The impact of hydrodynamic shear force on adhesion morphology and biofilm conformation of Bacillus sp.

Biofilm formation is crucial for subsequent biofouling. Various factors can affect the biofilm formation. Here we report the influence of hydrodynamic shear force on adhesion morphology and biofilm conformation of Bacillus sp. on stainless steel by a flow cell system. Static, laminar and turbulent conditions were selected for this study. The applicability of this flow cell was evaluated by computational fluid dynamics (CFD). Stable wall shear stresses were successfully obtained. The results showed that the spatial distribution of bacteria changed from single-cell to cluster under the effect of shear force and the higher shear force created smoother and denser clusters. The different morphology of clusters under different flow conditions was mainly due to the increased nutrient supply to the clusters with the increase of flow velocity. Under the effect of shear force, Bacillus sp. could change the shape and increase the production of extracellular polymeric substance which could reduce the effect of shear force and enhance the connection and adhesion, respectively. Under low shear force, biofilm preferred to form irregular and complicated structure which could lead to the formation of tower like biofilm and inhibit the external mass transfer . The results could shed some light on biofilm control strategies.