Vg was labeled by FITC, and FITC-labeled Vg was incubated with Gram-negative bacterium E. coli, Gram-positive bacterium S. aureus and fungus P. pastoris, respectively. After washing three times with 25 mM Tris-HCl buffer containing 137 mM NaCl and 3 mM KCl (TBS; pH 7.6), the microbes were harvested by centrifugation, applied to microscope slides, and observed under an Olympus BX51 fluorescence microscope. The microbes treated with FITC-labeled BSA and FITC-labeled apoB were processed under the same conditions. (A, D and G) Binding of FITC-labeled Vg to E. coli, S. aureus and P. pastoris; (B, E and H) Non-binding of FITC-labeled BSA to E. coli, S. aureus and P. pastoris; (C, F and I) Non-binding of FITC-labeled apoB to E. coli, S. aureus and P. pastoris. A, D and G are the images under a fluorescent field, while B, E, H, C, F and H are the merged images under fluorescent and bright field channels. Scale bars: 20 µm.