Moonlighting in the matrix

The biofilm matrix is a complex, heterogeneous mixture of polymers, macromolecules, small molecules, and higher-order particulate structures. The primary functions of some matrix components are specific for building biofilms. However, there are many components of the biofilm matrix that have primary cellular functions yet provide additional distinct 'moonlighting' functions when located in the biofilm matrix. Moonlighting matrix components include proteins and nucleic acids as well as higher-order structures such as membranes and bacteriophage. This review will describe some of the moonlighting matrix components found in Pseudomonas aeruginosa biofilms.