Effect of intraspecies interactions on Pseudomonas aeruginosa biofilm formation and gene expression

Abstract

Pseudomonas aeruginosa is a common pathogen of acute and chronic infections that can increase risk to burned patients and those with chronic wounds, especially when forming biofilms. These complex ecosystems are formed by several bacteria that communicate, cooperate, and compete with each other.  To enhance its survival capacity in such a competitive environment, P. aeruginosa produces secondary metabolites with a range of biological activities, among other factors. Here, we evaluated how such bioactive molecules mediate intraspecies interactions to modulate P. aeruginosa biofilm formation. An overall decrease in biofilm formation on the surface of stainless steel coupons was observed for both dual-strain and single-strain biofilms formed in the presence of secondary metabolites extracted from other P. aeruginosa strains. Modulation of biofilm formation by these metabolites during P. aeruginosa intraspecies interactions suggests a role for these molecules in strain competition. The most likely mechanism by which it occurs might be modulation of iron uptake. Among the genes analyzed, those related to import (tonB1) and biosynthesis (pvdS) of the siderophore pyoverdine were the most downregulated during exposure to the metabolite extracts. Exploring P. aeruginosa intraspecies interactions during biofilm formation might be an interesting approach to understand its lifestyle better and, thus, the mechanisms involved in the species’ biofilm formation.