2.4. SEM Observation of E. coli

All glasses and materials were sterilized at 120 °C for 40 min in an autoclave. When E. coli was grown to primary-log phase at 37 °C in a peptone culture, two groups of bacteria suspension were centrifuged at 4000 rpm for 5 min. The precipitate was resuspended in PBS buffer. In the same way, the bacteria were washed twice to thoroughly remove the culture medium. The cells were treated as follows. A (the control): the native cells in PBS with shaking for 1 h; B: the cells in PBS in the presence of BiVO₄ which is prepared under pH = 5 under iodine tungsten lamp with a UV filter (300 W, FoShan lighting). After photo-catalysis, the samples were processed before FESEM obervation. Glutaraldehyde was used to fix the protein (or lipid) in cells. Then the cells were dehydrated in a series of increasing concentration of ethanol (50, 60, 70, 80, 90, and 100%). Subsequently, the cells were fixed and dehydrated. They were observed by SEM (HITACHI, S-4800).