3.2. Contrast of developmental process of biofilm between pathogenic and non-pathogenic strains of V. parahaemolyticus
Biofilm formation of 22 pathogenic and 17 non-pathogenic V. parahaemolyticus strains ( Table 1) were tested to investigate whether V. parahaemolyticus biofilm-forming capacity is correlated to strain pathogenicity. As shown in Fig. 2, the effect of strain pathogenicity on biofilm formation was significant and influenced by temperature and incubation time. Statistically, biofilm produc-tion of pathogenic strains was significantly higher (p < 0.05) than non-pathogenic strains when cultured to 48 h at 25 _C (p ¼ 0.047) and 8 h, 12 h at 37 _C (p ¼ 0.02, 0.009, respectively), while no significant difference (p > 0.05) were observed at other time points at these temperatures.
3.3. Strain variability on the developmental process of biofilm
As illustrated in Fig. 1, the OD570nm values are variable under all the conditions in this study, indicating that strain variability is an important factor constraining the biofilm formation process and we used the coefficient of variation (CV, CV ¼ standard deviation/ mean _ 100%) of tested strains to quantify strain variability. As shown in Fig. 3, both temperature and incubation time are shown to affect strain variability. This variability is correlated to the in-cubation time and reached the peak at 12 h. Additionally, there is positive correlation between strain variability and incubation temperature for pathogenic and non-pathogenic strains, and vari-ability of non-pathogenic strains is greater than pathogenic strains at 37 _C (p < 0.01).