Tle1AHis required for the virulence and colonization ofA. hydrophilaNJ-35. A Determination of the LD50 values of the wild-type and tle1AH mutant strains in zebrafish. Zebrafish were intraperitoneally (i.p.) injected with tenfold serially diluted bacterial suspensions. The control group was i.p. injected with sterile PBS only. B Competitive assays of NJ-35 and Δtle1AH in crucian carp. Strains were mixed at a ratio of 1:1 and inoculated to fish by intraperitoneal injection. After 24 h, heart, hepatopancreas, spleen and kidney were harvested for counting of the number of colony-forming units (CFU) per gram of sample. Data are presented as the mean ± standard deviation (error bars) of three independent experiments. ***P < 0.001, **P < 0.01, *P < 0.05.