Pseudomonas aeruginosa DesB Plays a Role in Staphylococcus aureus Lysis through pqs Operon

Introduction: Pseudomonas aeruginosa, is ubiquitous spoilage organism in foods, and also is the causative pathogen of serious infections which usually exists with other pathogens like Staphylococcus aureus. P. aeruginosa lyses S. aureus in multispecies environments. Various virulence factors produced by P. aeruginosa are closely associated with the growth hindrance and lysis of S. aureus. DesB, an aerobic desaturase, is previously reported as an important enzyme for P. aeruginosa virulence factor production. However, the role of DesB in S. aureus lysis by P. aeruginosa is not yet known.

Purpose: The objective of present study is to elucidate the role of DesB in the relationship between P. aeruginosa and S. aureus, especially in the lysis of S. aureus by P. aeruginosa.

Methods: To investigate the effect of DesB on S. aureus lysis, overnight cultures of wild type P. aeruginosa and its derived mutants were spotted on S. aureus-contained agar plates, and diameters of the clear zones were measured. Wild type P. aeruginosa (WT) or its desB mutant was co-cultured with S. aureus, and growth of each bacterium was monitored. Furthermore, in order to examine if desB regulates pqsA and its upstream regulator mvfR at transcriptional level, the expression levels of these genes in WT and desB mutant were compared by qRT-PCR.

Results: A zone of clearing, indicating a lysis of S. aureus, was relatively smaller in desB mutant than in WT. The growth of S. aureus cultured with WT was reduced more rapidly compared with the one with desB mutant. In qRT-PCR, mvfR was slightly less expressed in desB mutant, whereas pqsA expression was changed in a 50-fold decrease in desB mutant compared to WT. It suggests that PQS acts as a mediator of DesB-involving S. aureus lysis.

Significance: These results indicate that P. aeruginosa DesB contributes to PQS-mediated S. aureus lysis in multispecies environment.