; 1098-5530
• DOI: 10.1128/JB.00362-19

Two clinical isolates of the opportunist pathogen named PAO1 and PA14 are commonly studied in research laboratories. Despite the isolates being closely related, PA14 exhibits increased virulence compared to that of PAO1 in various models. To determine which players are responsible for the hypervirulence phenotype of the PA14 strain, we elected a transcriptomic approach through RNA sequencing. We found 2,029 genes that are differentially expressed between the two strains, including several genes that are involved with or regulated by quorum sensing (QS), known to control most of the virulence factors in Among them, we chose to focus our study on QslA, an antiactivator of QS whose expression was barely detectable in the PA14 strain according our data. We hypothesized that lack of expression of in PA14 could be responsible for higher QS expression in the PA14 strain, possibly explaining its hypervirulence phenotype. After confirming that QslA protein was highly produced in PAO1 but not in the PA14 strain, we obtained evidence showing that a PAO1 deletion strain of has faster QS gene expression kinetics than PA14. Moreover, known virulence factors activated by QS, such as (i) pyocyanin production, (ii) H2-T6SS (type VI secretion system) gene expression, and (iii) Xcp-T2SS (type II secretion system) machinery production and secretion, were all lower in PAO1 than in PA14, due to higher expression. However, biofilm formation and cytotoxicity toward macrophages, although increased in PA14 compared to PAO1, were independent of QslA control. Together, our findings implicated differential expression as a major determinant of virulence factor expression in strains PAO1 and PA14. is an opportunistic pathogen responsible for acute nosocomial infections and chronic pulmonary infections. strain PA14 is known to be hypervirulent in different hosts. Despite several studies in the field, the underlining molecular mechanisms sustaining this phenotype remain enigmatic. Here we provide evidence that the PA14 strain has faster quorum sensing (QS) kinetics than the PAO1 strain, due to the lack of QslA expression, an antiactivator of QS. QS is a major regulator of virulence factors in ; therefore, we propose that the hypervirulent phenotype of the PA14 strain is, at least partially, due to the lack of QslA expression. This mechanism could be of great importance, as it could be conserved among other isolates.