Use of atomic force microscopy to observe the surface and the dynamic forming process of biofilms of Enterococcus faecalis

Objective To observe the surface of Enterococcus faecalis and the dynamic forming process of those biofilms using atomic force microscopy(AFM) in air condition.Methods The surface of Enterococcus faecalis which were dried in air were observed with AFM.We used the cellulose nitrate film to construct the Enterococcus faecalis biofilms model in vitro,and then placed the biofilms under AFM to observe the surface changes of biofilms' development.Results The cell surfaces of strain Enterococcus faecalis were not regular because of the presence of the amorphous substance on the colony surface,which congregated globular,fibrous structure.Gradually determined that at 6 h the initial biofilm formed and at 24 h the biofilms maintained the steady-state.AFM height images showed topographical changes due to biofilms' development,which were used to characterize several aspects of the bacterial surface,such as the presence of extracellular polymeric substance,and the biofilms' development stage.Conclusion Application of AFM in physiological conditions could be useful in observing Enterococcus faecalis surface ultrastructure and dynamic process of biofilms formation.