2.4. Preparation of bacterial culture and suspension
E. coli was used as the model bacterium in this study. It was
obtained by scrapping the E. coli colony from an overnight cultured
sample in LB agar plate. The E. coli suspension was prepared by
diluting the bacterial cell with fresh Mueller-Hinton broth (MHB)
with 1% glucose (w/v). The original bacterial density was adjusted
to match the turbidity of a 0.5 McFarland Standard (108 CFU/ml)
using MHB (with 1% glucose). Then the suspension was further
diluted with MHB to reach an appropriate cell density. The bacterial
suspensions with different cell density were used in subsequent
experiment. NOX strain (ATCC no. 49643) and P17 strain
(ATCC no. 49642) were used as the control bacteria, which were
cultured by the same methods as that for E. coli culture, except
that the cultural temperature for NOX strain was set at 28 °C.