Involvement of DNA in biofilm formation II: From bacterial adhesion to biofilm formation

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 enhanced bacterial attachment to solid surface in a concentration-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 nonspecific. 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 bacterium-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 description for the role of DNA in bacterial biofilm formation in natural environments.