Pseudomonas aeruginosa extracellular products inhibit staphylococcal growth, and disrupt established biofilms produced by Staphylococcus epidermidis

Abstract

Multiple bacterial species often coexist as communities, and compete for environmental resources. Here, we describe how an opportunistic pathogen,Pseudomonas aeruginosa, uses extracellular products to interact with the nosocomial pathogenStaphylococcus epidermidis.S. epidermidisbiofilms and planktonic cultures were challenged withP. aeruginosasupernatant cultures overnight. Results indicated that quorum-sensing-controlled factors fromP. aeruginosasupernatant inhibitedS. epidermidisgrowth in planktonic cultures. We also found thatP. aeruginosaextracellular products, mainly polysaccharides, disrupted establishedS. epidermidisbiofilms. Cellulase-treatedP. aeruginosasupernatant, and supernatant frompelA,pslFandpelApslBCDmutants, which are deficient in polysaccharide biosynthesis, diminished the disruption ofS. epidermidisbiofilms. In contrast,S. epidermidissupernatant in overnight cultures had no effect on establishedP. aeruginosabiofilms and planktonic growth. These findings reveal thatP. aeruginosaextracellular products are important microbial competition factors that overcome competition withS. epidermidis, and the results may provide clues for the development of a novel strategy for controllingS. epidermidisbiofilms.