The effect of extracellular DNA(eDNA) on bacterial attachment was characterized using Escherichia coli,DNase I,and several different kinds of DNA.Here,we showed that eDNA en-hanced bacterial attachment to solid surface in a concentra-tion-dependent way.Either plasmid DNA or chromosome DNA,even or eukaryotic DNA fragments showed the promotion effect,suggesting that the effect of DNA on bacterial attachment is non-specific.This promotion effect of eDNA is separable from that of conjunctive pili.In a static culture system,biofilm can form even with the presence of active DNase I.DNase I impaired bacte-rium-to-bacterium adhesion and microcolony formation efficiently but had little effect on bacterial attachment to a solid surface and mature biofilm.Consequently,this study provides a rational de-scription for the role of DNA in bacterial biofilm formation in natural environments.
