Role of LuxR-type regulators in fish pathogenic Aeromonas hydrophila

LuxR-type transcriptional factors are essential in many bacterial physiological processes. However, there have been no reports on their roles in Aeromonas hydrophila. In this study, six stable silent strains were constructed using shRNA. Significant decreases in the expression levels of luxR(05), luxR(08), luxR(19), luxR(11), luxR(164) and luxR(165) were shown in their respective strains by qRT-PCR. The luxR(05)-RNAi and luxR(164)-RNAi exhibit the most significant changes in sensitivity to kanamycin and gentamicin. The luxR(05)-RNAi showed minimum biofilm formation and the least motility, while luxR(164)-RNAi showed minimum biofilm formation, adhesion, growth and extracellular protease activity compared to the wild-type strain. In summary, the results of this paper suggest that all six luxR genes are involved in multiple physiological processes in A. hydrophila and that the roles of luxR(05) and luxR(164) are highly significant. The sensitivity of luxR(05)-RNAi and luxR(164)-RNAi to drugs may be closely related to biofilm formation. The luxR(05) may play an important role in the pathogenicity of A. hydrophila by regulating the movement, adhesion and biofilm formation of bacteria, whereas luxR(164) may be involved in similar functions by regulating bacterial adhesion, extracellular enzyme activity and growth. These results help further our understanding of the drug resistance and pathogenesis of A. hydrophila.