Table 2.

Characteristics of the mutant strains.

Characteristics	A. hydrophila LP-2	ΔORF01609	ΔORF01830	ΔORF03641
Biofilm formationa	0.84 ± 0.06	0.84 ± 0.12	0.83 ± 0.07	0.80 ± 0.12
Activity of ECPase (A442)b	0.34 ± 0.01	0.27 ± 0.01**	0.30 ± 0.02*	0.26 ± 0.01**
Hemolysis (%)c	4.27 ± 0.11	4.76 ± 0.19	4.01 ± 0.32	12.87 ± 0.18**
LD50 (cfu/mL)d	0.81 × 104	3.30 × 104**	2.90 × 104**	1.35 × 104

Values are the mean ± standard deviation of three independent trials. Significant differences between A. hydrophila LP-2 and each mutant strain are indicated by asterisks.

^*P < 0.05;

^**P < 0.01.

^a96-well-polypropylene plates incubated with bacteria for 48 h at 30°C and was measured using crystal violet staining method.

^bbacteria were cultured on 1.5% LB agar plates and incubated for 18 h at 30°C, then collected using PBS. And use azocasein assay for extracellular protease.

^cextracellular protease hemolytic activity was measured using defibrinated sheep blood. Culture supernatant was incubated with blood in PBS for 1 h at room temperature.

^dLD50s were evaluated in healthy zebrafish with the weight of 0.32 ± 0.06 g.