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BP: Fachverband Biologische Physik

BP 14: Poster Session II

BP 14.16: Poster

Dienstag, 10. März 2026, 18:00–21:00, P2

Effects of extracellular DNA on material properties of bacterial biofilms — •Mandus Aldag, Isabelle Wielert, Stephan Wimmi, and Berenike Maier — Institute for Biological Physics, University of Cologne

Many bacterial species form spatially structured biofilms that protect the bacteria from external stresses. In Neisseria gonorrhoeae, a human pathogen, early biofilms are characterized by the formation of spherical colonies with liquid-like local order via active attractions between single cells. An important component of biofilms is extracellular DNA (eDNA), that is predominantly released from lysed cells and is proposed to have biofilm-stabilizing properties. Here, we use a combination of confocal microscopy, laser tweezers and tolerance assays to explore the spatial distribution of eDNA and how it affects structure, dynamics and attractive forces in gonococcal colonies. We find that after 16h of growth, N. gonorrhoeae colonies show filamentous, network-like eDNA structures, that can span over large parts of the colony and often interconnect lysed cells. Treatment with DNase prevents the formation of the eDNA network while the spherical colony shape is maintained. Furthermore, we find that the presence of eDNA is associated with a lower bacterial within-colony motility, compared to DNase-treated colonies. The results suggest that even though gonococcal colonies can still form in DNase presence, eDNA affects the cohesive properties of cells within biofilms which potentially influences the biofilm’s susceptibility to antibiotics.

Keywords: Bacterial biofilms; Extracellular DNA; Antiobiotic tolerance; Extracellular matrix; Colony dynamics