WS11.02Lack of sirB2 gene stimulates virulence, invasion, and small colony variants emergence in Pseudomonas aeruginosa

Objectives

Pseudomonas aeruginosa is the leading cause of death in cystic fibrosis (CF) patients. The production of virulence factors and the complex adaptation to the host play a crucial role in its pathogenesis. However, knowledge of the genetic determinants that drive P. aeruginosa persistence in the host environment is limited. Based on previously collected transcriptional data from human samples, in this study was investigated the role of sirB2, a P. aeruginosa PA14 gene with unknow function and whose expression is enhanced in the CF lung environment.

Methods

In silico promoter analysis, molecular genetics and biochemical approaches were used to decipher the sirB2 gene regulation. The generation of PA14 mutants and whole-genome sequencing analysis allowed to investigate the role of sirB2 on heterogenous phenotypes known to be essential for P. aeruginosa persistence (i.e. biofilm formation, in vitro and in vivo virulence assays on different infection models).

Results

In P. aeruginosa, sirB2 gene belongs to the Vfr and AmrZ regulons, and its inactivation increases P. aeruginosa pathogenic potential in Galleria melonella. Similarly, gene deletion stimulates transepithelial migration and biofilm formation in an infection model based on air-liquid interface cultures of the airway epithelium. In this context the lack of sirB2 promotes the production of virulence determinants and the emergence of rugose small colony variants (RSCVs). RSCVs appearance depends on an increased rate of mutations in the wsp regulatory circuit, leading to increased c-di-GMP levels.

Conclusions

Our data identified the sirB2 gene as a novel genetic determinant underlying the appearance of heterogenous phenotypes typical of infections, through a mechanism involving specific genetic rearrangement in the PA14 genome.