The extracellular DNA lattice of bacterial biofilms is structurally related to Holliday junction recombination intermediates

Significance Most chronic and recurrent bacterial infections are the result of biofilms. Extracellular DNA (eDNA) is a ubiquitous and pivotal structural component of biofilms that protects the resident bacteria from the host immune system and antimicrobial agents. It is of the highest priority to characterize the structure of the eDNA to understand the development of bacterial biofilm communities. Here, we employed the prototypic Holliday junction-specific (HJ) DNA-binding protein RuvA and demonstrated that eDNA within biofilms formed by 3 human pathogens, uropathogenic Escherichia coli , nontypeable Haemophilus influenzae , and Staphylococcus epidermidis was structurally related to HJ recombination intermediates. We further demonstrated that this HJ-like structure was critical to the structural and mechanical integrity of the bacterial biofilm matrix.