Hyperbiofilm phenotype of Pseudomonas aeruginosa defective for the PlcB and PlcN secreted phospholipases.

Biofilms are dense communities of bacteria enmeshed in a protective extracellular matrix composed mainly of exopolysaccharides, extracellular DNA, proteins, and outer membrane vesicles (OMVs). Given the role of biofilms in antibiotic-tolerant and chronic infections, novel strategies are needed to block, disperse, or degrade biofilms. Enzymes that degrade the biofilm matrix are a promising new therapy. We screened mutants in many of the enzymes secreted by the type II secretion system (T2SS) and determined that the T2SS, and specifically phospholipases, play a role in biofilm formation. Mutations in the xcp secretion system and in the plcB and plcN phospholipases all resulted in hyperbiofilm phenotypes. PlcB has activity against many phospholipids, including the common bacterial membrane lipid phosphatidylethanolamine, and may degrade cell membrane debris or OMVs in the biofilm matrix. Exogenous phospholipase was shown to reduce aggregation and biofilm formation, suggesting its potential role as a novel enzymatic treatment to dissolve biofilms.