Incorporation of Collagen into <i>Pseudomonas aeruginosa</i> , <i>Staphylococcus aureus</i> , and <i>Burkholderia pseudomallei</i> Biofilms Modifies Their Viscoelasticity and Resistance against Phagocytosis

Biofilms are communities of microbes embedded in a matrix of extracellular polymeric substances and other components such as proteins. Matrix components can be produced by the microorganisms themselves but can also originate from the environment and then be incorporated into the biofilm. For example, we and our collaborators have recently shown that collagen, a host-produced protein that is abundant in many different infection sites, can be taken up into the matrices of <i><i>Pseudomonas aeruginosa</i></i> biofilms, altering biofilm mechanics. <i><i>P. aeruginosa</i></i>, <i>Staphylococcus aureus</i>, and <i>Burkholderia pseudomallei</i> are human pathogens notable for forming biofilms in vitro and in vivo in tissues rich in collagen such as lung and skin. Here, we show that the incorporation of Type I collagen into <i><i>P. aeruginosa</i></i>, <i>S. aureus</i>, and <i>B. pseudomallei</i> biofilms significantly alters their viscoelasticity and microstructure and hinders phagocytosis of biofilm bacteria by human neutrophils. Enzymatic degradation of collagen using collagenase reverses these effects, increasing biofilm susceptibility to neutrophils. Our findings suggest that host materials play significant roles in stabilizing biofilms and may present promising targets for therapeutic interventions.