Effect of the Flagellar Gene fliL on the Virulence of Pseudomonas plecoglossicida to Hybrid Grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂)

Pseudomonas plecoglossicida is the pathogen of visceral white spot disease in marine fish, which usually occurs at 16–19 °C and has resulted heavy economic losses. Our previous RNA sequencing revealed that expression fliL gene P. was significantly up-regulated during infection host. In order to study influence on virulence plecoglossicida, NZBD9 strain knocked out by homologous recombination method, gene-deleted (ΔfliL strain) constructed, complemented ΔfliL obtain C-ΔfliL strain. The growth curves strain, did not show significant differences. Compared with motility, adhesion, biofilm formation ability were tendered (p < 0.05); complement enhanced these abilities level results artificial experiments showed LD50 hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) 5.0 103 CFU/fish, 6.3 104 1.3 respectively. performed wild-type strains strains. A total 126 differentially expressed genes (DEGs) screened 0.05), 114 downregulated 12 upcontrolled, among several related six-type secretion system transport activity downregulated. DEGs aligned GO KEGG databases enriched 44 pathways 39 pathways, active ABC transporters both databases. These indicate movement, formation, adhesion may reduce affecting substance bacterial secretion.