Community-specific diffusion characteristics determine resistance of biofilms to oxidative stress

Biofilms are multicellular communities with a spatial structure. Different from single-cell scale diffusion in planktonic systems, the diffusion distance becomes the dimension of multicellular clusters in a biofilm. Such differences in diffusion behavior affect the tolerance and response to exogenous stress. Here, we found that at the same doses of exogenous hydrogen peroxide (H₂O₂), planktonic Escherichia coli were completely killed within two hours, whereas the biofilm resumed growth in six hours by building a catalase barrier to block H₂O₂ penetration, despite the growth burden. Unexpectedly, when we changed the carbon source from glucose to glycerol, H₂O₂ instantly counterintuitively boosted biofilm growth due to supplemental oxygen, which was the growth-limiting factor. We further demonstrated that the energy metabolism modes determined the growth-limiting factor, which then determined the two patterns of biofilms resistances to H₂O₂.