Comparative transcriptome analysis revealed the role and mechanism of a FeoC-like LuxR-type regulator in intracellular survival of Aeromonas hydrophila

Abstract

A. hydrophila is one of the most important pathogens in the aquaculture industry, and its drug-resistant strains continue to emerge due to the irregular use of drugs. Previous studies found A. hydrophila could survive in fish macrophages, so it was speculated that A. hydrophila may hide in host macrophages to escape the killing of drugs and other antibacterial factors. The mechanism of A. hydrophila survival in fish macrophages is worthy of further study. In this study, the expression of a FeoC-like LuxR-type regulator was stable silenced by shRNA to construct the silencing strain feoC-RNAi. And the intracellular survival rate of feoC-RNAi decreased by about 67.5% compared with that of the wild-type strain. Comprehensive transcriptome analysis suggested that this FeoC-like LuxR-type regulator may regulate at least 1286 genes. According to GO and KEGG analysis of these 1286 DEGs, it can be speculated that this regulator may affect A. hydrophila intracellular survival by regulating bacterial metal ion metabolism, chemotaxis, type IV pilus biogenesis and binding, then further regulate the bacterial intracellular survival. Further comparison on biological phenotype of A. hydrophila B11 and feoC-RNAi revealed this FeoC-like LuxR-type regulator could regulate the expression of genes related to iron and magnesium metabolism and greatly affect bacterial growth under the limited magnesium concentration, but has no effect on bacterial growth under the limited iron concentration. And inhibited expression of this FeoC-like LuxR-type regulator led to a decrease in chemotactic ability of A. hydrophila by about 60%, disappearance of pilus, and a decrease in adhesion by about 50%. So a conclusion could be made that this FeoC-like LuxR-type regulator might play a vital role in regulating the uptake of magnesium and the homeostasis of magnesium and iron, and chemotaxis, type IV pilus biogenesis and adhesion of A. hydrophila, then further protect bacteria from the microbicidal actions and keep survival in host macrophages.