Microbial biofilm matrix restricts phagocytic cells motility in a 3D-microfluidics phagocyte migration model

Microbes form biofilms by secreting exopolymeric substances that encase the resident communities in the natural environment and human infections. While biofilm matrix can block the phagocytosis of biofilm bacteria by migrating eukaryotic predators, such as phagocytes and amoebae, it is unclear if the biofilms can alter their motility. Here, as proof-of-concept, we developed a 3D-microfluidics phagocyte-biofilm model to investigate how pathogenic Pseudomonas aeruginosa biofilms affect the migration and motility of human macrophages. Wild-type P. aeruginosa PAO1 biofilms could impede macrophage motility. The pro-biofilm mutant Δ wspF could impede macrophage motility almost completely, but loss of exopolysaccharide in the biofilm-deficient mutant enabled macrophage movements. Specifically, exogenous addition of Psl exopolysaccharide to the biofilm-deficient mutant significantly hinder motility of macrophages and their ability to migrate across biofilm substrate. The persistent random walk (PRW) simulation model also accurately replicates this macrophage behavior, where macrophages encountered impeded motility in Psl-containing biofilms. Our findings shed light on the complex interplay between biofilm matrix components and eukaryotic cells, offering deeper insights into predator-prey interactions and providing potential strategies targeting biofilm-associated infections.