Bacteria attachment to surfaces – AFM force spectroscopy and physicochemical analyses

Understanding bacterial adhesion to surfaces requires knowledge of the forces that govern bacterial–surface interactions. Biofilm formation on stainless steel 316 (SS316) by three bacterial species was investigated by examining surface force interaction between the cells and metal surface using atomic force microscopy (AFM). Bacterial–metal adhesion force was quantified at different surface delay time from 0 to 60 s using AFM tip coated with three different bacterial species: Gram-negative Massilia timonae and Pseudomonas aeruginosa, and Gram-positive Bacillus subtilis. The results revealed that bacterial adhesion forces on SS316 surface by Gram-negative bacteria is higher (8.53 ± 1.40 nN and 7.88 ± 0.94 nN) when compared to Gram-positive bacteria (1.44 ± 0.21 nN). Physicochemical analysis on bacterial surface properties also revealed that M. timonae and P. aeruginosa showed higher hydrophobicity and surface charges than B. subtilis along with the capability of producing extracellular polymeric substances (EPS). The higher hydrophobicity, surface charges, and greater propensity to form EPS by M. timonae and P. aeruginosa led to high adhesive force on the metal surface.

Graphical abstractBacterial cell was successfully coated to AFM tip (a) to measure the adhesion force between bacteria and stainless steel surfaces (b) with various surface delays.Figure optionsDownload full-size imageDownload high-quality image (74 K)Download as PowerPoint slideHighlights► AFM force measurement using live bacteria. ► Nature of adhesion mechanism of bacteria on stainless steel were explored. ► Higher adhesion force on Gram-negative bacteria. ► Physicochemical analysis support force measurements. ► EPS production enhanced bacterial adhesion.