Effect of hutZEp mutation on cellular infection and replication. A Edwardsiella piscicida invasion of flounder gill cells (FG cells). FG cells were infected with the same dose of TX01 and TX01ΔhutZ for various amounts of time and washed with PBS. Then, FG cells were lysed, and the bacteria associated with and invaded into the host cells were enumerated. B Replication of E. piscicida in FG cells. After infecting with TX01 and TX01ΔhutZ for 2 h, FG cells were treated with gentamicin for 2 h. The cells were then incubated further for various amounts of time, and the number of intracellular bacteria was determined by plate counting. Data are the means of three independent experiments and are presented as the means ± SEMs (N = 3). N, the number of times the experiment was performed. *P < 0.05, **P < 0.01.