Effects of trxHEp mutation on resistance to serum and biofilm growth. A Survival of E. piscicida in fish serum. TX01, TX01∆trxH, and TX01∆trxHC were incubated with non-immune flounder serum or PBS (control). After incubation, the survival of the bacteria was determined by plate counting. B The biofilm forming capacity of E. piscicida. TX01, TX01∆trxH, and TX01∆trxHC were incubated in polystyrene plate and biofilm formation was determined by measuring the the A570 of final eluates. Data are presented as mean ± SEM (N = 3). N, the number of times the experiment was performed. **P < 0.01.